Avoid declarations in exception control flow

.github/actionlint.yaml

@@ -1,9 +0,0 @@
-# Configuration for the actionlint tool, which we run via pre-commit
-# to verify the correctness of the syntax in our GitHub Actions workflows.
-
-self-hosted-runner:
-  # Various runners we use that aren't recognized out-of-the-box by actionlint:
-  labels:
-    - depot-ubuntu-latest-8
-    - depot-ubuntu-22.04-16
-    - windows-latest-xlarge

.github/workflows/build-binaries.yml

@@ -53,7 +53,7 @@ jobs:
           args: --out dist
       - name: "Test sdist"
         run: |
-          pip install dist/"${PACKAGE_NAME}"-*.tar.gz --force-reinstall
+          pip install dist/${PACKAGE_NAME}-*.tar.gz --force-reinstall
           "${MODULE_NAME}" --help
           python -m "${MODULE_NAME}" --help
       - name: "Upload sdist"
@@ -125,7 +125,7 @@ jobs:
           args: --release --locked --out dist
       - name: "Test wheel - aarch64"
         run: |
-          pip install dist/"${PACKAGE_NAME}"-*.whl --force-reinstall
+          pip install dist/${PACKAGE_NAME}-*.whl --force-reinstall
           ruff --help
           python -m ruff --help
       - name: "Upload wheels"
@@ -186,7 +186,7 @@ jobs:
         if: ${{ !startsWith(matrix.platform.target, 'aarch64') }}
         shell: bash
         run: |
-          python -m pip install dist/"${PACKAGE_NAME}"-*.whl --force-reinstall
+          python -m pip install dist/${PACKAGE_NAME}-*.whl --force-reinstall
           "${MODULE_NAME}" --help
           python -m "${MODULE_NAME}" --help
       - name: "Upload wheels"
@@ -236,7 +236,7 @@ jobs:
       - name: "Test wheel"
         if: ${{ startsWith(matrix.target, 'x86_64') }}
         run: |
-          pip install dist/"${PACKAGE_NAME}"-*.whl --force-reinstall
+          pip install dist/${PACKAGE_NAME}-*.whl --force-reinstall
           "${MODULE_NAME}" --help
           python -m "${MODULE_NAME}" --help
       - name: "Upload wheels"

.github/workflows/build-docker.yml

@@ -142,7 +142,6 @@ jobs:
         # The printf will expand the base image with the `<RUFF_BASE_IMG>@sha256:<sha256> ...` for each sha256 in the directory
         # The final command becomes `docker buildx imagetools create -t tag1 -t tag2 ... <RUFF_BASE_IMG>@sha256:<sha256_1> <RUFF_BASE_IMG>@sha256:<sha256_2> ...`
         run: |
-          # shellcheck disable=SC2046
           docker buildx imagetools create \
             $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
             $(printf "${RUFF_BASE_IMG}@sha256:%s " *)
@@ -287,8 +286,6 @@ jobs:
         # The final command becomes `docker buildx imagetools create -t tag1 -t tag2 ... <RUFF_BASE_IMG>@sha256:<sha256_1> <RUFF_BASE_IMG>@sha256:<sha256_2> ...`
         run: |
           readarray -t lines <<< "$DOCKER_METADATA_OUTPUT_ANNOTATIONS"; annotations=(); for line in "${lines[@]}"; do annotations+=(--annotation "$line"); done
-
-          # shellcheck disable=SC2046
           docker buildx imagetools create \
             "${annotations[@]}" \
             $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \

.github/workflows/ci.yaml

@@ -290,9 +290,7 @@ jobs:
           file: "Cargo.toml"
           field: "workspace.package.rust-version"
       - name: "Install Rust toolchain"
-        env:
-          MSRV: ${{ steps.msrv.outputs.value }}
-        run: rustup default "${MSRV}"
+        run: rustup default ${{ steps.msrv.outputs.value }}
       - name: "Install mold"
         uses: rui314/setup-mold@v1
       - name: "Install cargo nextest"
@@ -308,8 +306,7 @@ jobs:
         shell: bash
         env:
           NEXTEST_PROFILE: "ci"
-          MSRV: ${{ steps.msrv.outputs.value }}
-        run: cargo "+${MSRV}" insta test --all-features --unreferenced reject --test-runner nextest
+        run: cargo +${{ steps.msrv.outputs.value }} insta test --all-features --unreferenced reject --test-runner nextest
 
   cargo-fuzz-build:
     name: "cargo fuzz build"
@@ -349,7 +346,7 @@ jobs:
       - uses: actions/checkout@v4
         with:
           persist-credentials: false
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v4
       - uses: actions/download-artifact@v4
         name: Download Ruff binary to test
         id: download-cached-binary
@@ -357,18 +354,16 @@ jobs:
           name: ruff
           path: ruff-to-test
       - name: Fuzz
-        env:
-          DOWNLOAD_PATH: ${{ steps.download-cached-binary.outputs.download-path }}
         run: |
           # Make executable, since artifact download doesn't preserve this
-          chmod +x "${DOWNLOAD_PATH}/ruff"
+          chmod +x ${{ steps.download-cached-binary.outputs.download-path }}/ruff
 
           (
             uvx \
-            --python="${PYTHON_VERSION}" \
+            --python=${{ env.PYTHON_VERSION }} \
             --from=./python/py-fuzzer \
             fuzz \
-            --test-executable="${DOWNLOAD_PATH}/ruff" \
+            --test-executable=${{ steps.download-cached-binary.outputs.download-path }}/ruff \
             --bin=ruff \
             0-500
           )
@@ -434,72 +429,64 @@ jobs:
 
       - name: Run `ruff check` stable ecosystem check
         if: ${{ needs.determine_changes.outputs.linter == 'true' }}
-        env:
-          DOWNLOAD_PATH: ${{ steps.ruff-target.outputs.download-path }}
         run: |
           # Make executable, since artifact download doesn't preserve this
-          chmod +x ./ruff "${DOWNLOAD_PATH}/ruff"
+          chmod +x ./ruff ${{ steps.ruff-target.outputs.download-path }}/ruff
 
           # Set pipefail to avoid hiding errors with tee
           set -eo pipefail
 
-          ruff-ecosystem check ./ruff "${DOWNLOAD_PATH}/ruff" --cache ./checkouts --output-format markdown | tee ecosystem-result-check-stable
+          ruff-ecosystem check ./ruff ${{ steps.ruff-target.outputs.download-path }}/ruff --cache ./checkouts --output-format markdown | tee ecosystem-result-check-stable
 
-          cat ecosystem-result-check-stable > "$GITHUB_STEP_SUMMARY"
+          cat ecosystem-result-check-stable > $GITHUB_STEP_SUMMARY
           echo "### Linter (stable)"  > ecosystem-result
           cat ecosystem-result-check-stable >> ecosystem-result
           echo "" >> ecosystem-result
 
       - name: Run `ruff check` preview ecosystem check
         if: ${{ needs.determine_changes.outputs.linter == 'true' }}
-        env:
-          DOWNLOAD_PATH: ${{ steps.ruff-target.outputs.download-path }}
         run: |
           # Make executable, since artifact download doesn't preserve this
-          chmod +x ./ruff "${DOWNLOAD_PATH}/ruff"
+          chmod +x ./ruff ${{ steps.ruff-target.outputs.download-path }}/ruff
 
           # Set pipefail to avoid hiding errors with tee
           set -eo pipefail
 
-          ruff-ecosystem check ./ruff "${DOWNLOAD_PATH}/ruff" --cache ./checkouts --output-format markdown --force-preview | tee ecosystem-result-check-preview
+          ruff-ecosystem check ./ruff ${{ steps.ruff-target.outputs.download-path }}/ruff --cache ./checkouts --output-format markdown --force-preview | tee ecosystem-result-check-preview
 
-          cat ecosystem-result-check-preview > "$GITHUB_STEP_SUMMARY"
+          cat ecosystem-result-check-preview > $GITHUB_STEP_SUMMARY
           echo "### Linter (preview)" >> ecosystem-result
           cat ecosystem-result-check-preview >> ecosystem-result
           echo "" >> ecosystem-result
 
       - name: Run `ruff format` stable ecosystem check
         if: ${{ needs.determine_changes.outputs.formatter == 'true' }}
-        env:
-          DOWNLOAD_PATH: ${{ steps.ruff-target.outputs.download-path }}
         run: |
           # Make executable, since artifact download doesn't preserve this
-          chmod +x ./ruff "${DOWNLOAD_PATH}/ruff"
+          chmod +x ./ruff ${{ steps.ruff-target.outputs.download-path }}/ruff
 
           # Set pipefail to avoid hiding errors with tee
           set -eo pipefail
 
-          ruff-ecosystem format ./ruff "${DOWNLOAD_PATH}/ruff" --cache ./checkouts --output-format markdown | tee ecosystem-result-format-stable
+          ruff-ecosystem format ./ruff ${{ steps.ruff-target.outputs.download-path }}/ruff --cache ./checkouts --output-format markdown | tee ecosystem-result-format-stable
 
-          cat ecosystem-result-format-stable > "$GITHUB_STEP_SUMMARY"
+          cat ecosystem-result-format-stable > $GITHUB_STEP_SUMMARY
           echo "### Formatter (stable)" >> ecosystem-result
           cat ecosystem-result-format-stable >> ecosystem-result
           echo "" >> ecosystem-result
 
       - name: Run `ruff format` preview ecosystem check
         if: ${{ needs.determine_changes.outputs.formatter == 'true' }}
-        env:
-          DOWNLOAD_PATH: ${{ steps.ruff-target.outputs.download-path }}
         run: |
           # Make executable, since artifact download doesn't preserve this
-          chmod +x ./ruff "${DOWNLOAD_PATH}/ruff"
+          chmod +x ./ruff ${{ steps.ruff-target.outputs.download-path }}/ruff
 
           # Set pipefail to avoid hiding errors with tee
           set -eo pipefail
 
-          ruff-ecosystem format ./ruff "${DOWNLOAD_PATH}/ruff" --cache ./checkouts --output-format markdown --force-preview | tee ecosystem-result-format-preview
+          ruff-ecosystem format ./ruff ${{ steps.ruff-target.outputs.download-path }}/ruff --cache ./checkouts --output-format markdown --force-preview | tee ecosystem-result-format-preview
 
-          cat ecosystem-result-format-preview > "$GITHUB_STEP_SUMMARY"
+          cat ecosystem-result-format-preview > $GITHUB_STEP_SUMMARY
           echo "### Formatter (preview)" >> ecosystem-result
           cat ecosystem-result-format-preview >> ecosystem-result
           echo "" >> ecosystem-result
@@ -554,7 +541,7 @@ jobs:
           args: --out dist
       - name: "Test wheel"
         run: |
-          pip install --force-reinstall --find-links dist "${PACKAGE_NAME}"
+          pip install --force-reinstall --find-links dist ${{ env.PACKAGE_NAME }}
           ruff --help
           python -m ruff --help
       - name: "Remove wheels from cache"
@@ -583,14 +570,13 @@ jobs:
           key: pre-commit-${{ hashFiles('.pre-commit-config.yaml') }}
       - name: "Run pre-commit"
         run: |
-          echo '```console' > "$GITHUB_STEP_SUMMARY"
+          echo '```console' > $GITHUB_STEP_SUMMARY
           # Enable color output for pre-commit and remove it for the summary
-          # Use --hook-stage=manual to enable slower pre-commit hooks that are skipped by default
-          SKIP=cargo-fmt,clippy,dev-generate-all pre-commit run --all-files --show-diff-on-failure --color=always --hook-stage=manual | \
-            tee >(sed -E 's/\x1B\[([0-9]{1,2}(;[0-9]{1,2})*)?[mGK]//g' >> "$GITHUB_STEP_SUMMARY") >&1
-          exit_code="${PIPESTATUS[0]}"
-          echo '```' >> "$GITHUB_STEP_SUMMARY"
-          exit "$exit_code"
+          SKIP=cargo-fmt,clippy,dev-generate-all pre-commit run --all-files --show-diff-on-failure --color=always | \
+            tee >(sed -E 's/\x1B\[([0-9]{1,2}(;[0-9]{1,2})*)?[mGK]//g' >> $GITHUB_STEP_SUMMARY) >&1
+          exit_code=${PIPESTATUS[0]}
+          echo '```' >> $GITHUB_STEP_SUMMARY
+          exit $exit_code
 
   docs:
     name: "mkdocs"
@@ -613,7 +599,7 @@ jobs:
       - name: "Install Rust toolchain"
         run: rustup show
       - name: Install uv
-        uses: astral-sh/setup-uv@v5
+        uses: astral-sh/setup-uv@v4
       - uses: Swatinem/rust-cache@v2
       - name: "Install Insiders dependencies"
         if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
@@ -651,7 +637,7 @@ jobs:
       - name: "Run checks"
         run: scripts/formatter_ecosystem_checks.sh
       - name: "Github step summary"
-        run: cat target/formatter-ecosystem/stats.txt > "$GITHUB_STEP_SUMMARY"
+        run: cat target/formatter-ecosystem/stats.txt > $GITHUB_STEP_SUMMARY
       - name: "Remove checkouts from cache"
         run: rm -r target/formatter-ecosystem
 
@@ -690,13 +676,11 @@ jobs:
           just install
 
       - name: Run ruff-lsp tests
-        env:
-          DOWNLOAD_PATH: ${{ steps.ruff-target.outputs.download-path }}
         run: |
           # Setup development binary
           pip uninstall --yes ruff
-          chmod +x "${DOWNLOAD_PATH}/ruff"
-          export PATH="${DOWNLOAD_PATH}:${PATH}"
+          chmod +x ${{ steps.ruff-target.outputs.download-path }}/ruff
+          export PATH=${{ steps.ruff-target.outputs.download-path }}:$PATH
           ruff version
 
           just test

.github/workflows/daily_fuzz.yaml

@@ -34,7 +34,7 @@ jobs:
       - uses: actions/checkout@v4
         with:
           persist-credentials: false
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v4
       - name: "Install Rust toolchain"
         run: rustup show
       - name: "Install mold"
@@ -46,7 +46,6 @@ jobs:
         run: cargo build --locked
       - name: Fuzz
         run: |
-          # shellcheck disable=SC2046
           (
             uvx \
             --python=3.12 \

.github/workflows/pr-comment.yaml

@@ -10,11 +10,12 @@ on:
         description: The ecosystem workflow that triggers the workflow run
         required: true
 
+permissions:
+  pull-requests: write
+
 jobs:
   comment:
     runs-on: ubuntu-latest
-    permissions:
-      pull-requests: write
     steps:
       - uses: dawidd6/action-download-artifact@v7
         name: Download pull request number
@@ -29,7 +30,7 @@ jobs:
         run: |
           if [[ -f pr-number ]]
           then
-            echo "pr-number=$(<pr-number)" >> "$GITHUB_OUTPUT"
+            echo "pr-number=$(<pr-number)" >> $GITHUB_OUTPUT
           fi
 
       - uses: dawidd6/action-download-artifact@v7
@@ -65,9 +66,9 @@ jobs:
           cat pr/ecosystem/ecosystem-result >> comment.txt
           echo "" >> comment.txt
 
-          echo 'comment<<EOF' >> "$GITHUB_OUTPUT"
-          cat comment.txt >> "$GITHUB_OUTPUT"
-          echo 'EOF' >> "$GITHUB_OUTPUT"
+          echo 'comment<<EOF' >> $GITHUB_OUTPUT
+          cat comment.txt >> $GITHUB_OUTPUT
+          echo 'EOF' >> $GITHUB_OUTPUT
 
       - name: Find existing comment
         uses: peter-evans/find-comment@v3

.github/workflows/publish-docs.yml

@@ -44,8 +44,8 @@ jobs:
           # Use version as display name for now
           display_name="$version"
 
-          echo "version=$version" >> "$GITHUB_ENV"
-          echo "display_name=$display_name" >> "$GITHUB_ENV"
+          echo "version=$version" >> $GITHUB_ENV
+          echo "display_name=$display_name" >> $GITHUB_ENV
 
       - name: "Set branch name"
         run: |
@@ -55,8 +55,8 @@ jobs:
           # characters disallowed in git branch names with hyphens
           branch_display_name="$(echo "${display_name}" | tr -c '[:alnum:]._' '-' | tr -s '-')"
 
-          echo "branch_name=update-docs-$branch_display_name-$timestamp" >> "$GITHUB_ENV"
-          echo "timestamp=$timestamp" >> "$GITHUB_ENV"
+          echo "branch_name=update-docs-$branch_display_name-$timestamp" >> $GITHUB_ENV
+          echo "timestamp=$timestamp" >> $GITHUB_ENV
 
       - name: "Add SSH key"
         if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
@@ -112,7 +112,7 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.ASTRAL_DOCS_PAT }}
         run: |
           # set the PR title
-          pull_request_title="Update ruff documentation for ${display_name}"
+          pull_request_title="Update ruff documentation for "${display_name}""
 
           # Delete any existing pull requests that are open for this version
           # by checking against pull_request_title because the new PR will
@@ -124,12 +124,10 @@ jobs:
           git push origin "${branch_name}"
 
           # create the PR
-          gh pr create \
-            --base=main \
-            --head="${branch_name}" \
-            --title="${pull_request_title}" \
-            --body="Automated documentation update for ${display_name}" \
-            --label="documentation"
+          gh pr create --base main --head "${branch_name}" \
+            --title "$pull_request_title" \
+            --body "Automated documentation update for "${display_name}"" \
+            --label "documentation"
 
       - name: "Merge Pull Request"
         if: ${{ inputs.plan != '' && !fromJson(inputs.plan).announcement_tag_is_implicit }}

.github/workflows/publish-pypi.yml

@@ -22,7 +22,7 @@ jobs:
       id-token: write
     steps:
       - name: "Install uv"
-        uses: astral-sh/setup-uv@v5
+        uses: astral-sh/setup-uv@v4
       - uses: actions/download-artifact@v4
         with:
           pattern: wheels-*

.github/workflows/sync_typeshed.yaml

@@ -59,7 +59,7 @@ jobs:
         run: |
           cd ruff
           git push --force origin typeshedbot/sync-typeshed
-          gh pr list --repo "$GITHUB_REPOSITORY" --head typeshedbot/sync-typeshed --json id --jq length | grep 1 && exit 0 # exit if there is existing pr
+          gh pr list --repo $GITHUB_REPOSITORY --head typeshedbot/sync-typeshed --json id --jq length | grep 1 && exit 0 # exit if there is existing pr
           gh pr create --title "Sync vendored typeshed stubs" --body "Close and reopen this PR to trigger CI" --label "internal"
 
   create-issue-on-failure:

.github/zizmor.yml

@@ -1,6 +0,0 @@
-# Configuration for the zizmor static analysis tool, run via pre-commit in CI
-# https://woodruffw.github.io/zizmor/configuration/
-rules:
-  dangerous-triggers:
-    ignore:
-      - pr-comment.yaml

.markdownlint.yaml

@@ -21,11 +21,3 @@ MD014: false
 MD024:
   # Allow when nested under different parents e.g. CHANGELOG.md
   siblings_only: true
-
-# MD046/code-block-style
-#
-# Ignore this because it conflicts with the code block style used in content
-# tabs of mkdocs-material which is to add a blank line after the content title.
-#
-# Ref: https://github.com/astral-sh/ruff/pull/15011#issuecomment-2544790854
-MD046: false

.pre-commit-config.yaml

@@ -2,7 +2,6 @@ fail_fast: false
 
 exclude: |
   (?x)^(
-    .github/workflows/release.yml|
     crates/red_knot_vendored/vendor/.*|
     crates/red_knot_workspace/resources/.*|
     crates/ruff_linter/resources/.*|
@@ -23,12 +22,13 @@ repos:
       - id: validate-pyproject
 
   - repo: https://github.com/executablebooks/mdformat
-    rev: 0.7.21
+    rev: 0.7.19
     hooks:
       - id: mdformat
         additional_dependencies:
-          - mdformat-mkdocs==4.0.0
-          - mdformat-footnote==0.1.1
+          - mdformat-mkdocs
+          - mdformat-admon
+          - mdformat-footnote
         exclude: |
           (?x)^(
             docs/formatter/black\.md
@@ -59,7 +59,7 @@ repos:
           - black==24.10.0
 
   - repo: https://github.com/crate-ci/typos
-    rev: v1.28.4
+    rev: v1.28.2
     hooks:
       - id: typos
 
@@ -73,7 +73,7 @@ repos:
         pass_filenames: false # This makes it a lot faster
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.8.4
+    rev: v0.8.2
     hooks:
       - id: ruff-format
       - id: ruff
@@ -88,37 +88,18 @@ repos:
       - id: prettier
         types: [yaml]
 
-  # zizmor detects security vulnerabilities in GitHub Actions workflows.
-  # Additional configuration for the tool is found in `.github/zizmor.yml`
   - repo: https://github.com/woodruffw/zizmor-pre-commit
-    rev: v0.10.0
+    rev: v0.8.0
     hooks:
       - id: zizmor
+        # `release.yml` is autogenerated by `dist`; security issues need to be fixed there
+        # (https://opensource.axo.dev/cargo-dist/)
+        exclude: .github/workflows/release.yml
 
   - repo: https://github.com/python-jsonschema/check-jsonschema
     rev: 0.30.0
     hooks:
       - id: check-github-workflows
 
-  # `actionlint` hook, for verifying correct syntax in GitHub Actions workflows.
-  # Some additional configuration for `actionlint` can be found in `.github/actionlint.yaml`.
-  - repo: https://github.com/rhysd/actionlint
-    rev: v1.7.5
-    hooks:
-      - id: actionlint
-        stages:
-          # This hook is disabled by default, since it's quite slow.
-          # To run all hooks *including* this hook, use `uvx pre-commit run -a --hook-stage=manual`.
-          # To run *just* this hook, use `uvx pre-commit run -a actionlint --hook-stage=manual`.
-          - manual
-        args:
-          - "-ignore=SC2129" # ignorable stylistic lint from shellcheck
-          - "-ignore=SC2016" # another shellcheck lint: seems to have false positives?
-        additional_dependencies:
-          # actionlint has a shellcheck integration which extracts shell scripts in `run:` steps from GitHub Actions
-          # and checks these with shellcheck. This is arguably its most useful feature,
-          # but the integration only works if shellcheck is installed
-          - "github.com/wasilibs/go-shellcheck/cmd/shellcheck@v0.10.0"
-
 ci:
   skip: [cargo-fmt, dev-generate-all]

CHANGELOG.md

@@ -1,74 +1,5 @@
 # Changelog
 
-## 0.8.5
-
-### Preview features
-
-- \[`airflow`\] Extend names moved from core to provider (`AIR303`) ([#15145](https://github.com/astral-sh/ruff/pull/15145), [#15159](https://github.com/astral-sh/ruff/pull/15159), [#15196](https://github.com/astral-sh/ruff/pull/15196), [#15216](https://github.com/astral-sh/ruff/pull/15216))
-- \[`airflow`\] Extend rule to check class attributes, methods, arguments (`AIR302`) ([#15054](https://github.com/astral-sh/ruff/pull/15054), [#15083](https://github.com/astral-sh/ruff/pull/15083))
-- \[`fastapi`\] Update `FAST002` to check keyword-only arguments ([#15119](https://github.com/astral-sh/ruff/pull/15119))
-- \[`flake8-type-checking`\] Disable `TC006` and `TC007` in stub files ([#15179](https://github.com/astral-sh/ruff/pull/15179))
-- \[`pylint`\] Detect nested methods correctly (`PLW1641`) ([#15032](https://github.com/astral-sh/ruff/pull/15032))
-- \[`ruff`\] Detect more strict-integer expressions (`RUF046`) ([#14833](https://github.com/astral-sh/ruff/pull/14833))
-- \[`ruff`\] Implement `falsy-dict-get-fallback` (`RUF056`) ([#15160](https://github.com/astral-sh/ruff/pull/15160))
-- \[`ruff`\] Implement `unnecessary-round` (`RUF057`) ([#14828](https://github.com/astral-sh/ruff/pull/14828))
-
-### Rule changes
-
-- Visit PEP 764 inline `TypedDict` keys as non-type-expressions ([#15073](https://github.com/astral-sh/ruff/pull/15073))
-- \[`flake8-comprehensions`\] Skip `C416` if comprehension contains unpacking ([#14909](https://github.com/astral-sh/ruff/pull/14909))
-- \[`flake8-pie`\] Allow `cast(SomeType, ...)` (`PIE796`) ([#15141](https://github.com/astral-sh/ruff/pull/15141))
-- \[`flake8-simplify`\] More precise inference for dictionaries (`SIM300`) ([#15164](https://github.com/astral-sh/ruff/pull/15164))
-- \[`flake8-use-pathlib`\] Catch redundant joins in `PTH201` and avoid syntax errors ([#15177](https://github.com/astral-sh/ruff/pull/15177))
-- \[`pycodestyle`\] Preserve original value format (`E731`) ([#15097](https://github.com/astral-sh/ruff/pull/15097))
-- \[`pydocstyle`\] Split on first whitespace character (`D403`) ([#15082](https://github.com/astral-sh/ruff/pull/15082))
-- \[`pyupgrade`\] Add all PEP-585 names to `UP006` rule ([#5454](https://github.com/astral-sh/ruff/pull/5454))
-
-### Configuration
-
-- \[`flake8-type-checking`\] Improve flexibility of `runtime-evaluated-decorators` ([#15204](https://github.com/astral-sh/ruff/pull/15204))
-- \[`pydocstyle`\] Add setting to ignore missing documentation for `*args` and `**kwargs` parameters (`D417`) ([#15210](https://github.com/astral-sh/ruff/pull/15210))
-- \[`ruff`\] Add an allowlist for `unsafe-markup-use` (`RUF035`) ([#15076](https://github.com/astral-sh/ruff/pull/15076))
-
-### Bug fixes
-
-- Fix type subscript on older python versions ([#15090](https://github.com/astral-sh/ruff/pull/15090))
-- Use `TypeChecker` for detecting `fastapi` routes ([#15093](https://github.com/astral-sh/ruff/pull/15093))
-- \[`pycodestyle`\] Avoid false positives and negatives related to type parameter default syntax (`E225`, `E251`) ([#15214](https://github.com/astral-sh/ruff/pull/15214))
-
-### Documentation
-
-- Fix incorrect doc in `shebang-not-executable` (`EXE001`) and add git+windows solution to executable bit ([#15208](https://github.com/astral-sh/ruff/pull/15208))
-- Rename rules currently not conforming to naming convention ([#15102](https://github.com/astral-sh/ruff/pull/15102))
-
-## 0.8.4
-
-### Preview features
-
-- \[`airflow`\] Extend `AIR302` with additional functions and classes ([#15015](https://github.com/astral-sh/ruff/pull/15015))
-- \[`airflow`\] Implement `moved-to-provider-in-3` for modules that has been moved to Airflow providers (`AIR303`) ([#14764](https://github.com/astral-sh/ruff/pull/14764))
-- \[`flake8-use-pathlib`\] Extend check for invalid path suffix to include the case `"."` (`PTH210`) ([#14902](https://github.com/astral-sh/ruff/pull/14902))
-- \[`perflint`\] Fix panic in `PERF401` when list variable is after the `for` loop ([#14971](https://github.com/astral-sh/ruff/pull/14971))
-- \[`perflint`\] Simplify finding the loop target in `PERF401` ([#15025](https://github.com/astral-sh/ruff/pull/15025))
-- \[`pylint`\] Preserve original value format (`PLR6104`) ([#14978](https://github.com/astral-sh/ruff/pull/14978))
-- \[`ruff`\] Avoid false positives for `RUF027` for typing context bindings ([#15037](https://github.com/astral-sh/ruff/pull/15037))
-- \[`ruff`\] Check for ambiguous pattern passed to `pytest.raises()` (`RUF043`) ([#14966](https://github.com/astral-sh/ruff/pull/14966))
-
-### Rule changes
-
-- \[`flake8-bandit`\] Check `S105` for annotated assignment ([#15059](https://github.com/astral-sh/ruff/pull/15059))
-- \[`flake8-pyi`\] More autofixes for `redundant-none-literal` (`PYI061`) ([#14872](https://github.com/astral-sh/ruff/pull/14872))
-- \[`pydocstyle`\] Skip leading whitespace for `D403` ([#14963](https://github.com/astral-sh/ruff/pull/14963))
-- \[`ruff`\] Skip `SQLModel` base classes for `mutable-class-default` (`RUF012`) ([#14949](https://github.com/astral-sh/ruff/pull/14949))
-
-### Bug
-
-- \[`perflint`\] Parenthesize walrus expressions in autofix for `manual-list-comprehension` (`PERF401`) ([#15050](https://github.com/astral-sh/ruff/pull/15050))
-
-### Server
-
-- Check diagnostic refresh support from client capability which enables dynamic configuration for various editors ([#15014](https://github.com/astral-sh/ruff/pull/15014))
-
 ## 0.8.3
 
 ### Preview features

CONTRIBUTING.md

@@ -467,7 +467,7 @@ cargo build --release && hyperfine --warmup 10 \
   "./target/release/ruff check ./crates/ruff_linter/resources/test/cpython/ --no-cache -e --select W505,E501"
 ```
 
-You can run `uv venv --project ./scripts/benchmarks`, activate the venv and then run `uv sync --project ./scripts/benchmarks` to create a working environment for the
+You can run `poetry install` from `./scripts/benchmarks` to create a working environment for the
 above. All reported benchmarks were computed using the versions specified by
 `./scripts/benchmarks/pyproject.toml` on Python 3.11.
 

Cargo.lock

@@ -117,9 +117,9 @@ dependencies = [
 
 [[package]]
 name = "anyhow"
-version = "1.0.95"
+version = "1.0.94"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34ac096ce696dc2fcabef30516bb13c0a68a11d30131d3df6f04711467681b04"
+checksum = "c1fd03a028ef38ba2276dce7e33fcd6369c158a1bca17946c4b1b701891c1ff7"
 
 [[package]]
 name = "append-only-vec"
@@ -220,9 +220,9 @@ checksum = "7f839cdf7e2d3198ac6ca003fd8ebc61715755f41c1cad15ff13df67531e00ed"
 
 [[package]]
 name = "bstr"
-version = "1.11.1"
+version = "1.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "786a307d683a5bf92e6fd5fd69a7eb613751668d1d8d67d802846dfe367c62c8"
+checksum = "1a68f1f47cdf0ec8ee4b941b2eee2a80cb796db73118c0dd09ac63fbe405be22"
 dependencies = [
  "memchr",
  "regex-automata 0.4.8",
@@ -314,9 +314,9 @@ dependencies = [
 
 [[package]]
 name = "chrono"
-version = "0.4.39"
+version = "0.4.38"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7e36cc9d416881d2e24f9a963be5fb1cd90966419ac844274161d10488b3e825"
+checksum = "a21f936df1771bf62b77f047b726c4625ff2e8aa607c01ec06e5a05bd8463401"
 dependencies = [
  "android-tzdata",
  "iana-time-zone",
@@ -413,7 +413,7 @@ dependencies = [
  "heck",
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -465,9 +465,9 @@ checksum = "acbf1af155f9b9ef647e42cdc158db4b64a1b61f743629225fde6f3e0be2a7c7"
 
 [[package]]
 name = "colored"
-version = "2.2.0"
+version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "117725a109d387c937a1533ce01b450cbde6b88abceea8473c4d7a85853cda3c"
+checksum = "cbf2150cce219b664a8a70df7a1f933836724b503f8a413af9365b4dcc4d90b8"
 dependencies = [
  "lazy_static",
  "windows-sys 0.48.0",
@@ -475,9 +475,9 @@ dependencies = [
 
 [[package]]
 name = "compact_str"
-version = "0.8.1"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3b79c4069c6cad78e2e0cdfcbd26275770669fb39fd308a752dc110e83b9af32"
+checksum = "6050c3a16ddab2e412160b31f2c871015704239bca62f72f6e5f0be631d3f644"
 dependencies = [
  "castaway",
  "cfg-if",
@@ -693,7 +693,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "strsim 0.10.0",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -704,7 +704,7 @@ checksum = "a668eda54683121533a393014d8692171709ff57a7d61f187b6e782719f8933f"
 dependencies = [
  "darling_core",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -774,7 +774,7 @@ dependencies = [
  "glob",
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -826,7 +826,7 @@ checksum = "97369cbbc041bc366949bc74d34658d6cda5621039731c6310521892a3a20ae0"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -877,9 +877,9 @@ dependencies = [
 
 [[package]]
 name = "env_logger"
-version = "0.11.6"
+version = "0.11.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcaee3d8e3cfc3fd92428d477bc97fc29ec8716d180c0d74c643bb26166660e0"
+checksum = "e13fa619b91fb2381732789fc5de83b45675e882f66623b7d8cb4f643017018d"
 dependencies = [
  "anstream",
  "anstyle",
@@ -923,9 +923,9 @@ checksum = "e8c02a5121d4ea3eb16a80748c74f5549a5665e4c21333c6098f283870fbdea6"
 
 [[package]]
 name = "fern"
-version = "0.7.1"
+version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4316185f709b23713e41e3195f90edef7fb00c3ed4adc79769cf09cc762a3b29"
+checksum = "69ff9c9d5fb3e6da8ac2f77ab76fe7e8087d512ce095200f8f29ac5b656cf6dc"
 dependencies = [
  "log",
 ]
@@ -1019,9 +1019,9 @@ dependencies = [
 
 [[package]]
 name = "glob"
-version = "0.3.2"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a8d1add55171497b4705a648c6b583acafb01d58050a51727785f0b2c8e0a2b2"
+checksum = "d2fabcfbdc87f4758337ca535fb41a6d701b65693ce38287d856d1674551ec9b"
 
 [[package]]
 name = "globset"
@@ -1246,7 +1246,7 @@ checksum = "1ec89e9337638ecdc08744df490b221a7399bf8d164eb52a665454e60e075ad6"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1420,7 +1420,7 @@ dependencies = [
  "heck",
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1521,9 +1521,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.169"
+version = "0.2.167"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b5aba8db14291edd000dfcc4d620c7ebfb122c613afb886ca8803fa4e128a20a"
+checksum = "09d6582e104315a817dff97f75133544b2e094ee22447d2acf4a74e189ba06fc"
 
 [[package]]
 name = "libcst"
@@ -1547,7 +1547,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a2ae40017ac09cd2c6a53504cb3c871c7f2b41466eac5bc66ba63f39073b467b"
 dependencies = [
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -1607,14 +1607,13 @@ checksum = "a7a70ba024b9dc04c27ea2f0c0548feb474ec5c54bba33a7f72f873a39d07b24"
 
 [[package]]
 name = "lsp-server"
-version = "0.7.8"
+version = "0.7.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9462c4dc73e17f971ec1f171d44bfffb72e65a130117233388a0ebc7ec5656f9"
+checksum = "550446e84739dcaf6d48a4a093973850669e13e8a34d8f8d64851041be267cd9"
 dependencies = [
  "crossbeam-channel",
  "log",
  "serde",
- "serde_derive",
  "serde_json",
 ]
 
@@ -2015,7 +2014,7 @@ dependencies = [
  "pest_meta",
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -2162,7 +2161,7 @@ dependencies = [
  "newtype-uuid",
  "quick-xml",
  "strip-ansi-escapes",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "uuid",
 ]
 
@@ -2197,9 +2196,9 @@ dependencies = [
 
 [[package]]
 name = "quote"
-version = "1.0.38"
+version = "1.0.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0e4dccaaaf89514f546c693ddc140f729f958c247918a13380cccc6078391acc"
+checksum = "b5b9d34b8991d19d98081b46eacdd8eb58c6f2b201139f7c5f643cc155a633af"
 dependencies = [
  "proc-macro2",
 ]
@@ -2289,7 +2288,6 @@ dependencies = [
  "compact_str",
  "countme",
  "dir-test",
- "drop_bomb",
  "hashbrown 0.15.2",
  "indexmap",
  "insta",
@@ -2307,7 +2305,6 @@ dependencies = [
  "ruff_python_literal",
  "ruff_python_parser",
  "ruff_python_stdlib",
- "ruff_python_trivia",
  "ruff_source_file",
  "ruff_text_size",
  "rustc-hash 2.1.0",
@@ -2317,7 +2314,7 @@ dependencies = [
  "static_assertions",
  "tempfile",
  "test-case",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "tracing",
 ]
 
@@ -2414,7 +2411,7 @@ dependencies = [
  "rustc-hash 2.1.0",
  "salsa",
  "serde",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "toml",
  "tracing",
 ]
@@ -2520,7 +2517,7 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.8.5"
+version = "0.8.3"
 dependencies = [
  "anyhow",
  "argfile",
@@ -2567,7 +2564,7 @@ dependencies = [
  "strum",
  "tempfile",
  "test-case",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "tikv-jemallocator",
  "toml",
  "tracing",
@@ -2637,7 +2634,7 @@ dependencies = [
  "salsa",
  "serde",
  "tempfile",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "tracing",
  "tracing-subscriber",
  "tracing-tree",
@@ -2739,7 +2736,7 @@ dependencies = [
 
 [[package]]
 name = "ruff_linter"
-version = "0.8.5"
+version = "0.8.3"
 dependencies = [
  "aho-corasick",
  "annotate-snippets 0.9.2",
@@ -2789,7 +2786,7 @@ dependencies = [
  "strum",
  "strum_macros",
  "test-case",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "toml",
  "typed-arena",
  "unicode-normalization",
@@ -2806,7 +2803,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "ruff_python_trivia",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -2823,7 +2820,7 @@ dependencies = [
  "serde_json",
  "serde_with",
  "test-case",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "uuid",
 ]
 
@@ -2895,7 +2892,7 @@ dependencies = [
  "similar",
  "smallvec",
  "static_assertions",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "tracing",
 ]
 
@@ -2969,7 +2966,6 @@ dependencies = [
  "rustc-hash 2.1.0",
  "schemars",
  "serde",
- "smallvec",
 ]
 
 [[package]]
@@ -3029,7 +3025,7 @@ dependencies = [
  "serde",
  "serde_json",
  "shellexpand",
- "thiserror 2.0.9",
+ "thiserror 2.0.6",
  "tracing",
  "tracing-subscriber",
 ]
@@ -3055,7 +3051,7 @@ dependencies = [
 
 [[package]]
 name = "ruff_wasm"
-version = "0.8.5"
+version = "0.8.3"
 dependencies = [
  "console_error_panic_hook",
  "console_log",
@@ -3197,7 +3193,7 @@ checksum = "e86697c916019a8588c99b5fac3cead74ec0b4b819707a682fd4d23fa0ce1ba1"
 [[package]]
 name = "salsa"
 version = "0.18.0"
-source = "git+https://github.com/salsa-rs/salsa.git?rev=3c7f1694c9efba751dbeeacfbc93b227586e316a#3c7f1694c9efba751dbeeacfbc93b227586e316a"
+source = "git+https://github.com/salsa-rs/salsa.git?rev=254c749b02cde2fd29852a7463a33e800b771758#254c749b02cde2fd29852a7463a33e800b771758"
 dependencies = [
  "append-only-vec",
  "arc-swap",
@@ -3207,7 +3203,6 @@ dependencies = [
  "indexmap",
  "lazy_static",
  "parking_lot",
- "rayon",
  "rustc-hash 2.1.0",
  "salsa-macro-rules",
  "salsa-macros",
@@ -3218,17 +3213,17 @@ dependencies = [
 [[package]]
 name = "salsa-macro-rules"
 version = "0.1.0"
-source = "git+https://github.com/salsa-rs/salsa.git?rev=3c7f1694c9efba751dbeeacfbc93b227586e316a#3c7f1694c9efba751dbeeacfbc93b227586e316a"
+source = "git+https://github.com/salsa-rs/salsa.git?rev=254c749b02cde2fd29852a7463a33e800b771758#254c749b02cde2fd29852a7463a33e800b771758"
 
 [[package]]
 name = "salsa-macros"
 version = "0.18.0"
-source = "git+https://github.com/salsa-rs/salsa.git?rev=3c7f1694c9efba751dbeeacfbc93b227586e316a#3c7f1694c9efba751dbeeacfbc93b227586e316a"
+source = "git+https://github.com/salsa-rs/salsa.git?rev=254c749b02cde2fd29852a7463a33e800b771758#254c749b02cde2fd29852a7463a33e800b771758"
 dependencies = [
  "heck",
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
  "synstructure",
 ]
 
@@ -3262,7 +3257,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "serde_derive_internals",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -3285,9 +3280,9 @@ checksum = "1c107b6f4780854c8b126e228ea8869f4d7b71260f962fefb57b996b8959ba6b"
 
 [[package]]
 name = "serde"
-version = "1.0.217"
+version = "1.0.215"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "02fc4265df13d6fa1d00ecff087228cc0a2b5f3c0e87e258d8b94a156e984c70"
+checksum = "6513c1ad0b11a9376da888e3e0baa0077f1aed55c17f50e7b2397136129fb88f"
 dependencies = [
  "serde_derive",
 ]
@@ -3305,13 +3300,13 @@ dependencies = [
 
 [[package]]
 name = "serde_derive"
-version = "1.0.217"
+version = "1.0.215"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5a9bf7cf98d04a2b28aead066b7496853d4779c9cc183c440dbac457641e19a0"
+checksum = "ad1e866f866923f252f05c889987993144fb74e722403468a4ebd70c3cd756c0"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -3322,14 +3317,14 @@ checksum = "330f01ce65a3a5fe59a60c82f3c9a024b573b8a6e875bd233fe5f934e71d54e3"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
 name = "serde_json"
-version = "1.0.134"
+version = "1.0.133"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d00f4175c42ee48b15416f6193a959ba3a0d67fc699a0db9ad12df9f83991c7d"
+checksum = "c7fceb2473b9166b2294ef05efcb65a3db80803f0b03ef86a5fc88a2b85ee377"
 dependencies = [
  "itoa",
  "memchr",
@@ -3345,7 +3340,7 @@ checksum = "6c64451ba24fc7a6a2d60fc75dd9c83c90903b19028d4eff35e88fc1e86564e9"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -3368,9 +3363,9 @@ dependencies = [
 
 [[package]]
 name = "serde_with"
-version = "3.12.0"
+version = "3.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d6b6f7f2fcb69f747921f79f3926bd1e203fce4fef62c268dd3abfb6d86029aa"
+checksum = "8e28bdad6db2b8340e449f7108f020b3b092e8583a9e3fb82713e1d4e71fe817"
 dependencies = [
  "serde",
  "serde_derive",
@@ -3379,14 +3374,14 @@ dependencies = [
 
 [[package]]
 name = "serde_with_macros"
-version = "3.12.0"
+version = "3.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8d00caa5193a3c8362ac2b73be6b9e768aa5a4b2f721d8f4b339600c3cb51f8e"
+checksum = "9d846214a9854ef724f3da161b426242d8de7c1fc7de2f89bb1efcb154dca79d"
 dependencies = [
  "darling",
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -3500,7 +3495,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "rustversion",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -3522,9 +3517,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.93"
+version = "2.0.90"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9c786062daee0d6db1132800e623df74274a0a87322d8e183338e01b3d98d058"
+checksum = "919d3b74a5dd0ccd15aeb8f93e7006bd9e14c295087c9896a110f490752bcf31"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -3539,7 +3534,7 @@ checksum = "c8af7666ab7b6390ab78131fb5b0fce11d6b7a6951602017c35fa82800708971"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -3602,7 +3597,7 @@ dependencies = [
  "cfg-if",
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -3613,7 +3608,7 @@ checksum = "5c89e72a01ed4c579669add59014b9a524d609c0c88c6a585ce37485879f6ffb"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
  "test-case-core",
 ]
 
@@ -3628,11 +3623,11 @@ dependencies = [
 
 [[package]]
 name = "thiserror"
-version = "2.0.9"
+version = "2.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f072643fd0190df67a8bab670c20ef5d8737177d6ac6b2e9a236cb096206b2cc"
+checksum = "8fec2a1820ebd077e2b90c4df007bebf344cd394098a13c563957d0afc83ea47"
 dependencies = [
- "thiserror-impl 2.0.9",
+ "thiserror-impl 2.0.6",
 ]
 
 [[package]]
@@ -3643,18 +3638,18 @@ checksum = "b607164372e89797d78b8e23a6d67d5d1038c1c65efd52e1389ef8b77caba2a6"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
 name = "thiserror-impl"
-version = "2.0.9"
+version = "2.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7b50fa271071aae2e6ee85f842e2e28ba8cd2c5fb67f11fcb1fd70b276f9e7d4"
+checksum = "d65750cab40f4ff1929fb1ba509e9914eb756131cef4210da8d5d700d26f6312"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -3776,7 +3771,7 @@ checksum = "395ae124c09f9e6918a2310af6038fba074bcf474ac352496d5910dd59a2226d"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -4046,7 +4041,7 @@ checksum = "6b91f57fe13a38d0ce9e28a03463d8d3c2468ed03d75375110ec71d93b449a08"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -4141,7 +4136,7 @@ dependencies = [
  "once_cell",
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
  "wasm-bindgen-shared",
 ]
 
@@ -4176,7 +4171,7 @@ checksum = "98c9ae5a76e46f4deecd0f0255cc223cfa18dc9b261213b8aa0c7b36f61b3f1d"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
  "wasm-bindgen-backend",
  "wasm-bindgen-shared",
 ]
@@ -4210,7 +4205,7 @@ checksum = "222ebde6ea87fbfa6bdd2e9f1fd8a91d60aee5db68792632176c4e16a74fc7d8"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -4513,7 +4508,7 @@ checksum = "28cc31741b18cb6f1d5ff12f5b7523e3d6eb0852bbbad19d73905511d9849b95"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
  "synstructure",
 ]
 
@@ -4534,7 +4529,7 @@ checksum = "9ce1b18ccd8e73a9321186f97e46f9f04b778851177567b1975109d26a08d2a6"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]
@@ -4554,7 +4549,7 @@ checksum = "0ea7b4a3637ea8669cedf0f1fd5c286a17f3de97b8dd5a70a6c167a1730e63a5"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
  "synstructure",
 ]
 
@@ -4583,7 +4578,7 @@ checksum = "6eafa6dfb17584ea3e2bd6e76e0cc15ad7af12b09abdd1ca55961bed9b1063c6"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.93",
+ "syn 2.0.90",
 ]
 
 [[package]]

Cargo.toml

@@ -118,8 +118,7 @@ rand = { version = "0.8.5" }
 rayon = { version = "1.10.0" }
 regex = { version = "1.10.2" }
 rustc-hash = { version = "2.0.0" }
-# When updating salsa, make sure to also update the revision in `fuzz/Cargo.toml`
-salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "3c7f1694c9efba751dbeeacfbc93b227586e316a" }
+salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "254c749b02cde2fd29852a7463a33e800b771758" }
 schemars = { version = "0.8.16" }
 seahash = { version = "4.1.0" }
 serde = { version = "1.0.197", features = ["derive"] }

README.md

@@ -140,8 +140,8 @@ curl -LsSf https://astral.sh/ruff/install.sh | sh
 powershell -c "irm https://astral.sh/ruff/install.ps1 | iex"
 
 # For a specific version.
-curl -LsSf https://astral.sh/ruff/0.8.5/install.sh | sh
-powershell -c "irm https://astral.sh/ruff/0.8.5/install.ps1 | iex"
+curl -LsSf https://astral.sh/ruff/0.8.3/install.sh | sh
+powershell -c "irm https://astral.sh/ruff/0.8.3/install.ps1 | iex"
 ```
 
 You can also install Ruff via [Homebrew](https://formulae.brew.sh/formula/ruff), [Conda](https://anaconda.org/conda-forge/ruff),
@@ -174,7 +174,7 @@ Ruff can also be used as a [pre-commit](https://pre-commit.com/) hook via [`ruff
 ```yaml
 - repo: https://github.com/astral-sh/ruff-pre-commit
   # Ruff version.
-  rev: v0.8.5
+  rev: v0.8.3
   hooks:
     # Run the linter.
     - id: ruff
@@ -196,7 +196,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: astral-sh/ruff-action@v3
+      - uses: astral-sh/ruff-action@v1
 ```
 
 ### Configuration<a id="configuration"></a>

crates/red_knot/src/main.rs

@@ -279,7 +279,7 @@ impl MainLoop {
         while let Ok(message) = self.receiver.recv() {
             match message {
                 MainLoopMessage::CheckWorkspace => {
-                    let db = db.clone();
+                    let db = db.snapshot();
                     let sender = self.sender.clone();
 
                     // Spawn a new task that checks the workspace. This needs to be done in a separate thread

crates/red_knot_python_semantic/Cargo.toml

@@ -20,14 +20,12 @@ ruff_python_stdlib = { workspace = true }
 ruff_source_file = { workspace = true }
 ruff_text_size = { workspace = true }
 ruff_python_literal = { workspace = true }
-ruff_python_trivia = { workspace = true }
 
 anyhow = { workspace = true }
 bitflags = { workspace = true }
 camino = { workspace = true }
 compact_str = { workspace = true }
 countme = { workspace = true }
-drop_bomb = { workspace = true }
 indexmap = { workspace = true }
 itertools = { workspace = true }
 ordermap = { workspace = true }
@@ -60,3 +58,4 @@ serde = ["ruff_db/serde", "dep:serde"]
 
 [lints]
 workspace = true
+

crates/red_knot_python_semantic/resources/mdtest/annotations/annotated.md

@@ -1,94 +0,0 @@
-# `Annotated`
-
-`Annotated` attaches arbitrary metadata to a given type.
-
-## Usages
-
-`Annotated[T, ...]` is equivalent to `T`: All metadata arguments are simply ignored.
-
-```py
-from typing_extensions import Annotated
-
-def _(x: Annotated[int, "foo"]):
-    reveal_type(x)  # revealed: int
-
-def _(x: Annotated[int, lambda: 0 + 1 * 2 // 3, _(4)]):
-    reveal_type(x)  # revealed: int
-
-def _(x: Annotated[int, "arbitrary", "metadata", "elements", "are", "fine"]):
-    reveal_type(x)  # revealed: int
-
-def _(x: Annotated[tuple[str, int], bytes]):
-    reveal_type(x)  # revealed: tuple[str, int]
-```
-
-## Parameterization
-
-It is invalid to parameterize `Annotated` with less than two arguments.
-
-```py
-from typing_extensions import Annotated
-
-# error: [invalid-type-form] "`Annotated` requires at least two arguments when used in an annotation or type expression"
-def _(x: Annotated):
-    reveal_type(x)  # revealed: Unknown
-
-def _(flag: bool):
-    if flag:
-        X = Annotated
-    else:
-        X = bool
-
-    # error: [invalid-type-form] "`Annotated` requires at least two arguments when used in an annotation or type expression"
-    def f(y: X):
-        reveal_type(y)  # revealed: Unknown | bool
-
-# error: [invalid-type-form] "`Annotated` requires at least two arguments when used in an annotation or type expression"
-def _(x: Annotated | bool):
-    reveal_type(x)  # revealed: Unknown | bool
-
-# error: [invalid-type-form]
-def _(x: Annotated[()]):
-    reveal_type(x)  # revealed: Unknown
-
-# error: [invalid-type-form]
-def _(x: Annotated[int]):
-    # `Annotated[T]` is invalid and will raise an error at runtime,
-    # but we treat it the same as `T` to provide better diagnostics later on.
-    # The subscription itself is still reported, regardless.
-    # Same for the `(int,)` form below.
-    reveal_type(x)  # revealed: int
-
-# error: [invalid-type-form]
-def _(x: Annotated[(int,)]):
-    reveal_type(x)  # revealed: int
-```
-
-## Inheritance
-
-### Correctly parameterized
-
-Inheriting from `Annotated[T, ...]` is equivalent to inheriting from `T` itself.
-
-```py
-from typing_extensions import Annotated
-
-# TODO: False positive
-# error: [invalid-base]
-class C(Annotated[int, "foo"]): ...
-
-# TODO: Should be `tuple[Literal[C], Literal[int], Literal[object]]`
-reveal_type(C.__mro__)  # revealed: tuple[Literal[C], Unknown, Literal[object]]
-```
-
-### Not parameterized
-
-```py
-from typing_extensions import Annotated
-
-# At runtime, this is an error.
-# error: [invalid-base]
-class C(Annotated): ...
-
-reveal_type(C.__mro__)  # revealed: tuple[Literal[C], Unknown, Literal[object]]
-```

crates/red_knot_python_semantic/resources/mdtest/annotations/any.md

@@ -77,7 +77,7 @@ def _(s: Subclass):
 ```py
 from typing import Any
 
-# error: [invalid-type-form] "Type `typing.Any` expected no type parameter"
+# error: [invalid-type-parameter] "Type `typing.Any` expected no type parameter"
 def f(x: Any[int]):
     reveal_type(x)  # revealed: Unknown
 ```

crates/red_knot_python_semantic/resources/mdtest/annotations/literal_string.md

@@ -27,19 +27,19 @@ def f():
 ```py
 from typing_extensions import Literal, LiteralString
 
-bad_union: Literal["hello", LiteralString]  # error: [invalid-type-form]
-bad_nesting: Literal[LiteralString]  # error: [invalid-type-form]
+bad_union: Literal["hello", LiteralString]  # error: [invalid-literal-parameter]
+bad_nesting: Literal[LiteralString]  # error: [invalid-literal-parameter]
 ```
 
-### Parameterized
+### Parametrized
 
-`LiteralString` cannot be parameterized.
+`LiteralString` cannot be parametrized.
 
 ```py
 from typing_extensions import LiteralString
 
-a: LiteralString[str]  # error: [invalid-type-form]
-b: LiteralString["foo"]  # error: [invalid-type-form]
+a: LiteralString[str]  # error: [invalid-type-parameter]
+b: LiteralString["foo"]  # error: [invalid-type-parameter]
 ```
 
 ### As a base class
@@ -73,12 +73,12 @@ qux = (foo, bar)
 reveal_type(qux)  # revealed: tuple[Literal["foo"], Literal["bar"]]
 
 # TODO: Infer "LiteralString"
-reveal_type(foo.join(qux))  # revealed: @Todo(Attribute access on `StringLiteral` types)
+reveal_type(foo.join(qux))  # revealed: @Todo(call todo)
 
 template: LiteralString = "{}, {}"
 reveal_type(template)  # revealed: Literal["{}, {}"]
 # TODO: Infer `LiteralString`
-reveal_type(template.format(foo, bar))  # revealed: @Todo(Attribute access on `StringLiteral` types)
+reveal_type(template.format(foo, bar))  # revealed: @Todo(call todo)
 ```
 
 ### Assignability

crates/red_knot_python_semantic/resources/mdtest/annotations/never.md

@@ -21,7 +21,7 @@ reveal_type(stop())
 ```py
 from typing_extensions import NoReturn, Never, Any
 
-# error: [invalid-type-form] "Type `typing.Never` expected no type parameter"
+# error: [invalid-type-parameter] "Type `typing.Never` expected no type parameter"
 x: Never[int]
 a1: NoReturn
 a2: Never
@@ -47,9 +47,7 @@ def f():
 
 ## `typing.Never`
 
-`typing.Never` is only available in Python 3.11 and later.
-
-### Python 3.11
+`typing.Never` is only available in Python 3.11 and later:
 
 ```toml
 [environment]
@@ -59,17 +57,8 @@ python-version = "3.11"
 ```py
 from typing import Never
 
-reveal_type(Never)  # revealed: typing.Never
-```
+x: Never
 
-### Python 3.10
-
-```toml
-[environment]
-python-version = "3.10"
-```
-
-```py
-# error: [unresolved-import]
-from typing import Never
+def f():
+    reveal_type(x)  # revealed: Never
 ```

crates/red_knot_python_semantic/resources/mdtest/annotations/stdlib_typing_aliases.md

@@ -3,59 +3,43 @@
 The `typing` module has various aliases to other stdlib classes. These are a legacy feature, but
 still need to be supported by a type checker.
 
-## Correspondence
+## Currently unsupported
 
-All of the following symbols can be mapped one-to-one with the actual type:
+Support for most of these symbols is currently a TODO:
 
 ```py
 import typing
 
 def f(
-    list_bare: typing.List,
-    list_parametrized: typing.List[int],
-    dict_bare: typing.Dict,
-    dict_parametrized: typing.Dict[int, str],
-    set_bare: typing.Set,
-    set_parametrized: typing.Set[int],
-    frozen_set_bare: typing.FrozenSet,
-    frozen_set_parametrized: typing.FrozenSet[str],
-    chain_map_bare: typing.ChainMap,
-    chain_map_parametrized: typing.ChainMap[int],
-    counter_bare: typing.Counter,
-    counter_parametrized: typing.Counter[int],
-    default_dict_bare: typing.DefaultDict,
-    default_dict_parametrized: typing.DefaultDict[str, int],
-    deque_bare: typing.Deque,
-    deque_parametrized: typing.Deque[str],
-    ordered_dict_bare: typing.OrderedDict,
-    ordered_dict_parametrized: typing.OrderedDict[int, str],
+    a: typing.List,
+    b: typing.List[int],
+    c: typing.Dict,
+    d: typing.Dict[int, str],
+    e: typing.DefaultDict,
+    f: typing.DefaultDict[str, int],
+    g: typing.Set,
+    h: typing.Set[int],
+    i: typing.FrozenSet,
+    j: typing.FrozenSet[str],
+    k: typing.OrderedDict,
+    l: typing.OrderedDict[int, str],
+    m: typing.Counter,
+    n: typing.Counter[int],
 ):
-    reveal_type(list_bare)  # revealed: list
-    reveal_type(list_parametrized)  # revealed: list
-
-    reveal_type(dict_bare)  # revealed: dict
-    reveal_type(dict_parametrized)  # revealed: dict
-
-    reveal_type(set_bare)  # revealed: set
-    reveal_type(set_parametrized)  # revealed: set
-
-    reveal_type(frozen_set_bare)  # revealed: frozenset
-    reveal_type(frozen_set_parametrized)  # revealed: frozenset
-
-    reveal_type(chain_map_bare)  # revealed: ChainMap
-    reveal_type(chain_map_parametrized)  # revealed: ChainMap
-
-    reveal_type(counter_bare)  # revealed: Counter
-    reveal_type(counter_parametrized)  # revealed: Counter
-
-    reveal_type(default_dict_bare)  # revealed: defaultdict
-    reveal_type(default_dict_parametrized)  # revealed: defaultdict
-
-    reveal_type(deque_bare)  # revealed: deque
-    reveal_type(deque_parametrized)  # revealed: deque
-
-    reveal_type(ordered_dict_bare)  # revealed: OrderedDict
-    reveal_type(ordered_dict_parametrized)  # revealed: OrderedDict
+    reveal_type(a)  # revealed: @Todo(Unsupported or invalid type in a type expression)
+    reveal_type(b)  # revealed: @Todo(typing.List alias)
+    reveal_type(c)  # revealed: @Todo(Unsupported or invalid type in a type expression)
+    reveal_type(d)  # revealed: @Todo(typing.Dict alias)
+    reveal_type(e)  # revealed: @Todo(Unsupported or invalid type in a type expression)
+    reveal_type(f)  # revealed: @Todo(typing.DefaultDict[] alias)
+    reveal_type(g)  # revealed: @Todo(Unsupported or invalid type in a type expression)
+    reveal_type(h)  # revealed: @Todo(typing.Set alias)
+    reveal_type(i)  # revealed: @Todo(Unsupported or invalid type in a type expression)
+    reveal_type(j)  # revealed: @Todo(typing.FrozenSet alias)
+    reveal_type(k)  # revealed: @Todo(Unsupported or invalid type in a type expression)
+    reveal_type(l)  # revealed: @Todo(typing.OrderedDict alias)
+    reveal_type(m)  # revealed: @Todo(Unsupported or invalid type in a type expression)
+    reveal_type(n)  # revealed: @Todo(typing.Counter[] alias)
 ```
 
 ## Inheritance
@@ -65,63 +49,35 @@ The aliases can be inherited from. Some of these are still partially or wholly T
 ```py
 import typing
 
-####################
-### Built-ins
-
-class ListSubclass(typing.List): ...
+class A(typing.Dict): ...
 
 # TODO: should have `Generic`, should not have `Unknown`
-# revealed: tuple[Literal[ListSubclass], Literal[list], Unknown, Literal[object]]
-reveal_type(ListSubclass.__mro__)
+reveal_type(A.__mro__)  # revealed: tuple[Literal[A], Literal[dict], Unknown, Literal[object]]
 
-class DictSubclass(typing.Dict): ...
+class B(typing.List): ...
 
 # TODO: should have `Generic`, should not have `Unknown`
-# revealed: tuple[Literal[DictSubclass], Literal[dict], Unknown, Literal[object]]
-reveal_type(DictSubclass.__mro__)
+reveal_type(B.__mro__)  # revealed: tuple[Literal[B], Literal[list], Unknown, Literal[object]]
 
-class SetSubclass(typing.Set): ...
+class C(typing.Set): ...
 
 # TODO: should have `Generic`, should not have `Unknown`
-# revealed: tuple[Literal[SetSubclass], Literal[set], Unknown, Literal[object]]
-reveal_type(SetSubclass.__mro__)
+reveal_type(C.__mro__)  # revealed: tuple[Literal[C], Literal[set], Unknown, Literal[object]]
 
-class FrozenSetSubclass(typing.FrozenSet): ...
+class D(typing.FrozenSet): ...
 
 # TODO: should have `Generic`, should not have `Unknown`
-# revealed: tuple[Literal[FrozenSetSubclass], Literal[frozenset], Unknown, Literal[object]]
-reveal_type(FrozenSetSubclass.__mro__)
+reveal_type(D.__mro__)  # revealed: tuple[Literal[D], Literal[frozenset], Unknown, Literal[object]]
 
-####################
-### `collections`
+class E(typing.DefaultDict): ...
 
-class ChainMapSubclass(typing.ChainMap): ...
+reveal_type(E.__mro__)  # revealed: tuple[Literal[E], @Todo(Support for more typing aliases as base classes), Literal[object]]
 
-# TODO: Should be (ChainMapSubclass, ChainMap, MutableMapping, Mapping, Collection, Sized, Iterable, Container, Generic, object)
-# revealed: tuple[Literal[ChainMapSubclass], Literal[ChainMap], Unknown, Literal[object]]
-reveal_type(ChainMapSubclass.__mro__)
+class F(typing.OrderedDict): ...
 
-class CounterSubclass(typing.Counter): ...
+reveal_type(F.__mro__)  # revealed: tuple[Literal[F], @Todo(Support for more typing aliases as base classes), Literal[object]]
 
-# TODO: Should be (CounterSubclass, Counter, dict, MutableMapping, Mapping, Collection, Sized, Iterable, Container, Generic, object)
-# revealed: tuple[Literal[CounterSubclass], Literal[Counter], Unknown, Literal[object]]
-reveal_type(CounterSubclass.__mro__)
+class G(typing.Counter): ...
 
-class DefaultDictSubclass(typing.DefaultDict): ...
-
-# TODO: Should be (DefaultDictSubclass, defaultdict, dict, MutableMapping, Mapping, Collection, Sized, Iterable, Container, Generic, object)
-# revealed: tuple[Literal[DefaultDictSubclass], Literal[defaultdict], Unknown, Literal[object]]
-reveal_type(DefaultDictSubclass.__mro__)
-
-class DequeSubclass(typing.Deque): ...
-
-# TODO: Should be (DequeSubclass, deque, MutableSequence, Sequence, Reversible, Collection, Sized, Iterable, Container, Generic, object)
-# revealed: tuple[Literal[DequeSubclass], Literal[deque], Unknown, Literal[object]]
-reveal_type(DequeSubclass.__mro__)
-
-class OrderedDictSubclass(typing.OrderedDict): ...
-
-# TODO: Should be (OrderedDictSubclass, OrderedDict, dict, MutableMapping, Mapping, Collection, Sized, Iterable, Container, Generic, object)
-# revealed: tuple[Literal[OrderedDictSubclass], Literal[OrderedDict], Unknown, Literal[object]]
-reveal_type(OrderedDictSubclass.__mro__)
+reveal_type(G.__mro__)  # revealed: tuple[Literal[G], @Todo(Support for more typing aliases as base classes), Literal[object]]
 ```

crates/red_knot_python_semantic/resources/mdtest/annotations/unsupported_special_forms.md

@@ -51,7 +51,7 @@ class D(TypeIs): ...  # error: [invalid-base]
 class E(Concatenate): ...  # error: [invalid-base]
 class F(Callable): ...
 
-reveal_type(F.__mro__)  # revealed: tuple[Literal[F], @Todo(Support for Callable as a base class), Literal[object]]
+reveal_type(F.__mro__)  # revealed: tuple[Literal[F], @Todo(Support for more typing aliases as base classes), Literal[object]]
 ```
 
 ## Subscriptability
@@ -61,11 +61,11 @@ Some of these are not subscriptable:
 ```py
 from typing_extensions import Self, TypeAlias
 
-X: TypeAlias[T] = int  # error: [invalid-type-form]
+X: TypeAlias[T] = int  # error: [invalid-type-parameter]
 
 class Foo[T]:
-    # error: [invalid-type-form] "Special form `typing.Self` expected no type parameter"
-    # error: [invalid-type-form] "Special form `typing.Self` expected no type parameter"
+    # error: [invalid-type-parameter] "Special form `typing.Self` expected no type parameter"
+    # error: [invalid-type-parameter] "Special form `typing.Self` expected no type parameter"
     def method(self: Self[int]) -> Self[int]:
         reveal_type(self)  # revealed: Unknown
 ```

crates/red_knot_python_semantic/resources/mdtest/assignment/annotations.md

@@ -33,6 +33,8 @@ b: tuple[int] = (42,)
 c: tuple[str, int] = ("42", 42)
 d: tuple[tuple[str, str], tuple[int, int]] = (("foo", "foo"), (42, 42))
 e: tuple[str, ...] = ()
+# TODO: we should not emit this error
+# error: [call-possibly-unbound-method] "Method `__class_getitem__` of type `Literal[tuple]` is possibly unbound"
 f: tuple[str, *tuple[int, ...], bytes] = ("42", b"42")
 g: tuple[str, Unpack[tuple[int, ...]], bytes] = ("42", b"42")
 h: tuple[list[int], list[int]] = ([], [])

crates/red_knot_python_semantic/resources/mdtest/attributes.md

@@ -1,6 +1,4 @@
-# Attributes
-
-Tests for attribute access on various kinds of types.
+# Class attributes
 
 ## Union of attributes
 
@@ -157,67 +155,3 @@ class Foo: ...
 
 reveal_type(Foo.__class__)  # revealed: Literal[type]
 ```
-
-## Function-literal attributes
-
-Most attribute accesses on function-literal types are delegated to `types.FunctionType`, since all
-functions are instances of that class:
-
-```py path=a.py
-def f(): ...
-
-reveal_type(f.__defaults__)  # revealed: @Todo(instance attributes)
-reveal_type(f.__kwdefaults__)  # revealed: @Todo(instance attributes)
-```
-
-Some attributes are special-cased, however:
-
-```py path=b.py
-def f(): ...
-
-reveal_type(f.__get__)  # revealed: @Todo(`__get__` method on functions)
-reveal_type(f.__call__)  # revealed: @Todo(`__call__` method on functions)
-```
-
-## Int-literal attributes
-
-Most attribute accesses on int-literal types are delegated to `builtins.int`, since all literal
-integers are instances of that class:
-
-```py path=a.py
-reveal_type((2).bit_length)  # revealed: @Todo(instance attributes)
-reveal_type((2).denominator)  # revealed: @Todo(instance attributes)
-```
-
-Some attributes are special-cased, however:
-
-```py path=b.py
-reveal_type((2).numerator)  # revealed: Literal[2]
-reveal_type((2).real)  # revealed: Literal[2]
-```
-
-## Literal `bool` attributes
-
-Most attribute accesses on bool-literal types are delegated to `builtins.bool`, since all literal
-bols are instances of that class:
-
-```py path=a.py
-reveal_type(True.__and__)  # revealed: @Todo(instance attributes)
-reveal_type(False.__or__)  # revealed: @Todo(instance attributes)
-```
-
-Some attributes are special-cased, however:
-
-```py path=b.py
-reveal_type(True.numerator)  # revealed: Literal[1]
-reveal_type(False.real)  # revealed: Literal[0]
-```
-
-## Bytes-literal attributes
-
-All attribute access on literal `bytes` types is currently delegated to `buitins.bytes`:
-
-```py
-reveal_type(b"foo".join)  # revealed: @Todo(instance attributes)
-reveal_type(b"foo".endswith)  # revealed: @Todo(instance attributes)
-```

crates/red_knot_python_semantic/resources/mdtest/boolean/short_circuit.md

@@ -32,10 +32,13 @@ def _(flag: bool):
 
 ```py
 if True or (x := 1):
-    # error: [unresolved-reference]
-    reveal_type(x)  # revealed: Unknown
+    # TODO: infer that the second arm is never executed, and raise `unresolved-reference`.
+    # error: [possibly-unresolved-reference]
+    reveal_type(x)  # revealed: Literal[1]
 
 if True and (x := 1):
+    # TODO: infer that the second arm is always executed, do not raise a diagnostic
+    # error: [possibly-unresolved-reference]
     reveal_type(x)  # revealed: Literal[1]
 ```
 

crates/red_knot_python_semantic/resources/mdtest/comparison/non_bool_returns.md

@@ -31,10 +31,10 @@ class C:
     def __lt__(self, other) -> C: ...
 
 x = A() < B() < C()
-reveal_type(x)  # revealed: A & ~AlwaysTruthy | B
+reveal_type(x)  # revealed: A | B
 
 y = 0 < 1 < A() < 3
-reveal_type(y)  # revealed: Literal[False] | A
+reveal_type(y)  # revealed: bool | A
 
 z = 10 < 0 < A() < B() < C()
 reveal_type(z)  # revealed: Literal[False]

crates/red_knot_python_semantic/resources/mdtest/declaration/error.md

@@ -19,17 +19,14 @@ def _(flag: bool):
     x = 1  # error: [conflicting-declarations] "Conflicting declared types for `x`: str, int"
 ```
 
-## Incompatible declarations for 2 (out of 3) types
+## Partial declarations
 
 ```py
-def _(flag1: bool, flag2: bool):
-    if flag1:
-        x: str
-    elif flag2:
+def _(flag: bool):
+    if flag:
         x: int
 
-    # Here, the declared type for `x` is `int | str | Unknown`.
-    x = 1  # error: [conflicting-declarations] "Conflicting declared types for `x`: str, int"
+    x = 1  # error: [conflicting-declarations] "Conflicting declared types for `x`: Unknown, int"
 ```
 
 ## Incompatible declarations with bad assignment
@@ -45,31 +42,3 @@ def _(flag: bool):
     # error: [invalid-assignment]
     x = b"foo"
 ```
-
-## No errors
-
-Currently, we avoid raising the conflicting-declarations for the following cases:
-
-### Partial declarations
-
-```py
-def _(flag: bool):
-    if flag:
-        x: int
-
-    x = 1
-```
-
-### Partial declarations in try-except
-
-Refer to <https://github.com/astral-sh/ruff/issues/13966>
-
-```py
-def _():
-    try:
-        x: int = 1
-    except:
-        x = 2
-
-    x = 3
-```

crates/red_knot_python_semantic/resources/mdtest/exception/basic.md

@@ -90,83 +90,3 @@ def foo(
         # TODO: should emit a diagnostic here:
         reveal_type(g)  # revealed: @Todo(full tuple[...] support)
 ```
-
-## Object raised is not an exception
-
-```py
-try:
-    raise AttributeError()  # fine
-except:
-    ...
-
-try:
-    raise FloatingPointError  # fine
-except:
-    ...
-
-try:
-    raise 1  # error: [invalid-raise]
-except:
-    ...
-
-try:
-    raise int  # error: [invalid-raise]
-except:
-    ...
-
-def _(e: Exception | type[Exception]):
-    raise e  # fine
-
-def _(e: Exception | type[Exception] | None):
-    raise e  # error: [invalid-raise]
-```
-
-## Exception cause is not an exception
-
-```py
-try:
-    raise EOFError() from GeneratorExit  # fine
-except:
-    ...
-
-try:
-    raise StopIteration from MemoryError()  # fine
-except:
-    ...
-
-try:
-    raise BufferError() from None  # fine
-except:
-    ...
-
-try:
-    raise ZeroDivisionError from False  # error: [invalid-raise]
-except:
-    ...
-
-try:
-    raise SystemExit from bool()  # error: [invalid-raise]
-except:
-    ...
-
-try:
-    raise
-except KeyboardInterrupt as e:  # fine
-    reveal_type(e)  # revealed: KeyboardInterrupt
-    raise LookupError from e  # fine
-
-try:
-    raise
-except int as e:  # error: [invalid-exception-caught]
-    reveal_type(e)  # revealed: Unknown
-    raise KeyError from e
-
-def _(e: Exception | type[Exception]):
-    raise ModuleNotFoundError from e  # fine
-
-def _(e: Exception | type[Exception] | None):
-    raise IndexError from e  # fine
-
-def _(e: int | None):
-    raise IndexError from e  # error: [invalid-raise]
-```

crates/red_knot_python_semantic/resources/mdtest/expression/boolean.md

@@ -10,8 +10,8 @@ def _(foo: str):
     reveal_type(False or "z")  # revealed: Literal["z"]
     reveal_type(False or True)  # revealed: Literal[True]
     reveal_type(False or False)  # revealed: Literal[False]
-    reveal_type(foo or False)  # revealed: str & ~AlwaysFalsy | Literal[False]
-    reveal_type(foo or True)  # revealed: str & ~AlwaysFalsy | Literal[True]
+    reveal_type(foo or False)  # revealed: str | Literal[False]
+    reveal_type(foo or True)  # revealed: str | Literal[True]
 ```
 
 ## AND
@@ -20,8 +20,8 @@ def _(foo: str):
 def _(foo: str):
     reveal_type(True and False)  # revealed: Literal[False]
     reveal_type(False and True)  # revealed: Literal[False]
-    reveal_type(foo and False)  # revealed: str & ~AlwaysTruthy | Literal[False]
-    reveal_type(foo and True)  # revealed: str & ~AlwaysTruthy | Literal[True]
+    reveal_type(foo and False)  # revealed: str | Literal[False]
+    reveal_type(foo and True)  # revealed: str | Literal[True]
     reveal_type("x" and "y" and "z")  # revealed: Literal["z"]
     reveal_type("x" and "y" and "")  # revealed: Literal[""]
     reveal_type("" and "y")  # revealed: Literal[""]

crates/red_knot_python_semantic/resources/mdtest/expression/if.md

@@ -7,7 +7,7 @@ def _(flag: bool):
     reveal_type(1 if flag else 2)  # revealed: Literal[1, 2]
 ```
 
-## Statically known conditions in if-expressions
+## Statically known branches
 
 ```py
 reveal_type(1 if True else 2)  # revealed: Literal[1]

crates/red_knot_python_semantic/resources/mdtest/final.md

@@ -1,31 +0,0 @@
-# Tests for the `@typing(_extensions).final` decorator
-
-## Cannot subclass
-
-Don't do this:
-
-```py
-import typing_extensions
-from typing import final
-
-@final
-class A: ...
-
-class B(A): ...  # error: 9 [subclass-of-final-class] "Class `B` cannot inherit from final class `A`"
-
-@typing_extensions.final
-class C: ...
-
-class D(C): ...  # error: [subclass-of-final-class]
-class E: ...
-class F: ...
-class G: ...
-
-# fmt: off
-class H(
-    E,
-    F,
-    A,  # error: [subclass-of-final-class]
-    G,
-): ...
-```

crates/red_knot_python_semantic/resources/mdtest/import/basic.md

@@ -25,82 +25,3 @@ reveal_type(D)  # revealed: Literal[C]
 ```py path=b.py
 class C: ...
 ```
-
-## Nested
-
-```py
-import a.b
-
-reveal_type(a.b.C)  # revealed: Literal[C]
-```
-
-```py path=a/__init__.py
-```
-
-```py path=a/b.py
-class C: ...
-```
-
-## Deeply nested
-
-```py
-import a.b.c
-
-reveal_type(a.b.c.C)  # revealed: Literal[C]
-```
-
-```py path=a/__init__.py
-```
-
-```py path=a/b/__init__.py
-```
-
-```py path=a/b/c.py
-class C: ...
-```
-
-## Nested with rename
-
-```py
-import a.b as b
-
-reveal_type(b.C)  # revealed: Literal[C]
-```
-
-```py path=a/__init__.py
-```
-
-```py path=a/b.py
-class C: ...
-```
-
-## Deeply nested with rename
-
-```py
-import a.b.c as c
-
-reveal_type(c.C)  # revealed: Literal[C]
-```
-
-```py path=a/__init__.py
-```
-
-```py path=a/b/__init__.py
-```
-
-```py path=a/b/c.py
-class C: ...
-```
-
-## Unresolvable submodule imports
-
-```py
-# Topmost component resolvable, submodule not resolvable:
-import a.foo  # error: [unresolved-import] "Cannot resolve import `a.foo`"
-
-# Topmost component unresolvable:
-import b.foo  # error: [unresolved-import] "Cannot resolve import `b.foo`"
-```
-
-```py path=a/__init__.py
-```

crates/red_knot_python_semantic/resources/mdtest/import/builtins.md

@@ -3,6 +3,6 @@
 ```py
 import builtins
 
-x = builtins.chr
-reveal_type(x)  # revealed: Literal[chr]
+x = builtins.copyright
+reveal_type(x)  # revealed: Literal[copyright]
 ```

crates/red_knot_python_semantic/resources/mdtest/import/conflicts.md

@@ -1,75 +0,0 @@
-# Conflicting attributes and submodules
-
-## Via import
-
-```py
-import a.b
-
-reveal_type(a.b)  # revealed: <module 'a.b'>
-```
-
-```py path=a/__init__.py
-b = 42
-```
-
-```py path=a/b.py
-```
-
-## Via from/import
-
-```py
-from a import b
-
-reveal_type(b)  # revealed: Literal[42]
-```
-
-```py path=a/__init__.py
-b = 42
-```
-
-```py path=a/b.py
-```
-
-## Via both
-
-```py
-import a.b
-from a import b
-
-reveal_type(b)  # revealed: <module 'a.b'>
-reveal_type(a.b)  # revealed: <module 'a.b'>
-```
-
-```py path=a/__init__.py
-b = 42
-```
-
-```py path=a/b.py
-```
-
-## Via both (backwards)
-
-In this test, we infer a different type for `b` than the runtime behavior of the Python interpreter.
-The interpreter will not load the submodule `a.b` during the `from a import b` statement, since `a`
-contains a non-module attribute named `b`. (See the [definition][from-import] of a `from...import`
-statement for details.) However, because our import tracking is flow-insensitive, we will see that
-`a.b` is imported somewhere in the file, and therefore assume that the `from...import` statement
-sees the submodule as the value of `b` instead of the integer.
-
-```py
-from a import b
-import a.b
-
-# Python would say `Literal[42]` for `b`
-reveal_type(b)  # revealed: <module 'a.b'>
-reveal_type(a.b)  # revealed: <module 'a.b'>
-```
-
-```py path=a/__init__.py
-b = 42
-```
-
-```py path=a/b.py
-```
-
-[from-import]: https://docs.python.org/3/reference/simple_stmts.html#the-import-statement

crates/red_knot_python_semantic/resources/mdtest/import/invalid_syntax.md

@@ -7,25 +7,3 @@ from import bar  # error: [invalid-syntax]
 
 reveal_type(bar)  # revealed: Unknown
 ```
-
-## Invalid nested module import
-
-TODO: This is correctly flagged as an error, but we could clean up the diagnostics that we report.
-
-```py
-# TODO: No second diagnostic
-# error: [invalid-syntax] "Expected ',', found '.'"
-# error: [unresolved-import] "Module `a` has no member `c`"
-from a import b.c
-
-# TODO: Should these be inferred as Unknown?
-reveal_type(b)  # revealed: <module 'a.b'>
-reveal_type(b.c)  # revealed: Literal[1]
-```
-
-```py path=a/__init__.py
-```
-
-```py path=a/b.py
-c = 1
-```

crates/red_knot_python_semantic/resources/mdtest/import/relative.md

@@ -121,44 +121,23 @@ X = 42
 ```
 
 ```py path=package/bar.py
-from . import foo
+# TODO: support submodule imports
+from . import foo  # error: [unresolved-import]
 
-reveal_type(foo.X)  # revealed: Literal[42]
+y = foo.X
+
+# TODO: should be `Literal[42]`
+reveal_type(y)  # revealed: Unknown
 ```
 
 ## Non-existent + bare to module
 
-This test verifies that we emit an error when we try to import a symbol that is neither a submodule
-nor an attribute of `package`.
-
 ```py path=package/__init__.py
 ```
 
 ```py path=package/bar.py
+# TODO: support submodule imports
 from . import foo  # error: [unresolved-import]
 
 reveal_type(foo)  # revealed: Unknown
 ```
-
-## Import submodule from self
-
-We don't currently consider `from...import` statements when building up the `imported_modules` set
-in the semantic index. When accessing an attribute of a module, we only consider it a potential
-submodule when that submodule name appears in the `imported_modules` set. That means that submodules
-that are imported via `from...import` are not visible to our type inference if you also access that
-submodule via the attribute on its parent package.
-
-```py path=package/__init__.py
-```
-
-```py path=package/foo.py
-X = 42
-```
-
-```py path=package/bar.py
-from . import foo
-import package
-
-# error: [unresolved-attribute] "Type `<module 'package'>` has no attribute `foo`"
-reveal_type(package.foo.X)  # revealed: Unknown
-```

crates/red_knot_python_semantic/resources/mdtest/import/tracking.md

@@ -1,100 +0,0 @@
-# Tracking imported modules
-
-These tests depend on how we track which modules have been imported. There are currently two
-characteristics of our module tracking that can lead to inaccuracies:
-
-- Imports are tracked on a per-file basis. At runtime, importing a submodule in one file makes that
-    submodule globally available via any reference to the containing package. We will flag an error
-    if a file tries to access a submodule without there being an import of that submodule _in that
-    same file_.
-
-    This is a purposeful decision, and not one we plan to change. If a module wants to re-export some
-    other module that it imports, there are ways to do that (tested below) that are blessed by the
-    typing spec and that are visible to our file-scoped import tracking.
-
-- Imports are tracked flow-insensitively: submodule accesses are allowed and resolved if that
-    submodule is imported _anywhere in the file_. This handles the common case where all imports are
-    grouped at the top of the file, and is easiest to implement. We might revisit this decision and
-    track submodule imports flow-sensitively, in which case we will have to update the assertions in
-    some of these tests.
-
-## Import submodule later in file
-
-This test highlights our flow-insensitive analysis, since we access the `a.b` submodule before it
-has been imported.
-
-```py
-import a
-
-# Would be an error with flow-sensitive tracking
-reveal_type(a.b.C)  # revealed: Literal[C]
-
-import a.b
-```
-
-```py path=a/__init__.py
-```
-
-```py path=a/b.py
-class C: ...
-```
-
-## Rename a re-export
-
-This test highlights how import tracking is local to each file, but specifically to the file where a
-containing module is first referenced. This allows the main module to see that `q.a` contains a
-submodule `b`, even though `a.b` is never imported in the main module.
-
-```py
-from q import a, b
-
-reveal_type(b)  # revealed: <module 'a.b'>
-reveal_type(b.C)  # revealed: Literal[C]
-
-reveal_type(a.b)  # revealed: <module 'a.b'>
-reveal_type(a.b.C)  # revealed: Literal[C]
-```
-
-```py path=a/__init__.py
-```
-
-```py path=a/b.py
-class C: ...
-```
-
-```py path=q.py
-import a as a
-import a.b as b
-```
-
-## Attribute overrides submodule
-
-Technically, either a submodule or a non-module attribute could shadow the other, depending on the
-ordering of when the submodule is loaded relative to the parent module's `__init__.py` file being
-evaluated. We have chosen to always have the submodule take priority. (This matches pyright's
-current behavior, and opposite of mypy's current behavior.)
-
-```py
-import sub.b
-import attr.b
-
-# In the Python interpreter, `attr.b` is Literal[1]
-reveal_type(sub.b)  # revealed: <module 'sub.b'>
-reveal_type(attr.b)  # revealed: <module 'attr.b'>
-```
-
-```py path=sub/__init__.py
-b = 1
-```
-
-```py path=sub/b.py
-```
-
-```py path=attr/__init__.py
-from . import b as _
-
-b = 1
-```
-
-```py path=attr/b.py
-```

crates/red_knot_python_semantic/resources/mdtest/literal/ellipsis.md

@@ -1,23 +1,7 @@
 # Ellipsis literals
 
-## Python 3.9
-
-```toml
-[environment]
-python-version = "3.9"
-```
+## Simple
 
 ```py
-reveal_type(...)  # revealed: ellipsis
-```
-
-## Python 3.10
-
-```toml
-[environment]
-python-version = "3.10"
-```
-
-```py
-reveal_type(...)  # revealed: EllipsisType
+reveal_type(...)  # revealed: EllipsisType | ellipsis
 ```

crates/red_knot_python_semantic/resources/mdtest/literal/literal.md

@@ -45,19 +45,19 @@ def f():
     # TODO: This should be Color.RED
     reveal_type(b1)  # revealed: Literal[0]
 
-# error: [invalid-type-form]
+# error: [invalid-literal-parameter]
 invalid1: Literal[3 + 4]
-# error: [invalid-type-form]
+# error: [invalid-literal-parameter]
 invalid2: Literal[4 + 3j]
-# error: [invalid-type-form]
+# error: [invalid-literal-parameter]
 invalid3: Literal[(3, 4)]
 
 hello = "hello"
 invalid4: Literal[
-    1 + 2,  # error: [invalid-type-form]
+    1 + 2,  # error: [invalid-literal-parameter]
     "foo",
-    hello,  # error: [invalid-type-form]
-    (1, 2, 3),  # error: [invalid-type-form]
+    hello,  # error: [invalid-literal-parameter]
+    (1, 2, 3),  # error: [invalid-literal-parameter]
 ]
 ```
 
@@ -91,13 +91,3 @@ a1: Literal[26]
 def f():
     reveal_type(a1)  # revealed: Literal[26]
 ```
-
-## Invalid
-
-```py
-from typing import Literal
-
-# error: [invalid-type-form] "`Literal` requires at least one argument when used in a type expression"
-def _(x: Literal):
-    reveal_type(x)  # revealed: Unknown
-```

crates/red_knot_python_semantic/resources/mdtest/metaclass.md

@@ -68,7 +68,7 @@ class B(metaclass=M2): ...
 # error: [conflicting-metaclass] "The metaclass of a derived class (`C`) must be a subclass of the metaclasses of all its bases, but `M1` (metaclass of base class `A`) and `M2` (metaclass of base class `B`) have no subclass relationship"
 class C(A, B): ...
 
-reveal_type(C.__class__)  # revealed: type[Unknown]
+reveal_type(C.__class__)  # revealed: Unknown
 ```
 
 ## Conflict (2)
@@ -85,7 +85,7 @@ class A(metaclass=M1): ...
 # error: [conflicting-metaclass] "The metaclass of a derived class (`B`) must be a subclass of the metaclasses of all its bases, but `M2` (metaclass of `B`) and `M1` (metaclass of base class `A`) have no subclass relationship"
 class B(A, metaclass=M2): ...
 
-reveal_type(B.__class__)  # revealed: type[Unknown]
+reveal_type(B.__class__)  # revealed: Unknown
 ```
 
 ## Common metaclass
@@ -129,7 +129,7 @@ class C(metaclass=M12): ...
 # error: [conflicting-metaclass] "The metaclass of a derived class (`D`) must be a subclass of the metaclasses of all its bases, but `M1` (metaclass of base class `A`) and `M2` (metaclass of base class `B`) have no subclass relationship"
 class D(A, B, C): ...
 
-reveal_type(D.__class__)  # revealed: type[Unknown]
+reveal_type(D.__class__)  # revealed: Unknown
 ```
 
 ## Unknown
@@ -183,7 +183,7 @@ class A(B): ...  # error: [cyclic-class-definition]
 class B(C): ...  # error: [cyclic-class-definition]
 class C(A): ...  # error: [cyclic-class-definition]
 
-reveal_type(A.__class__)  # revealed: type[Unknown]
+reveal_type(A.__class__)  # revealed: Unknown
 ```
 
 ## PEP 695 generic

crates/red_knot_python_semantic/resources/mdtest/narrow/issubclass.md

@@ -95,14 +95,10 @@ def _(t: type[object]):
 
 ### Handling of `None`
 
-`types.NoneType` is only available in Python 3.10 and later:
-
-```toml
-[environment]
-python-version = "3.10"
-```
-
 ```py
+# TODO: this error should ideally go away once we (1) understand `sys.version_info` branches,
+# and (2) set the target Python version for this test to 3.10.
+# error: [possibly-unbound-import] "Member `NoneType` of module `types` is possibly unbound"
 from types import NoneType
 
 def _(flag: bool):

crates/red_knot_python_semantic/resources/mdtest/narrow/truthiness.md

@@ -1,315 +0,0 @@
-# Narrowing For Truthiness Checks (`if x` or `if not x`)
-
-## Value Literals
-
-```py
-def foo() -> Literal[0, -1, True, False, "", "foo", b"", b"bar", None] | tuple[()]:
-    return 0
-
-x = foo()
-
-if x:
-    reveal_type(x)  # revealed: Literal[-1] | Literal[True] | Literal["foo"] | Literal[b"bar"]
-else:
-    reveal_type(x)  # revealed: Literal[0] | Literal[False] | Literal[""] | Literal[b""] | None | tuple[()]
-
-if not x:
-    reveal_type(x)  # revealed: Literal[0] | Literal[False] | Literal[""] | Literal[b""] | None | tuple[()]
-else:
-    reveal_type(x)  # revealed: Literal[-1] | Literal[True] | Literal["foo"] | Literal[b"bar"]
-
-if x and not x:
-    reveal_type(x)  # revealed: Never
-else:
-    reveal_type(x)  # revealed: Literal[-1, 0] | bool | Literal["", "foo"] | Literal[b"", b"bar"] | None | tuple[()]
-
-if not (x and not x):
-    reveal_type(x)  # revealed: Literal[-1, 0] | bool | Literal["", "foo"] | Literal[b"", b"bar"] | None | tuple[()]
-else:
-    reveal_type(x)  # revealed: Never
-
-if x or not x:
-    reveal_type(x)  # revealed: Literal[-1, 0] | bool | Literal["foo", ""] | Literal[b"bar", b""] | None | tuple[()]
-else:
-    reveal_type(x)  # revealed: Never
-
-if not (x or not x):
-    reveal_type(x)  # revealed: Never
-else:
-    reveal_type(x)  # revealed: Literal[-1, 0] | bool | Literal["foo", ""] | Literal[b"bar", b""] | None | tuple[()]
-
-if (isinstance(x, int) or isinstance(x, str)) and x:
-    reveal_type(x)  # revealed: Literal[-1] | Literal[True] | Literal["foo"]
-else:
-    reveal_type(x)  # revealed: Literal[b"", b"bar"] | None | tuple[()] | Literal[0] | Literal[False] | Literal[""]
-```
-
-## Function Literals
-
-Basically functions are always truthy.
-
-```py
-def flag() -> bool:
-    return True
-
-def foo(hello: int) -> bytes:
-    return b""
-
-def bar(world: str, *args, **kwargs) -> float:
-    return 0.0
-
-x = foo if flag() else bar
-
-if x:
-    reveal_type(x)  # revealed: Literal[foo, bar]
-else:
-    reveal_type(x)  # revealed: Never
-```
-
-## Mutable Truthiness
-
-### Truthiness of Instances
-
-The boolean value of an instance is not always consistent. For example, `__bool__` can be customized
-to return random values, or in the case of a `list()`, the result depends on the number of elements
-in the list. Therefore, these types should not be narrowed by `if x` or `if not x`.
-
-```py
-class A: ...
-class B: ...
-
-def f(x: A | B):
-    if x:
-        reveal_type(x)  # revealed: A & ~AlwaysFalsy | B & ~AlwaysFalsy
-    else:
-        reveal_type(x)  # revealed: A & ~AlwaysTruthy | B & ~AlwaysTruthy
-
-    if x and not x:
-        reveal_type(x)  # revealed: A & ~AlwaysFalsy & ~AlwaysTruthy | B & ~AlwaysFalsy & ~AlwaysTruthy
-    else:
-        reveal_type(x)  # revealed: A & ~AlwaysTruthy | B & ~AlwaysTruthy | A & ~AlwaysFalsy | B & ~AlwaysFalsy
-
-    if x or not x:
-        reveal_type(x)  # revealed: A & ~AlwaysFalsy | B & ~AlwaysFalsy | A & ~AlwaysTruthy | B & ~AlwaysTruthy
-    else:
-        reveal_type(x)  # revealed: A & ~AlwaysTruthy & ~AlwaysFalsy | B & ~AlwaysTruthy & ~AlwaysFalsy
-```
-
-### Truthiness of Types
-
-Also, types may not be Truthy. This is because `__bool__` can be customized via a metaclass.
-Although this is a very rare case, we may consider metaclass checks in the future to handle this
-more accurately.
-
-```py
-def flag() -> bool:
-    return True
-
-x = int if flag() else str
-reveal_type(x)  # revealed: Literal[int, str]
-
-if x:
-    reveal_type(x)  # revealed: Literal[int] & ~AlwaysFalsy | Literal[str] & ~AlwaysFalsy
-else:
-    reveal_type(x)  # revealed: Literal[int] & ~AlwaysTruthy | Literal[str] & ~AlwaysTruthy
-```
-
-## Determined Truthiness
-
-Some custom classes can have a boolean value that is consistently determined as either `True` or
-`False`, regardless of the instance's state. This is achieved by defining a `__bool__` method that
-always returns a fixed value.
-
-These types can always be fully narrowed in boolean contexts, as shown below:
-
-```py
-class T:
-    def __bool__(self) -> Literal[True]:
-        return True
-
-class F:
-    def __bool__(self) -> Literal[False]:
-        return False
-
-t = T()
-
-if t:
-    reveal_type(t)  # revealed: T
-else:
-    reveal_type(t)  # revealed: Never
-
-f = F()
-
-if f:
-    reveal_type(f)  # revealed: Never
-else:
-    reveal_type(f)  # revealed: F
-```
-
-## Narrowing Complex Intersection and Union
-
-```py
-class A: ...
-class B: ...
-
-def flag() -> bool:
-    return True
-
-def instance() -> A | B:
-    return A()
-
-def literals() -> Literal[0, 42, "", "hello"]:
-    return 42
-
-x = instance()
-y = literals()
-
-if isinstance(x, str) and not isinstance(x, B):
-    reveal_type(x)  # revealed: A & str & ~B
-    reveal_type(y)  # revealed: Literal[0, 42] | Literal["", "hello"]
-
-    z = x if flag() else y
-
-    reveal_type(z)  # revealed: A & str & ~B | Literal[0, 42] | Literal["", "hello"]
-
-    if z:
-        reveal_type(z)  # revealed: A & str & ~B & ~AlwaysFalsy | Literal[42] | Literal["hello"]
-    else:
-        reveal_type(z)  # revealed: A & str & ~B & ~AlwaysTruthy | Literal[0] | Literal[""]
-```
-
-## Narrowing Multiple Variables
-
-```py
-def f(x: Literal[0, 1], y: Literal["", "hello"]):
-    if x and y and not x and not y:
-        reveal_type(x)  # revealed: Never
-        reveal_type(y)  # revealed: Never
-    else:
-        # ~(x or not x) and ~(y or not y)
-        reveal_type(x)  # revealed: Literal[0, 1]
-        reveal_type(y)  # revealed: Literal["", "hello"]
-
-    if (x or not x) and (y and not y):
-        reveal_type(x)  # revealed: Literal[0, 1]
-        reveal_type(y)  # revealed: Never
-    else:
-        # ~(x or not x) or ~(y and not y)
-        reveal_type(x)  # revealed: Literal[0, 1]
-        reveal_type(y)  # revealed: Literal["", "hello"]
-```
-
-## ControlFlow Merging
-
-After merging control flows, when we take the union of all constraints applied in each branch, we
-should return to the original state.
-
-```py
-class A: ...
-
-x = A()
-
-if x and not x:
-    y = x
-    reveal_type(y)  # revealed: A & ~AlwaysFalsy & ~AlwaysTruthy
-else:
-    y = x
-    reveal_type(y)  # revealed: A & ~AlwaysTruthy | A & ~AlwaysFalsy
-
-# TODO: It should be A. We should improve UnionBuilder or IntersectionBuilder. (issue #15023)
-reveal_type(y)  # revealed: A & ~AlwaysTruthy | A & ~AlwaysFalsy
-```
-
-## Truthiness of classes
-
-```py
-class MetaAmbiguous(type):
-    def __bool__(self) -> bool: ...
-
-class MetaFalsy(type):
-    def __bool__(self) -> Literal[False]: ...
-
-class MetaTruthy(type):
-    def __bool__(self) -> Literal[True]: ...
-
-class MetaDeferred(type):
-    def __bool__(self) -> MetaAmbiguous: ...
-
-class AmbiguousClass(metaclass=MetaAmbiguous): ...
-class FalsyClass(metaclass=MetaFalsy): ...
-class TruthyClass(metaclass=MetaTruthy): ...
-class DeferredClass(metaclass=MetaDeferred): ...
-
-def _(
-    a: type[AmbiguousClass],
-    t: type[TruthyClass],
-    f: type[FalsyClass],
-    d: type[DeferredClass],
-    ta: type[TruthyClass | AmbiguousClass],
-    af: type[AmbiguousClass] | type[FalsyClass],
-    flag: bool,
-):
-    reveal_type(ta)  # revealed: type[TruthyClass] | type[AmbiguousClass]
-    if ta:
-        reveal_type(ta)  # revealed: type[TruthyClass] | type[AmbiguousClass] & ~AlwaysFalsy
-
-    reveal_type(af)  # revealed: type[AmbiguousClass] | type[FalsyClass]
-    if af:
-        reveal_type(af)  # revealed: type[AmbiguousClass] & ~AlwaysFalsy
-
-    # TODO: Emit a diagnostic (`d` is not valid in boolean context)
-    if d:
-        # TODO: Should be `Unknown`
-        reveal_type(d)  # revealed: type[DeferredClass] & ~AlwaysFalsy
-
-    tf = TruthyClass if flag else FalsyClass
-    reveal_type(tf)  # revealed: Literal[TruthyClass, FalsyClass]
-
-    if tf:
-        reveal_type(tf)  # revealed: Literal[TruthyClass]
-    else:
-        reveal_type(tf)  # revealed: Literal[FalsyClass]
-```
-
-## Narrowing in chained boolean expressions
-
-```py
-from typing import Literal
-
-class A: ...
-
-def _(x: Literal[0, 1]):
-    reveal_type(x or A())  # revealed: Literal[1] | A
-    reveal_type(x and A())  # revealed: Literal[0] | A
-
-def _(x: str):
-    reveal_type(x or A())  # revealed: str & ~AlwaysFalsy | A
-    reveal_type(x and A())  # revealed: str & ~AlwaysTruthy | A
-
-def _(x: bool | str):
-    reveal_type(x or A())  # revealed: Literal[True] | str & ~AlwaysFalsy | A
-    reveal_type(x and A())  # revealed: Literal[False] | str & ~AlwaysTruthy | A
-
-class Falsy:
-    def __bool__(self) -> Literal[False]: ...
-
-class Truthy:
-    def __bool__(self) -> Literal[True]: ...
-
-def _(x: Falsy | Truthy):
-    reveal_type(x or A())  # revealed: Truthy | A
-    reveal_type(x and A())  # revealed: Falsy | A
-
-class MetaFalsy(type):
-    def __bool__(self) -> Literal[False]: ...
-
-class MetaTruthy(type):
-    def __bool__(self) -> Literal[True]: ...
-
-class FalsyClass(metaclass=MetaFalsy): ...
-class TruthyClass(metaclass=MetaTruthy): ...
-
-def _(x: type[FalsyClass] | type[TruthyClass]):
-    reveal_type(x or A())  # revealed: type[TruthyClass] | A
-    reveal_type(x and A())  # revealed: type[FalsyClass] | A
-```

crates/red_knot_python_semantic/resources/mdtest/scopes/builtin.md

@@ -10,10 +10,10 @@ def returns_bool() -> bool:
     return True
 
 if returns_bool():
-    chr = 1
+    copyright = 1
 
 def f():
-    reveal_type(chr)  # revealed: Literal[chr] | Literal[1]
+    reveal_type(copyright)  # revealed: Literal[copyright] | Literal[1]
 ```
 
 ## Conditionally global or builtin, with annotation
@@ -25,8 +25,8 @@ def returns_bool() -> bool:
     return True
 
 if returns_bool():
-    chr: int = 1
+    copyright: int = 1
 
 def f():
-    reveal_type(chr)  # revealed: Literal[chr] | int
+    reveal_type(copyright)  # revealed: Literal[copyright] | int
 ```

crates/red_knot_python_semantic/resources/mdtest/shadowing/function.md

@@ -25,29 +25,3 @@ def f(): ...
 
 f: int = 1
 ```
-
-## Explicit shadowing involving `def` statements
-
-Since a `def` statement is a declaration, one `def` can shadow another `def`, or shadow a previous
-non-`def` declaration, without error.
-
-```py
-f = 1
-reveal_type(f)  # revealed: Literal[1]
-
-def f(): ...
-
-reveal_type(f)  # revealed: Literal[f]
-
-def f(x: int) -> int:
-    raise NotImplementedError
-
-reveal_type(f)  # revealed: Literal[f]
-
-f: int = 1
-reveal_type(f)  # revealed: Literal[1]
-
-def f(): ...
-
-reveal_type(f)  # revealed: Literal[f]
-```

crates/red_knot_python_semantic/resources/mdtest/slots.md

@@ -1,184 +0,0 @@
-# `__slots__`
-
-## Not specified and empty
-
-```py
-class A: ...
-
-class B:
-    __slots__ = ()
-
-class C:
-    __slots__ = ("lorem", "ipsum")
-
-class AB(A, B): ...  # fine
-class AC(A, C): ...  # fine
-class BC(B, C): ...  # fine
-class ABC(A, B, C): ...  # fine
-```
-
-## Incompatible tuples
-
-```py
-class A:
-    __slots__ = ("a", "b")
-
-class B:
-    __slots__ = ("c", "d")
-
-class C(
-    A,  # error: [incompatible-slots]
-    B,  # error: [incompatible-slots]
-): ...
-```
-
-## Same value
-
-```py
-class A:
-    __slots__ = ("a", "b")
-
-class B:
-    __slots__ = ("a", "b")
-
-class C(
-    A,  # error: [incompatible-slots]
-    B,  # error: [incompatible-slots]
-): ...
-```
-
-## Strings
-
-```py
-class A:
-    __slots__ = "abc"
-
-class B:
-    __slots__ = ("abc",)
-
-class AB(
-    A,  # error: [incompatible-slots]
-    B,  # error: [incompatible-slots]
-): ...
-```
-
-## Invalid
-
-TODO: Emit diagnostics
-
-```py
-class NonString1:
-    __slots__ = 42
-
-class NonString2:
-    __slots__ = b"ar"
-
-class NonIdentifier1:
-    __slots__ = "42"
-
-class NonIdentifier2:
-    __slots__ = ("lorem", "42")
-
-class NonIdentifier3:
-    __slots__ = (e for e in ("lorem", "42"))
-```
-
-## Inheritance
-
-```py
-class A:
-    __slots__ = ("a", "b")
-
-class B(A): ...
-
-class C:
-    __slots__ = ("c", "d")
-
-class D(C): ...
-class E(
-    B,  # error: [incompatible-slots]
-    D,  # error: [incompatible-slots]
-): ...
-```
-
-## Single solid base
-
-```py
-class A:
-    __slots__ = ("a", "b")
-
-class B(A): ...
-class C(A): ...
-class D(B, A): ...  # fine
-class E(B, C, A): ...  # fine
-```
-
-## False negatives
-
-### Possibly unbound
-
-```py
-def _(flag: bool):
-    class A:
-        if flag:
-            __slots__ = ("a", "b")
-
-    class B:
-        __slots__ = ("c", "d")
-
-    # Might or might not be fine at runtime
-    class C(A, B): ...
-```
-
-### Bound but with different types
-
-```py
-def _(flag: bool):
-    class A:
-        if flag:
-            __slots__ = ("a", "b")
-        else:
-            __slots__ = ()
-
-    class B:
-        __slots__ = ("c", "d")
-
-    # Might or might not be fine at runtime
-    class C(A, B): ...
-```
-
-### Non-tuples
-
-```py
-class A:
-    __slots__ = ["a", "b"]  # This is treated as "dynamic"
-
-class B:
-    __slots__ = ("c", "d")
-
-# False negative: [incompatible-slots]
-class C(A, B): ...
-```
-
-### Post-hoc modifications
-
-```py
-class A:
-    __slots__ = ()
-    __slots__ += ("a", "b")
-
-reveal_type(A.__slots__)  # revealed: @Todo(Support for more binary expressions)
-
-class B:
-    __slots__ = ("c", "d")
-
-# False negative: [incompatible-slots]
-class C(A, B): ...
-```
-
-### Built-ins with implicit layouts
-
-```py
-# False negative: [incompatible-slots]
-class A(int, str): ...
-```

crates/red_knot_python_semantic/resources/mdtest/subscript/tuple.md

@@ -81,7 +81,10 @@ python-version = "3.9"
 ```
 
 ```py
-# TODO: `tuple[int, str]` is a valid base (generics)
+# TODO:
+#  * `tuple.__class_getitem__` is always bound on 3.9 (`sys.version_info`)
+#  * `tuple[int, str]` is a valid base (generics)
+# error: [call-possibly-unbound-method] "Method `__class_getitem__` of type `Literal[tuple]` is possibly unbound"
 # error: [invalid-base] "Invalid class base with type `GenericAlias` (all bases must be a class, `Any`, `Unknown` or `Todo`)"
 class A(tuple[int, str]): ...
 

crates/red_knot_python_semantic/resources/mdtest/suppressions/knot_ignore.md

@@ -1,182 +0,0 @@
-# Suppressing errors with `knot: ignore`
-
-Type check errors can be suppressed by a `knot: ignore` comment on the same line as the violation.
-
-## Simple `knot: ignore`
-
-```py
-a = 4 + test  # knot: ignore
-```
-
-## Suppressing a specific code
-
-```py
-a = 4 + test  # knot: ignore[unresolved-reference]
-```
-
-## Unused suppression
-
-```py
-test = 10
-# error: [unused-ignore-comment] "Unused `knot: ignore` directive: 'possibly-unresolved-reference'"
-a = test + 3  # knot: ignore[possibly-unresolved-reference]
-```
-
-## Unused suppression if the error codes don't match
-
-```py
-# error: [unresolved-reference]
-# error: [unused-ignore-comment] "Unused `knot: ignore` directive: 'possibly-unresolved-reference'"
-a = test + 3  # knot: ignore[possibly-unresolved-reference]
-```
-
-## Suppressed unused comment
-
-```py
-# error: [unused-ignore-comment]
-a = 10 / 2  # knot: ignore[division-by-zero]
-a = 10 / 2  # knot: ignore[division-by-zero, unused-ignore-comment]
-a = 10 / 2  # knot: ignore[unused-ignore-comment, division-by-zero]
-a = 10 / 2  # knot: ignore[unused-ignore-comment] # type: ignore
-a = 10 / 2  # type: ignore # knot: ignore[unused-ignore-comment]
-```
-
-## Unused ignore comment
-
-```py
-# error: [unused-ignore-comment] "Unused `knot: ignore` directive: 'unused-ignore-comment'"
-a = 10 / 0  # knot: ignore[division-by-zero, unused-ignore-comment]
-```
-
-## Multiple unused comments
-
-Today, Red Knot emits a diagnostic for every unused code. We might want to group the codes by
-comment at some point in the future.
-
-```py
-# error: [unused-ignore-comment] "Unused `knot: ignore` directive: 'division-by-zero'"
-# error: [unused-ignore-comment] "Unused `knot: ignore` directive: 'unresolved-reference'"
-a = 10 / 2  # knot: ignore[division-by-zero, unresolved-reference]
-
-# error: [unused-ignore-comment] "Unused `knot: ignore` directive: 'invalid-assignment'"
-# error: [unused-ignore-comment] "Unused `knot: ignore` directive: 'unresolved-reference'"
-a = 10 / 0  # knot: ignore[invalid-assignment, division-by-zero, unresolved-reference]
-```
-
-## Multiple suppressions
-
-```py
-# fmt: off
-def test(a: f"f-string type annotation", b: b"byte-string-type-annotation"): ...  # knot: ignore[fstring-type-annotation, byte-string-type-annotation]
-```
-
-## Can't suppress syntax errors
-
-<!-- blacken-docs:off -->
-
-```py
-# error: [invalid-syntax]
-# error: [unused-ignore-comment]
-def test(  # knot: ignore
-```
-
-<!-- blacken-docs:on -->
-
-## Can't suppress `revealed-type` diagnostics
-
-```py
-a = 10
-# revealed: Literal[10]
-# error: [unknown-rule] "Unknown rule `revealed-type`"
-reveal_type(a)  # knot: ignore[revealed-type]
-```
-
-## Extra whitespace in type ignore comments is allowed
-
-```py
-a = 10 / 0  # knot   :   ignore
-a = 10 / 0  # knot: ignore  [    division-by-zero   ]
-```
-
-## Whitespace is optional
-
-```py
-# fmt: off
-a = 10 / 0  #knot:ignore[division-by-zero]
-```
-
-## Trailing codes comma
-
-Trailing commas in the codes section are allowed:
-
-```py
-a = 10 / 0  # knot: ignore[division-by-zero,]
-```
-
-## Invalid characters in codes
-
-```py
-# error: [division-by-zero]
-# error: [invalid-ignore-comment] "Invalid `knot: ignore` comment: expected a alphanumeric character or `-` or `_` as code"
-a = 10 / 0  # knot: ignore[*-*]
-```
-
-## Trailing whitespace
-
-<!-- blacken-docs:off -->
-
-```py
-a = 10 / 0  # knot: ignore[division-by-zero]      
-            #                               ^^^^^^ trailing whitespace
-```
-
-<!-- blacken-docs:on -->
-
-## Missing comma
-
-A missing comma results in an invalid suppression comment. We may want to recover from this in the
-future.
-
-```py
-# error: [unresolved-reference]
-# error: [invalid-ignore-comment] "Invalid `knot: ignore` comment: expected a comma separating the rule codes"
-a = x / 0  # knot: ignore[division-by-zero unresolved-reference]
-```
-
-## Missing closing bracket
-
-```py
-# error: [unresolved-reference] "Name `x` used when not defined"
-# error: [invalid-ignore-comment] "Invalid `knot: ignore` comment: expected a comma separating the rule codes"
-a = x / 2  # knot: ignore[unresolved-reference
-```
-
-## Empty codes
-
-An empty codes array suppresses no-diagnostics and is always useless
-
-```py
-# error: [division-by-zero]
-# error: [unused-ignore-comment] "Unused `knot: ignore` without a code"
-a = 4 / 0  # knot: ignore[]
-```
-
-## File-level suppression comments
-
-File level suppression comments are currently intentionally unsupported because we've yet to decide
-if they should use a different syntax that also supports enabling rules or changing the rule's
-severity: `knot: possibly-undefined-reference=error`
-
-```py
-# error: [unused-ignore-comment]
-# knot: ignore[division-by-zero]
-
-a = 4 / 0  # error: [division-by-zero]
-```
-
-## Unknown rule
-
-```py
-# error: [unknown-rule] "Unknown rule `is-equal-14`"
-a = 10 + 4  # knot: ignore[is-equal-14]
-```

crates/red_knot_python_semantic/resources/mdtest/suppressions/no_type_check.md

@@ -1,118 +0,0 @@
-# `@no_type_check`
-
-> If a type checker supports the `no_type_check` decorator for functions, it should suppress all
-> type errors for the def statement and its body including any nested functions or classes. It
-> should also ignore all parameter and return type annotations and treat the function as if it were
-> unannotated. [source](https://typing.readthedocs.io/en/latest/spec/directives.html#no-type-check)
-
-## Error in the function body
-
-```py
-from typing import no_type_check
-
-@no_type_check
-def test() -> int:
-    return a + 5
-```
-
-## Error in nested function
-
-```py
-from typing import no_type_check
-
-@no_type_check
-def test() -> int:
-    def nested():
-        return a + 5
-```
-
-## Error in nested class
-
-```py
-from typing import no_type_check
-
-@no_type_check
-def test() -> int:
-    class Nested:
-        def inner(self):
-            return a + 5
-```
-
-## Error in preceding decorator
-
-Don't suppress diagnostics for decorators appearing before the `no_type_check` decorator.
-
-```py
-from typing import no_type_check
-
-@unknown_decorator  # error: [unresolved-reference]
-@no_type_check
-def test() -> int:
-    return a + 5
-```
-
-## Error in following decorator
-
-Unlike Pyright and mypy, suppress diagnostics appearing after the `no_type_check` decorator. We do
-this because it more closely matches Python's runtime semantics of decorators. For more details, see
-the discussion on the
-[PR adding `@no_type_check` support](https://github.com/astral-sh/ruff/pull/15122#discussion_r1896869411).
-
-```py
-from typing import no_type_check
-
-@no_type_check
-@unknown_decorator
-def test() -> int:
-    return a + 5
-```
-
-## Error in default value
-
-```py
-from typing import no_type_check
-
-@no_type_check
-def test(a: int = "test"):
-    return x + 5
-```
-
-## Error in return value position
-
-```py
-from typing import no_type_check
-
-@no_type_check
-def test() -> Undefined:
-    return x + 5
-```
-
-## `no_type_check` on classes isn't supported
-
-Red Knot does not support decorating classes with `no_type_check`. The behaviour of `no_type_check`
-when applied to classes is
-[not specified currently](https://typing.readthedocs.io/en/latest/spec/directives.html#no-type-check),
-and is not supported by Pyright or mypy.
-
-A future improvement might be to emit a diagnostic if a `no_type_check` annotation is applied to a
-class.
-
-```py
-from typing import no_type_check
-
-@no_type_check
-class Test:
-    def test(self):
-        return a + 5  # error: [unresolved-reference]
-```
-
-## `type: ignore` comments in `@no_type_check` blocks
-
-```py
-from typing import no_type_check
-
-@no_type_check
-def test():
-    # error: [unused-ignore-comment] "Unused `knot: ignore` directive: 'unresolved-reference'"
-    return x + 5  # knot: ignore[unresolved-reference]
-```

crates/red_knot_python_semantic/resources/mdtest/suppressions/type_ignore.md

@@ -1,162 +0,0 @@
-# Suppressing errors with `type: ignore`
-
-Type check errors can be suppressed by a `type: ignore` comment on the same line as the violation.
-
-## Simple `type: ignore`
-
-```py
-a = 4 + test  # type: ignore
-```
-
-## Multiline ranges
-
-A diagnostic with a multiline range can be suppressed by a comment on the same line as the
-diagnostic's start or end. This is the same behavior as Mypy's.
-
-```py
-# fmt: off
-y = (
-    4 / 0  # type: ignore
-)
-
-y = (
-    4 /  # type: ignore
-    0
-)
-
-y = (
-    4 /
-    0  # type: ignore
-)
-```
-
-Pyright diverges from this behavior and instead applies a suppression if its range intersects with
-the diagnostic range. This can be problematic for nested expressions because a suppression in a
-child expression now suppresses errors in the outer expression.
-
-For example, the `type: ignore` comment in this example suppresses the error of adding `2` to
-`"test"` and adding `"other"` to the result of the cast.
-
-```py path=nested.py
-# fmt: off
-from typing import cast
-
-y = (
-    cast(int, "test" +
-            # TODO: Remove the expected error after implementing `invalid-operator` for binary expressions
-            # error: [unused-ignore-comment]
-            2 # type: ignore
-    )
-    + "other"  # TODO: expected-error[invalid-operator]
-)
-```
-
-Mypy flags the second usage.
-
-## Before opening parenthesis
-
-A suppression that applies to all errors before the opening parenthesis.
-
-```py
-a: Test = (  # type: ignore
-  Test()  # error: [unresolved-reference]
-)  # fmt: skip
-```
-
-## Multiline string
-
-```py
-a: int = 4
-a = """
-  This is a multiline string and the suppression is at its end
-"""  # type: ignore
-```
-
-## Line continuations
-
-Suppressions after a line continuation apply to all previous lines.
-
-```py
-# fmt: off
-a = test \
-  + 2  # type: ignore
-
-a = test \
-  + a \
-  + 2  # type: ignore
-```
-
-## Codes
-
-Mypy supports `type: ignore[code]`. Red Knot doesn't understand mypy's rule names. Therefore, ignore
-the codes and suppress all errors.
-
-```py
-a = test  # type: ignore[name-defined]
-```
-
-## Nested comments
-
-```py
-# fmt: off
-a = test \
-  + 2  # fmt: skip # type: ignore
-
-a = test \
-  + 2  # type: ignore # fmt: skip
-```
-
-## Misspelled `type: ignore`
-
-```py
-# error: [unresolved-reference]
-# error: [invalid-ignore-comment]
-a = test + 2  # type: ignoree
-```
-
-## Invalid - ignore on opening parentheses
-
-`type: ignore` comments after an opening parentheses suppress any type errors inside the parentheses
-in Pyright. Neither Ruff, nor mypy support this and neither does Red Knot.
-
-```py
-# fmt: off
-# error: [unused-ignore-comment]
-a = (  # type: ignore
-    test + 4  # error: [unresolved-reference]
-)
-```
-
-## File level suppression
-
-```py
-# type: ignore
-
-a = 10 / 0
-b = a / 0
-```
-
-## File level suppression with leading shebang
-
-```py
-#!/usr/bin/env/python
-# type: ignore
-
-a = 10 / 0
-b = a / 0
-```
-
-## Invalid own-line suppression
-
-```py
-"""
-File level suppressions must come before any non-trivia token,
-including module docstrings. 
-"""
-
-# error: [unused-ignore-comment] "Unused blanket `type: ignore` directive"
-# type: ignore
-
-a = 10 / 0  # error: [division-by-zero]
-b = a / 0  # error: [division-by-zero]
-```

crates/red_knot_python_semantic/resources/mdtest/sys_platform.md

@@ -1,71 +0,0 @@
-# `sys.platform`
-
-## Default value
-
-When no target platform is specified, we fall back to the type of `sys.platform` declared in
-typeshed:
-
-```toml
-[environment]
-# No python-platform entry
-```
-
-```py
-import sys
-
-reveal_type(sys.platform)  # revealed: str
-```
-
-## Explicit selection of `all` platforms
-
-```toml
-[environment]
-python-platform = "all"
-```
-
-```py
-import sys
-
-reveal_type(sys.platform)  # revealed: str
-```
-
-## Explicit selection of a specific platform
-
-```toml
-[environment]
-python-platform = "linux"
-```
-
-```py
-import sys
-
-reveal_type(sys.platform)  # revealed: Literal["linux"]
-```
-
-## Testing for a specific platform
-
-### Exact comparison
-
-```toml
-[environment]
-python-platform = "freebsd8"
-```
-
-```py
-import sys
-
-reveal_type(sys.platform == "freebsd8")  # revealed: Literal[True]
-reveal_type(sys.platform == "linux")  # revealed: Literal[False]
-```
-
-### Substring comparison
-
-It is [recommended](https://docs.python.org/3/library/sys.html#sys.platform) to use
-`sys.platform.startswith(...)` for platform checks. This is not yet supported in type inference:
-
-```py
-import sys
-
-reveal_type(sys.platform.startswith("freebsd"))  # revealed: @Todo(instance attributes)
-reveal_type(sys.platform.startswith("linux"))  # revealed: @Todo(instance attributes)
-```

crates/red_knot_python_semantic/resources/mdtest/type_of/any.md

@@ -1,20 +1,13 @@
 # `type[Any]`
 
-This file contains tests for non-fully-static `type[]` types, such as `type[Any]` and
-`type[Unknown]`.
-
 ## Simple
 
 ```py
-def f(x: type[Any], y: type[str]):
+def f(x: type[Any]):
     reveal_type(x)  # revealed: type[Any]
     # TODO: could be `<object.__repr__ type> & Any`
     reveal_type(x.__repr__)  # revealed: Any
 
-    # type[str] and type[Any] are assignable to each other
-    a: type[str] = x
-    b: type[Any] = y
-
 class A: ...
 
 x: type[Any] = object
@@ -77,26 +70,3 @@ def test(x: Any, y: SomethingUnknown):
     reveal_type(y.__class__)  # revealed: type[Unknown]
     reveal_type(y.__class__.__class__.__class__.__class__)  # revealed: type[Unknown]
 ```
-
-## `type[Unknown]` has similar properties to `type[Any]`
-
-```py
-import abc
-from typing import Any
-from does_not_exist import SomethingUnknown  # error: [unresolved-import]
-
-has_unknown_type = SomethingUnknown.__class__
-reveal_type(has_unknown_type)  # revealed: type[Unknown]
-
-def test(x: type[str], y: type[Any]):
-    """Both `type[Any]` and `type[Unknown]` are assignable to all `type[]` types"""
-    a: type[Any] = x
-    b: type[str] = y
-    c: type[Any] = has_unknown_type
-    d: type[str] = has_unknown_type
-
-def test2(a: type[Any]):
-    """`type[Any]` and `type[Unknown]` are also assignable to all instances of `type` subclasses"""
-    b: abc.ABCMeta = a
-    b: abc.ABCMeta = has_unknown_type
-```

crates/red_knot_python_semantic/resources/mdtest/type_of/basic.md

@@ -61,8 +61,10 @@ class B: ...
 ```py path=a/test.py
 import a.b
 
+# TODO: no diagnostic
+# error: [unresolved-attribute]
 def f(c: type[a.b.C]):
-    reveal_type(c)  # revealed: type[C]
+    reveal_type(c)  # revealed: @Todo(unsupported type[X] special form)
 ```
 
 ```py path=a/__init__.py

crates/red_knot_python_semantic/resources/mdtest/unary/custom.md

@@ -1,165 +0,0 @@
-# Custom unary operations
-
-## Class instances
-
-```py
-class Yes:
-    def __pos__(self) -> bool:
-        return False
-
-    def __neg__(self) -> str:
-        return "negative"
-
-    def __invert__(self) -> int:
-        return 17
-
-class Sub(Yes): ...
-class No: ...
-
-reveal_type(+Yes())  # revealed: bool
-reveal_type(-Yes())  # revealed: str
-reveal_type(~Yes())  # revealed: int
-
-reveal_type(+Sub())  # revealed: bool
-reveal_type(-Sub())  # revealed: str
-reveal_type(~Sub())  # revealed: int
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `No`"
-reveal_type(+No())  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `No`"
-reveal_type(-No())  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `No`"
-reveal_type(~No())  # revealed: Unknown
-```
-
-## Classes
-
-```py
-class Yes:
-    def __pos__(self) -> bool:
-        return False
-
-    def __neg__(self) -> str:
-        return "negative"
-
-    def __invert__(self) -> int:
-        return 17
-
-class Sub(Yes): ...
-class No: ...
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `Literal[Yes]`"
-reveal_type(+Yes)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `Literal[Yes]`"
-reveal_type(-Yes)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `Literal[Yes]`"
-reveal_type(~Yes)  # revealed: Unknown
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `Literal[Sub]`"
-reveal_type(+Sub)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `Literal[Sub]`"
-reveal_type(-Sub)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `Literal[Sub]`"
-reveal_type(~Sub)  # revealed: Unknown
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `Literal[No]`"
-reveal_type(+No)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `Literal[No]`"
-reveal_type(-No)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `Literal[No]`"
-reveal_type(~No)  # revealed: Unknown
-```
-
-## Function literals
-
-```py
-def f():
-    pass
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `Literal[f]`"
-reveal_type(+f)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `Literal[f]`"
-reveal_type(-f)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `Literal[f]`"
-reveal_type(~f)  # revealed: Unknown
-```
-
-## Subclass
-
-```py
-class Yes:
-    def __pos__(self) -> bool:
-        return False
-
-    def __neg__(self) -> str:
-        return "negative"
-
-    def __invert__(self) -> int:
-        return 17
-
-class Sub(Yes): ...
-class No: ...
-
-def yes() -> type[Yes]:
-    return Yes
-
-def sub() -> type[Sub]:
-    return Sub
-
-def no() -> type[No]:
-    return No
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `type[Yes]`"
-reveal_type(+yes())  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `type[Yes]`"
-reveal_type(-yes())  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `type[Yes]`"
-reveal_type(~yes())  # revealed: Unknown
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `type[Sub]`"
-reveal_type(+sub())  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `type[Sub]`"
-reveal_type(-sub())  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `type[Sub]`"
-reveal_type(~sub())  # revealed: Unknown
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `type[No]`"
-reveal_type(+no())  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `type[No]`"
-reveal_type(-no())  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `type[No]`"
-reveal_type(~no())  # revealed: Unknown
-```
-
-## Metaclass
-
-```py
-class Meta(type):
-    def __pos__(self) -> bool:
-        return False
-
-    def __neg__(self) -> str:
-        return "negative"
-
-    def __invert__(self) -> int:
-        return 17
-
-class Yes(metaclass=Meta): ...
-class Sub(Yes): ...
-class No: ...
-
-reveal_type(+Yes)  # revealed: bool
-reveal_type(-Yes)  # revealed: str
-reveal_type(~Yes)  # revealed: int
-
-reveal_type(+Sub)  # revealed: bool
-reveal_type(-Sub)  # revealed: str
-reveal_type(~Sub)  # revealed: int
-
-# error: [unsupported-operator] "Unary operator `+` is unsupported for type `Literal[No]`"
-reveal_type(+No)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `-` is unsupported for type `Literal[No]`"
-reveal_type(-No)  # revealed: Unknown
-# error: [unsupported-operator] "Unary operator `~` is unsupported for type `Literal[No]`"
-reveal_type(~No)  # revealed: Unknown
-```

crates/red_knot_python_semantic/resources/mdtest/unpacking.md

@@ -61,7 +61,7 @@ reveal_type(c)  # revealed: Literal[4]
 ### Uneven unpacking (1)
 
 ```py
-# error: [invalid-assignment] "Not enough values to unpack (expected 3, got 2)"
+# TODO: Add diagnostic (there aren't enough values to unpack)
 (a, b, c) = (1, 2)
 reveal_type(a)  # revealed: Literal[1]
 reveal_type(b)  # revealed: Literal[2]
@@ -71,7 +71,7 @@ reveal_type(c)  # revealed: Unknown
 ### Uneven unpacking (2)
 
 ```py
-# error: [invalid-assignment] "Too many values to unpack (expected 2, got 3)"
+# TODO: Add diagnostic (too many values to unpack)
 (a, b) = (1, 2, 3)
 reveal_type(a)  # revealed: Literal[1]
 reveal_type(b)  # revealed: Literal[2]
@@ -80,7 +80,7 @@ reveal_type(b)  # revealed: Literal[2]
 ### Starred expression (1)
 
 ```py
-# error: [invalid-assignment] "Not enough values to unpack (expected 3 or more, got 2)"
+# TODO: Add diagnostic (need more values to unpack)
 [a, *b, c, d] = (1, 2)
 reveal_type(a)  # revealed: Literal[1]
 # TODO: Should be list[Any] once support for assigning to starred expression is added
@@ -133,7 +133,7 @@ reveal_type(c)  # revealed: @Todo(starred unpacking)
 ### Starred expression (6)
 
 ```py
-# error: [invalid-assignment] "Not enough values to unpack (expected 5 or more, got 1)"
+# TODO: Add diagnostic (need more values to unpack)
 (a, b, c, *d, e, f) = (1,)
 reveal_type(a)  # revealed: Literal[1]
 reveal_type(b)  # revealed: Unknown
@@ -199,7 +199,7 @@ reveal_type(b)  # revealed: LiteralString
 ### Uneven unpacking (1)
 
 ```py
-# error: [invalid-assignment] "Not enough values to unpack (expected 3, got 2)"
+# TODO: Add diagnostic (there aren't enough values to unpack)
 a, b, c = "ab"
 reveal_type(a)  # revealed: LiteralString
 reveal_type(b)  # revealed: LiteralString
@@ -209,7 +209,7 @@ reveal_type(c)  # revealed: Unknown
 ### Uneven unpacking (2)
 
 ```py
-# error: [invalid-assignment] "Too many values to unpack (expected 2, got 3)"
+# TODO: Add diagnostic (too many values to unpack)
 a, b = "abc"
 reveal_type(a)  # revealed: LiteralString
 reveal_type(b)  # revealed: LiteralString
@@ -218,7 +218,7 @@ reveal_type(b)  # revealed: LiteralString
 ### Starred expression (1)
 
 ```py
-# error: [invalid-assignment] "Not enough values to unpack (expected 3 or more, got 2)"
+# TODO: Add diagnostic (need more values to unpack)
 (a, *b, c, d) = "ab"
 reveal_type(a)  # revealed: LiteralString
 # TODO: Should be list[LiteralString] once support for assigning to starred expression is added
@@ -271,7 +271,7 @@ reveal_type(c)  # revealed: @Todo(starred unpacking)
 ### Unicode
 
 ```py
-# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
+# TODO: Add diagnostic (need more values to unpack)
 (a, b) = "é"
 
 reveal_type(a)  # revealed: LiteralString
@@ -281,7 +281,7 @@ reveal_type(b)  # revealed: Unknown
 ### Unicode escape (1)
 
 ```py
-# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
+# TODO: Add diagnostic (need more values to unpack)
 (a, b) = "\u9E6C"
 
 reveal_type(a)  # revealed: LiteralString
@@ -291,7 +291,7 @@ reveal_type(b)  # revealed: Unknown
 ### Unicode escape (2)
 
 ```py
-# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
+# TODO: Add diagnostic (need more values to unpack)
 (a, b) = "\U0010FFFF"
 
 reveal_type(a)  # revealed: LiteralString
@@ -306,273 +306,3 @@ reveal_type(b)  # revealed: Unknown
 reveal_type(a)  # revealed: LiteralString
 reveal_type(b)  # revealed: LiteralString
 ```
-
-## Union
-
-### Same types
-
-Union of two tuples of equal length and each element is of the same type.
-
-```py
-def _(arg: tuple[int, int] | tuple[int, int]):
-    (a, b) = arg
-    reveal_type(a)  # revealed: int
-    reveal_type(b)  # revealed: int
-```
-
-### Mixed types (1)
-
-Union of two tuples of equal length and one element differs in its type.
-
-```py
-def _(arg: tuple[int, int] | tuple[int, str]):
-    a, b = arg
-    reveal_type(a)  # revealed: int
-    reveal_type(b)  # revealed: int | str
-```
-
-### Mixed types (2)
-
-Union of two tuples of equal length and both the element types are different.
-
-```py
-def _(arg: tuple[int, str] | tuple[str, int]):
-    a, b = arg
-    reveal_type(a)  # revealed: int | str
-    reveal_type(b)  # revealed: str | int
-```
-
-### Mixed types (3)
-
-Union of three tuples of equal length and various combination of element types:
-
-1. All same types
-1. One different type
-1. All different types
-
-```py
-def _(arg: tuple[int, int, int] | tuple[int, str, bytes] | tuple[int, int, str]):
-    a, b, c = arg
-    reveal_type(a)  # revealed: int
-    reveal_type(b)  # revealed: int | str
-    reveal_type(c)  # revealed: int | bytes | str
-```
-
-### Nested
-
-```py
-def _(arg: tuple[int, tuple[str, bytes]] | tuple[tuple[int, bytes], Literal["ab"]]):
-    a, (b, c) = arg
-    reveal_type(a)  # revealed: int | tuple[int, bytes]
-    reveal_type(b)  # revealed: str
-    reveal_type(c)  # revealed: bytes | LiteralString
-```
-
-### Starred expression
-
-```py
-def _(arg: tuple[int, bytes, int] | tuple[int, int, str, int, bytes]):
-    a, *b, c = arg
-    reveal_type(a)  # revealed: int
-    # TODO: Should be `list[bytes | int | str]`
-    reveal_type(b)  # revealed: @Todo(starred unpacking)
-    reveal_type(c)  # revealed: int | bytes
-```
-
-### Size mismatch (1)
-
-```py
-def _(arg: tuple[int, bytes, int] | tuple[int, int, str, int, bytes]):
-    # error: [invalid-assignment] "Too many values to unpack (expected 2, got 3)"
-    # error: [invalid-assignment] "Too many values to unpack (expected 2, got 5)"
-    a, b = arg
-    reveal_type(a)  # revealed: int
-    reveal_type(b)  # revealed: bytes | int
-```
-
-### Size mismatch (2)
-
-```py
-def _(arg: tuple[int, bytes] | tuple[int, str]):
-    # error: [invalid-assignment] "Not enough values to unpack (expected 3, got 2)"
-    # error: [invalid-assignment] "Not enough values to unpack (expected 3, got 2)"
-    a, b, c = arg
-    reveal_type(a)  # revealed: int
-    reveal_type(b)  # revealed: bytes | str
-    reveal_type(c)  # revealed: Unknown
-```
-
-### Same literal types
-
-```py
-def _(flag: bool):
-    if flag:
-        value = (1, 2)
-    else:
-        value = (3, 4)
-
-    a, b = value
-    reveal_type(a)  # revealed: Literal[1, 3]
-    reveal_type(b)  # revealed: Literal[2, 4]
-```
-
-### Mixed literal types
-
-```py
-def _(flag: bool):
-    if flag:
-        value = (1, 2)
-    else:
-        value = ("a", "b")
-
-    a, b = value
-    reveal_type(a)  # revealed: Literal[1] | Literal["a"]
-    reveal_type(b)  # revealed: Literal[2] | Literal["b"]
-```
-
-### Typing literal
-
-```py
-from typing import Literal
-
-def _(arg: tuple[int, int] | Literal["ab"]):
-    a, b = arg
-    reveal_type(a)  # revealed: int | LiteralString
-    reveal_type(b)  # revealed: int | LiteralString
-```
-
-### Custom iterator (1)
-
-```py
-class Iterator:
-    def __next__(self) -> tuple[int, int] | tuple[int, str]:
-        return (1, 2)
-
-class Iterable:
-    def __iter__(self) -> Iterator:
-        return Iterator()
-
-((a, b), c) = Iterable()
-reveal_type(a)  # revealed: int
-reveal_type(b)  # revealed: int | str
-reveal_type(c)  # revealed: tuple[int, int] | tuple[int, str]
-```
-
-### Custom iterator (2)
-
-```py
-class Iterator:
-    def __next__(self) -> bytes:
-        return b""
-
-class Iterable:
-    def __iter__(self) -> Iterator:
-        return Iterator()
-
-def _(arg: tuple[int, str] | Iterable):
-    a, b = arg
-    reveal_type(a)  # revealed: int | bytes
-    reveal_type(b)  # revealed: str | bytes
-```
-
-## For statement
-
-Unpacking in a `for` statement.
-
-### Same types
-
-```py
-def _(arg: tuple[tuple[int, int], tuple[int, int]]):
-    for a, b in arg:
-        reveal_type(a)  # revealed: int
-        reveal_type(b)  # revealed: int
-```
-
-### Mixed types (1)
-
-```py
-def _(arg: tuple[tuple[int, int], tuple[int, str]]):
-    for a, b in arg:
-        reveal_type(a)  # revealed: int
-        reveal_type(b)  # revealed: int | str
-```
-
-### Mixed types (2)
-
-```py
-def _(arg: tuple[tuple[int, str], tuple[str, int]]):
-    for a, b in arg:
-        reveal_type(a)  # revealed: int | str
-        reveal_type(b)  # revealed: str | int
-```
-
-### Mixed types (3)
-
-```py
-def _(arg: tuple[tuple[int, int, int], tuple[int, str, bytes], tuple[int, int, str]]):
-    for a, b, c in arg:
-        reveal_type(a)  # revealed: int
-        reveal_type(b)  # revealed: int | str
-        reveal_type(c)  # revealed: int | bytes | str
-```
-
-### Same literal values
-
-```py
-for a, b in ((1, 2), (3, 4)):
-    reveal_type(a)  # revealed: Literal[1, 3]
-    reveal_type(b)  # revealed: Literal[2, 4]
-```
-
-### Mixed literal values (1)
-
-```py
-for a, b in ((1, 2), ("a", "b")):
-    reveal_type(a)  # revealed: Literal[1] | Literal["a"]
-    reveal_type(b)  # revealed: Literal[2] | Literal["b"]
-```
-
-### Mixed literals values (2)
-
-```py
-# error: "Object of type `Literal[1]` is not iterable"
-# error: "Object of type `Literal[2]` is not iterable"
-# error: "Object of type `Literal[4]` is not iterable"
-# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
-for a, b in (1, 2, (3, "a"), 4, (5, "b"), "c"):
-    reveal_type(a)  # revealed: Unknown | Literal[3, 5] | LiteralString
-    reveal_type(b)  # revealed: Unknown | Literal["a", "b"]
-```
-
-### Custom iterator (1)
-
-```py
-class Iterator:
-    def __next__(self) -> tuple[int, int]:
-        return (1, 2)
-
-class Iterable:
-    def __iter__(self) -> Iterator:
-        return Iterator()
-
-for a, b in Iterable():
-    reveal_type(a)  # revealed: int
-    reveal_type(b)  # revealed: int
-```
-
-### Custom iterator (2)
-
-```py
-class Iterator:
-    def __next__(self) -> bytes:
-        return b""
-
-class Iterable:
-    def __iter__(self) -> Iterator:
-        return Iterator()
-
-def _(arg: tuple[tuple[int, str], Iterable]):
-    for a, b in arg:
-        reveal_type(a)  # revealed: int | bytes
-        reveal_type(b)  # revealed: str | bytes
-```

crates/red_knot_python_semantic/resources/mdtest/with/async.md

@@ -17,5 +17,5 @@ class Manager:
 
 async def test():
     async with Manager() as f:
-        reveal_type(f)  # revealed: @Todo(async `with` statement)
+        reveal_type(f)  # revealed: @Todo(async with statement)
 ```

crates/red_knot_python_semantic/src/ast_node_ref.rs

@@ -43,7 +43,7 @@ impl<T> AstNodeRef<T> {
     }
 
     /// Returns a reference to the wrapped node.
-    pub const fn node(&self) -> &T {
+    pub fn node(&self) -> &T {
         // SAFETY: Holding on to `parsed` ensures that the AST to which `node` belongs is still
         // alive and not moved.
         unsafe { self.node.as_ref() }

crates/red_knot_python_semantic/src/db.rs

@@ -1,4 +1,4 @@
-use crate::lint::{LintRegistry, RuleSelection};
+use crate::lint::RuleSelection;
 use ruff_db::files::File;
 use ruff_db::{Db as SourceDb, Upcast};
 
@@ -8,8 +8,6 @@ pub trait Db: SourceDb + Upcast<dyn SourceDb> {
     fn is_file_open(&self, file: File) -> bool;
 
     fn rule_selection(&self) -> &RuleSelection;
-
-    fn lint_registry(&self) -> &LintRegistry;
 }
 
 #[cfg(test)]
@@ -18,10 +16,10 @@ pub(crate) mod tests {
 
     use crate::program::{Program, SearchPathSettings};
     use crate::python_version::PythonVersion;
-    use crate::{default_lint_registry, ProgramSettings, PythonPlatform};
+    use crate::{default_lint_registry, ProgramSettings};
 
     use super::Db;
-    use crate::lint::{LintRegistry, RuleSelection};
+    use crate::lint::RuleSelection;
     use anyhow::Context;
     use ruff_db::files::{File, Files};
     use ruff_db::system::{DbWithTestSystem, System, SystemPathBuf, TestSystem};
@@ -29,7 +27,6 @@ pub(crate) mod tests {
     use ruff_db::{Db as SourceDb, Upcast};
 
     #[salsa::db]
-    #[derive(Clone)]
     pub(crate) struct TestDb {
         storage: salsa::Storage<Self>,
         files: Files,
@@ -47,7 +44,7 @@ pub(crate) mod tests {
                 vendored: red_knot_vendored::file_system().clone(),
                 events: Arc::default(),
                 files: Files::default(),
-                rule_selection: Arc::new(RuleSelection::from_registry(default_lint_registry())),
+                rule_selection: Arc::new(RuleSelection::from_registry(&default_lint_registry())),
             }
         }
 
@@ -114,10 +111,6 @@ pub(crate) mod tests {
         fn rule_selection(&self) -> &RuleSelection {
             &self.rule_selection
         }
-
-        fn lint_registry(&self) -> &LintRegistry {
-            default_lint_registry()
-        }
     }
 
     #[salsa::db]
@@ -133,8 +126,6 @@ pub(crate) mod tests {
     pub(crate) struct TestDbBuilder<'a> {
         /// Target Python version
         python_version: PythonVersion,
-        /// Target Python platform
-        python_platform: PythonPlatform,
         /// Path to a custom typeshed directory
         custom_typeshed: Option<SystemPathBuf>,
         /// Path and content pairs for files that should be present
@@ -145,7 +136,6 @@ pub(crate) mod tests {
         pub(crate) fn new() -> Self {
             Self {
                 python_version: PythonVersion::default(),
-                python_platform: PythonPlatform::default(),
                 custom_typeshed: None,
                 files: vec![],
             }
@@ -182,7 +172,6 @@ pub(crate) mod tests {
                 &db,
                 &ProgramSettings {
                     python_version: self.python_version,
-                    python_platform: self.python_platform,
                     search_paths,
                 },
             )

crates/red_knot_python_semantic/src/lib.rs

@@ -3,12 +3,10 @@ use std::hash::BuildHasherDefault;
 use rustc_hash::FxHasher;
 
 use crate::lint::{LintRegistry, LintRegistryBuilder};
-use crate::suppression::{INVALID_IGNORE_COMMENT, UNKNOWN_RULE, UNUSED_IGNORE_COMMENT};
 pub use db::Db;
 pub use module_name::ModuleName;
-pub use module_resolver::{resolve_module, system_module_search_paths, KnownModule, Module};
+pub use module_resolver::{resolve_module, system_module_search_paths, Module};
 pub use program::{Program, ProgramSettings, SearchPathSettings, SitePackages};
-pub use python_platform::PythonPlatform;
 pub use python_version::PythonVersion;
 pub use semantic_model::{HasTy, SemanticModel};
 
@@ -19,36 +17,26 @@ mod module_name;
 mod module_resolver;
 mod node_key;
 mod program;
-mod python_platform;
 mod python_version;
 pub mod semantic_index;
 mod semantic_model;
 pub(crate) mod site_packages;
 mod stdlib;
-mod suppression;
 pub(crate) mod symbol;
 pub mod types;
 mod unpack;
 mod util;
-mod visibility_constraints;
 
 type FxOrderSet<V> = ordermap::set::OrderSet<V, BuildHasherDefault<FxHasher>>;
 
-/// Returns the default registry with all known semantic lints.
-pub fn default_lint_registry() -> &'static LintRegistry {
-    static REGISTRY: std::sync::LazyLock<LintRegistry> = std::sync::LazyLock::new(|| {
-        let mut registry = LintRegistryBuilder::default();
-        register_lints(&mut registry);
-        registry.build()
-    });
-
-    &REGISTRY
+/// Creates a new registry with all known semantic lints.
+pub fn default_lint_registry() -> LintRegistry {
+    let mut registry = LintRegistryBuilder::default();
+    register_lints(&mut registry);
+    registry.build()
 }
 
 /// Register all known semantic lints.
 pub fn register_lints(registry: &mut LintRegistryBuilder) {
     types::register_lints(registry);
-    registry.register_lint(&UNUSED_IGNORE_COMMENT);
-    registry.register_lint(&UNKNOWN_RULE);
-    registry.register_lint(&INVALID_IGNORE_COMMENT);
 }

crates/red_knot_python_semantic/src/lint.rs

@@ -321,7 +321,7 @@ impl LintRegistryBuilder {
     }
 }
 
-#[derive(Default, Debug, Clone)]
+#[derive(Default, Debug)]
 pub struct LintRegistry {
     lints: Vec<LintId>,
     by_name: FxHashMap<&'static str, LintEntry>,
@@ -374,7 +374,7 @@ impl LintRegistry {
     }
 }
 
-#[derive(Error, Debug, Clone, PartialEq, Eq)]
+#[derive(Error, Debug, Clone)]
 pub enum GetLintError {
     /// The name maps to this removed lint.
     #[error("lint {0} has been removed")]
@@ -385,7 +385,7 @@ pub enum GetLintError {
     Unknown(String),
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+#[derive(Debug, PartialEq, Eq)]
 pub enum LintEntry {
     /// An existing lint rule. Can be in preview, stable or deprecated.
     Lint(LintId),
@@ -444,11 +444,6 @@ impl RuleSelection {
         self.lints.get(&lint).copied()
     }
 
-    /// Returns `true` if the `lint` is enabled.
-    pub fn is_enabled(&self, lint: LintId) -> bool {
-        self.severity(lint).is_some()
-    }
-
     /// Enables `lint` and configures with the given `severity`.
     ///
     /// Overrides any previous configuration for the lint.

crates/red_knot_python_semantic/src/module_name.rs

@@ -186,26 +186,6 @@ impl ModuleName {
         self.0.push('.');
         self.0.push_str(other);
     }
-
-    /// Returns an iterator of this module name and all of its parent modules.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use red_knot_python_semantic::ModuleName;
-    ///
-    /// assert_eq!(
-    ///     ModuleName::new_static("foo.bar.baz").unwrap().ancestors().collect::<Vec<_>>(),
-    ///     vec![
-    ///         ModuleName::new_static("foo.bar.baz").unwrap(),
-    ///         ModuleName::new_static("foo.bar").unwrap(),
-    ///         ModuleName::new_static("foo").unwrap(),
-    ///     ],
-    /// );
-    /// ```
-    pub fn ancestors(&self) -> impl Iterator<Item = Self> {
-        std::iter::successors(Some(self.clone()), Self::parent)
-    }
 }
 
 impl Deref for ModuleName {

crates/red_knot_python_semantic/src/module_resolver/mod.rs

@@ -1,6 +1,6 @@
 use std::iter::FusedIterator;
 
-pub use module::{KnownModule, Module};
+pub use module::Module;
 pub use resolver::resolve_module;
 pub(crate) use resolver::{file_to_module, SearchPaths};
 use ruff_db::system::SystemPath;

crates/red_knot_python_semantic/src/module_resolver/module.rs

@@ -7,7 +7,7 @@ use super::path::SearchPath;
 use crate::module_name::ModuleName;
 
 /// Representation of a Python module.
-#[derive(Clone, PartialEq, Eq, Hash)]
+#[derive(Clone, PartialEq, Eq)]
 pub struct Module {
     inner: Arc<ModuleInner>,
 }
@@ -19,14 +19,12 @@ impl Module {
         search_path: SearchPath,
         file: File,
     ) -> Self {
-        let known = KnownModule::try_from_search_path_and_name(&search_path, &name);
         Self {
             inner: Arc::new(ModuleInner {
                 name,
                 kind,
                 search_path,
                 file,
-                known,
             }),
         }
     }
@@ -41,16 +39,6 @@ impl Module {
         self.inner.file
     }
 
-    /// Is this a module that we special-case somehow? If so, which one?
-    pub fn known(&self) -> Option<KnownModule> {
-        self.inner.known
-    }
-
-    /// Does this module represent the given known module?
-    pub fn is_known(&self, known_module: KnownModule) -> bool {
-        self.known() == Some(known_module)
-    }
-
     /// The search path from which the module was resolved.
     pub(crate) fn search_path(&self) -> &SearchPath {
         &self.inner.search_path
@@ -73,13 +61,12 @@ impl std::fmt::Debug for Module {
     }
 }
 
-#[derive(PartialEq, Eq, Hash)]
+#[derive(PartialEq, Eq)]
 struct ModuleInner {
     name: ModuleName,
     kind: ModuleKind,
     search_path: SearchPath,
     file: File,
-    known: Option<KnownModule>,
 }
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
@@ -96,62 +83,3 @@ impl ModuleKind {
         matches!(self, ModuleKind::Package)
     }
 }
-
-/// Enumeration of various core stdlib modules in which important types are located
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub enum KnownModule {
-    Builtins,
-    Types,
-    Typeshed,
-    TypingExtensions,
-    Typing,
-    Sys,
-    #[allow(dead_code)]
-    Abc, // currently only used in tests
-    Collections,
-}
-
-impl KnownModule {
-    pub const fn as_str(self) -> &'static str {
-        match self {
-            Self::Builtins => "builtins",
-            Self::Types => "types",
-            Self::Typing => "typing",
-            Self::Typeshed => "_typeshed",
-            Self::TypingExtensions => "typing_extensions",
-            Self::Sys => "sys",
-            Self::Abc => "abc",
-            Self::Collections => "collections",
-        }
-    }
-
-    pub fn name(self) -> ModuleName {
-        let self_as_str = self.as_str();
-        ModuleName::new_static(self_as_str)
-            .unwrap_or_else(|| panic!("{self_as_str} should be a valid module name!"))
-    }
-
-    pub(crate) fn try_from_search_path_and_name(
-        search_path: &SearchPath,
-        name: &ModuleName,
-    ) -> Option<Self> {
-        if !search_path.is_standard_library() {
-            return None;
-        }
-        match name.as_str() {
-            "builtins" => Some(Self::Builtins),
-            "types" => Some(Self::Types),
-            "typing" => Some(Self::Typing),
-            "_typeshed" => Some(Self::Typeshed),
-            "typing_extensions" => Some(Self::TypingExtensions),
-            "sys" => Some(Self::Sys),
-            "abc" => Some(Self::Abc),
-            "collections" => Some(Self::Collections),
-            _ => None,
-        }
-    }
-
-    pub const fn is_typing(self) -> bool {
-        matches!(self, Self::Typing)
-    }
-}

crates/red_knot_python_semantic/src/module_resolver/resolver.rs

@@ -73,15 +73,6 @@ enum SystemOrVendoredPathRef<'a> {
     Vendored(&'a VendoredPath),
 }
 
-impl std::fmt::Display for SystemOrVendoredPathRef<'_> {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            SystemOrVendoredPathRef::System(system) => system.fmt(f),
-            SystemOrVendoredPathRef::Vendored(vendored) => vendored.fmt(f),
-        }
-    }
-}
-
 /// Resolves the module for the file with the given id.
 ///
 /// Returns `None` if the file is not a module locatable via any of the known search paths.
@@ -721,8 +712,8 @@ mod tests {
     use crate::module_name::ModuleName;
     use crate::module_resolver::module::ModuleKind;
     use crate::module_resolver::testing::{FileSpec, MockedTypeshed, TestCase, TestCaseBuilder};
+    use crate::ProgramSettings;
     use crate::PythonVersion;
-    use crate::{ProgramSettings, PythonPlatform};
 
     use super::*;
 
@@ -1262,7 +1253,7 @@ mod tests {
     fn symlink() -> anyhow::Result<()> {
         use anyhow::Context;
 
-        use crate::{program::Program, PythonPlatform};
+        use crate::program::Program;
         use ruff_db::system::{OsSystem, SystemPath};
 
         use crate::db::tests::TestDb;
@@ -1296,7 +1287,6 @@ mod tests {
             &db,
             &ProgramSettings {
                 python_version: PythonVersion::PY38,
-                python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
                     src_root: src.clone(),
@@ -1802,7 +1792,6 @@ not_a_directory
             &db,
             &ProgramSettings {
                 python_version: PythonVersion::default(),
-                python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
                     src_root: SystemPathBuf::from("/src"),

crates/red_knot_python_semantic/src/module_resolver/testing.rs

@@ -4,7 +4,7 @@ use ruff_db::vendored::VendoredPathBuf;
 use crate::db::tests::TestDb;
 use crate::program::{Program, SearchPathSettings};
 use crate::python_version::PythonVersion;
-use crate::{ProgramSettings, PythonPlatform, SitePackages};
+use crate::{ProgramSettings, SitePackages};
 
 /// A test case for the module resolver.
 ///
@@ -101,7 +101,6 @@ pub(crate) struct UnspecifiedTypeshed;
 pub(crate) struct TestCaseBuilder<T> {
     typeshed_option: T,
     python_version: PythonVersion,
-    python_platform: PythonPlatform,
     first_party_files: Vec<FileSpec>,
     site_packages_files: Vec<FileSpec>,
 }
@@ -148,7 +147,6 @@ impl TestCaseBuilder<UnspecifiedTypeshed> {
         Self {
             typeshed_option: UnspecifiedTypeshed,
             python_version: PythonVersion::default(),
-            python_platform: PythonPlatform::default(),
             first_party_files: vec![],
             site_packages_files: vec![],
         }
@@ -159,14 +157,12 @@ impl TestCaseBuilder<UnspecifiedTypeshed> {
         let TestCaseBuilder {
             typeshed_option: _,
             python_version,
-            python_platform,
             first_party_files,
             site_packages_files,
         } = self;
         TestCaseBuilder {
             typeshed_option: VendoredTypeshed,
             python_version,
-            python_platform,
             first_party_files,
             site_packages_files,
         }
@@ -180,7 +176,6 @@ impl TestCaseBuilder<UnspecifiedTypeshed> {
         let TestCaseBuilder {
             typeshed_option: _,
             python_version,
-            python_platform,
             first_party_files,
             site_packages_files,
         } = self;
@@ -188,7 +183,6 @@ impl TestCaseBuilder<UnspecifiedTypeshed> {
         TestCaseBuilder {
             typeshed_option: typeshed,
             python_version,
-            python_platform,
             first_party_files,
             site_packages_files,
         }
@@ -218,7 +212,6 @@ impl TestCaseBuilder<MockedTypeshed> {
         let TestCaseBuilder {
             typeshed_option,
             python_version,
-            python_platform,
             first_party_files,
             site_packages_files,
         } = self;
@@ -234,7 +227,6 @@ impl TestCaseBuilder<MockedTypeshed> {
             &db,
             &ProgramSettings {
                 python_version,
-                python_platform,
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
                     src_root: src.clone(),
@@ -277,7 +269,6 @@ impl TestCaseBuilder<VendoredTypeshed> {
         let TestCaseBuilder {
             typeshed_option: VendoredTypeshed,
             python_version,
-            python_platform,
             first_party_files,
             site_packages_files,
         } = self;
@@ -292,7 +283,6 @@ impl TestCaseBuilder<VendoredTypeshed> {
             &db,
             &ProgramSettings {
                 python_version,
-                python_platform,
                 search_paths: SearchPathSettings {
                     site_packages: SitePackages::Known(vec![site_packages.clone()]),
                     ..SearchPathSettings::new(src.clone())

crates/red_knot_python_semantic/src/program.rs

@@ -1,4 +1,3 @@
-use crate::python_platform::PythonPlatform;
 use crate::python_version::PythonVersion;
 use anyhow::Context;
 use salsa::Durability;
@@ -13,8 +12,6 @@ use crate::Db;
 pub struct Program {
     pub python_version: PythonVersion,
 
-    pub python_platform: PythonPlatform,
-
     #[return_ref]
     pub(crate) search_paths: SearchPaths,
 }
@@ -23,7 +20,6 @@ impl Program {
     pub fn from_settings(db: &dyn Db, settings: &ProgramSettings) -> anyhow::Result<Self> {
         let ProgramSettings {
             python_version,
-            python_platform,
             search_paths,
         } = settings;
 
@@ -32,11 +28,9 @@ impl Program {
         let search_paths = SearchPaths::from_settings(db, search_paths)
             .with_context(|| "Invalid search path settings")?;
 
-        Ok(
-            Program::builder(*python_version, python_platform.clone(), search_paths)
-                .durability(Durability::HIGH)
-                .new(db),
-        )
+        Ok(Program::builder(settings.python_version, search_paths)
+            .durability(Durability::HIGH)
+            .new(db))
     }
 
     pub fn update_search_paths(
@@ -63,7 +57,6 @@ impl Program {
 #[cfg_attr(feature = "serde", derive(serde::Serialize))]
 pub struct ProgramSettings {
     pub python_version: PythonVersion,
-    pub python_platform: PythonPlatform,
     pub search_paths: SearchPathSettings,
 }
 

crates/red_knot_python_semantic/src/python_platform.rs

@@ -1,19 +0,0 @@
-/// The target platform to assume when resolving types.
-#[derive(Debug, Clone, Default, PartialEq, Eq)]
-#[cfg_attr(
-    feature = "serde",
-    derive(serde::Serialize, serde::Deserialize),
-    serde(rename_all = "kebab-case")
-)]
-pub enum PythonPlatform {
-    /// Do not make any assumptions about the target platform.
-    #[default]
-    All,
-    /// Assume a specific target platform like `linux`, `darwin` or `win32`.
-    ///
-    /// We use a string (instead of individual enum variants), as the set of possible platforms
-    /// may change over time. See <https://docs.python.org/3/library/sys.html#sys.platform> for
-    /// some known platform identifiers.
-    #[cfg_attr(feature = "serde", serde(untagged))]
-    Identifier(String),
-}

crates/red_knot_python_semantic/src/semantic_index.rs

@@ -1,14 +1,13 @@
 use std::iter::FusedIterator;
 use std::sync::Arc;
 
-use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};
+use rustc_hash::{FxBuildHasher, FxHashMap};
 use salsa::plumbing::AsId;
 
 use ruff_db::files::File;
 use ruff_db::parsed::parsed_module;
 use ruff_index::{IndexSlice, IndexVec};
 
-use crate::module_name::ModuleName;
 use crate::semantic_index::ast_ids::node_key::ExpressionNodeKey;
 use crate::semantic_index::ast_ids::AstIds;
 use crate::semantic_index::builder::SemanticIndexBuilder;
@@ -29,8 +28,7 @@ pub mod symbol;
 mod use_def;
 
 pub(crate) use self::use_def::{
-    BindingWithConstraints, BindingWithConstraintsIterator, DeclarationWithConstraint,
-    DeclarationsIterator, ScopedVisibilityConstraintId,
+    BindingWithConstraints, BindingWithConstraintsIterator, DeclarationsIterator,
 };
 
 type SymbolMap = hashbrown::HashMap<ScopedSymbolId, (), FxBuildHasher>;
@@ -62,22 +60,6 @@ pub(crate) fn symbol_table<'db>(db: &'db dyn Db, scope: ScopeId<'db>) -> Arc<Sym
     index.symbol_table(scope.file_scope_id(db))
 }
 
-/// Returns the set of modules that are imported anywhere in `file`.
-///
-/// This set only considers `import` statements, not `from...import` statements, because:
-///
-///   - In `from foo import bar`, we cannot determine whether `foo.bar` is a submodule (and is
-///     therefore imported) without looking outside the content of this file.  (We could turn this
-///     into a _potentially_ imported modules set, but that would change how it's used in our type
-///     inference logic.)
-///
-///   - We cannot resolve relative imports (which aren't allowed in `import` statements) without
-///     knowing the name of the current module, and whether it's a package.
-#[salsa::tracked]
-pub(crate) fn imported_modules<'db>(db: &'db dyn Db, file: File) -> Arc<FxHashSet<ModuleName>> {
-    semantic_index(db, file).imported_modules.clone()
-}
-
 /// Returns the use-def map for a specific `scope`.
 ///
 /// Using [`use_def_map`] over [`semantic_index`] has the advantage that
@@ -134,9 +116,6 @@ pub(crate) struct SemanticIndex<'db> {
     /// changing a file invalidates all dependents.
     ast_ids: IndexVec<FileScopeId, AstIds>,
 
-    /// The set of modules that are imported anywhere within this file.
-    imported_modules: Arc<FxHashSet<ModuleName>>,
-
     /// Flags about the global scope (code usage impacting inference)
     has_future_annotations: bool,
 }
@@ -379,12 +358,14 @@ mod tests {
     impl UseDefMap<'_> {
         fn first_public_binding(&self, symbol: ScopedSymbolId) -> Option<Definition<'_>> {
             self.public_bindings(symbol)
-                .find_map(|constrained_binding| constrained_binding.binding)
+                .next()
+                .map(|constrained_binding| constrained_binding.binding)
         }
 
         fn first_binding_at_use(&self, use_id: ScopedUseId) -> Option<Definition<'_>> {
             self.bindings_at_use(use_id)
-                .find_map(|constrained_binding| constrained_binding.binding)
+                .next()
+                .map(|constrained_binding| constrained_binding.binding)
         }
     }
 

crates/red_knot_python_semantic/src/semantic_index/builder.rs

@@ -1,7 +1,7 @@
 use std::sync::Arc;
 
 use except_handlers::TryNodeContextStackManager;
-use rustc_hash::{FxHashMap, FxHashSet};
+use rustc_hash::FxHashMap;
 
 use ruff_db::files::File;
 use ruff_db::parsed::ParsedModule;
@@ -9,12 +9,11 @@ use ruff_index::IndexVec;
 use ruff_python_ast as ast;
 use ruff_python_ast::name::Name;
 use ruff_python_ast::visitor::{walk_expr, walk_pattern, walk_stmt, Visitor};
+use ruff_python_ast::{BoolOp, Expr};
 
 use crate::ast_node_ref::AstNodeRef;
-use crate::module_name::ModuleName;
 use crate::semantic_index::ast_ids::node_key::ExpressionNodeKey;
 use crate::semantic_index::ast_ids::AstIdsBuilder;
-use crate::semantic_index::constraint::PatternConstraintKind;
 use crate::semantic_index::definition::{
     AssignmentDefinitionNodeRef, ComprehensionDefinitionNodeRef, Definition, DefinitionNodeKey,
     DefinitionNodeRef, ForStmtDefinitionNodeRef, ImportFromDefinitionNodeRef,
@@ -24,12 +23,9 @@ use crate::semantic_index::symbol::{
     FileScopeId, NodeWithScopeKey, NodeWithScopeRef, Scope, ScopeId, ScopedSymbolId,
     SymbolTableBuilder,
 };
-use crate::semantic_index::use_def::{
-    FlowSnapshot, ScopedConstraintId, ScopedVisibilityConstraintId, UseDefMapBuilder,
-};
+use crate::semantic_index::use_def::{FlowSnapshot, UseDefMapBuilder};
 use crate::semantic_index::SemanticIndex;
-use crate::unpack::{Unpack, UnpackValue};
-use crate::visibility_constraints::VisibilityConstraint;
+use crate::unpack::Unpack;
 use crate::Db;
 
 use super::constraint::{Constraint, ConstraintNode, PatternConstraint};
@@ -83,7 +79,6 @@ pub(super) struct SemanticIndexBuilder<'db> {
     scopes_by_expression: FxHashMap<ExpressionNodeKey, FileScopeId>,
     definitions_by_node: FxHashMap<DefinitionNodeKey, Definition<'db>>,
     expressions_by_node: FxHashMap<ExpressionNodeKey, Expression<'db>>,
-    imported_modules: FxHashSet<ModuleName>,
 }
 
 impl<'db> SemanticIndexBuilder<'db> {
@@ -110,8 +105,6 @@ impl<'db> SemanticIndexBuilder<'db> {
             scopes_by_node: FxHashMap::default(),
             definitions_by_node: FxHashMap::default(),
             expressions_by_node: FxHashMap::default(),
-
-            imported_modules: FxHashSet::default(),
         };
 
         builder.push_scope_with_parent(NodeWithScopeRef::Module, None);
@@ -212,7 +205,11 @@ impl<'db> SemanticIndexBuilder<'db> {
     }
 
     fn flow_merge(&mut self, state: FlowSnapshot) {
-        self.current_use_def_map_mut().merge(state);
+        self.current_use_def_map_mut().merge(state, false);
+    }
+
+    fn flow_merge_no_declarations(&mut self, state: FlowSnapshot) {
+        self.current_use_def_map_mut().merge(state, true);
     }
 
     fn add_symbol(&mut self, name: Name) -> ScopedSymbolId {
@@ -288,7 +285,11 @@ impl<'db> SemanticIndexBuilder<'db> {
         constraint
     }
 
-    fn build_constraint(&mut self, constraint_node: &ast::Expr) -> Constraint<'db> {
+    fn record_constraint(&mut self, constraint: Constraint<'db>) {
+        self.current_use_def_map_mut().record_constraint(constraint);
+    }
+
+    fn build_constraint(&mut self, constraint_node: &Expr) -> Constraint<'db> {
         let expression = self.add_standalone_expression(constraint_node);
         Constraint {
             node: ConstraintNode::Expression(expression),
@@ -296,89 +297,12 @@ impl<'db> SemanticIndexBuilder<'db> {
         }
     }
 
-    /// Adds a new constraint to the list of all constraints, but does not record it. Returns the
-    /// constraint ID for later recording using [`SemanticIndexBuilder::record_constraint_id`].
-    fn add_constraint(&mut self, constraint: Constraint<'db>) -> ScopedConstraintId {
-        self.current_use_def_map_mut().add_constraint(constraint)
-    }
-
-    /// Negates a constraint and adds it to the list of all constraints, does not record it.
-    fn add_negated_constraint(
-        &mut self,
-        constraint: Constraint<'db>,
-    ) -> (Constraint<'db>, ScopedConstraintId) {
-        let negated = Constraint {
-            node: constraint.node,
-            is_positive: false,
-        };
-        let id = self.current_use_def_map_mut().add_constraint(negated);
-        (negated, id)
-    }
-
-    /// Records a previously added constraint by adding it to all live bindings.
-    fn record_constraint_id(&mut self, constraint: ScopedConstraintId) {
+    fn record_negated_constraint(&mut self, constraint: Constraint<'db>) {
         self.current_use_def_map_mut()
-            .record_constraint_id(constraint);
-    }
-
-    /// Adds and records a constraint, i.e. adds it to all live bindings.
-    fn record_constraint(&mut self, constraint: Constraint<'db>) {
-        self.current_use_def_map_mut().record_constraint(constraint);
-    }
-
-    /// Negates the given constraint and then adds it to all live bindings.
-    fn record_negated_constraint(&mut self, constraint: Constraint<'db>) -> ScopedConstraintId {
-        let (_, id) = self.add_negated_constraint(constraint);
-        self.record_constraint_id(id);
-        id
-    }
-
-    /// Adds a new visibility constraint, but does not record it. Returns the constraint ID
-    /// for later recording using [`SemanticIndexBuilder::record_visibility_constraint_id`].
-    fn add_visibility_constraint(
-        &mut self,
-        constraint: VisibilityConstraint<'db>,
-    ) -> ScopedVisibilityConstraintId {
-        self.current_use_def_map_mut()
-            .add_visibility_constraint(constraint)
-    }
-
-    /// Records a previously added visibility constraint by applying it to all live bindings
-    /// and declarations.
-    fn record_visibility_constraint_id(&mut self, constraint: ScopedVisibilityConstraintId) {
-        self.current_use_def_map_mut()
-            .record_visibility_constraint_id(constraint);
-    }
-
-    /// Negates the given visibility constraint and then adds it to all live bindings and declarations.
-    fn record_negated_visibility_constraint(
-        &mut self,
-        constraint: ScopedVisibilityConstraintId,
-    ) -> ScopedVisibilityConstraintId {
-        self.current_use_def_map_mut()
-            .record_visibility_constraint(VisibilityConstraint::VisibleIfNot(constraint))
-    }
-
-    /// Records a visibility constraint by applying it to all live bindings and declarations.
-    fn record_visibility_constraint(
-        &mut self,
-        constraint: Constraint<'db>,
-    ) -> ScopedVisibilityConstraintId {
-        self.current_use_def_map_mut()
-            .record_visibility_constraint(VisibilityConstraint::VisibleIf(constraint))
-    }
-
-    /// Records a [`VisibilityConstraint::Ambiguous`] constraint.
-    fn record_ambiguous_visibility(&mut self) -> ScopedVisibilityConstraintId {
-        self.current_use_def_map_mut()
-            .record_visibility_constraint(VisibilityConstraint::Ambiguous)
-    }
-
-    /// Simplifies (resets) visibility constraints on all live bindings and declarations that did
-    /// not see any new definitions since the given snapshot.
-    fn simplify_visibility_constraints(&mut self, snapshot: FlowSnapshot) {
-        self.current_use_def_map_mut()
-            .simplify_visibility_constraints(snapshot);
+            .record_constraint(Constraint {
+                node: constraint.node,
+                is_positive: false,
+            });
     }
 
     fn push_assignment(&mut self, assignment: CurrentAssignment<'db>) {
@@ -400,37 +324,30 @@ impl<'db> SemanticIndexBuilder<'db> {
 
     fn add_pattern_constraint(
         &mut self,
-        subject: Expression<'db>,
+        subject: &ast::Expr,
         pattern: &ast::Pattern,
-        guard: Option<&ast::Expr>,
-    ) -> Constraint<'db> {
-        let guard = guard.map(|guard| self.add_standalone_expression(guard));
-
-        let kind = match pattern {
-            ast::Pattern::MatchValue(pattern) => {
-                let value = self.add_standalone_expression(&pattern.value);
-                PatternConstraintKind::Value(value, guard)
-            }
-            ast::Pattern::MatchSingleton(singleton) => {
-                PatternConstraintKind::Singleton(singleton.value, guard)
-            }
-            _ => PatternConstraintKind::Unsupported,
+    ) -> PatternConstraint<'db> {
+        #[allow(unsafe_code)]
+        let (subject, pattern) = unsafe {
+            (
+                AstNodeRef::new(self.module.clone(), subject),
+                AstNodeRef::new(self.module.clone(), pattern),
+            )
         };
-
         let pattern_constraint = PatternConstraint::new(
             self.db,
             self.file,
             self.current_scope(),
             subject,
-            kind,
+            pattern,
             countme::Count::default(),
         );
-        let constraint = Constraint {
-            node: ConstraintNode::Pattern(pattern_constraint),
-            is_positive: true,
-        };
-        self.current_use_def_map_mut().record_constraint(constraint);
-        constraint
+        self.current_use_def_map_mut()
+            .record_constraint(Constraint {
+                node: ConstraintNode::Pattern(pattern_constraint),
+                is_positive: true,
+            });
+        pattern_constraint
     }
 
     /// Record an expression that needs to be a Salsa ingredient, because we need to infer its type
@@ -645,7 +562,6 @@ impl<'db> SemanticIndexBuilder<'db> {
             scopes_by_expression: self.scopes_by_expression,
             scopes_by_node: self.scopes_by_node,
             use_def_maps,
-            imported_modules: Arc::new(self.imported_modules),
             has_future_annotations: self.has_future_annotations,
         }
     }
@@ -749,12 +665,6 @@ where
             }
             ast::Stmt::Import(node) => {
                 for alias in &node.names {
-                    // Mark the imported module, and all of its parents, as being imported in this
-                    // file.
-                    if let Some(module_name) = ModuleName::new(&alias.name) {
-                        self.imported_modules.extend(module_name.ancestors());
-                    }
-
                     let symbol_name = if let Some(asname) = &alias.asname {
                         asname.id.clone()
                     } else {
@@ -809,7 +719,7 @@ where
                                     unsafe {
                                         AstNodeRef::new(self.module.clone(), target)
                                     },
-                                    UnpackValue::Assign(value),
+                                    value,
                                     countme::Count::default(),
                                 )),
                             })
@@ -882,10 +792,6 @@ where
                 let constraint = self.record_expression_constraint(&node.test);
                 let mut constraints = vec![constraint];
                 self.visit_body(&node.body);
-
-                let visibility_constraint_id = self.record_visibility_constraint(constraint);
-                let mut vis_constraints = vec![visibility_constraint_id];
-
                 let mut post_clauses: Vec<FlowSnapshot> = vec![];
                 let elif_else_clauses = node
                     .elif_else_clauses
@@ -912,31 +818,15 @@ where
                     for constraint in &constraints {
                         self.record_negated_constraint(*constraint);
                     }
-
-                    let elif_constraint = if let Some(elif_test) = clause_test {
+                    if let Some(elif_test) = clause_test {
                         self.visit_expr(elif_test);
-                        let constraint = self.record_expression_constraint(elif_test);
-                        constraints.push(constraint);
-                        Some(constraint)
-                    } else {
-                        None
-                    };
+                        constraints.push(self.record_expression_constraint(elif_test));
+                    }
                     self.visit_body(clause_body);
-
-                    for id in &vis_constraints {
-                        self.record_negated_visibility_constraint(*id);
-                    }
-                    if let Some(elif_constraint) = elif_constraint {
-                        let id = self.record_visibility_constraint(elif_constraint);
-                        vis_constraints.push(id);
-                    }
                 }
-
                 for post_clause_state in post_clauses {
                     self.flow_merge(post_clause_state);
                 }
-
-                self.simplify_visibility_constraints(pre_if);
             }
             ast::Stmt::While(ast::StmtWhile {
                 test,
@@ -959,8 +849,6 @@ where
                 self.visit_body(body);
                 self.set_inside_loop(outer_loop_state);
 
-                let vis_constraint_id = self.record_visibility_constraint(constraint);
-
                 // Get the break states from the body of this loop, and restore the saved outer
                 // ones.
                 let break_states =
@@ -968,21 +856,15 @@ where
 
                 // We may execute the `else` clause without ever executing the body, so merge in
                 // the pre-loop state before visiting `else`.
-                self.flow_merge(pre_loop.clone());
+                self.flow_merge(pre_loop);
                 self.record_negated_constraint(constraint);
                 self.visit_body(orelse);
-                self.record_negated_visibility_constraint(vis_constraint_id);
 
                 // Breaking out of a while loop bypasses the `else` clause, so merge in the break
                 // states after visiting `else`.
                 for break_state in break_states {
-                    let snapshot = self.flow_snapshot();
-                    self.flow_restore(break_state);
-                    self.record_visibility_constraint(constraint);
-                    self.flow_merge(snapshot);
+                    self.flow_merge(break_state);
                 }
-
-                self.simplify_visibility_constraints(pre_loop);
             }
             ast::Stmt::With(ast::StmtWith {
                 items,
@@ -1020,47 +902,16 @@ where
                     orelse,
                 },
             ) => {
-                debug_assert_eq!(&self.current_assignments, &[]);
-
-                let iter_expr = self.add_standalone_expression(iter);
+                self.add_standalone_expression(iter);
                 self.visit_expr(iter);
 
-                self.record_ambiguous_visibility();
-
                 let pre_loop = self.flow_snapshot();
                 let saved_break_states = std::mem::take(&mut self.loop_break_states);
 
-                let current_assignment = match &**target {
-                    ast::Expr::List(_) | ast::Expr::Tuple(_) => Some(CurrentAssignment::For {
-                        node: for_stmt,
-                        first: true,
-                        unpack: Some(Unpack::new(
-                            self.db,
-                            self.file,
-                            self.current_scope(),
-                            #[allow(unsafe_code)]
-                            unsafe {
-                                AstNodeRef::new(self.module.clone(), target)
-                            },
-                            UnpackValue::Iterable(iter_expr),
-                            countme::Count::default(),
-                        )),
-                    }),
-                    ast::Expr::Name(_) => Some(CurrentAssignment::For {
-                        node: for_stmt,
-                        unpack: None,
-                        first: false,
-                    }),
-                    _ => None,
-                };
-
-                if let Some(current_assignment) = current_assignment {
-                    self.push_assignment(current_assignment);
-                }
+                debug_assert_eq!(&self.current_assignments, &[]);
+                self.push_assignment(for_stmt.into());
                 self.visit_expr(target);
-                if current_assignment.is_some() {
-                    self.pop_assignment();
-                }
+                self.pop_assignment();
 
                 // TODO: Definitions created by loop variables
                 // (and definitions created inside the body)
@@ -1089,63 +940,32 @@ where
                 cases,
                 range: _,
             }) => {
-                let subject_expr = self.add_standalone_expression(subject);
+                self.add_standalone_expression(subject);
                 self.visit_expr(subject);
 
                 let after_subject = self.flow_snapshot();
                 let Some((first, remaining)) = cases.split_first() else {
                     return;
                 };
-
-                let first_constraint_id = self.add_pattern_constraint(
-                    subject_expr,
-                    &first.pattern,
-                    first.guard.as_deref(),
-                );
-
+                self.add_pattern_constraint(subject, &first.pattern);
                 self.visit_match_case(first);
 
-                let first_vis_constraint_id =
-                    self.record_visibility_constraint(first_constraint_id);
-                let mut vis_constraints = vec![first_vis_constraint_id];
-
                 let mut post_case_snapshots = vec![];
                 for case in remaining {
                     post_case_snapshots.push(self.flow_snapshot());
                     self.flow_restore(after_subject.clone());
-                    let constraint_id = self.add_pattern_constraint(
-                        subject_expr,
-                        &case.pattern,
-                        case.guard.as_deref(),
-                    );
+                    self.add_pattern_constraint(subject, &case.pattern);
                     self.visit_match_case(case);
-
-                    for id in &vis_constraints {
-                        self.record_negated_visibility_constraint(*id);
-                    }
-                    let vis_constraint_id = self.record_visibility_constraint(constraint_id);
-                    vis_constraints.push(vis_constraint_id);
                 }
-
-                // If there is no final wildcard match case, pretend there is one. This is similar to how
-                // we add an implicit `else` block in if-elif chains, in case it's not present.
+                for post_clause_state in post_case_snapshots {
+                    self.flow_merge(post_clause_state);
+                }
                 if !cases
                     .last()
                     .is_some_and(|case| case.guard.is_none() && case.pattern.is_wildcard())
                 {
-                    post_case_snapshots.push(self.flow_snapshot());
-                    self.flow_restore(after_subject.clone());
-
-                    for id in &vis_constraints {
-                        self.record_negated_visibility_constraint(*id);
-                    }
+                    self.flow_merge(after_subject);
                 }
-
-                for post_clause_state in post_case_snapshots {
-                    self.flow_merge(post_clause_state);
-                }
-
-                self.simplify_visibility_constraints(after_subject);
             }
             ast::Stmt::Try(ast::StmtTry {
                 body,
@@ -1155,8 +975,6 @@ where
                 is_star,
                 range: _,
             }) => {
-                self.record_ambiguous_visibility();
-
                 // Save the state prior to visiting any of the `try` block.
                 //
                 // Potentially none of the `try` block could have been executed prior to executing
@@ -1188,7 +1006,7 @@ where
                     // Prepare for visiting the `except` block(s)
                     self.flow_restore(pre_try_block_state);
                     for state in try_block_snapshots {
-                        self.flow_merge(state);
+                        self.flow_merge_no_declarations(state);
                     }
 
                     let pre_except_state = self.flow_snapshot();
@@ -1311,18 +1129,12 @@ where
                         Some(CurrentAssignment::AugAssign(aug_assign)) => {
                             self.add_definition(symbol, aug_assign);
                         }
-                        Some(CurrentAssignment::For {
-                            node,
-                            first,
-                            unpack,
-                        }) => {
+                        Some(CurrentAssignment::For(node)) => {
                             self.add_definition(
                                 symbol,
                                 ForStmtDefinitionNodeRef {
-                                    unpack,
-                                    first,
                                     iterable: &node.iter,
-                                    name: name_node,
+                                    target: name_node,
                                     is_async: node.is_async,
                                 },
                             );
@@ -1358,9 +1170,7 @@ where
                     }
                 }
 
-                if let Some(
-                    CurrentAssignment::Assign { first, .. } | CurrentAssignment::For { first, .. },
-                ) = self.current_assignment_mut()
+                if let Some(CurrentAssignment::Assign { first, .. }) = self.current_assignment_mut()
                 {
                     *first = false;
                 }
@@ -1405,19 +1215,19 @@ where
             ast::Expr::If(ast::ExprIf {
                 body, test, orelse, ..
             }) => {
+                // TODO detect statically known truthy or falsy test (via type inference, not naive
+                // AST inspection, so we can't simplify here, need to record test expression for
+                // later checking)
                 self.visit_expr(test);
                 let pre_if = self.flow_snapshot();
                 let constraint = self.record_expression_constraint(test);
                 self.visit_expr(body);
-                let visibility_constraint = self.record_visibility_constraint(constraint);
                 let post_body = self.flow_snapshot();
-                self.flow_restore(pre_if.clone());
+                self.flow_restore(pre_if);
 
                 self.record_negated_constraint(constraint);
                 self.visit_expr(orelse);
-                self.record_negated_visibility_constraint(visibility_constraint);
                 self.flow_merge(post_body);
-                self.simplify_visibility_constraints(pre_if);
             }
             ast::Expr::ListComp(
                 list_comprehension @ ast::ExprListComp {
@@ -1474,55 +1284,27 @@ where
                 range: _,
                 op,
             }) => {
-                let pre_op = self.flow_snapshot();
-
+                // TODO detect statically known truthy or falsy values (via type inference, not naive
+                // AST inspection, so we can't simplify here, need to record test expression for
+                // later checking)
                 let mut snapshots = vec![];
-                let mut visibility_constraints = vec![];
 
                 for (index, value) in values.iter().enumerate() {
                     self.visit_expr(value);
-
-                    for vid in &visibility_constraints {
-                        self.record_visibility_constraint_id(*vid);
-                    }
-
-                    // For the last value, we don't need to model control flow. There is short-circuiting
-                    // anymore.
+                    // In the last value we don't need to take a snapshot nor add a constraint
                     if index < values.len() - 1 {
-                        let constraint = self.build_constraint(value);
-                        let (constraint, constraint_id) = match op {
-                            ast::BoolOp::And => (constraint, self.add_constraint(constraint)),
-                            ast::BoolOp::Or => self.add_negated_constraint(constraint),
-                        };
-                        let visibility_constraint = self
-                            .add_visibility_constraint(VisibilityConstraint::VisibleIf(constraint));
-
-                        let after_expr = self.flow_snapshot();
-
-                        // We first model the short-circuiting behavior. We take the short-circuit
-                        // path here if all of the previous short-circuit paths were not taken, so
-                        // we record all previously existing visibility constraints, and negate the
-                        // one for the current expression.
-                        for vid in &visibility_constraints {
-                            self.record_visibility_constraint_id(*vid);
-                        }
-                        self.record_negated_visibility_constraint(visibility_constraint);
+                        // Snapshot is taken after visiting the expression but before adding the constraint.
                         snapshots.push(self.flow_snapshot());
-
-                        // Then we model the non-short-circuiting behavior. Here, we need to delay
-                        // the application of the visibility constraint until after the expression
-                        // has been evaluated, so we only push it onto the stack here.
-                        self.flow_restore(after_expr);
-                        self.record_constraint_id(constraint_id);
-                        visibility_constraints.push(visibility_constraint);
+                        let constraint = self.build_constraint(value);
+                        match op {
+                            BoolOp::And => self.record_constraint(constraint),
+                            BoolOp::Or => self.record_negated_constraint(constraint),
+                        }
                     }
                 }
-
                 for snapshot in snapshots {
                     self.flow_merge(snapshot);
                 }
-
-                self.simplify_visibility_constraints(pre_op);
             }
             _ => {
                 walk_expr(self, expr);
@@ -1602,11 +1384,7 @@ enum CurrentAssignment<'a> {
     },
     AnnAssign(&'a ast::StmtAnnAssign),
     AugAssign(&'a ast::StmtAugAssign),
-    For {
-        node: &'a ast::StmtFor,
-        first: bool,
-        unpack: Option<Unpack<'a>>,
-    },
+    For(&'a ast::StmtFor),
     Named(&'a ast::ExprNamed),
     Comprehension {
         node: &'a ast::Comprehension,
@@ -1630,6 +1408,12 @@ impl<'a> From<&'a ast::StmtAugAssign> for CurrentAssignment<'a> {
     }
 }
 
+impl<'a> From<&'a ast::StmtFor> for CurrentAssignment<'a> {
+    fn from(value: &'a ast::StmtFor) -> Self {
+        Self::For(value)
+    }
+}
+
 impl<'a> From<&'a ast::ExprNamed> for CurrentAssignment<'a> {
     fn from(value: &'a ast::ExprNamed) -> Self {
         Self::Named(value)

crates/red_knot_python_semantic/src/semantic_index/constraint.rs

@@ -1,6 +1,7 @@
 use ruff_db::files::File;
-use ruff_python_ast::Singleton;
+use ruff_python_ast as ast;
 
+use crate::ast_node_ref::AstNodeRef;
 use crate::db::Db;
 use crate::semantic_index::expression::Expression;
 use crate::semantic_index::symbol::{FileScopeId, ScopeId};
@@ -17,14 +18,6 @@ pub(crate) enum ConstraintNode<'db> {
     Pattern(PatternConstraint<'db>),
 }
 
-/// Pattern kinds for which we support type narrowing and/or static visibility analysis.
-#[derive(Debug, Clone, PartialEq)]
-pub(crate) enum PatternConstraintKind<'db> {
-    Singleton(Singleton, Option<Expression<'db>>),
-    Value(Expression<'db>, Option<Expression<'db>>),
-    Unsupported,
-}
-
 #[salsa::tracked]
 pub(crate) struct PatternConstraint<'db> {
     #[id]
@@ -35,11 +28,11 @@ pub(crate) struct PatternConstraint<'db> {
 
     #[no_eq]
     #[return_ref]
-    pub(crate) subject: Expression<'db>,
+    pub(crate) subject: AstNodeRef<ast::Expr>,
 
     #[no_eq]
     #[return_ref]
-    pub(crate) kind: PatternConstraintKind<'db>,
+    pub(crate) pattern: AstNodeRef<ast::Pattern>,
 
     #[no_eq]
     count: countme::Count<PatternConstraint<'static>>,

crates/red_knot_python_semantic/src/semantic_index/definition.rs

@@ -1,14 +1,13 @@
 use ruff_db::files::File;
 use ruff_db::parsed::ParsedModule;
 use ruff_python_ast as ast;
-use ruff_text_size::{Ranged, TextRange};
 
 use crate::ast_node_ref::AstNodeRef;
 use crate::module_resolver::file_to_module;
 use crate::node_key::NodeKey;
 use crate::semantic_index::symbol::{FileScopeId, ScopeId, ScopedSymbolId};
 use crate::unpack::Unpack;
-use crate::{Db, KnownModule};
+use crate::Db;
 
 /// A definition of a symbol.
 ///
@@ -63,16 +62,17 @@ impl<'db> Definition<'db> {
     }
 
     pub(crate) fn is_builtin_definition(self, db: &'db dyn Db) -> bool {
-        file_to_module(db, self.file(db))
-            .is_some_and(|module| module.is_known(KnownModule::Builtins))
+        file_to_module(db, self.file(db)).is_some_and(|module| {
+            module.search_path().is_standard_library() && matches!(&**module.name(), "builtins")
+        })
     }
 
     /// Return true if this symbol was defined in the `typing` or `typing_extensions` modules
     pub(crate) fn is_typing_definition(self, db: &'db dyn Db) -> bool {
-        matches!(
-            file_to_module(db, self.file(db)).and_then(|module| module.known()),
-            Some(KnownModule::Typing | KnownModule::TypingExtensions)
-        )
+        file_to_module(db, self.file(db)).is_some_and(|module| {
+            module.search_path().is_standard_library()
+                && matches!(&**module.name(), "typing" | "typing_extensions")
+        })
     }
 }
 
@@ -225,10 +225,8 @@ pub(crate) struct WithItemDefinitionNodeRef<'a> {
 
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct ForStmtDefinitionNodeRef<'a> {
-    pub(crate) unpack: Option<Unpack<'a>>,
     pub(crate) iterable: &'a ast::Expr,
-    pub(crate) name: &'a ast::ExprName,
-    pub(crate) first: bool,
+    pub(crate) target: &'a ast::ExprName,
     pub(crate) is_async: bool,
 }
 
@@ -300,16 +298,12 @@ impl<'db> DefinitionNodeRef<'db> {
                 DefinitionKind::AugmentedAssignment(AstNodeRef::new(parsed, augmented_assignment))
             }
             DefinitionNodeRef::For(ForStmtDefinitionNodeRef {
-                unpack,
                 iterable,
-                name,
-                first,
+                target,
                 is_async,
             }) => DefinitionKind::For(ForStmtDefinitionKind {
-                target: TargetKind::from(unpack),
                 iterable: AstNodeRef::new(parsed.clone(), iterable),
-                name: AstNodeRef::new(parsed, name),
-                first,
+                target: AstNodeRef::new(parsed, target),
                 is_async,
             }),
             DefinitionNodeRef::Comprehension(ComprehensionDefinitionNodeRef {
@@ -388,12 +382,10 @@ impl<'db> DefinitionNodeRef<'db> {
             Self::AnnotatedAssignment(node) => node.into(),
             Self::AugmentedAssignment(node) => node.into(),
             Self::For(ForStmtDefinitionNodeRef {
-                unpack: _,
                 iterable: _,
-                name,
-                first: _,
+                target,
                 is_async: _,
-            }) => name.into(),
+            }) => target.into(),
             Self::Comprehension(ComprehensionDefinitionNodeRef { target, .. }) => target.into(),
             Self::VariadicPositionalParameter(node) => node.into(),
             Self::VariadicKeywordParameter(node) => node.into(),
@@ -460,7 +452,7 @@ pub enum DefinitionKind<'db> {
     Assignment(AssignmentDefinitionKind<'db>),
     AnnotatedAssignment(AstNodeRef<ast::StmtAnnAssign>),
     AugmentedAssignment(AstNodeRef<ast::StmtAugAssign>),
-    For(ForStmtDefinitionKind<'db>),
+    For(ForStmtDefinitionKind),
     Comprehension(ComprehensionDefinitionKind),
     VariadicPositionalParameter(AstNodeRef<ast::Parameter>),
     VariadicKeywordParameter(AstNodeRef<ast::Parameter>),
@@ -474,37 +466,6 @@ pub enum DefinitionKind<'db> {
 }
 
 impl DefinitionKind<'_> {
-    /// Returns the [`TextRange`] of the definition target.
-    ///
-    /// A definition target would mainly be the node representing the symbol being defined i.e.,
-    /// [`ast::ExprName`] or [`ast::Identifier`] but could also be other nodes.
-    ///
-    /// This is mainly used for logging and debugging purposes.
-    pub(crate) fn target_range(&self) -> TextRange {
-        match self {
-            DefinitionKind::Import(alias) => alias.range(),
-            DefinitionKind::ImportFrom(import) => import.alias().range(),
-            DefinitionKind::Function(function) => function.name.range(),
-            DefinitionKind::Class(class) => class.name.range(),
-            DefinitionKind::TypeAlias(type_alias) => type_alias.name.range(),
-            DefinitionKind::NamedExpression(named) => named.target.range(),
-            DefinitionKind::Assignment(assignment) => assignment.name().range(),
-            DefinitionKind::AnnotatedAssignment(assign) => assign.target.range(),
-            DefinitionKind::AugmentedAssignment(aug_assign) => aug_assign.target.range(),
-            DefinitionKind::For(for_stmt) => for_stmt.name().range(),
-            DefinitionKind::Comprehension(comp) => comp.target().range(),
-            DefinitionKind::VariadicPositionalParameter(parameter) => parameter.name.range(),
-            DefinitionKind::VariadicKeywordParameter(parameter) => parameter.name.range(),
-            DefinitionKind::Parameter(parameter) => parameter.parameter.name.range(),
-            DefinitionKind::WithItem(with_item) => with_item.target().range(),
-            DefinitionKind::MatchPattern(match_pattern) => match_pattern.identifier.range(),
-            DefinitionKind::ExceptHandler(handler) => handler.node().range(),
-            DefinitionKind::TypeVar(type_var) => type_var.name.range(),
-            DefinitionKind::ParamSpec(param_spec) => param_spec.name.range(),
-            DefinitionKind::TypeVarTuple(type_var_tuple) => type_var_tuple.name.range(),
-        }
-    }
-
     pub(crate) fn category(&self) -> DefinitionCategory {
         match self {
             // functions, classes, and imports always bind, and we consider them declarations
@@ -677,32 +638,22 @@ impl WithItemDefinitionKind {
 }
 
 #[derive(Clone, Debug)]
-pub struct ForStmtDefinitionKind<'db> {
-    target: TargetKind<'db>,
+pub struct ForStmtDefinitionKind {
     iterable: AstNodeRef<ast::Expr>,
-    name: AstNodeRef<ast::ExprName>,
-    first: bool,
+    target: AstNodeRef<ast::ExprName>,
     is_async: bool,
 }
 
-impl<'db> ForStmtDefinitionKind<'db> {
+impl ForStmtDefinitionKind {
     pub(crate) fn iterable(&self) -> &ast::Expr {
         self.iterable.node()
     }
 
-    pub(crate) fn target(&self) -> TargetKind<'db> {
-        self.target
+    pub(crate) fn target(&self) -> &ast::ExprName {
+        self.target.node()
     }
 
-    pub(crate) fn name(&self) -> &ast::ExprName {
-        self.name.node()
-    }
-
-    pub(crate) const fn is_first(&self) -> bool {
-        self.first
-    }
-
-    pub(crate) const fn is_async(&self) -> bool {
+    pub(crate) fn is_async(&self) -> bool {
         self.is_async
     }
 }
@@ -778,6 +729,12 @@ impl From<&ast::StmtAugAssign> for DefinitionNodeKey {
     }
 }
 
+impl From<&ast::StmtFor> for DefinitionNodeKey {
+    fn from(value: &ast::StmtFor) -> Self {
+        Self(NodeKey::from_node(value))
+    }
+}
+
 impl From<&ast::Parameter> for DefinitionNodeKey {
     fn from(node: &ast::Parameter) -> Self {
         Self(NodeKey::from_node(node))

crates/red_knot_python_semantic/src/semantic_index/symbol.rs

@@ -463,7 +463,10 @@ impl NodeWithScopeKind {
     }
 
     pub fn expect_function(&self) -> &ast::StmtFunctionDef {
-        self.as_function().expect("expected function")
+        match self {
+            Self::Function(function) => function.node(),
+            _ => panic!("expected function"),
+        }
     }
 
     pub fn expect_type_alias(&self) -> &ast::StmtTypeAlias {
@@ -472,13 +475,6 @@ impl NodeWithScopeKind {
             _ => panic!("expected type alias"),
         }
     }
-
-    pub const fn as_function(&self) -> Option<&ast::StmtFunctionDef> {
-        match self {
-            Self::Function(function) => Some(function.node()),
-            _ => None,
-        }
-    }
 }
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]

crates/red_knot_python_semantic/src/semantic_index/use_def.rs

@@ -169,11 +169,17 @@
 //! indexvecs in the [`UseDefMap`].
 //!
 //! There is another special kind of possible "definition" for a symbol: there might be a path from
-//! the scope entry to a given use in which the symbol is never bound. We model this with a special
-//! "unbound" definition (a `None` entry at the start of the `all_definitions` vector). If that
-//! sentinel definition is present in the live bindings at a given use, it means that there is a
-//! possible path through control flow in which that symbol is unbound. Similarly, if that sentinel
-//! is present in the live declarations, it means that the symbol is (possibly) undeclared.
+//! the scope entry to a given use in which the symbol is never bound.
+//!
+//! The simplest way to model "unbound" would be as a "binding" itself: the initial "binding" for
+//! each symbol in a scope. But actually modeling it this way would unnecessarily increase the
+//! number of [`Definition`]s that Salsa must track. Since "unbound" is special in that all symbols
+//! share it, and it doesn't have any additional per-symbol state, and constraints are irrelevant
+//! to it, we can represent it more efficiently: we use the `may_be_unbound` boolean on the
+//! [`SymbolBindings`] struct. If this flag is `true` for a use of a symbol, it means the symbol
+//! has a path to the use in which it is never bound. If this flag is `false`, it means we've
+//! eliminated the possibility of unbound: every control flow path to the use includes a binding
+//! for this symbol.
 //!
 //! To build a [`UseDefMap`], the [`UseDefMapBuilder`] is notified of each new use, definition, and
 //! constraint as they are encountered by the
@@ -184,13 +190,11 @@
 //! end of the scope, it records the state for each symbol as the public definitions of that
 //! symbol.
 //!
-//! Let's walk through the above example. Initially we do not have any record of `x`. When we add
-//! the new symbol (before we process the first binding), we create a new undefined `SymbolState`
-//! which has a single live binding (the "unbound" definition) and a single live declaration (the
-//! "undeclared" definition). When we see `x = 1`, we record that as the sole live binding of `x`.
-//! The "unbound" binding is no longer visible. Then we see `x = 2`, and we replace `x = 1` as the
-//! sole live binding of `x`. When we get to `y = x`, we record that the live bindings for that use
-//! of `x` are just the `x = 2` definition.
+//! Let's walk through the above example. Initially we record for `x` that it has no bindings, and
+//! may be unbound. When we see `x = 1`, we record that as the sole live binding of `x`, and flip
+//! `may_be_unbound` to `false`. Then we see `x = 2`, and we replace `x = 1` as the sole live
+//! binding of `x`. When we get to `y = x`, we record that the live bindings for that use of `x`
+//! are just the `x = 2` definition.
 //!
 //! Then we hit the `if` branch. We visit the `test` node (`flag` in this case), since that will
 //! happen regardless. Then we take a pre-branch snapshot of the current state for all symbols,
@@ -203,8 +207,8 @@
 //! be the pre-if conditions; if we are entering the `else` clause, we know that the `if` test
 //! failed and we didn't execute the `if` body. So we first reset the builder to the pre-if state,
 //! using the snapshot we took previously (meaning we now have `x = 2` as the sole binding for `x`
-//! again), and record a *negative* `flag` constraint for all live bindings (`x = 2`). We then
-//! visit the `else` clause, where `x = 4` replaces `x = 2` as the sole live binding of `x`.
+//! again), then visit the `else` clause, where `x = 4` replaces `x = 2` as the sole live binding
+//! of `x`.
 //!
 //! Now we reach the end of the if/else, and want to visit the following code. The state here needs
 //! to reflect that we might have gone through the `if` branch, or we might have gone through the
@@ -213,58 +217,18 @@
 //! snapshot (which has `x = 3` as the only live binding). The result of this merge is that we now
 //! have two live bindings of `x`: `x = 3` and `x = 4`.
 //!
-//! Another piece of information that the `UseDefMap` needs to provide are visibility constraints.
-//! These are similar to the narrowing constraints, but apply to bindings and declarations within a
-//! control flow path. Consider the following example:
-//! ```py
-//! x = 1
-//! if test:
-//!     x = 2
-//!     y = "y"
-//! ```
-//! In principle, there are two possible control flow paths here. However, if we can statically
-//! infer `test` to be always truthy or always falsy (that is, `__bool__` of `test` is of type
-//! `Literal[True]` or `Literal[False]`), we can rule out one of the possible paths. To support
-//! this feature, we record a visibility constraint of `test` to all live bindings and declarations
-//! *after* visiting the body of the `if` statement. And we record a negative visibility constraint
-//! `~test` to all live bindings/declarations in the (implicit) `else` branch. For the example
-//! above, we would record the following visibility constraints (adding the implicit "unbound"
-//! definitions for clarity):
-//! ```py
-//! x = <unbound>  # not live, shadowed by `x = 1`
-//! y = <unbound>  # visibility constraint: ~test
-//!
-//! x = 1  # visibility constraint: ~test
-//! if test:
-//!     x = 2  # visibility constraint: test
-//!     y = "y"  # visibility constraint: test
-//! ```
-//! When we encounter a use of `x` after this `if` statement, we would record two live bindings: `x
-//! = 1` with a constraint of `~test`, and `x = 2` with a constraint of `test`. In type inference,
-//! when we iterate over all live bindings, we can evaluate these constraints to determine if a
-//! particular binding is actually visible. For example, if `test` is always truthy, we only see
-//! the `x = 2` binding. If `test` is always falsy, we only see the `x = 1` binding. And if the
-//! `__bool__` method of `test` returns type `bool`, we can see both bindings.
-//!
-//! Note that we also record visibility constraints for the start of the scope. This is important
-//! to determine if a symbol is definitely bound, possibly unbound, or definitely unbound. In the
-//! example above, The `y = <unbound>` binding is constrained by `~test`, so `y` would only be
-//! definitely-bound if `test` is always truthy.
-//!
 //! The [`UseDefMapBuilder`] itself just exposes methods for taking a snapshot, resetting to a
 //! snapshot, and merging a snapshot into the current state. The logic using these methods lives in
 //! [`SemanticIndexBuilder`](crate::semantic_index::builder::SemanticIndexBuilder), e.g. where it
 //! visits a `StmtIf` node.
 use self::symbol_state::{
     BindingIdWithConstraintsIterator, ConstraintIdIterator, DeclarationIdIterator,
-    ScopedDefinitionId, SymbolBindings, SymbolDeclarations, SymbolState,
+    ScopedConstraintId, ScopedDefinitionId, SymbolBindings, SymbolDeclarations, SymbolState,
 };
-pub(crate) use self::symbol_state::{ScopedConstraintId, ScopedVisibilityConstraintId};
 use crate::semantic_index::ast_ids::ScopedUseId;
 use crate::semantic_index::definition::Definition;
 use crate::semantic_index::symbol::ScopedSymbolId;
-use crate::semantic_index::use_def::symbol_state::DeclarationIdWithConstraint;
-use crate::visibility_constraints::{VisibilityConstraint, VisibilityConstraints};
+use crate::symbol::Boundness;
 use ruff_index::IndexVec;
 use rustc_hash::FxHashMap;
 
@@ -273,20 +237,14 @@ use super::constraint::Constraint;
 mod bitset;
 mod symbol_state;
 
-type AllConstraints<'db> = IndexVec<ScopedConstraintId, Constraint<'db>>;
-
 /// Applicable definitions and constraints for every use of a name.
 #[derive(Debug, PartialEq, Eq)]
 pub(crate) struct UseDefMap<'db> {
-    /// Array of [`Definition`] in this scope. Only the first entry should be `None`;
-    /// this represents the implicit "unbound"/"undeclared" definition of every symbol.
-    all_definitions: IndexVec<ScopedDefinitionId, Option<Definition<'db>>>,
+    /// Array of [`Definition`] in this scope.
+    all_definitions: IndexVec<ScopedDefinitionId, Definition<'db>>,
 
     /// Array of [`Constraint`] in this scope.
-    all_constraints: AllConstraints<'db>,
-
-    /// Array of [`VisibilityConstraint`]s in this scope.
-    visibility_constraints: VisibilityConstraints<'db>,
+    all_constraints: IndexVec<ScopedConstraintId, Constraint<'db>>,
 
     /// [`SymbolBindings`] reaching a [`ScopedUseId`].
     bindings_by_use: IndexVec<ScopedUseId, SymbolBindings>,
@@ -317,6 +275,14 @@ impl<'db> UseDefMap<'db> {
         self.bindings_iterator(&self.bindings_by_use[use_id])
     }
 
+    pub(crate) fn use_boundness(&self, use_id: ScopedUseId) -> Boundness {
+        if self.bindings_by_use[use_id].may_be_unbound() {
+            Boundness::PossiblyUnbound
+        } else {
+            Boundness::Bound
+        }
+    }
+
     pub(crate) fn public_bindings(
         &self,
         symbol: ScopedSymbolId,
@@ -324,6 +290,14 @@ impl<'db> UseDefMap<'db> {
         self.bindings_iterator(self.public_symbols[symbol].bindings())
     }
 
+    pub(crate) fn public_boundness(&self, symbol: ScopedSymbolId) -> Boundness {
+        if self.public_symbols[symbol].may_be_unbound() {
+            Boundness::PossiblyUnbound
+        } else {
+            Boundness::Bound
+        }
+    }
+
     pub(crate) fn bindings_at_declaration(
         &self,
         declaration: Definition<'db>,
@@ -336,10 +310,10 @@ impl<'db> UseDefMap<'db> {
         }
     }
 
-    pub(crate) fn declarations_at_binding<'map>(
-        &'map self,
+    pub(crate) fn declarations_at_binding(
+        &self,
         binding: Definition<'db>,
-    ) -> DeclarationsIterator<'map, 'db> {
+    ) -> DeclarationsIterator<'_, 'db> {
         if let SymbolDefinitions::Declarations(declarations) =
             &self.definitions_by_definition[&binding]
         {
@@ -349,34 +323,37 @@ impl<'db> UseDefMap<'db> {
         }
     }
 
-    pub(crate) fn public_declarations<'map>(
-        &'map self,
+    pub(crate) fn public_declarations(
+        &self,
         symbol: ScopedSymbolId,
-    ) -> DeclarationsIterator<'map, 'db> {
+    ) -> DeclarationsIterator<'_, 'db> {
         let declarations = self.public_symbols[symbol].declarations();
         self.declarations_iterator(declarations)
     }
 
-    fn bindings_iterator<'map>(
-        &'map self,
-        bindings: &'map SymbolBindings,
-    ) -> BindingWithConstraintsIterator<'map, 'db> {
+    pub(crate) fn has_public_declarations(&self, symbol: ScopedSymbolId) -> bool {
+        !self.public_symbols[symbol].declarations().is_empty()
+    }
+
+    fn bindings_iterator<'a>(
+        &'a self,
+        bindings: &'a SymbolBindings,
+    ) -> BindingWithConstraintsIterator<'a, 'db> {
         BindingWithConstraintsIterator {
             all_definitions: &self.all_definitions,
             all_constraints: &self.all_constraints,
-            visibility_constraints: &self.visibility_constraints,
             inner: bindings.iter(),
         }
     }
 
-    fn declarations_iterator<'map>(
-        &'map self,
-        declarations: &'map SymbolDeclarations,
-    ) -> DeclarationsIterator<'map, 'db> {
+    fn declarations_iterator<'a>(
+        &'a self,
+        declarations: &'a SymbolDeclarations,
+    ) -> DeclarationsIterator<'a, 'db> {
         DeclarationsIterator {
             all_definitions: &self.all_definitions,
-            visibility_constraints: &self.visibility_constraints,
             inner: declarations.iter(),
+            may_be_undeclared: declarations.may_be_undeclared(),
         }
     }
 }
@@ -390,9 +367,8 @@ enum SymbolDefinitions {
 
 #[derive(Debug)]
 pub(crate) struct BindingWithConstraintsIterator<'map, 'db> {
-    all_definitions: &'map IndexVec<ScopedDefinitionId, Option<Definition<'db>>>,
-    all_constraints: &'map AllConstraints<'db>,
-    pub(crate) visibility_constraints: &'map VisibilityConstraints<'db>,
+    all_definitions: &'map IndexVec<ScopedDefinitionId, Definition<'db>>,
+    all_constraints: &'map IndexVec<ScopedConstraintId, Constraint<'db>>,
     inner: BindingIdWithConstraintsIterator<'map>,
 }
 
@@ -400,17 +376,14 @@ impl<'map, 'db> Iterator for BindingWithConstraintsIterator<'map, 'db> {
     type Item = BindingWithConstraints<'map, 'db>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        let all_constraints = self.all_constraints;
-
         self.inner
             .next()
-            .map(|binding_id_with_constraints| BindingWithConstraints {
-                binding: self.all_definitions[binding_id_with_constraints.definition],
+            .map(|def_id_with_constraints| BindingWithConstraints {
+                binding: self.all_definitions[def_id_with_constraints.definition],
                 constraints: ConstraintsIterator {
-                    all_constraints,
-                    constraint_ids: binding_id_with_constraints.constraint_ids,
+                    all_constraints: self.all_constraints,
+                    constraint_ids: def_id_with_constraints.constraint_ids,
                 },
-                visibility_constraint: binding_id_with_constraints.visibility_constraint,
             })
     }
 }
@@ -418,13 +391,12 @@ impl<'map, 'db> Iterator for BindingWithConstraintsIterator<'map, 'db> {
 impl std::iter::FusedIterator for BindingWithConstraintsIterator<'_, '_> {}
 
 pub(crate) struct BindingWithConstraints<'map, 'db> {
-    pub(crate) binding: Option<Definition<'db>>,
+    pub(crate) binding: Definition<'db>,
     pub(crate) constraints: ConstraintsIterator<'map, 'db>,
-    pub(crate) visibility_constraint: ScopedVisibilityConstraintId,
 }
 
 pub(crate) struct ConstraintsIterator<'map, 'db> {
-    all_constraints: &'map AllConstraints<'db>,
+    all_constraints: &'map IndexVec<ScopedConstraintId, Constraint<'db>>,
     constraint_ids: ConstraintIdIterator<'map>,
 }
 
@@ -441,31 +413,22 @@ impl<'db> Iterator for ConstraintsIterator<'_, 'db> {
 impl std::iter::FusedIterator for ConstraintsIterator<'_, '_> {}
 
 pub(crate) struct DeclarationsIterator<'map, 'db> {
-    all_definitions: &'map IndexVec<ScopedDefinitionId, Option<Definition<'db>>>,
-    pub(crate) visibility_constraints: &'map VisibilityConstraints<'db>,
+    all_definitions: &'map IndexVec<ScopedDefinitionId, Definition<'db>>,
     inner: DeclarationIdIterator<'map>,
+    may_be_undeclared: bool,
 }
 
-pub(crate) struct DeclarationWithConstraint<'db> {
-    pub(crate) declaration: Option<Definition<'db>>,
-    pub(crate) visibility_constraint: ScopedVisibilityConstraintId,
+impl DeclarationsIterator<'_, '_> {
+    pub(crate) fn may_be_undeclared(&self) -> bool {
+        self.may_be_undeclared
+    }
 }
 
 impl<'db> Iterator for DeclarationsIterator<'_, 'db> {
-    type Item = DeclarationWithConstraint<'db>;
+    type Item = Definition<'db>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.inner.next().map(
-            |DeclarationIdWithConstraint {
-                 definition,
-                 visibility_constraint,
-             }| {
-                DeclarationWithConstraint {
-                    declaration: self.all_definitions[definition],
-                    visibility_constraint,
-                }
-            },
-        )
+        self.inner.next().map(|def_id| self.all_definitions[def_id])
     }
 }
 
@@ -475,25 +438,15 @@ impl std::iter::FusedIterator for DeclarationsIterator<'_, '_> {}
 #[derive(Clone, Debug)]
 pub(super) struct FlowSnapshot {
     symbol_states: IndexVec<ScopedSymbolId, SymbolState>,
-    scope_start_visibility: ScopedVisibilityConstraintId,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub(super) struct UseDefMapBuilder<'db> {
     /// Append-only array of [`Definition`].
-    all_definitions: IndexVec<ScopedDefinitionId, Option<Definition<'db>>>,
+    all_definitions: IndexVec<ScopedDefinitionId, Definition<'db>>,
 
     /// Append-only array of [`Constraint`].
-    all_constraints: AllConstraints<'db>,
-
-    /// Append-only array of [`VisibilityConstraint`].
-    visibility_constraints: VisibilityConstraints<'db>,
-
-    /// A constraint which describes the visibility of the unbound/undeclared state, i.e.
-    /// whether or not the start of the scope is visible. This is important for cases like
-    /// `if True: x = 1; use(x)` where we need to hide the implicit "x = unbound" binding
-    /// in the "else" branch.
-    scope_start_visibility: ScopedVisibilityConstraintId,
+    all_constraints: IndexVec<ScopedConstraintId, Constraint<'db>>,
 
     /// Live bindings at each so-far-recorded use.
     bindings_by_use: IndexVec<ScopedUseId, SymbolBindings>,
@@ -505,30 +458,14 @@ pub(super) struct UseDefMapBuilder<'db> {
     symbol_states: IndexVec<ScopedSymbolId, SymbolState>,
 }
 
-impl Default for UseDefMapBuilder<'_> {
-    fn default() -> Self {
-        Self {
-            all_definitions: IndexVec::from_iter([None]),
-            all_constraints: IndexVec::new(),
-            visibility_constraints: VisibilityConstraints::default(),
-            scope_start_visibility: ScopedVisibilityConstraintId::ALWAYS_TRUE,
-            bindings_by_use: IndexVec::new(),
-            definitions_by_definition: FxHashMap::default(),
-            symbol_states: IndexVec::new(),
-        }
-    }
-}
-
 impl<'db> UseDefMapBuilder<'db> {
     pub(super) fn add_symbol(&mut self, symbol: ScopedSymbolId) {
-        let new_symbol = self
-            .symbol_states
-            .push(SymbolState::undefined(self.scope_start_visibility));
+        let new_symbol = self.symbol_states.push(SymbolState::undefined());
         debug_assert_eq!(symbol, new_symbol);
     }
 
     pub(super) fn record_binding(&mut self, symbol: ScopedSymbolId, binding: Definition<'db>) {
-        let def_id = self.all_definitions.push(Some(binding));
+        let def_id = self.all_definitions.push(binding);
         let symbol_state = &mut self.symbol_states[symbol];
         self.definitions_by_definition.insert(
             binding,
@@ -537,82 +474,10 @@ impl<'db> UseDefMapBuilder<'db> {
         symbol_state.record_binding(def_id);
     }
 
-    pub(super) fn add_constraint(&mut self, constraint: Constraint<'db>) -> ScopedConstraintId {
-        self.all_constraints.push(constraint)
-    }
-
-    pub(super) fn record_constraint_id(&mut self, constraint: ScopedConstraintId) {
+    pub(super) fn record_constraint(&mut self, constraint: Constraint<'db>) {
+        let constraint_id = self.all_constraints.push(constraint);
         for state in &mut self.symbol_states {
-            state.record_constraint(constraint);
-        }
-    }
-
-    pub(super) fn record_constraint(&mut self, constraint: Constraint<'db>) -> ScopedConstraintId {
-        let new_constraint_id = self.add_constraint(constraint);
-        self.record_constraint_id(new_constraint_id);
-        new_constraint_id
-    }
-
-    pub(super) fn add_visibility_constraint(
-        &mut self,
-        constraint: VisibilityConstraint<'db>,
-    ) -> ScopedVisibilityConstraintId {
-        self.visibility_constraints.add(constraint)
-    }
-
-    pub(super) fn record_visibility_constraint_id(
-        &mut self,
-        constraint: ScopedVisibilityConstraintId,
-    ) {
-        for state in &mut self.symbol_states {
-            state.record_visibility_constraint(&mut self.visibility_constraints, constraint);
-        }
-
-        self.scope_start_visibility = self
-            .visibility_constraints
-            .add_and_constraint(self.scope_start_visibility, constraint);
-    }
-
-    pub(super) fn record_visibility_constraint(
-        &mut self,
-        constraint: VisibilityConstraint<'db>,
-    ) -> ScopedVisibilityConstraintId {
-        let new_constraint_id = self.add_visibility_constraint(constraint);
-        self.record_visibility_constraint_id(new_constraint_id);
-        new_constraint_id
-    }
-
-    /// This method resets the visibility constraints for all symbols to a previous state
-    /// *if* there have been no new declarations or bindings since then. Consider the
-    /// following example:
-    /// ```py
-    /// x = 0
-    /// y = 0
-    /// if test_a:
-    ///     y = 1
-    /// elif test_b:
-    ///     y = 2
-    /// elif test_c:
-    ///    y = 3
-    ///
-    /// # RESET
-    /// ```
-    /// We build a complex visibility constraint for the `y = 0` binding. We build the same
-    /// constraint for the `x = 0` binding as well, but at the `RESET` point, we can get rid
-    /// of it, as the `if`-`elif`-`elif` chain doesn't include any new bindings of `x`.
-    pub(super) fn simplify_visibility_constraints(&mut self, snapshot: FlowSnapshot) {
-        debug_assert!(self.symbol_states.len() >= snapshot.symbol_states.len());
-
-        self.scope_start_visibility = snapshot.scope_start_visibility;
-
-        // Note that this loop terminates when we reach a symbol not present in the snapshot.
-        // This means we keep visibility constraints for all new symbols, which is intended,
-        // since these symbols have been introduced in the corresponding branch, which might
-        // be subject to visibility constraints. We only simplify/reset visibility constraints
-        // for symbols that have the same bindings and declarations present compared to the
-        // snapshot.
-        for (current, snapshot) in self.symbol_states.iter_mut().zip(snapshot.symbol_states) {
-            current.simplify_visibility_constraints(snapshot);
+            state.record_constraint(constraint_id);
         }
     }
 
@@ -621,7 +486,7 @@ impl<'db> UseDefMapBuilder<'db> {
         symbol: ScopedSymbolId,
         declaration: Definition<'db>,
     ) {
-        let def_id = self.all_definitions.push(Some(declaration));
+        let def_id = self.all_definitions.push(declaration);
         let symbol_state = &mut self.symbol_states[symbol];
         self.definitions_by_definition.insert(
             declaration,
@@ -636,7 +501,7 @@ impl<'db> UseDefMapBuilder<'db> {
         definition: Definition<'db>,
     ) {
         // We don't need to store anything in self.definitions_by_definition.
-        let def_id = self.all_definitions.push(Some(definition));
+        let def_id = self.all_definitions.push(definition);
         let symbol_state = &mut self.symbol_states[symbol];
         symbol_state.record_declaration(def_id);
         symbol_state.record_binding(def_id);
@@ -655,7 +520,6 @@ impl<'db> UseDefMapBuilder<'db> {
     pub(super) fn snapshot(&self) -> FlowSnapshot {
         FlowSnapshot {
             symbol_states: self.symbol_states.clone(),
-            scope_start_visibility: self.scope_start_visibility,
         }
     }
 
@@ -669,21 +533,18 @@ impl<'db> UseDefMapBuilder<'db> {
 
         // Restore the current visible-definitions state to the given snapshot.
         self.symbol_states = snapshot.symbol_states;
-        self.scope_start_visibility = snapshot.scope_start_visibility;
 
         // If the snapshot we are restoring is missing some symbols we've recorded since, we need
         // to fill them in so the symbol IDs continue to line up. Since they don't exist in the
         // snapshot, the correct state to fill them in with is "undefined".
-        self.symbol_states.resize(
-            num_symbols,
-            SymbolState::undefined(self.scope_start_visibility),
-        );
+        self.symbol_states
+            .resize(num_symbols, SymbolState::undefined());
     }
 
     /// Merge the given snapshot into the current state, reflecting that we might have taken either
     /// path to get here. The new state for each symbol should include definitions from both the
     /// prior state and the snapshot.
-    pub(super) fn merge(&mut self, snapshot: FlowSnapshot) {
+    pub(super) fn merge(&mut self, snapshot: FlowSnapshot, exclude_declarations: bool) {
         // We never remove symbols from `symbol_states` (it's an IndexVec, and the symbol
         // IDs must line up), so the current number of known symbols must always be equal to or
         // greater than the number of known symbols in a previously-taken snapshot.
@@ -692,19 +553,13 @@ impl<'db> UseDefMapBuilder<'db> {
         let mut snapshot_definitions_iter = snapshot.symbol_states.into_iter();
         for current in &mut self.symbol_states {
             if let Some(snapshot) = snapshot_definitions_iter.next() {
-                current.merge(snapshot, &mut self.visibility_constraints);
+                current.merge(snapshot, exclude_declarations);
             } else {
-                current.merge(
-                    SymbolState::undefined(snapshot.scope_start_visibility),
-                    &mut self.visibility_constraints,
-                );
                 // Symbol not present in snapshot, so it's unbound/undeclared from that path.
+                current.set_may_be_unbound();
+                current.set_may_be_undeclared();
             }
         }
-
-        self.scope_start_visibility = self
-            .visibility_constraints
-            .add_or_constraint(self.scope_start_visibility, snapshot.scope_start_visibility);
     }
 
     pub(super) fn finish(mut self) -> UseDefMap<'db> {
@@ -717,7 +572,6 @@ impl<'db> UseDefMapBuilder<'db> {
         UseDefMap {
             all_definitions: self.all_definitions,
             all_constraints: self.all_constraints,
-            visibility_constraints: self.visibility_constraints,
             bindings_by_use: self.bindings_by_use,
             public_symbols: self.symbol_states,
             definitions_by_definition: self.definitions_by_definition,

crates/red_knot_python_semantic/src/semantic_index/use_def/bitset.rs

@@ -32,6 +32,10 @@ impl<const B: usize> BitSet<B> {
         bitset
     }
 
+    pub(super) fn is_empty(&self) -> bool {
+        self.blocks().iter().all(|&b| b == 0)
+    }
+
     /// Convert from Inline to Heap, if needed, and resize the Heap vector, if needed.
     fn resize(&mut self, value: u32) {
         let num_blocks_needed = (value / 64) + 1;
@@ -93,6 +97,19 @@ impl<const B: usize> BitSet<B> {
         }
     }
 
+    /// Union in-place with another [`BitSet`].
+    pub(super) fn union(&mut self, other: &BitSet<B>) {
+        let mut max_len = self.blocks().len();
+        let other_len = other.blocks().len();
+        if other_len > max_len {
+            max_len = other_len;
+            self.resize_blocks(max_len);
+        }
+        for (my_block, other_block) in self.blocks_mut().iter_mut().zip(other.blocks()) {
+            *my_block |= other_block;
+        }
+    }
+
     /// Return an iterator over the values (in ascending order) in this [`BitSet`].
     pub(super) fn iter(&self) -> BitSetIterator<'_, B> {
         let blocks = self.blocks();
@@ -222,6 +239,59 @@ mod tests {
         assert_bitset(&b1, &[89]);
     }
 
+    #[test]
+    fn union() {
+        let mut b1 = BitSet::<1>::with(2);
+        let b2 = BitSet::<1>::with(4);
+
+        b1.union(&b2);
+        assert_bitset(&b1, &[2, 4]);
+    }
+
+    #[test]
+    fn union_mixed_1() {
+        let mut b1 = BitSet::<1>::with(4);
+        let mut b2 = BitSet::<1>::with(4);
+        b1.insert(89);
+        b2.insert(5);
+
+        b1.union(&b2);
+        assert_bitset(&b1, &[4, 5, 89]);
+    }
+
+    #[test]
+    fn union_mixed_2() {
+        let mut b1 = BitSet::<1>::with(4);
+        let mut b2 = BitSet::<1>::with(4);
+        b1.insert(23);
+        b2.insert(89);
+
+        b1.union(&b2);
+        assert_bitset(&b1, &[4, 23, 89]);
+    }
+
+    #[test]
+    fn union_heap() {
+        let mut b1 = BitSet::<1>::with(4);
+        let mut b2 = BitSet::<1>::with(4);
+        b1.insert(89);
+        b2.insert(90);
+
+        b1.union(&b2);
+        assert_bitset(&b1, &[4, 89, 90]);
+    }
+
+    #[test]
+    fn union_heap_2() {
+        let mut b1 = BitSet::<1>::with(89);
+        let mut b2 = BitSet::<1>::with(89);
+        b1.insert(91);
+        b2.insert(90);
+
+        b1.union(&b2);
+        assert_bitset(&b1, &[89, 90, 91]);
+    }
+
     #[test]
     fn multiple_blocks() {
         let mut b = BitSet::<2>::with(120);
@@ -229,4 +299,11 @@ mod tests {
         assert!(matches!(b, BitSet::Inline(_)));
         assert_bitset(&b, &[45, 120]);
     }
+
+    #[test]
+    fn empty() {
+        let b = BitSet::<1>::default();
+
+        assert!(b.is_empty());
+    }
 }

crates/red_knot_python_semantic/src/semantic_index/use_def/symbol_state.rs

@@ -43,8 +43,6 @@
 //!
 //! Tracking live declarations is simpler, since constraints are not involved, but otherwise very
 //! similar to tracking live bindings.
-use crate::semantic_index::use_def::VisibilityConstraints;
-
 use super::bitset::{BitSet, BitSetIterator};
 use ruff_index::newtype_index;
 use smallvec::SmallVec;
@@ -53,18 +51,9 @@ use smallvec::SmallVec;
 #[newtype_index]
 pub(super) struct ScopedDefinitionId;
 
-impl ScopedDefinitionId {
-    /// A special ID that is used to describe an implicit start-of-scope state. When
-    /// we see that this definition is live, we know that the symbol is (possibly)
-    /// unbound or undeclared at a given usage site.
-    /// When creating a use-def-map builder, we always add an empty `None` definition
-    /// at index 0, so this ID is always present.
-    pub(super) const UNBOUND: ScopedDefinitionId = ScopedDefinitionId::from_u32(0);
-}
-
 /// A newtype-index for a constraint expression in a particular scope.
 #[newtype_index]
-pub(crate) struct ScopedConstraintId;
+pub(super) struct ScopedConstraintId;
 
 /// Can reference this * 64 total definitions inline; more will fall back to the heap.
 const INLINE_BINDING_BLOCKS: usize = 3;
@@ -86,97 +75,58 @@ const INLINE_CONSTRAINT_BLOCKS: usize = 2;
 /// Can keep inline this many live bindings per symbol at a given time; more will go to heap.
 const INLINE_BINDINGS_PER_SYMBOL: usize = 4;
 
-/// Which constraints apply to a given binding?
-type Constraints = BitSet<INLINE_CONSTRAINT_BLOCKS>;
-
-type InlineConstraintArray = [Constraints; INLINE_BINDINGS_PER_SYMBOL];
-
-/// One [`BitSet`] of applicable [`ScopedConstraintId`]s per live binding.
-type ConstraintsPerBinding = SmallVec<InlineConstraintArray>;
-
-/// Iterate over all constraints for a single binding.
-type ConstraintsIterator<'a> = std::slice::Iter<'a, Constraints>;
+/// One [`BitSet`] of applicable [`ScopedConstraintId`] per live binding.
+type InlineConstraintArray = [BitSet<INLINE_CONSTRAINT_BLOCKS>; INLINE_BINDINGS_PER_SYMBOL];
+type Constraints = SmallVec<InlineConstraintArray>;
+type ConstraintsIterator<'a> = std::slice::Iter<'a, BitSet<INLINE_CONSTRAINT_BLOCKS>>;
 type ConstraintsIntoIterator = smallvec::IntoIter<InlineConstraintArray>;
 
-/// A newtype-index for a visibility constraint in a particular scope.
-#[newtype_index]
-pub(crate) struct ScopedVisibilityConstraintId;
-
-impl ScopedVisibilityConstraintId {
-    /// A special ID that is used for an "always true" / "always visible" constraint.
-    /// When we create a new [`VisibilityConstraints`] object, this constraint is always
-    /// present at index 0.
-    pub(crate) const ALWAYS_TRUE: ScopedVisibilityConstraintId =
-        ScopedVisibilityConstraintId::from_u32(0);
-}
-
-const INLINE_VISIBILITY_CONSTRAINTS: usize = 4;
-type InlineVisibilityConstraintsArray =
-    [ScopedVisibilityConstraintId; INLINE_VISIBILITY_CONSTRAINTS];
-
-/// One [`ScopedVisibilityConstraintId`] per live declaration.
-type VisibilityConstraintPerDeclaration = SmallVec<InlineVisibilityConstraintsArray>;
-
-/// One [`ScopedVisibilityConstraintId`] per live binding.
-type VisibilityConstraintPerBinding = SmallVec<InlineVisibilityConstraintsArray>;
-
-/// Iterator over the visibility constraints for all live bindings/declarations.
-type VisibilityConstraintsIterator<'a> = std::slice::Iter<'a, ScopedVisibilityConstraintId>;
-
-type VisibilityConstraintsIntoIterator = smallvec::IntoIter<InlineVisibilityConstraintsArray>;
-
-/// Live declarations for a single symbol at some point in control flow, with their
-/// corresponding visibility constraints.
+/// Live declarations for a single symbol at some point in control flow.
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub(super) struct SymbolDeclarations {
     /// [`BitSet`]: which declarations (as [`ScopedDefinitionId`]) can reach the current location?
-    pub(crate) live_declarations: Declarations,
+    live_declarations: Declarations,
 
-    /// For each live declaration, which visibility constraint applies to it?
-    pub(crate) visibility_constraints: VisibilityConstraintPerDeclaration,
+    /// Could the symbol be un-declared at this point?
+    may_be_undeclared: bool,
 }
 
 impl SymbolDeclarations {
-    fn undeclared(scope_start_visibility: ScopedVisibilityConstraintId) -> Self {
+    fn undeclared() -> Self {
         Self {
-            live_declarations: Declarations::with(0),
-            visibility_constraints: VisibilityConstraintPerDeclaration::from_iter([
-                scope_start_visibility,
-            ]),
+            live_declarations: Declarations::default(),
+            may_be_undeclared: true,
         }
     }
 
     /// Record a newly-encountered declaration for this symbol.
     fn record_declaration(&mut self, declaration_id: ScopedDefinitionId) {
         self.live_declarations = Declarations::with(declaration_id.into());
-
-        self.visibility_constraints = VisibilityConstraintPerDeclaration::with_capacity(1);
-        self.visibility_constraints
-            .push(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        self.may_be_undeclared = false;
     }
 
-    /// Add given visibility constraint to all live declarations.
-    pub(super) fn record_visibility_constraint(
-        &mut self,
-        visibility_constraints: &mut VisibilityConstraints,
-        constraint: ScopedVisibilityConstraintId,
-    ) {
-        for existing in &mut self.visibility_constraints {
-            *existing = visibility_constraints.add_and_constraint(*existing, constraint);
-        }
+    /// Add undeclared as a possibility for this symbol.
+    fn set_may_be_undeclared(&mut self) {
+        self.may_be_undeclared = true;
     }
 
     /// Return an iterator over live declarations for this symbol.
     pub(super) fn iter(&self) -> DeclarationIdIterator {
         DeclarationIdIterator {
-            declarations: self.live_declarations.iter(),
-            visibility_constraints: self.visibility_constraints.iter(),
+            inner: self.live_declarations.iter(),
         }
     }
+
+    pub(super) fn is_empty(&self) -> bool {
+        self.live_declarations.is_empty()
+    }
+
+    pub(super) fn may_be_undeclared(&self) -> bool {
+        self.may_be_undeclared
+    }
 }
 
-/// Live bindings for a single symbol at some point in control flow. Each live binding comes
-/// with a set of narrowing constraints and a visibility constraint.
+/// Live bindings and narrowing constraints for a single symbol at some point in control flow.
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub(super) struct SymbolBindings {
     /// [`BitSet`]: which bindings (as [`ScopedDefinitionId`]) can reach the current location?
@@ -186,34 +136,34 @@ pub(super) struct SymbolBindings {
     ///
     /// This is a [`smallvec::SmallVec`] which should always have one [`BitSet`] of constraints per
     /// binding in `live_bindings`.
-    constraints: ConstraintsPerBinding,
+    constraints: Constraints,
 
-    /// For each live binding, which visibility constraint applies to it?
-    visibility_constraints: VisibilityConstraintPerBinding,
+    /// Could the symbol be unbound at this point?
+    may_be_unbound: bool,
 }
 
 impl SymbolBindings {
-    fn unbound(scope_start_visibility: ScopedVisibilityConstraintId) -> Self {
+    fn unbound() -> Self {
         Self {
-            live_bindings: Bindings::with(ScopedDefinitionId::UNBOUND.as_u32()),
-            constraints: ConstraintsPerBinding::from_iter([Constraints::default()]),
-            visibility_constraints: VisibilityConstraintPerBinding::from_iter([
-                scope_start_visibility,
-            ]),
+            live_bindings: Bindings::default(),
+            constraints: Constraints::default(),
+            may_be_unbound: true,
         }
     }
 
+    /// Add Unbound as a possibility for this symbol.
+    fn set_may_be_unbound(&mut self) {
+        self.may_be_unbound = true;
+    }
+
     /// Record a newly-encountered binding for this symbol.
     pub(super) fn record_binding(&mut self, binding_id: ScopedDefinitionId) {
         // The new binding replaces all previous live bindings in this path, and has no
         // constraints.
         self.live_bindings = Bindings::with(binding_id.into());
-        self.constraints = ConstraintsPerBinding::with_capacity(1);
-        self.constraints.push(Constraints::default());
-
-        self.visibility_constraints = VisibilityConstraintPerBinding::with_capacity(1);
-        self.visibility_constraints
-            .push(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        self.constraints = Constraints::with_capacity(1);
+        self.constraints.push(BitSet::default());
+        self.may_be_unbound = false;
     }
 
     /// Add given constraint to all live bindings.
@@ -223,25 +173,17 @@ impl SymbolBindings {
         }
     }
 
-    /// Add given visibility constraint to all live bindings.
-    pub(super) fn record_visibility_constraint(
-        &mut self,
-        visibility_constraints: &mut VisibilityConstraints,
-        constraint: ScopedVisibilityConstraintId,
-    ) {
-        for existing in &mut self.visibility_constraints {
-            *existing = visibility_constraints.add_and_constraint(*existing, constraint);
-        }
-    }
-
-    /// Iterate over currently live bindings for this symbol
+    /// Iterate over currently live bindings for this symbol.
     pub(super) fn iter(&self) -> BindingIdWithConstraintsIterator {
         BindingIdWithConstraintsIterator {
             definitions: self.live_bindings.iter(),
             constraints: self.constraints.iter(),
-            visibility_constraints: self.visibility_constraints.iter(),
         }
     }
+
+    pub(super) fn may_be_unbound(&self) -> bool {
+        self.may_be_unbound
+    }
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -252,16 +194,20 @@ pub(super) struct SymbolState {
 
 impl SymbolState {
     /// Return a new [`SymbolState`] representing an unbound, undeclared symbol.
-    pub(super) fn undefined(scope_start_visibility: ScopedVisibilityConstraintId) -> Self {
+    pub(super) fn undefined() -> Self {
         Self {
-            declarations: SymbolDeclarations::undeclared(scope_start_visibility),
-            bindings: SymbolBindings::unbound(scope_start_visibility),
+            declarations: SymbolDeclarations::undeclared(),
+            bindings: SymbolBindings::unbound(),
         }
     }
 
+    /// Add Unbound as a possibility for this symbol.
+    pub(super) fn set_may_be_unbound(&mut self) {
+        self.bindings.set_may_be_unbound();
+    }
+
     /// Record a newly-encountered binding for this symbol.
     pub(super) fn record_binding(&mut self, binding_id: ScopedDefinitionId) {
-        debug_assert_ne!(binding_id, ScopedDefinitionId::UNBOUND);
         self.bindings.record_binding(binding_id);
     }
 
@@ -270,26 +216,9 @@ impl SymbolState {
         self.bindings.record_constraint(constraint_id);
     }
 
-    /// Add given visibility constraint to all live bindings.
-    pub(super) fn record_visibility_constraint(
-        &mut self,
-        visibility_constraints: &mut VisibilityConstraints,
-        constraint: ScopedVisibilityConstraintId,
-    ) {
-        self.bindings
-            .record_visibility_constraint(visibility_constraints, constraint);
-        self.declarations
-            .record_visibility_constraint(visibility_constraints, constraint);
-    }
-
-    pub(super) fn simplify_visibility_constraints(&mut self, snapshot_state: SymbolState) {
-        if self.bindings.live_bindings == snapshot_state.bindings.live_bindings {
-            self.bindings.visibility_constraints = snapshot_state.bindings.visibility_constraints;
-        }
-        if self.declarations.live_declarations == snapshot_state.declarations.live_declarations {
-            self.declarations.visibility_constraints =
-                snapshot_state.declarations.visibility_constraints;
-        }
+    /// Add undeclared as a possibility for this symbol.
+    pub(super) fn set_may_be_undeclared(&mut self) {
+        self.declarations.set_may_be_undeclared();
     }
 
     /// Record a newly-encountered declaration of this symbol.
@@ -298,31 +227,37 @@ impl SymbolState {
     }
 
     /// Merge another [`SymbolState`] into this one.
-    pub(super) fn merge(
-        &mut self,
-        b: SymbolState,
-        visibility_constraints: &mut VisibilityConstraints,
-    ) {
+    pub(super) fn merge(&mut self, b: SymbolState, exclude_declarations: bool) {
         let mut a = Self {
             bindings: SymbolBindings {
                 live_bindings: Bindings::default(),
-                constraints: ConstraintsPerBinding::default(),
-                visibility_constraints: VisibilityConstraintPerBinding::default(),
+                constraints: Constraints::default(),
+                may_be_unbound: self.bindings.may_be_unbound || b.bindings.may_be_unbound,
             },
-            declarations: SymbolDeclarations {
-                live_declarations: self.declarations.live_declarations.clone(),
-                visibility_constraints: VisibilityConstraintPerDeclaration::default(),
+            declarations: {
+                if exclude_declarations {
+                    self.declarations.clone()
+                } else {
+                    SymbolDeclarations {
+                        live_declarations: self.declarations.live_declarations.clone(),
+                        may_be_undeclared: self.declarations.may_be_undeclared
+                            || b.declarations.may_be_undeclared,
+                    }
+                }
             },
         };
 
         std::mem::swap(&mut a, self);
+        if !exclude_declarations {
+            self.declarations
+                .live_declarations
+                .union(&b.declarations.live_declarations);
+        }
 
         let mut a_defs_iter = a.bindings.live_bindings.iter();
         let mut b_defs_iter = b.bindings.live_bindings.iter();
         let mut a_constraints_iter = a.bindings.constraints.into_iter();
         let mut b_constraints_iter = b.bindings.constraints.into_iter();
-        let mut a_vis_constraints_iter = a.bindings.visibility_constraints.into_iter();
-        let mut b_vis_constraints_iter = b.bindings.visibility_constraints.into_iter();
 
         let mut opt_a_def: Option<u32> = a_defs_iter.next();
         let mut opt_b_def: Option<u32> = b_defs_iter.next();
@@ -334,30 +269,17 @@ impl SymbolState {
         // path is irrelevant.
 
         // Helper to push `def`, with constraints in `constraints_iter`, onto `self`.
-        let push = |def,
-                    constraints_iter: &mut ConstraintsIntoIterator,
-                    visibility_constraints_iter: &mut VisibilityConstraintsIntoIterator,
-                    merged: &mut Self| {
+        let push = |def, constraints_iter: &mut ConstraintsIntoIterator, merged: &mut Self| {
             merged.bindings.live_bindings.insert(def);
-            // SAFETY: we only ever create SymbolState using [`SymbolState::undefined`], which adds
-            // one "unbound" definition with corresponding narrowing and visibility constraints, or
-            // using [`SymbolState::record_binding`] or [`SymbolState::record_declaration`], which
-            // similarly add one definition with corresponding constraints. [`SymbolState::merge`]
-            // always pushes one definition and one constraint bitset and one visibility constraint
-            // together (just below), so the number of definitions and the number of constraints can
-            // never get out of sync.
+            // SAFETY: we only ever create SymbolState with either no definitions and no constraint
+            // bitsets (`::unbound`) or one definition and one constraint bitset (`::with`), and
+            // `::merge` always pushes one definition and one constraint bitset together (just
+            // below), so the number of definitions and the number of constraint bitsets can never
             // get out of sync.
             let constraints = constraints_iter
                 .next()
                 .expect("definitions and constraints length mismatch");
-            let visibility_constraints = visibility_constraints_iter
-                .next()
-                .expect("definitions and visibility_constraints length mismatch");
             merged.bindings.constraints.push(constraints);
-            merged
-                .bindings
-                .visibility_constraints
-                .push(visibility_constraints);
         };
 
         loop {
@@ -365,139 +287,50 @@ impl SymbolState {
                 (Some(a_def), Some(b_def)) => match a_def.cmp(&b_def) {
                     std::cmp::Ordering::Less => {
                         // Next definition ID is only in `a`, push it to `self` and advance `a`.
-                        push(
-                            a_def,
-                            &mut a_constraints_iter,
-                            &mut a_vis_constraints_iter,
-                            self,
-                        );
+                        push(a_def, &mut a_constraints_iter, self);
                         opt_a_def = a_defs_iter.next();
                     }
                     std::cmp::Ordering::Greater => {
                         // Next definition ID is only in `b`, push it to `self` and advance `b`.
-                        push(
-                            b_def,
-                            &mut b_constraints_iter,
-                            &mut b_vis_constraints_iter,
-                            self,
-                        );
+                        push(b_def, &mut b_constraints_iter, self);
                         opt_b_def = b_defs_iter.next();
                     }
                     std::cmp::Ordering::Equal => {
                         // Next definition is in both; push to `self` and intersect constraints.
-                        push(
-                            a_def,
-                            &mut b_constraints_iter,
-                            &mut b_vis_constraints_iter,
-                            self,
-                        );
-
-                        // SAFETY: see comment in `push` above.
+                        push(a_def, &mut b_constraints_iter, self);
+                        // SAFETY: we only ever create SymbolState with either no definitions and
+                        // no constraint bitsets (`::unbound`) or one definition and one constraint
+                        // bitset (`::with`), and `::merge` always pushes one definition and one
+                        // constraint bitset together (just below), so the number of definitions
+                        // and the number of constraint bitsets can never get out of sync.
                         let a_constraints = a_constraints_iter
                             .next()
                             .expect("definitions and constraints length mismatch");
-                        let current_constraints = self.bindings.constraints.last_mut().unwrap();
-
                         // If the same definition is visible through both paths, any constraint
                         // that applies on only one path is irrelevant to the resulting type from
                         // unioning the two paths, so we intersect the constraints.
-                        current_constraints.intersect(&a_constraints);
-
-                        // For visibility constraints, we merge them using a ternary OR operation:
-                        let a_vis_constraint = a_vis_constraints_iter
-                            .next()
-                            .expect("visibility_constraints length mismatch");
-                        let current_vis_constraint =
-                            self.bindings.visibility_constraints.last_mut().unwrap();
-                        *current_vis_constraint = visibility_constraints
-                            .add_or_constraint(*current_vis_constraint, a_vis_constraint);
-
+                        self.bindings
+                            .constraints
+                            .last_mut()
+                            .unwrap()
+                            .intersect(&a_constraints);
                         opt_a_def = a_defs_iter.next();
                         opt_b_def = b_defs_iter.next();
                     }
                 },
                 (Some(a_def), None) => {
                     // We've exhausted `b`, just push the def from `a` and move on to the next.
-                    push(
-                        a_def,
-                        &mut a_constraints_iter,
-                        &mut a_vis_constraints_iter,
-                        self,
-                    );
+                    push(a_def, &mut a_constraints_iter, self);
                     opt_a_def = a_defs_iter.next();
                 }
                 (None, Some(b_def)) => {
                     // We've exhausted `a`, just push the def from `b` and move on to the next.
-                    push(
-                        b_def,
-                        &mut b_constraints_iter,
-                        &mut b_vis_constraints_iter,
-                        self,
-                    );
+                    push(b_def, &mut b_constraints_iter, self);
                     opt_b_def = b_defs_iter.next();
                 }
                 (None, None) => break,
             }
         }
-
-        // Same as above, but for declarations.
-        let mut a_decls_iter = a.declarations.live_declarations.iter();
-        let mut b_decls_iter = b.declarations.live_declarations.iter();
-        let mut a_vis_constraints_iter = a.declarations.visibility_constraints.into_iter();
-        let mut b_vis_constraints_iter = b.declarations.visibility_constraints.into_iter();
-
-        let mut opt_a_decl: Option<u32> = a_decls_iter.next();
-        let mut opt_b_decl: Option<u32> = b_decls_iter.next();
-
-        let push = |decl,
-                    vis_constraints_iter: &mut VisibilityConstraintsIntoIterator,
-                    merged: &mut Self| {
-            merged.declarations.live_declarations.insert(decl);
-            let vis_constraints = vis_constraints_iter
-                .next()
-                .expect("declarations and visibility_constraints length mismatch");
-            merged
-                .declarations
-                .visibility_constraints
-                .push(vis_constraints);
-        };
-
-        loop {
-            match (opt_a_decl, opt_b_decl) {
-                (Some(a_decl), Some(b_decl)) => match a_decl.cmp(&b_decl) {
-                    std::cmp::Ordering::Less => {
-                        push(a_decl, &mut a_vis_constraints_iter, self);
-                        opt_a_decl = a_decls_iter.next();
-                    }
-                    std::cmp::Ordering::Greater => {
-                        push(b_decl, &mut b_vis_constraints_iter, self);
-                        opt_b_decl = b_decls_iter.next();
-                    }
-                    std::cmp::Ordering::Equal => {
-                        push(a_decl, &mut b_vis_constraints_iter, self);
-
-                        let a_vis_constraint = a_vis_constraints_iter
-                            .next()
-                            .expect("declarations and visibility_constraints length mismatch");
-                        let current = self.declarations.visibility_constraints.last_mut().unwrap();
-                        *current =
-                            visibility_constraints.add_or_constraint(*current, a_vis_constraint);
-
-                        opt_a_decl = a_decls_iter.next();
-                        opt_b_decl = b_decls_iter.next();
-                    }
-                },
-                (Some(a_decl), None) => {
-                    push(a_decl, &mut a_vis_constraints_iter, self);
-                    opt_a_decl = a_decls_iter.next();
-                }
-                (None, Some(b_decl)) => {
-                    push(b_decl, &mut b_vis_constraints_iter, self);
-                    opt_b_decl = b_decls_iter.next();
-                }
-                (None, None) => break,
-            }
-        }
     }
 
     pub(super) fn bindings(&self) -> &SymbolBindings {
@@ -507,44 +340,47 @@ impl SymbolState {
     pub(super) fn declarations(&self) -> &SymbolDeclarations {
         &self.declarations
     }
+
+    /// Could the symbol be unbound?
+    pub(super) fn may_be_unbound(&self) -> bool {
+        self.bindings.may_be_unbound()
+    }
+}
+
+/// The default state of a symbol, if we've seen no definitions of it, is undefined (that is,
+/// both unbound and undeclared).
+impl Default for SymbolState {
+    fn default() -> Self {
+        SymbolState::undefined()
+    }
 }
 
 /// A single binding (as [`ScopedDefinitionId`]) with an iterator of its applicable
-/// narrowing constraints ([`ScopedConstraintId`]) and a corresponding visibility
-/// visibility constraint ([`ScopedVisibilityConstraintId`]).
+/// [`ScopedConstraintId`].
 #[derive(Debug)]
-pub(super) struct BindingIdWithConstraints<'map> {
+pub(super) struct BindingIdWithConstraints<'a> {
     pub(super) definition: ScopedDefinitionId,
-    pub(super) constraint_ids: ConstraintIdIterator<'map>,
-    pub(super) visibility_constraint: ScopedVisibilityConstraintId,
+    pub(super) constraint_ids: ConstraintIdIterator<'a>,
 }
 
 #[derive(Debug)]
-pub(super) struct BindingIdWithConstraintsIterator<'map> {
-    definitions: BindingsIterator<'map>,
-    constraints: ConstraintsIterator<'map>,
-    visibility_constraints: VisibilityConstraintsIterator<'map>,
+pub(super) struct BindingIdWithConstraintsIterator<'a> {
+    definitions: BindingsIterator<'a>,
+    constraints: ConstraintsIterator<'a>,
 }
 
-impl<'map> Iterator for BindingIdWithConstraintsIterator<'map> {
-    type Item = BindingIdWithConstraints<'map>;
+impl<'a> Iterator for BindingIdWithConstraintsIterator<'a> {
+    type Item = BindingIdWithConstraints<'a>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        match (
-            self.definitions.next(),
-            self.constraints.next(),
-            self.visibility_constraints.next(),
-        ) {
-            (None, None, None) => None,
-            (Some(def), Some(constraints), Some(visibility_constraint_id)) => {
-                Some(BindingIdWithConstraints {
-                    definition: ScopedDefinitionId::from_u32(def),
-                    constraint_ids: ConstraintIdIterator {
-                        wrapped: constraints.iter(),
-                    },
-                    visibility_constraint: *visibility_constraint_id,
-                })
-            }
+        match (self.definitions.next(), self.constraints.next()) {
+            (None, None) => None,
+            (Some(def), Some(constraints)) => Some(BindingIdWithConstraints {
+                definition: ScopedDefinitionId::from_u32(def),
+                constraint_ids: ConstraintIdIterator {
+                    wrapped: constraints.iter(),
+                },
+            }),
             // SAFETY: see above.
             _ => unreachable!("definitions and constraints length mismatch"),
         }
@@ -568,34 +404,16 @@ impl Iterator for ConstraintIdIterator<'_> {
 
 impl std::iter::FusedIterator for ConstraintIdIterator<'_> {}
 
-/// A single declaration (as [`ScopedDefinitionId`]) with a corresponding visibility
-/// visibility constraint ([`ScopedVisibilityConstraintId`]).
 #[derive(Debug)]
-pub(super) struct DeclarationIdWithConstraint {
-    pub(super) definition: ScopedDefinitionId,
-    pub(super) visibility_constraint: ScopedVisibilityConstraintId,
-}
-
-pub(super) struct DeclarationIdIterator<'map> {
-    pub(crate) declarations: DeclarationsIterator<'map>,
-    pub(crate) visibility_constraints: VisibilityConstraintsIterator<'map>,
+pub(super) struct DeclarationIdIterator<'a> {
+    inner: DeclarationsIterator<'a>,
 }
 
 impl Iterator for DeclarationIdIterator<'_> {
-    type Item = DeclarationIdWithConstraint;
+    type Item = ScopedDefinitionId;
 
     fn next(&mut self) -> Option<Self::Item> {
-        match (self.declarations.next(), self.visibility_constraints.next()) {
-            (None, None) => None,
-            (Some(declaration), Some(&visibility_constraint)) => {
-                Some(DeclarationIdWithConstraint {
-                    definition: ScopedDefinitionId::from_u32(declaration),
-                    visibility_constraint,
-                })
-            }
-            // SAFETY: see above.
-            _ => unreachable!("declarations and visibility_constraints length mismatch"),
-        }
+        self.inner.next().map(ScopedDefinitionId::from_u32)
     }
 }
 
@@ -603,172 +421,176 @@ impl std::iter::FusedIterator for DeclarationIdIterator<'_> {}
 
 #[cfg(test)]
 mod tests {
-    use super::*;
+    use super::{ScopedConstraintId, ScopedDefinitionId, SymbolState};
 
-    #[track_caller]
-    fn assert_bindings(symbol: &SymbolState, expected: &[&str]) {
+    fn assert_bindings(symbol: &SymbolState, may_be_unbound: bool, expected: &[&str]) {
+        assert_eq!(symbol.may_be_unbound(), may_be_unbound);
         let actual = symbol
             .bindings()
             .iter()
             .map(|def_id_with_constraints| {
-                let def_id = def_id_with_constraints.definition;
-                let def = if def_id == ScopedDefinitionId::UNBOUND {
-                    "unbound".into()
-                } else {
-                    def_id.as_u32().to_string()
-                };
-                let constraints = def_id_with_constraints
-                    .constraint_ids
-                    .map(ScopedConstraintId::as_u32)
-                    .map(|idx| idx.to_string())
-                    .collect::<Vec<_>>()
-                    .join(", ");
-                format!("{def}<{constraints}>")
+                format!(
+                    "{}<{}>",
+                    def_id_with_constraints.definition.as_u32(),
+                    def_id_with_constraints
+                        .constraint_ids
+                        .map(ScopedConstraintId::as_u32)
+                        .map(|idx| idx.to_string())
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                )
             })
             .collect::<Vec<_>>();
         assert_eq!(actual, expected);
     }
 
-    #[track_caller]
-    pub(crate) fn assert_declarations(symbol: &SymbolState, expected: &[&str]) {
+    pub(crate) fn assert_declarations(
+        symbol: &SymbolState,
+        may_be_undeclared: bool,
+        expected: &[u32],
+    ) {
+        assert_eq!(symbol.declarations.may_be_undeclared(), may_be_undeclared);
         let actual = symbol
             .declarations()
             .iter()
-            .map(
-                |DeclarationIdWithConstraint {
-                     definition,
-                     visibility_constraint: _,
-                 }| {
-                    if definition == ScopedDefinitionId::UNBOUND {
-                        "undeclared".into()
-                    } else {
-                        definition.as_u32().to_string()
-                    }
-                },
-            )
+            .map(ScopedDefinitionId::as_u32)
             .collect::<Vec<_>>();
         assert_eq!(actual, expected);
     }
 
     #[test]
     fn unbound() {
-        let sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let sym = SymbolState::undefined();
 
-        assert_bindings(&sym, &["unbound<>"]);
+        assert_bindings(&sym, true, &[]);
     }
 
     #[test]
     fn with() {
-        let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
-        sym.record_binding(ScopedDefinitionId::from_u32(1));
+        let mut sym = SymbolState::undefined();
+        sym.record_binding(ScopedDefinitionId::from_u32(0));
 
-        assert_bindings(&sym, &["1<>"]);
+        assert_bindings(&sym, false, &["0<>"]);
+    }
+
+    #[test]
+    fn set_may_be_unbound() {
+        let mut sym = SymbolState::undefined();
+        sym.record_binding(ScopedDefinitionId::from_u32(0));
+        sym.set_may_be_unbound();
+
+        assert_bindings(&sym, true, &["0<>"]);
     }
 
     #[test]
     fn record_constraint() {
-        let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
-        sym.record_binding(ScopedDefinitionId::from_u32(1));
+        let mut sym = SymbolState::undefined();
+        sym.record_binding(ScopedDefinitionId::from_u32(0));
         sym.record_constraint(ScopedConstraintId::from_u32(0));
 
-        assert_bindings(&sym, &["1<0>"]);
+        assert_bindings(&sym, false, &["0<0>"]);
     }
 
     #[test]
     fn merge() {
-        let mut visibility_constraints = VisibilityConstraints::default();
-
         // merging the same definition with the same constraint keeps the constraint
-        let mut sym1a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
-        sym1a.record_binding(ScopedDefinitionId::from_u32(1));
-        sym1a.record_constraint(ScopedConstraintId::from_u32(0));
+        let mut sym0a = SymbolState::undefined();
+        sym0a.record_binding(ScopedDefinitionId::from_u32(0));
+        sym0a.record_constraint(ScopedConstraintId::from_u32(0));
 
-        let mut sym1b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
-        sym1b.record_binding(ScopedDefinitionId::from_u32(1));
-        sym1b.record_constraint(ScopedConstraintId::from_u32(0));
+        let mut sym0b = SymbolState::undefined();
+        sym0b.record_binding(ScopedDefinitionId::from_u32(0));
+        sym0b.record_constraint(ScopedConstraintId::from_u32(0));
 
-        sym1a.merge(sym1b, &mut visibility_constraints);
-        let mut sym1 = sym1a;
-        assert_bindings(&sym1, &["1<0>"]);
+        sym0a.merge(sym0b, false);
+        let mut sym0 = sym0a;
+        assert_bindings(&sym0, false, &["0<0>"]);
 
         // merging the same definition with differing constraints drops all constraints
-        let mut sym2a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
-        sym2a.record_binding(ScopedDefinitionId::from_u32(2));
-        sym2a.record_constraint(ScopedConstraintId::from_u32(1));
+        let mut sym1a = SymbolState::undefined();
+        sym1a.record_binding(ScopedDefinitionId::from_u32(1));
+        sym1a.record_constraint(ScopedConstraintId::from_u32(1));
 
-        let mut sym1b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
-        sym1b.record_binding(ScopedDefinitionId::from_u32(2));
+        let mut sym1b = SymbolState::undefined();
+        sym1b.record_binding(ScopedDefinitionId::from_u32(1));
         sym1b.record_constraint(ScopedConstraintId::from_u32(2));
 
-        sym2a.merge(sym1b, &mut visibility_constraints);
-        let sym2 = sym2a;
-        assert_bindings(&sym2, &["2<>"]);
+        sym1a.merge(sym1b, false);
+        let sym1 = sym1a;
+        assert_bindings(&sym1, false, &["1<>"]);
 
         // merging a constrained definition with unbound keeps both
-        let mut sym3a = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
-        sym3a.record_binding(ScopedDefinitionId::from_u32(3));
-        sym3a.record_constraint(ScopedConstraintId::from_u32(3));
+        let mut sym2a = SymbolState::undefined();
+        sym2a.record_binding(ScopedDefinitionId::from_u32(2));
+        sym2a.record_constraint(ScopedConstraintId::from_u32(3));
 
-        let sym2b = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let sym2b = SymbolState::undefined();
 
-        sym3a.merge(sym2b, &mut visibility_constraints);
-        let sym3 = sym3a;
-        assert_bindings(&sym3, &["unbound<>", "3<3>"]);
+        sym2a.merge(sym2b, false);
+        let sym2 = sym2a;
+        assert_bindings(&sym2, true, &["2<3>"]);
 
         // merging different definitions keeps them each with their existing constraints
-        sym1.merge(sym3, &mut visibility_constraints);
-        let sym = sym1;
-        assert_bindings(&sym, &["unbound<>", "1<0>", "3<3>"]);
+        sym0.merge(sym2, false);
+        let sym = sym0;
+        assert_bindings(&sym, true, &["0<0>", "2<3>"]);
     }
 
     #[test]
     fn no_declaration() {
-        let sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let sym = SymbolState::undefined();
 
-        assert_declarations(&sym, &["undeclared"]);
+        assert_declarations(&sym, true, &[]);
     }
 
     #[test]
     fn record_declaration() {
-        let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let mut sym = SymbolState::undefined();
         sym.record_declaration(ScopedDefinitionId::from_u32(1));
 
-        assert_declarations(&sym, &["1"]);
+        assert_declarations(&sym, false, &[1]);
     }
 
     #[test]
     fn record_declaration_override() {
-        let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let mut sym = SymbolState::undefined();
         sym.record_declaration(ScopedDefinitionId::from_u32(1));
         sym.record_declaration(ScopedDefinitionId::from_u32(2));
 
-        assert_declarations(&sym, &["2"]);
+        assert_declarations(&sym, false, &[2]);
     }
 
     #[test]
     fn record_declaration_merge() {
-        let mut visibility_constraints = VisibilityConstraints::default();
-        let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let mut sym = SymbolState::undefined();
         sym.record_declaration(ScopedDefinitionId::from_u32(1));
 
-        let mut sym2 = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let mut sym2 = SymbolState::undefined();
         sym2.record_declaration(ScopedDefinitionId::from_u32(2));
 
-        sym.merge(sym2, &mut visibility_constraints);
+        sym.merge(sym2, false);
 
-        assert_declarations(&sym, &["1", "2"]);
+        assert_declarations(&sym, false, &[1, 2]);
     }
 
     #[test]
     fn record_declaration_merge_partial_undeclared() {
-        let mut visibility_constraints = VisibilityConstraints::default();
-        let mut sym = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let mut sym = SymbolState::undefined();
         sym.record_declaration(ScopedDefinitionId::from_u32(1));
 
-        let sym2 = SymbolState::undefined(ScopedVisibilityConstraintId::ALWAYS_TRUE);
+        let sym2 = SymbolState::undefined();
 
-        sym.merge(sym2, &mut visibility_constraints);
+        sym.merge(sym2, false);
 
-        assert_declarations(&sym, &["undeclared", "1"]);
+        assert_declarations(&sym, true, &[1]);
+    }
+
+    #[test]
+    fn set_may_be_undeclared() {
+        let mut sym = SymbolState::undefined();
+        sym.record_declaration(ScopedDefinitionId::from_u32(0));
+        sym.set_may_be_undeclared();
+
+        assert_declarations(&sym, true, &[0]);
     }
 }

crates/red_knot_python_semantic/src/stdlib.rs

@@ -1,19 +1,53 @@
-use crate::module_resolver::{resolve_module, KnownModule};
+use crate::module_name::ModuleName;
+use crate::module_resolver::resolve_module;
 use crate::semantic_index::global_scope;
 use crate::semantic_index::symbol::ScopeId;
 use crate::symbol::Symbol;
 use crate::types::global_symbol;
 use crate::Db;
 
-/// Lookup the type of `symbol` in a given known module
+/// Enumeration of various core stdlib modules, for which we have dedicated Salsa queries.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum CoreStdlibModule {
+    Builtins,
+    Types,
+    Typeshed,
+    TypingExtensions,
+    Typing,
+    Sys,
+    #[allow(dead_code)]
+    Abc, // currently only used in tests
+}
+
+impl CoreStdlibModule {
+    pub(crate) const fn as_str(self) -> &'static str {
+        match self {
+            Self::Builtins => "builtins",
+            Self::Types => "types",
+            Self::Typing => "typing",
+            Self::Typeshed => "_typeshed",
+            Self::TypingExtensions => "typing_extensions",
+            Self::Sys => "sys",
+            Self::Abc => "abc",
+        }
+    }
+
+    pub(crate) fn name(self) -> ModuleName {
+        let self_as_str = self.as_str();
+        ModuleName::new_static(self_as_str)
+            .unwrap_or_else(|| panic!("{self_as_str} should be a valid module name!"))
+    }
+}
+
+/// Lookup the type of `symbol` in a given core module
 ///
-/// Returns `Symbol::Unbound` if the given known module cannot be resolved for some reason
-pub(crate) fn known_module_symbol<'db>(
+/// Returns `Symbol::Unbound` if the given core module cannot be resolved for some reason
+pub(crate) fn core_module_symbol<'db>(
     db: &'db dyn Db,
-    known_module: KnownModule,
+    core_module: CoreStdlibModule,
     symbol: &str,
 ) -> Symbol<'db> {
-    resolve_module(db, &known_module.name())
+    resolve_module(db, &core_module.name())
         .map(|module| global_symbol(db, module.file(), symbol))
         .unwrap_or(Symbol::Unbound)
 }
@@ -23,7 +57,7 @@ pub(crate) fn known_module_symbol<'db>(
 /// Returns `Symbol::Unbound` if the `builtins` module isn't available for some reason.
 #[inline]
 pub(crate) fn builtins_symbol<'db>(db: &'db dyn Db, symbol: &str) -> Symbol<'db> {
-    known_module_symbol(db, KnownModule::Builtins, symbol)
+    core_module_symbol(db, CoreStdlibModule::Builtins, symbol)
 }
 
 /// Lookup the type of `symbol` in the `typing` module namespace.
@@ -32,7 +66,7 @@ pub(crate) fn builtins_symbol<'db>(db: &'db dyn Db, symbol: &str) -> Symbol<'db>
 #[inline]
 #[cfg(test)]
 pub(crate) fn typing_symbol<'db>(db: &'db dyn Db, symbol: &str) -> Symbol<'db> {
-    known_module_symbol(db, KnownModule::Typing, symbol)
+    core_module_symbol(db, CoreStdlibModule::Typing, symbol)
 }
 
 /// Lookup the type of `symbol` in the `typing_extensions` module namespace.
@@ -40,13 +74,13 @@ pub(crate) fn typing_symbol<'db>(db: &'db dyn Db, symbol: &str) -> Symbol<'db> {
 /// Returns `Symbol::Unbound` if the `typing_extensions` module isn't available for some reason.
 #[inline]
 pub(crate) fn typing_extensions_symbol<'db>(db: &'db dyn Db, symbol: &str) -> Symbol<'db> {
-    known_module_symbol(db, KnownModule::TypingExtensions, symbol)
+    core_module_symbol(db, CoreStdlibModule::TypingExtensions, symbol)
 }
 
 /// Get the scope of a core stdlib module.
 ///
 /// Can return `None` if a custom typeshed is used that is missing the core module in question.
-fn core_module_scope(db: &dyn Db, core_module: KnownModule) -> Option<ScopeId<'_>> {
+fn core_module_scope(db: &dyn Db, core_module: CoreStdlibModule) -> Option<ScopeId<'_>> {
     resolve_module(db, &core_module.name()).map(|module| global_scope(db, module.file()))
 }
 
@@ -54,5 +88,5 @@ fn core_module_scope(db: &dyn Db, core_module: KnownModule) -> Option<ScopeId<'_
 ///
 /// Can return `None` if a custom typeshed is used that is missing `builtins.pyi`.
 pub(crate) fn builtins_module_scope(db: &dyn Db) -> Option<ScopeId<'_>> {
-    core_module_scope(db, KnownModule::Builtins)
+    core_module_scope(db, CoreStdlibModule::Builtins)
 }

crates/red_knot_python_semantic/src/symbol.rs

@@ -35,7 +35,7 @@ impl Boundness {
 /// possibly_unbound:  Symbol::Type(Type::IntLiteral(2), Boundness::PossiblyUnbound),
 /// non_existent:      Symbol::Unbound,
 /// ```
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq)]
 pub(crate) enum Symbol<'db> {
     Type(Type<'db>, Boundness),
     Unbound,

crates/red_knot_python_semantic/src/types/builder.rs

@@ -30,8 +30,6 @@ use crate::types::{InstanceType, IntersectionType, KnownClass, Type, UnionType};
 use crate::{Db, FxOrderSet};
 use smallvec::SmallVec;
 
-use super::Truthiness;
-
 pub(crate) struct UnionBuilder<'db> {
     elements: Vec<Type<'db>>,
     db: &'db dyn Db,
@@ -245,22 +243,15 @@ impl<'db> InnerIntersectionBuilder<'db> {
             }
         } else {
             // ~Literal[True] & bool = Literal[False]
-            // ~AlwaysTruthy & bool = Literal[False]
             if let Type::Instance(InstanceType { class }) = new_positive {
                 if class.is_known(db, KnownClass::Bool) {
-                    if let Some(new_type) = self
+                    if let Some(&Type::BooleanLiteral(value)) = self
                         .negative
                         .iter()
-                        .find(|element| {
-                            element.is_boolean_literal()
-                                | matches!(element, Type::AlwaysFalsy | Type::AlwaysTruthy)
-                        })
-                        .map(|element| {
-                            Type::BooleanLiteral(element.bool(db) != Truthiness::AlwaysTrue)
-                        })
+                        .find(|element| element.is_boolean_literal())
                     {
                         *self = Self::default();
-                        self.positive.insert(new_type);
+                        self.positive.insert(Type::BooleanLiteral(!value));
                         return;
                     }
                 }
@@ -327,15 +318,15 @@ impl<'db> InnerIntersectionBuilder<'db> {
                 // simplify the representation.
                 self.add_positive(db, ty);
             }
-            // bool & ~Literal[True] = Literal[False]
-            // bool & ~AlwaysTruthy = Literal[False]
-            Type::BooleanLiteral(_) | Type::AlwaysFalsy | Type::AlwaysTruthy
-                if self.positive.contains(&KnownClass::Bool.to_instance(db)) =>
+            // ~Literal[True] & bool = Literal[False]
+            Type::BooleanLiteral(bool)
+                if self
+                    .positive
+                    .iter()
+                    .any(|pos| *pos == KnownClass::Bool.to_instance(db)) =>
             {
                 *self = Self::default();
-                self.positive.insert(Type::BooleanLiteral(
-                    new_negative.bool(db) != Truthiness::AlwaysTrue,
-                ));
+                self.positive.insert(Type::BooleanLiteral(!bool));
             }
             _ => {
                 let mut to_remove = SmallVec::<[usize; 1]>::new();
@@ -389,7 +380,7 @@ mod tests {
     use super::{IntersectionBuilder, IntersectionType, Type, UnionType};
 
     use crate::db::tests::{setup_db, TestDb};
-    use crate::types::{global_symbol, todo_type, KnownClass, Truthiness, UnionBuilder};
+    use crate::types::{global_symbol, todo_type, KnownClass, UnionBuilder};
 
     use ruff_db::files::system_path_to_file;
     use ruff_db::system::DbWithTestSystem;
@@ -1006,43 +997,42 @@ mod tests {
         assert_eq!(ty, expected);
     }
 
-    #[test_case(Type::BooleanLiteral(true))]
-    #[test_case(Type::BooleanLiteral(false))]
-    #[test_case(Type::AlwaysTruthy)]
-    #[test_case(Type::AlwaysFalsy)]
-    fn build_intersection_simplify_split_bool(t_splitter: Type) {
+    #[test_case(true)]
+    #[test_case(false)]
+    fn build_intersection_simplify_split_bool(bool_value: bool) {
         let db = setup_db();
-        let bool_value = t_splitter.bool(&db) == Truthiness::AlwaysTrue;
+
+        let t_bool = KnownClass::Bool.to_instance(&db);
+        let t_boolean_literal = Type::BooleanLiteral(bool_value);
 
         // We add t_object in various orders (in first or second position) in
         // the tests below to ensure that the boolean simplification eliminates
         // everything from the intersection, not just `bool`.
         let t_object = KnownClass::Object.to_instance(&db);
-        let t_bool = KnownClass::Bool.to_instance(&db);
 
         let ty = IntersectionBuilder::new(&db)
             .add_positive(t_object)
             .add_positive(t_bool)
-            .add_negative(t_splitter)
+            .add_negative(t_boolean_literal)
             .build();
         assert_eq!(ty, Type::BooleanLiteral(!bool_value));
 
         let ty = IntersectionBuilder::new(&db)
             .add_positive(t_bool)
             .add_positive(t_object)
-            .add_negative(t_splitter)
+            .add_negative(t_boolean_literal)
             .build();
         assert_eq!(ty, Type::BooleanLiteral(!bool_value));
 
         let ty = IntersectionBuilder::new(&db)
             .add_positive(t_object)
-            .add_negative(t_splitter)
+            .add_negative(t_boolean_literal)
             .add_positive(t_bool)
             .build();
         assert_eq!(ty, Type::BooleanLiteral(!bool_value));
 
         let ty = IntersectionBuilder::new(&db)
-            .add_negative(t_splitter)
+            .add_negative(t_boolean_literal)
             .add_positive(t_object)
             .add_positive(t_bool)
             .build();

crates/red_knot_python_semantic/src/types/call.rs

@@ -1,5 +1,4 @@
-use super::context::InferContext;
-use super::diagnostic::CALL_NON_CALLABLE;
+use super::diagnostic::{TypeCheckDiagnosticsBuilder, CALL_NON_CALLABLE};
 use super::{Severity, Type, TypeArrayDisplay, UnionBuilder};
 use crate::Db;
 use ruff_db::diagnostic::DiagnosticId;
@@ -87,23 +86,24 @@ impl<'db> CallOutcome<'db> {
     }
 
     /// Get the return type of the call, emitting default diagnostics if needed.
-    pub(super) fn unwrap_with_diagnostic(
+    pub(super) fn unwrap_with_diagnostic<'a>(
         &self,
-        context: &InferContext<'db>,
+        db: &'db dyn Db,
         node: ast::AnyNodeRef,
+        diagnostics: &'a mut TypeCheckDiagnosticsBuilder<'db>,
     ) -> Type<'db> {
-        match self.return_ty_result(context, node) {
+        match self.return_ty_result(db, node, diagnostics) {
             Ok(return_ty) => return_ty,
             Err(NotCallableError::Type {
                 not_callable_ty,
                 return_ty,
             }) => {
-                context.report_lint(
+                diagnostics.add_lint(
                     &CALL_NON_CALLABLE,
                     node,
                     format_args!(
                         "Object of type `{}` is not callable",
-                        not_callable_ty.display(context.db())
+                        not_callable_ty.display(db)
                     ),
                 );
                 return_ty
@@ -113,13 +113,13 @@ impl<'db> CallOutcome<'db> {
                 called_ty,
                 return_ty,
             }) => {
-                context.report_lint(
+                diagnostics.add_lint(
                     &CALL_NON_CALLABLE,
                     node,
                     format_args!(
                         "Object of type `{}` is not callable (due to union element `{}`)",
-                        called_ty.display(context.db()),
-                        not_callable_ty.display(context.db()),
+                        called_ty.display(db),
+                        not_callable_ty.display(db),
                     ),
                 );
                 return_ty
@@ -129,13 +129,13 @@ impl<'db> CallOutcome<'db> {
                 called_ty,
                 return_ty,
             }) => {
-                context.report_lint(
+                diagnostics.add_lint(
                     &CALL_NON_CALLABLE,
                     node,
                     format_args!(
                         "Object of type `{}` is not callable (due to union elements {})",
-                        called_ty.display(context.db()),
-                        not_callable_tys.display(context.db()),
+                        called_ty.display(db),
+                        not_callable_tys.display(db),
                     ),
                 );
                 return_ty
@@ -144,12 +144,12 @@ impl<'db> CallOutcome<'db> {
                 callable_ty: called_ty,
                 return_ty,
             }) => {
-                context.report_lint(
+                diagnostics.add_lint(
                     &CALL_NON_CALLABLE,
                     node,
                     format_args!(
                         "Object of type `{}` is not callable (possibly unbound `__call__` method)",
-                        called_ty.display(context.db())
+                        called_ty.display(db)
                     ),
                 );
                 return_ty
@@ -158,10 +158,11 @@ impl<'db> CallOutcome<'db> {
     }
 
     /// Get the return type of the call as a result.
-    pub(super) fn return_ty_result(
+    pub(super) fn return_ty_result<'a>(
         &self,
-        context: &InferContext<'db>,
+        db: &'db dyn Db,
         node: ast::AnyNodeRef,
+        diagnostics: &'a mut TypeCheckDiagnosticsBuilder<'db>,
     ) -> Result<Type<'db>, NotCallableError<'db>> {
         match self {
             Self::Callable { return_ty } => Ok(*return_ty),
@@ -169,11 +170,11 @@ impl<'db> CallOutcome<'db> {
                 return_ty,
                 revealed_ty,
             } => {
-                context.report_diagnostic(
+                diagnostics.add(
                     node,
                     DiagnosticId::RevealedType,
                     Severity::Info,
-                    format_args!("Revealed type is `{}`", revealed_ty.display(context.db())),
+                    format_args!("Revealed type is `{}`", revealed_ty.display(db)),
                 );
                 Ok(*return_ty)
             }
@@ -186,16 +187,14 @@ impl<'db> CallOutcome<'db> {
                 call_outcome,
             } => Err(NotCallableError::PossiblyUnboundDunderCall {
                 callable_ty: *called_ty,
-                return_ty: call_outcome
-                    .return_ty(context.db())
-                    .unwrap_or(Type::Unknown),
+                return_ty: call_outcome.return_ty(db).unwrap_or(Type::Unknown),
             }),
             Self::Union {
                 outcomes,
                 called_ty,
             } => {
                 let mut not_callable = vec![];
-                let mut union_builder = UnionBuilder::new(context.db());
+                let mut union_builder = UnionBuilder::new(db);
                 let mut revealed = false;
                 for outcome in outcomes {
                     let return_ty = match outcome {
@@ -211,10 +210,10 @@ impl<'db> CallOutcome<'db> {
                                 *return_ty
                             } else {
                                 revealed = true;
-                                outcome.unwrap_with_diagnostic(context, node)
+                                outcome.unwrap_with_diagnostic(db, node, diagnostics)
                             }
                         }
-                        _ => outcome.unwrap_with_diagnostic(context, node),
+                        _ => outcome.unwrap_with_diagnostic(db, node, diagnostics),
                     };
                     union_builder = union_builder.add(return_ty);
                 }

crates/red_knot_python_semantic/src/types/class_base.rs

@@ -1,185 +0,0 @@
-use crate::types::{
-    todo_type, Class, ClassLiteralType, KnownClass, KnownInstanceType, TodoType, Type,
-};
-use crate::Db;
-use itertools::Either;
-
-/// Enumeration of the possible kinds of types we allow in class bases.
-///
-/// This is much more limited than the [`Type`] enum:
-/// all types that would be invalid to have as a class base are
-/// transformed into [`ClassBase::Unknown`]
-#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, salsa::Update)]
-pub enum ClassBase<'db> {
-    Any,
-    Unknown,
-    Todo(TodoType),
-    Class(Class<'db>),
-}
-
-impl<'db> ClassBase<'db> {
-    pub fn display(self, db: &'db dyn Db) -> impl std::fmt::Display + 'db {
-        struct Display<'db> {
-            base: ClassBase<'db>,
-            db: &'db dyn Db,
-        }
-
-        impl std::fmt::Display for Display<'_> {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                match self.base {
-                    ClassBase::Any => f.write_str("Any"),
-                    ClassBase::Todo(todo) => todo.fmt(f),
-                    ClassBase::Unknown => f.write_str("Unknown"),
-                    ClassBase::Class(class) => write!(f, "<class '{}'>", class.name(self.db)),
-                }
-            }
-        }
-
-        Display { base: self, db }
-    }
-
-    /// Return a `ClassBase` representing the class `builtins.object`
-    pub(super) fn object(db: &'db dyn Db) -> Self {
-        KnownClass::Object
-            .to_class_literal(db)
-            .into_class_literal()
-            .map_or(Self::Unknown, |ClassLiteralType { class }| {
-                Self::Class(class)
-            })
-    }
-
-    /// Attempt to resolve `ty` into a `ClassBase`.
-    ///
-    /// Return `None` if `ty` is not an acceptable type for a class base.
-    pub(super) fn try_from_ty(db: &'db dyn Db, ty: Type<'db>) -> Option<Self> {
-        match ty {
-            Type::Any => Some(Self::Any),
-            Type::Unknown => Some(Self::Unknown),
-            Type::Todo(todo) => Some(Self::Todo(todo)),
-            Type::ClassLiteral(ClassLiteralType { class }) => Some(Self::Class(class)),
-            Type::Union(_) => None, // TODO -- forces consideration of multiple possible MROs?
-            Type::Intersection(_) => None, // TODO -- probably incorrect?
-            Type::Instance(_) => None, // TODO -- handle `__mro_entries__`?
-            Type::Never
-            | Type::BooleanLiteral(_)
-            | Type::FunctionLiteral(_)
-            | Type::BytesLiteral(_)
-            | Type::IntLiteral(_)
-            | Type::StringLiteral(_)
-            | Type::LiteralString
-            | Type::Tuple(_)
-            | Type::SliceLiteral(_)
-            | Type::ModuleLiteral(_)
-            | Type::SubclassOf(_)
-            | Type::AlwaysFalsy
-            | Type::AlwaysTruthy => None,
-            Type::KnownInstance(known_instance) => match known_instance {
-                KnownInstanceType::TypeVar(_)
-                | KnownInstanceType::TypeAliasType(_)
-                | KnownInstanceType::Annotated
-                | KnownInstanceType::Literal
-                | KnownInstanceType::LiteralString
-                | KnownInstanceType::Union
-                | KnownInstanceType::NoReturn
-                | KnownInstanceType::Never
-                | KnownInstanceType::Final
-                | KnownInstanceType::NotRequired
-                | KnownInstanceType::TypeGuard
-                | KnownInstanceType::TypeIs
-                | KnownInstanceType::TypingSelf
-                | KnownInstanceType::Unpack
-                | KnownInstanceType::ClassVar
-                | KnownInstanceType::Concatenate
-                | KnownInstanceType::Required
-                | KnownInstanceType::TypeAlias
-                | KnownInstanceType::ReadOnly
-                | KnownInstanceType::Optional => None,
-                KnownInstanceType::Any => Some(Self::Any),
-                // TODO: Classes inheriting from `typing.Type` et al. also have `Generic` in their MRO
-                KnownInstanceType::Dict => {
-                    Self::try_from_ty(db, KnownClass::Dict.to_class_literal(db))
-                }
-                KnownInstanceType::List => {
-                    Self::try_from_ty(db, KnownClass::List.to_class_literal(db))
-                }
-                KnownInstanceType::Type => {
-                    Self::try_from_ty(db, KnownClass::Type.to_class_literal(db))
-                }
-                KnownInstanceType::Tuple => {
-                    Self::try_from_ty(db, KnownClass::Tuple.to_class_literal(db))
-                }
-                KnownInstanceType::Set => {
-                    Self::try_from_ty(db, KnownClass::Set.to_class_literal(db))
-                }
-                KnownInstanceType::FrozenSet => {
-                    Self::try_from_ty(db, KnownClass::FrozenSet.to_class_literal(db))
-                }
-                KnownInstanceType::ChainMap => {
-                    Self::try_from_ty(db, KnownClass::ChainMap.to_class_literal(db))
-                }
-                KnownInstanceType::Counter => {
-                    Self::try_from_ty(db, KnownClass::Counter.to_class_literal(db))
-                }
-                KnownInstanceType::DefaultDict => {
-                    Self::try_from_ty(db, KnownClass::DefaultDict.to_class_literal(db))
-                }
-                KnownInstanceType::Deque => {
-                    Self::try_from_ty(db, KnownClass::Deque.to_class_literal(db))
-                }
-                KnownInstanceType::OrderedDict => {
-                    Self::try_from_ty(db, KnownClass::OrderedDict.to_class_literal(db))
-                }
-                KnownInstanceType::Callable => {
-                    Self::try_from_ty(db, todo_type!("Support for Callable as a base class"))
-                }
-            },
-        }
-    }
-
-    pub(super) fn into_class(self) -> Option<Class<'db>> {
-        match self {
-            Self::Class(class) => Some(class),
-            _ => None,
-        }
-    }
-
-    /// Iterate over the MRO of this base
-    pub(super) fn mro(
-        self,
-        db: &'db dyn Db,
-    ) -> Either<impl Iterator<Item = ClassBase<'db>>, impl Iterator<Item = ClassBase<'db>>> {
-        match self {
-            ClassBase::Any => Either::Left([ClassBase::Any, ClassBase::object(db)].into_iter()),
-            ClassBase::Unknown => {
-                Either::Left([ClassBase::Unknown, ClassBase::object(db)].into_iter())
-            }
-            ClassBase::Todo(todo) => {
-                Either::Left([ClassBase::Todo(todo), ClassBase::object(db)].into_iter())
-            }
-            ClassBase::Class(class) => Either::Right(class.iter_mro(db)),
-        }
-    }
-}
-
-impl<'db> From<Class<'db>> for ClassBase<'db> {
-    fn from(value: Class<'db>) -> Self {
-        ClassBase::Class(value)
-    }
-}
-
-impl<'db> From<ClassBase<'db>> for Type<'db> {
-    fn from(value: ClassBase<'db>) -> Self {
-        match value {
-            ClassBase::Any => Type::Any,
-            ClassBase::Todo(todo) => Type::Todo(todo),
-            ClassBase::Unknown => Type::Unknown,
-            ClassBase::Class(class) => Type::class_literal(class),
-        }
-    }
-}
-
-impl<'db> From<&ClassBase<'db>> for Type<'db> {
-    fn from(value: &ClassBase<'db>) -> Self {
-        Self::from(*value)
-    }
-}

crates/red_knot_python_semantic/src/types/context.rs

@@ -1,197 +0,0 @@
-use std::fmt;
-
-use drop_bomb::DebugDropBomb;
-use ruff_db::{
-    diagnostic::{DiagnosticId, Severity},
-    files::File,
-};
-use ruff_python_ast::AnyNodeRef;
-use ruff_text_size::Ranged;
-
-use super::{binding_ty, KnownFunction, TypeCheckDiagnostic, TypeCheckDiagnostics};
-
-use crate::semantic_index::semantic_index;
-use crate::semantic_index::symbol::ScopeId;
-use crate::{
-    lint::{LintId, LintMetadata},
-    suppression::suppressions,
-    Db,
-};
-
-/// Context for inferring the types of a single file.
-///
-/// One context exists for at least for every inferred region but it's
-/// possible that inferring a sub-region, like an unpack assignment, creates
-/// a sub-context.
-///
-/// Tracks the reported diagnostics of the inferred region.
-///
-/// ## Consuming
-/// It's important that the context is explicitly consumed before dropping by calling
-/// [`InferContext::finish`] and the returned diagnostics must be stored
-/// on the current [`TypeInference`](super::infer::TypeInference) result.
-pub(crate) struct InferContext<'db> {
-    db: &'db dyn Db,
-    scope: ScopeId<'db>,
-    file: File,
-    diagnostics: std::cell::RefCell<TypeCheckDiagnostics>,
-    no_type_check: InNoTypeCheck,
-    bomb: DebugDropBomb,
-}
-
-impl<'db> InferContext<'db> {
-    pub(crate) fn new(db: &'db dyn Db, scope: ScopeId<'db>) -> Self {
-        Self {
-            db,
-            scope,
-            file: scope.file(db),
-            diagnostics: std::cell::RefCell::new(TypeCheckDiagnostics::default()),
-            no_type_check: InNoTypeCheck::default(),
-            bomb: DebugDropBomb::new("`InferContext` needs to be explicitly consumed by calling `::finish` to prevent accidental loss of diagnostics."),
-        }
-    }
-
-    /// The file for which the types are inferred.
-    pub(crate) fn file(&self) -> File {
-        self.file
-    }
-
-    pub(crate) fn db(&self) -> &'db dyn Db {
-        self.db
-    }
-
-    pub(crate) fn extend<T>(&mut self, other: &T)
-    where
-        T: WithDiagnostics,
-    {
-        self.diagnostics.get_mut().extend(other.diagnostics());
-    }
-
-    /// Reports a lint located at `node`.
-    pub(super) fn report_lint(
-        &self,
-        lint: &'static LintMetadata,
-        node: AnyNodeRef,
-        message: fmt::Arguments,
-    ) {
-        if !self.db.is_file_open(self.file) {
-            return;
-        }
-
-        // Skip over diagnostics if the rule is disabled.
-        let Some(severity) = self.db.rule_selection().severity(LintId::of(lint)) else {
-            return;
-        };
-
-        if self.is_in_no_type_check() {
-            return;
-        }
-
-        let suppressions = suppressions(self.db, self.file);
-
-        if let Some(suppression) = suppressions.find_suppression(node.range(), LintId::of(lint)) {
-            self.diagnostics.borrow_mut().mark_used(suppression.id());
-            return;
-        }
-
-        self.report_diagnostic(node, DiagnosticId::Lint(lint.name()), severity, message);
-    }
-
-    /// Adds a new diagnostic.
-    ///
-    /// The diagnostic does not get added if the rule isn't enabled for this file.
-    pub(super) fn report_diagnostic(
-        &self,
-        node: AnyNodeRef,
-        id: DiagnosticId,
-        severity: Severity,
-        message: fmt::Arguments,
-    ) {
-        if !self.db.is_file_open(self.file) {
-            return;
-        }
-
-        // TODO: Don't emit the diagnostic if:
-        // * The enclosing node contains any syntax errors
-        // * The rule is disabled for this file. We probably want to introduce a new query that
-        //   returns a rule selector for a given file that respects the package's settings,
-        //   any global pragma comments in the file, and any per-file-ignores.
-
-        self.diagnostics.borrow_mut().push(TypeCheckDiagnostic {
-            file: self.file,
-            id,
-            message: message.to_string(),
-            range: node.range(),
-            severity,
-        });
-    }
-
-    pub(super) fn set_in_no_type_check(&mut self, no_type_check: InNoTypeCheck) {
-        self.no_type_check = no_type_check;
-    }
-
-    fn is_in_no_type_check(&self) -> bool {
-        match self.no_type_check {
-            InNoTypeCheck::Possibly => {
-                // Accessing the semantic index here is fine because
-                // the index belongs to the same file as for which we emit the diagnostic.
-                let index = semantic_index(self.db, self.file);
-
-                let scope_id = self.scope.file_scope_id(self.db);
-
-                // Inspect all ancestor function scopes by walking bottom up and infer the function's type.
-                let mut function_scope_tys = index
-                    .ancestor_scopes(scope_id)
-                    .filter_map(|(_, scope)| scope.node().as_function())
-                    .filter_map(|function| {
-                        binding_ty(self.db, index.definition(function)).into_function_literal()
-                    });
-
-                // Iterate over all functions and test if any is decorated with `@no_type_check`.
-                function_scope_tys.any(|function_ty| {
-                    function_ty
-                        .decorators(self.db)
-                        .iter()
-                        .filter_map(|decorator| decorator.into_function_literal())
-                        .any(|decorator_ty| {
-                            decorator_ty.is_known(self.db, KnownFunction::NoTypeCheck)
-                        })
-                })
-            }
-            InNoTypeCheck::Yes => true,
-        }
-    }
-
-    #[must_use]
-    pub(crate) fn finish(mut self) -> TypeCheckDiagnostics {
-        self.bomb.defuse();
-        let mut diagnostics = self.diagnostics.into_inner();
-        diagnostics.shrink_to_fit();
-        diagnostics
-    }
-}
-
-impl fmt::Debug for InferContext<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.debug_struct("TyContext")
-            .field("file", &self.file)
-            .field("diagnostics", &self.diagnostics)
-            .field("defused", &self.bomb)
-            .finish()
-    }
-}
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Default)]
-pub(crate) enum InNoTypeCheck {
-    /// The inference might be in a `no_type_check` block but only if any
-    /// ancestor function is decorated with `@no_type_check`.
-    #[default]
-    Possibly,
-
-    /// The inference is known to be in an `@no_type_check` decorated function.
-    Yes,
-}
-
-pub(crate) trait WithDiagnostics {
-    fn diagnostics(&self) -> &TypeCheckDiagnostics;
-}

crates/red_knot_python_semantic/src/types/display.rs

@@ -6,7 +6,7 @@ use ruff_db::display::FormatterJoinExtension;
 use ruff_python_ast::str::Quote;
 use ruff_python_literal::escape::AsciiEscape;
 
-use crate::types::class_base::ClassBase;
+use crate::types::mro::ClassBase;
 use crate::types::{
     ClassLiteralType, InstanceType, IntersectionType, KnownClass, StringLiteralType,
     SubclassOfType, Type, UnionType,
@@ -79,8 +79,8 @@ impl Display for DisplayRepresentation<'_> {
             // `[Type::Todo]`'s display should be explicit that is not a valid display of
             // any other type
             Type::Todo(todo) => write!(f, "@Todo{todo}"),
-            Type::ModuleLiteral(module) => {
-                write!(f, "<module '{}'>", module.module(self.db).name())
+            Type::ModuleLiteral(file) => {
+                write!(f, "<module '{:?}'>", file.path(self.db))
             }
             // TODO functions and classes should display using a fully qualified name
             Type::ClassLiteral(ClassLiteralType { class }) => f.write_str(class.name(self.db)),
@@ -140,8 +140,6 @@ impl Display for DisplayRepresentation<'_> {
                 }
                 f.write_str("]")
             }
-            Type::AlwaysTruthy => f.write_str("AlwaysTruthy"),
-            Type::AlwaysFalsy => f.write_str("AlwaysFalsy"),
         }
     }
 }
@@ -324,12 +322,6 @@ impl<'db> TypeArrayDisplay<'db> for Vec<Type<'db>> {
     }
 }
 
-impl<'db> TypeArrayDisplay<'db> for [Type<'db>] {
-    fn display(&self, db: &'db dyn Db) -> DisplayTypeArray {
-        DisplayTypeArray { types: self, db }
-    }
-}
-
 pub(crate) struct DisplayTypeArray<'b, 'db> {
     types: &'b [Type<'db>],
     db: &'db dyn Db,

crates/red_knot_python_semantic/src/types/mro.rs

@@ -1,10 +1,10 @@
 use std::collections::VecDeque;
 use std::ops::Deref;
 
+use itertools::Either;
 use rustc_hash::FxHashSet;
 
-use crate::types::class_base::ClassBase;
-use crate::types::{Class, KnownClass, Type};
+use super::{todo_type, Class, ClassLiteralType, KnownClass, KnownInstanceType, TodoType, Type};
 use crate::Db;
 
 /// The inferred method resolution order of a given class.
@@ -117,7 +117,7 @@ impl<'db> Mro<'db> {
                     for (index, base) in valid_bases
                         .iter()
                         .enumerate()
-                        .filter_map(|(index, base)| Some((index, base.into_class()?)))
+                        .filter_map(|(index, base)| Some((index, base.into_class_literal_type()?)))
                     {
                         if !seen_bases.insert(base) {
                             duplicate_bases.push((index, base));
@@ -287,6 +287,174 @@ pub(super) enum MroErrorKind<'db> {
     UnresolvableMro { bases_list: Box<[ClassBase<'db>]> },
 }
 
+/// Enumeration of the possible kinds of types we allow in class bases.
+///
+/// This is much more limited than the [`Type`] enum:
+/// all types that would be invalid to have as a class base are
+/// transformed into [`ClassBase::Unknown`]
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, salsa::Update)]
+pub enum ClassBase<'db> {
+    Any,
+    Unknown,
+    Todo(TodoType),
+    Class(Class<'db>),
+}
+
+impl<'db> ClassBase<'db> {
+    pub fn display(self, db: &'db dyn Db) -> impl std::fmt::Display + 'db {
+        struct Display<'db> {
+            base: ClassBase<'db>,
+            db: &'db dyn Db,
+        }
+
+        impl std::fmt::Display for Display<'_> {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                match self.base {
+                    ClassBase::Any => f.write_str("Any"),
+                    ClassBase::Todo(todo) => todo.fmt(f),
+                    ClassBase::Unknown => f.write_str("Unknown"),
+                    ClassBase::Class(class) => write!(f, "<class '{}'>", class.name(self.db)),
+                }
+            }
+        }
+
+        Display { base: self, db }
+    }
+
+    /// Return a `ClassBase` representing the class `builtins.object`
+    fn object(db: &'db dyn Db) -> Self {
+        KnownClass::Object
+            .to_class_literal(db)
+            .into_class_literal()
+            .map_or(Self::Unknown, |ClassLiteralType { class }| {
+                Self::Class(class)
+            })
+    }
+
+    /// Attempt to resolve `ty` into a `ClassBase`.
+    ///
+    /// Return `None` if `ty` is not an acceptable type for a class base.
+    pub(super) fn try_from_ty(db: &'db dyn Db, ty: Type<'db>) -> Option<Self> {
+        match ty {
+            Type::Any => Some(Self::Any),
+            Type::Unknown => Some(Self::Unknown),
+            Type::Todo(todo) => Some(Self::Todo(todo)),
+            Type::ClassLiteral(ClassLiteralType { class }) => Some(Self::Class(class)),
+            Type::Union(_) => None, // TODO -- forces consideration of multiple possible MROs?
+            Type::Intersection(_) => None, // TODO -- probably incorrect?
+            Type::Instance(_) => None, // TODO -- handle `__mro_entries__`?
+            Type::Never
+            | Type::BooleanLiteral(_)
+            | Type::FunctionLiteral(_)
+            | Type::BytesLiteral(_)
+            | Type::IntLiteral(_)
+            | Type::StringLiteral(_)
+            | Type::LiteralString
+            | Type::Tuple(_)
+            | Type::SliceLiteral(_)
+            | Type::ModuleLiteral(_)
+            | Type::SubclassOf(_) => None,
+            Type::KnownInstance(known_instance) => match known_instance {
+                KnownInstanceType::TypeVar(_)
+                | KnownInstanceType::TypeAliasType(_)
+                | KnownInstanceType::Literal
+                | KnownInstanceType::LiteralString
+                | KnownInstanceType::Union
+                | KnownInstanceType::NoReturn
+                | KnownInstanceType::Never
+                | KnownInstanceType::Final
+                | KnownInstanceType::NotRequired
+                | KnownInstanceType::TypeGuard
+                | KnownInstanceType::TypeIs
+                | KnownInstanceType::TypingSelf
+                | KnownInstanceType::Unpack
+                | KnownInstanceType::ClassVar
+                | KnownInstanceType::Concatenate
+                | KnownInstanceType::Required
+                | KnownInstanceType::TypeAlias
+                | KnownInstanceType::ReadOnly
+                | KnownInstanceType::Optional => None,
+                KnownInstanceType::Any => Some(Self::Any),
+                // TODO: Classes inheriting from `typing.Type` et al. also have `Generic` in their MRO
+                KnownInstanceType::Dict => {
+                    ClassBase::try_from_ty(db, KnownClass::Dict.to_class_literal(db))
+                }
+                KnownInstanceType::List => {
+                    ClassBase::try_from_ty(db, KnownClass::List.to_class_literal(db))
+                }
+                KnownInstanceType::Type => {
+                    ClassBase::try_from_ty(db, KnownClass::Type.to_class_literal(db))
+                }
+                KnownInstanceType::Tuple => {
+                    ClassBase::try_from_ty(db, KnownClass::Tuple.to_class_literal(db))
+                }
+                KnownInstanceType::Set => {
+                    ClassBase::try_from_ty(db, KnownClass::Set.to_class_literal(db))
+                }
+                KnownInstanceType::FrozenSet => {
+                    ClassBase::try_from_ty(db, KnownClass::FrozenSet.to_class_literal(db))
+                }
+                KnownInstanceType::Callable
+                | KnownInstanceType::ChainMap
+                | KnownInstanceType::Counter
+                | KnownInstanceType::DefaultDict
+                | KnownInstanceType::Deque
+                | KnownInstanceType::OrderedDict => Self::try_from_ty(
+                    db,
+                    todo_type!("Support for more typing aliases as base classes"),
+                ),
+            },
+        }
+    }
+
+    fn into_class_literal_type(self) -> Option<Class<'db>> {
+        match self {
+            Self::Class(class) => Some(class),
+            _ => None,
+        }
+    }
+
+    /// Iterate over the MRO of this base
+    fn mro(
+        self,
+        db: &'db dyn Db,
+    ) -> Either<impl Iterator<Item = ClassBase<'db>>, impl Iterator<Item = ClassBase<'db>>> {
+        match self {
+            ClassBase::Any => Either::Left([ClassBase::Any, ClassBase::object(db)].into_iter()),
+            ClassBase::Unknown => {
+                Either::Left([ClassBase::Unknown, ClassBase::object(db)].into_iter())
+            }
+            ClassBase::Todo(todo) => {
+                Either::Left([ClassBase::Todo(todo), ClassBase::object(db)].into_iter())
+            }
+            ClassBase::Class(class) => Either::Right(class.iter_mro(db)),
+        }
+    }
+}
+
+impl<'db> From<Class<'db>> for ClassBase<'db> {
+    fn from(value: Class<'db>) -> Self {
+        ClassBase::Class(value)
+    }
+}
+
+impl<'db> From<ClassBase<'db>> for Type<'db> {
+    fn from(value: ClassBase<'db>) -> Self {
+        match value {
+            ClassBase::Any => Type::Any,
+            ClassBase::Todo(todo) => Type::Todo(todo),
+            ClassBase::Unknown => Type::Unknown,
+            ClassBase::Class(class) => Type::class_literal(class),
+        }
+    }
+}
+
+impl<'db> From<&ClassBase<'db>> for Type<'db> {
+    fn from(value: &ClassBase<'db>) -> Self {
+        Self::from(*value)
+    }
+}
+
 /// Implementation of the [C3-merge algorithm] for calculating a Python class's
 /// [method resolution order].
 ///

crates/red_knot_python_semantic/src/types/narrow.rs

@@ -1,7 +1,5 @@
 use crate::semantic_index::ast_ids::HasScopedExpressionId;
-use crate::semantic_index::constraint::{
-    Constraint, ConstraintNode, PatternConstraint, PatternConstraintKind,
-};
+use crate::semantic_index::constraint::{Constraint, ConstraintNode, PatternConstraint};
 use crate::semantic_index::definition::Definition;
 use crate::semantic_index::expression::Expression;
 use crate::semantic_index::symbol::{ScopeId, ScopedSymbolId, SymbolTable};
@@ -198,7 +196,6 @@ impl<'db> NarrowingConstraintsBuilder<'db> {
         is_positive: bool,
     ) -> Option<NarrowingConstraints<'db>> {
         match expression_node {
-            ast::Expr::Name(name) => Some(self.evaluate_expr_name(name, is_positive)),
             ast::Expr::Compare(expr_compare) => {
                 self.evaluate_expr_compare(expr_compare, expression, is_positive)
             }
@@ -218,12 +215,31 @@ impl<'db> NarrowingConstraintsBuilder<'db> {
     ) -> Option<NarrowingConstraints<'db>> {
         let subject = pattern.subject(self.db);
 
-        match pattern.kind(self.db) {
-            PatternConstraintKind::Singleton(singleton, _guard) => {
-                self.evaluate_match_pattern_singleton(*subject, *singleton)
+        match pattern.pattern(self.db).node() {
+            ast::Pattern::MatchValue(_) => {
+                None // TODO
+            }
+            ast::Pattern::MatchSingleton(singleton_pattern) => {
+                self.evaluate_match_pattern_singleton(subject, singleton_pattern)
+            }
+            ast::Pattern::MatchSequence(_) => {
+                None // TODO
+            }
+            ast::Pattern::MatchMapping(_) => {
+                None // TODO
+            }
+            ast::Pattern::MatchClass(_) => {
+                None // TODO
+            }
+            ast::Pattern::MatchStar(_) => {
+                None // TODO
+            }
+            ast::Pattern::MatchAs(_) => {
+                None // TODO
+            }
+            ast::Pattern::MatchOr(_) => {
+                None // TODO
             }
-            // TODO: support more pattern kinds
-            PatternConstraintKind::Value(..) | PatternConstraintKind::Unsupported => None,
         }
     }
 
@@ -238,31 +254,6 @@ impl<'db> NarrowingConstraintsBuilder<'db> {
         }
     }
 
-    fn evaluate_expr_name(
-        &mut self,
-        expr_name: &ast::ExprName,
-        is_positive: bool,
-    ) -> NarrowingConstraints<'db> {
-        let ast::ExprName { id, .. } = expr_name;
-
-        let symbol = self
-            .symbols()
-            .symbol_id_by_name(id)
-            .expect("Should always have a symbol for every Name node");
-        let mut constraints = NarrowingConstraints::default();
-
-        constraints.insert(
-            symbol,
-            if is_positive {
-                Type::AlwaysFalsy.negate(self.db)
-            } else {
-                Type::AlwaysTruthy.negate(self.db)
-            },
-        );
-
-        constraints
-    }
-
     fn evaluate_expr_compare(
         &mut self,
         expr_compare: &ast::ExprCompare,
@@ -466,14 +457,14 @@ impl<'db> NarrowingConstraintsBuilder<'db> {
 
     fn evaluate_match_pattern_singleton(
         &mut self,
-        subject: Expression<'db>,
-        singleton: ast::Singleton,
+        subject: &ast::Expr,
+        pattern: &ast::PatternMatchSingleton,
     ) -> Option<NarrowingConstraints<'db>> {
-        if let Some(ast::ExprName { id, .. }) = subject.node_ref(self.db).as_name_expr() {
+        if let Some(ast::ExprName { id, .. }) = subject.as_name_expr() {
             // SAFETY: we should always have a symbol for every Name node.
             let symbol = self.symbols().symbol_id_by_name(id).unwrap();
 
-            let ty = match singleton {
+            let ty = match pattern.value {
                 ast::Singleton::None => Type::none(self.db),
                 ast::Singleton::True => Type::BooleanLiteral(true),
                 ast::Singleton::False => Type::BooleanLiteral(false),

crates/red_knot_python_semantic/src/types/property_tests.rs

@@ -65,18 +65,9 @@ fn arbitrary_core_type(g: &mut Gen) -> Ty {
         Ty::BuiltinClassLiteral("bool"),
         Ty::BuiltinClassLiteral("object"),
         Ty::BuiltinInstance("type"),
-        Ty::AbcInstance("ABC"),
-        Ty::AbcInstance("ABCMeta"),
         Ty::SubclassOfAny,
         Ty::SubclassOfBuiltinClass("object"),
         Ty::SubclassOfBuiltinClass("str"),
-        Ty::SubclassOfBuiltinClass("type"),
-        Ty::AbcClassLiteral("ABC"),
-        Ty::AbcClassLiteral("ABCMeta"),
-        Ty::SubclassOfAbcClass("ABC"),
-        Ty::SubclassOfAbcClass("ABCMeta"),
-        Ty::AlwaysTruthy,
-        Ty::AlwaysFalsy,
     ])
     .unwrap()
     .clone()

crates/red_knot_python_semantic/src/types/slots.rs

@@ -1,103 +0,0 @@
-use ruff_python_ast as ast;
-
-use crate::db::Db;
-use crate::symbol::{Boundness, Symbol};
-use crate::types::class_base::ClassBase;
-use crate::types::diagnostic::report_base_with_incompatible_slots;
-use crate::types::{Class, ClassLiteralType, Type};
-
-use super::InferContext;
-
-#[derive(Copy, Clone, Debug, Eq, PartialEq)]
-enum SlotsKind {
-    /// `__slots__` is not found in the class.
-    NotSpecified,
-    /// `__slots__` is defined but empty: `__slots__ = ()`.
-    Empty,
-    /// `__slots__` is defined and is not empty: `__slots__ = ("a", "b")`.
-    NotEmpty,
-    /// `__slots__` is defined but its value is dynamic:
-    /// * `__slots__ = tuple(a for a in b)`
-    /// * `__slots__ = ["a", "b"]`
-    Dynamic,
-}
-
-impl SlotsKind {
-    fn from(db: &dyn Db, base: Class) -> Self {
-        let Symbol::Type(slots_ty, bound) = base.own_class_member(db, "__slots__") else {
-            return Self::NotSpecified;
-        };
-
-        if matches!(bound, Boundness::PossiblyUnbound) {
-            return Self::Dynamic;
-        };
-
-        match slots_ty {
-            // __slots__ = ("a", "b")
-            Type::Tuple(tuple) => {
-                if tuple.elements(db).is_empty() {
-                    Self::Empty
-                } else {
-                    Self::NotEmpty
-                }
-            }
-
-            // __slots__ = "abc"  # Same as `("abc",)`
-            Type::StringLiteral(_) => Self::NotEmpty,
-
-            _ => Self::Dynamic,
-        }
-    }
-}
-
-pub(super) fn check_class_slots(context: &InferContext, class: Class, node: &ast::StmtClassDef) {
-    let db = context.db();
-
-    let mut first_with_solid_base = None;
-    let mut common_solid_base = None;
-    let mut found_second = false;
-
-    for (index, base) in class.explicit_bases(db).iter().enumerate() {
-        let Type::ClassLiteral(ClassLiteralType { class: base }) = base else {
-            continue;
-        };
-
-        let solid_base = base.iter_mro(db).find_map(|current| {
-            let ClassBase::Class(current) = current else {
-                return None;
-            };
-
-            match SlotsKind::from(db, current) {
-                SlotsKind::NotEmpty => Some(current),
-                SlotsKind::NotSpecified | SlotsKind::Empty => None,
-                SlotsKind::Dynamic => None,
-            }
-        });
-
-        if solid_base.is_none() {
-            continue;
-        }
-
-        let base_node = &node.bases()[index];
-
-        if first_with_solid_base.is_none() {
-            first_with_solid_base = Some(index);
-            common_solid_base = solid_base;
-            continue;
-        }
-
-        if solid_base == common_solid_base {
-            continue;
-        }
-
-        found_second = true;
-        report_base_with_incompatible_slots(context, base_node);
-    }
-
-    if found_second {
-        if let Some(index) = first_with_solid_base {
-            let base_node = &node.bases()[index];
-            report_base_with_incompatible_slots(context, base_node);
-        };
-    }
-}

crates/red_knot_python_semantic/src/types/string_annotation.rs

@@ -1,13 +1,13 @@
+use ruff_db::files::File;
 use ruff_db::source::source_text;
 use ruff_python_ast::str::raw_contents;
 use ruff_python_ast::{self as ast, ModExpression, StringFlags};
 use ruff_python_parser::{parse_expression_range, Parsed};
 use ruff_text_size::Ranged;
 
-use crate::declare_lint;
 use crate::lint::{Level, LintStatus};
-
-use super::context::InferContext;
+use crate::types::diagnostic::{TypeCheckDiagnostics, TypeCheckDiagnosticsBuilder};
+use crate::{declare_lint, Db};
 
 declare_lint! {
     /// ## What it does
@@ -127,23 +127,24 @@ declare_lint! {
     }
 }
 
+type AnnotationParseResult = Result<Parsed<ModExpression>, TypeCheckDiagnostics>;
+
 /// Parses the given expression as a string annotation.
 pub(crate) fn parse_string_annotation(
-    context: &InferContext,
+    db: &dyn Db,
+    file: File,
     string_expr: &ast::ExprStringLiteral,
-) -> Option<Parsed<ModExpression>> {
-    let file = context.file();
-    let db = context.db();
-
+) -> AnnotationParseResult {
     let _span = tracing::trace_span!("parse_string_annotation", string=?string_expr.range(), file=%file.path(db)).entered();
 
     let source = source_text(db.upcast(), file);
     let node_text = &source[string_expr.range()];
+    let mut diagnostics = TypeCheckDiagnosticsBuilder::new(db, file);
 
     if let [string_literal] = string_expr.value.as_slice() {
         let prefix = string_literal.flags.prefix();
         if prefix.is_raw() {
-            context.report_lint(
+            diagnostics.add_lint(
                 &RAW_STRING_TYPE_ANNOTATION,
                 string_literal.into(),
                 format_args!("Type expressions cannot use raw string literal"),
@@ -166,8 +167,8 @@ pub(crate) fn parse_string_annotation(
             // """ = 1
             // ```
             match parse_expression_range(source.as_str(), range_excluding_quotes) {
-                Ok(parsed) => return Some(parsed),
-                Err(parse_error) => context.report_lint(
+                Ok(parsed) => return Ok(parsed),
+                Err(parse_error) => diagnostics.add_lint(
                     &INVALID_SYNTAX_IN_FORWARD_ANNOTATION,
                     string_literal.into(),
                     format_args!("Syntax error in forward annotation: {}", parse_error.error),
@@ -176,7 +177,7 @@ pub(crate) fn parse_string_annotation(
         } else {
             // The raw contents of the string doesn't match the parsed content. This could be the
             // case for annotations that contain escape sequences.
-            context.report_lint(
+            diagnostics.add_lint(
                 &ESCAPE_CHARACTER_IN_FORWARD_ANNOTATION,
                 string_expr.into(),
                 format_args!("Type expressions cannot contain escape characters"),
@@ -184,12 +185,12 @@ pub(crate) fn parse_string_annotation(
         }
     } else {
         // String is implicitly concatenated.
-        context.report_lint(
+        diagnostics.add_lint(
             &IMPLICIT_CONCATENATED_STRING_TYPE_ANNOTATION,
             string_expr.into(),
             format_args!("Type expressions cannot span multiple string literals"),
         );
     }
 
-    None
+    Err(diagnostics.finish())
 }

crates/red_knot_python_semantic/src/types/unpacker.rs

@@ -1,249 +1,126 @@
 use std::borrow::Cow;
-use std::cmp::Ordering;
-
-use rustc_hash::FxHashMap;
 
+use ruff_db::files::File;
 use ruff_python_ast::{self as ast, AnyNodeRef};
+use rustc_hash::FxHashMap;
 
 use crate::semantic_index::ast_ids::{HasScopedExpressionId, ScopedExpressionId};
 use crate::semantic_index::symbol::ScopeId;
-use crate::types::{infer_expression_types, todo_type, Type, TypeCheckDiagnostics};
-use crate::unpack::UnpackValue;
+use crate::types::{todo_type, Type, TypeCheckDiagnostics, TypeCheckDiagnosticsBuilder};
 use crate::Db;
 
-use super::context::{InferContext, WithDiagnostics};
-use super::diagnostic::INVALID_ASSIGNMENT;
-use super::{TupleType, UnionType};
-
 /// Unpacks the value expression type to their respective targets.
 pub(crate) struct Unpacker<'db> {
-    context: InferContext<'db>,
-    scope: ScopeId<'db>,
+    db: &'db dyn Db,
     targets: FxHashMap<ScopedExpressionId, Type<'db>>,
+    diagnostics: TypeCheckDiagnosticsBuilder<'db>,
 }
 
 impl<'db> Unpacker<'db> {
-    pub(crate) fn new(db: &'db dyn Db, scope: ScopeId<'db>) -> Self {
+    pub(crate) fn new(db: &'db dyn Db, file: File) -> Self {
         Self {
-            context: InferContext::new(db, scope),
+            db,
             targets: FxHashMap::default(),
-            scope,
+            diagnostics: TypeCheckDiagnosticsBuilder::new(db, file),
         }
     }
 
-    fn db(&self) -> &'db dyn Db {
-        self.context.db()
-    }
-
-    /// Unpack the value to the target expression.
-    pub(crate) fn unpack(&mut self, target: &ast::Expr, value: UnpackValue<'db>) {
-        debug_assert!(
-            matches!(target, ast::Expr::List(_) | ast::Expr::Tuple(_)),
-            "Unpacking target must be a list or tuple expression"
-        );
-
-        let mut value_ty = infer_expression_types(self.db(), value.expression())
-            .expression_ty(value.scoped_expression_id(self.db(), self.scope));
-
-        if value.is_iterable() {
-            // If the value is an iterable, then the type that needs to be unpacked is the iterator
-            // type.
-            value_ty = value_ty
-                .iterate(self.db())
-                .unwrap_with_diagnostic(&self.context, value.as_any_node_ref(self.db()));
-        }
-
-        self.unpack_inner(target, value_ty);
-    }
-
-    fn unpack_inner(&mut self, target: &ast::Expr, value_ty: Type<'db>) {
+    pub(crate) fn unpack(&mut self, target: &ast::Expr, value_ty: Type<'db>, scope: ScopeId<'db>) {
         match target {
             ast::Expr::Name(target_name) => {
-                self.targets.insert(
-                    target_name.scoped_expression_id(self.db(), self.scope),
-                    value_ty,
-                );
+                self.targets
+                    .insert(target_name.scoped_expression_id(self.db, scope), value_ty);
             }
             ast::Expr::Starred(ast::ExprStarred { value, .. }) => {
-                self.unpack_inner(value, value_ty);
+                self.unpack(value, value_ty, scope);
             }
             ast::Expr::List(ast::ExprList { elts, .. })
-            | ast::Expr::Tuple(ast::ExprTuple { elts, .. }) => {
-                // Initialize the vector of target types, one for each target.
-                //
-                // This is mainly useful for the union type where the target type at index `n` is
-                // going to be a union of types from every union type element at index `n`.
-                //
-                // For example, if the type is `tuple[int, int] | tuple[int, str]` and the target
-                // has two elements `(a, b)`, then
-                // * The type of `a` will be a union of `int` and `int` which are at index 0 in the
-                //   first and second tuple respectively which resolves to an `int`.
-                // * Similarly, the type of `b` will be a union of `int` and `str` which are at
-                //   index 1 in the first and second tuple respectively which will be `int | str`.
-                let mut target_types = vec![vec![]; elts.len()];
+            | ast::Expr::Tuple(ast::ExprTuple { elts, .. }) => match value_ty {
+                Type::Tuple(tuple_ty) => {
+                    let starred_index = elts.iter().position(ast::Expr::is_starred_expr);
 
-                let unpack_types = match value_ty {
-                    Type::Union(union_ty) => union_ty.elements(self.db()),
-                    _ => std::slice::from_ref(&value_ty),
-                };
+                    let element_types = if let Some(starred_index) = starred_index {
+                        if tuple_ty.len(self.db) >= elts.len() - 1 {
+                            let mut element_types = Vec::with_capacity(elts.len());
+                            element_types.extend_from_slice(
+                                // SAFETY: Safe because of the length check above.
+                                &tuple_ty.elements(self.db)[..starred_index],
+                            );
 
-                for ty in unpack_types.iter().copied() {
-                    // Deconstruct certain types to delegate the inference back to the tuple type
-                    // for correct handling of starred expressions.
-                    let ty = match ty {
-                        Type::StringLiteral(string_literal_ty) => {
-                            // We could go further and deconstruct to an array of `StringLiteral`
-                            // with each individual character, instead of just an array of
-                            // `LiteralString`, but there would be a cost and it's not clear that
-                            // it's worth it.
-                            Type::tuple(
-                                self.db(),
-                                std::iter::repeat(Type::LiteralString)
-                                    .take(string_literal_ty.python_len(self.db())),
-                            )
-                        }
-                        _ => ty,
-                    };
+                            // E.g., in `(a, *b, c, d) = ...`, the index of starred element `b`
+                            // is 1 and the remaining elements after that are 2.
+                            let remaining = elts.len() - (starred_index + 1);
+                            // This index represents the type of the last element that belongs
+                            // to the starred expression, in an exclusive manner.
+                            let starred_end_index = tuple_ty.len(self.db) - remaining;
+                            // SAFETY: Safe because of the length check above.
+                            let _starred_element_types =
+                                &tuple_ty.elements(self.db)[starred_index..starred_end_index];
+                            // TODO: Combine the types into a list type. If the
+                            // starred_element_types is empty, then it should be `List[Any]`.
+                            // combine_types(starred_element_types);
+                            element_types.push(todo_type!("starred unpacking"));
 
-                    if let Some(tuple_ty) = ty.into_tuple() {
-                        let tuple_ty_elements = self.tuple_ty_elements(target, elts, tuple_ty);
-
-                        match elts.len().cmp(&tuple_ty_elements.len()) {
-                            Ordering::Less => {
-                                self.context.report_lint(
-                                    &INVALID_ASSIGNMENT,
-                                    target.into(),
-                                    format_args!(
-                                        "Too many values to unpack (expected {}, got {})",
-                                        elts.len(),
-                                        tuple_ty_elements.len()
-                                    ),
-                                );
-                            }
-                            Ordering::Greater => {
-                                self.context.report_lint(
-                                    &INVALID_ASSIGNMENT,
-                                    target.into(),
-                                    format_args!(
-                                        "Not enough values to unpack (expected {}, got {})",
-                                        elts.len(),
-                                        tuple_ty_elements.len()
-                                    ),
-                                );
-                            }
-                            Ordering::Equal => {}
-                        }
-
-                        for (index, ty) in tuple_ty_elements.iter().enumerate() {
-                            if let Some(element_types) = target_types.get_mut(index) {
-                                element_types.push(*ty);
-                            }
+                            element_types.extend_from_slice(
+                                // SAFETY: Safe because of the length check above.
+                                &tuple_ty.elements(self.db)[starred_end_index..],
+                            );
+                            Cow::Owned(element_types)
+                        } else {
+                            let mut element_types = tuple_ty.elements(self.db).to_vec();
+                            // Subtract 1 to insert the starred expression type at the correct
+                            // index.
+                            element_types.resize(elts.len() - 1, Type::Unknown);
+                            // TODO: This should be `list[Unknown]`
+                            element_types.insert(starred_index, todo_type!("starred unpacking"));
+                            Cow::Owned(element_types)
                         }
                     } else {
-                        let ty = if ty.is_literal_string() {
-                            Type::LiteralString
-                        } else {
-                            ty.iterate(self.db())
-                                .unwrap_with_diagnostic(&self.context, AnyNodeRef::from(target))
-                        };
-                        for target_type in &mut target_types {
-                            target_type.push(ty);
-                        }
+                        Cow::Borrowed(tuple_ty.elements(self.db).as_ref())
+                    };
+
+                    for (index, element) in elts.iter().enumerate() {
+                        self.unpack(
+                            element,
+                            element_types.get(index).copied().unwrap_or(Type::Unknown),
+                            scope,
+                        );
                     }
                 }
-
-                for (index, element) in elts.iter().enumerate() {
-                    // SAFETY: `target_types` is initialized with the same length as `elts`.
-                    let element_ty = match target_types[index].as_slice() {
-                        [] => Type::Unknown,
-                        types => UnionType::from_elements(self.db(), types),
-                    };
-                    self.unpack_inner(element, element_ty);
+                Type::StringLiteral(string_literal_ty) => {
+                    // Deconstruct the string literal to delegate the inference back to the
+                    // tuple type for correct handling of starred expressions. We could go
+                    // further and deconstruct to an array of `StringLiteral` with each
+                    // individual character, instead of just an array of `LiteralString`, but
+                    // there would be a cost and it's not clear that it's worth it.
+                    let value_ty = Type::tuple(
+                        self.db,
+                        std::iter::repeat(Type::LiteralString)
+                            .take(string_literal_ty.python_len(self.db)),
+                    );
+                    self.unpack(target, value_ty, scope);
                 }
-            }
+                _ => {
+                    let value_ty = if value_ty.is_literal_string() {
+                        Type::LiteralString
+                    } else {
+                        value_ty
+                            .iterate(self.db)
+                            .unwrap_with_diagnostic(AnyNodeRef::from(target), &mut self.diagnostics)
+                    };
+                    for element in elts {
+                        self.unpack(element, value_ty, scope);
+                    }
+                }
+            },
             _ => {}
         }
     }
 
-    /// Returns the [`Type`] elements inside the given [`TupleType`] taking into account that there
-    /// can be a starred expression in the `elements`.
-    fn tuple_ty_elements(
-        &self,
-        expr: &ast::Expr,
-        targets: &[ast::Expr],
-        tuple_ty: TupleType<'db>,
-    ) -> Cow<'_, [Type<'db>]> {
-        // If there is a starred expression, it will consume all of the types at that location.
-        let Some(starred_index) = targets.iter().position(ast::Expr::is_starred_expr) else {
-            // Otherwise, the types will be unpacked 1-1 to the targets.
-            return Cow::Borrowed(tuple_ty.elements(self.db()).as_ref());
-        };
-
-        if tuple_ty.len(self.db()) >= targets.len() - 1 {
-            // This branch is only taken when there are enough elements in the tuple type to
-            // combine for the starred expression. So, the arithmetic and indexing operations are
-            // safe to perform.
-            let mut element_types = Vec::with_capacity(targets.len());
-
-            // Insert all the elements before the starred expression.
-            element_types.extend_from_slice(
-                // SAFETY: Safe because of the length check above.
-                &tuple_ty.elements(self.db())[..starred_index],
-            );
-
-            // The number of target expressions that are remaining after the starred expression.
-            // For example, in `(a, *b, c, d) = ...`, the index of starred element `b` is 1 and the
-            // remaining elements after that are 2.
-            let remaining = targets.len() - (starred_index + 1);
-
-            // This index represents the position of the last element that belongs to the starred
-            // expression, in an exclusive manner. For example, in `(a, *b, c) = (1, 2, 3, 4)`, the
-            // starred expression `b` will consume the elements `Literal[2]` and `Literal[3]` and
-            // the index value would be 3.
-            let starred_end_index = tuple_ty.len(self.db()) - remaining;
-
-            // SAFETY: Safe because of the length check above.
-            let _starred_element_types =
-                &tuple_ty.elements(self.db())[starred_index..starred_end_index];
-            // TODO: Combine the types into a list type. If the
-            // starred_element_types is empty, then it should be `List[Any]`.
-            // combine_types(starred_element_types);
-            element_types.push(todo_type!("starred unpacking"));
-
-            // Insert the types remaining that aren't consumed by the starred expression.
-            element_types.extend_from_slice(
-                // SAFETY: Safe because of the length check above.
-                &tuple_ty.elements(self.db())[starred_end_index..],
-            );
-
-            Cow::Owned(element_types)
-        } else {
-            self.context.report_lint(
-                &INVALID_ASSIGNMENT,
-                expr.into(),
-                format_args!(
-                    "Not enough values to unpack (expected {} or more, got {})",
-                    targets.len() - 1,
-                    tuple_ty.len(self.db())
-                ),
-            );
-
-            let mut element_types = tuple_ty.elements(self.db()).to_vec();
-
-            // Subtract 1 to insert the starred expression type at the correct
-            // index.
-            element_types.resize(targets.len() - 1, Type::Unknown);
-            // TODO: This should be `list[Unknown]`
-            element_types.insert(starred_index, todo_type!("starred unpacking"));
-
-            Cow::Owned(element_types)
-        }
-    }
-
     pub(crate) fn finish(mut self) -> UnpackResult<'db> {
         self.targets.shrink_to_fit();
         UnpackResult {
-            diagnostics: self.context.finish(),
+            diagnostics: self.diagnostics.finish(),
             targets: self.targets,
         }
     }
@@ -259,10 +136,8 @@ impl<'db> UnpackResult<'db> {
     pub(crate) fn get(&self, expr_id: ScopedExpressionId) -> Option<Type<'db>> {
         self.targets.get(&expr_id).copied()
     }
-}
 
-impl WithDiagnostics for UnpackResult<'_> {
-    fn diagnostics(&self) -> &TypeCheckDiagnostics {
+    pub(crate) fn diagnostics(&self) -> &TypeCheckDiagnostics {
         &self.diagnostics
     }
 }

crates/red_knot_python_semantic/src/unpack.rs

@@ -1,9 +1,7 @@
 use ruff_db::files::File;
-use ruff_python_ast::{self as ast, AnyNodeRef};
-use ruff_text_size::{Ranged, TextRange};
+use ruff_python_ast::{self as ast};
 
 use crate::ast_node_ref::AstNodeRef;
-use crate::semantic_index::ast_ids::{HasScopedExpressionId, ScopedExpressionId};
 use crate::semantic_index::expression::Expression;
 use crate::semantic_index::symbol::{FileScopeId, ScopeId};
 use crate::Db;
@@ -43,7 +41,7 @@ pub(crate) struct Unpack<'db> {
     /// The ingredient representing the value expression of the unpacking. For example, in
     /// `(a, b) = (1, 2)`, the value expression is `(1, 2)`.
     #[no_eq]
-    pub(crate) value: UnpackValue<'db>,
+    pub(crate) value: Expression<'db>,
 
     #[no_eq]
     count: countme::Count<Unpack<'static>>,
@@ -54,48 +52,4 @@ impl<'db> Unpack<'db> {
     pub(crate) fn scope(self, db: &'db dyn Db) -> ScopeId<'db> {
         self.file_scope(db).to_scope_id(db, self.file(db))
     }
-
-    /// Returns the range of the unpack target expression.
-    pub(crate) fn range(self, db: &'db dyn Db) -> TextRange {
-        self.target(db).range()
-    }
-}
-
-/// The expression that is being unpacked.
-#[derive(Clone, Copy, Debug)]
-pub(crate) enum UnpackValue<'db> {
-    /// An iterable expression like the one in a `for` loop or a comprehension.
-    Iterable(Expression<'db>),
-    /// An expression that is being assigned to a target.
-    Assign(Expression<'db>),
-}
-
-impl<'db> UnpackValue<'db> {
-    /// Returns `true` if the value is an iterable expression.
-    pub(crate) const fn is_iterable(self) -> bool {
-        matches!(self, UnpackValue::Iterable(_))
-    }
-
-    /// Returns the underlying [`Expression`] that is being unpacked.
-    pub(crate) const fn expression(self) -> Expression<'db> {
-        match self {
-            UnpackValue::Assign(expr) | UnpackValue::Iterable(expr) => expr,
-        }
-    }
-
-    /// Returns the [`ScopedExpressionId`] of the underlying expression.
-    pub(crate) fn scoped_expression_id(
-        self,
-        db: &'db dyn Db,
-        scope: ScopeId<'db>,
-    ) -> ScopedExpressionId {
-        self.expression()
-            .node_ref(db)
-            .scoped_expression_id(db, scope)
-    }
-
-    /// Returns the expression as an [`AnyNodeRef`].
-    pub(crate) fn as_any_node_ref(self, db: &'db dyn Db) -> AnyNodeRef<'db> {
-        self.expression().node_ref(db).node().into()
-    }
 }

crates/red_knot_python_semantic/src/visibility_constraints.rs

@@ -1,338 +0,0 @@
-//! # Visibility constraints
-//!
-//! During semantic index building, we collect visibility constraints for each binding and
-//! declaration. These constraints are then used during type-checking to determine the static
-//! visibility of a certain definition. This allows us to re-analyze control flow during type
-//! checking, potentially "hiding" some branches that we can statically determine to never be
-//! taken. Consider the following example first. We added implicit "unbound" definitions at the
-//! start of the scope. Note how visibility constraints can apply to bindings outside of the
-//! if-statement:
-//! ```py
-//! x = <unbound>  # not a live binding for the use of x below, shadowed by `x = 1`
-//! y = <unbound>  # visibility constraint: ~test
-//!
-//! x = 1  # visibility constraint: ~test
-//! if test:
-//!     x = 2  # visibility constraint: test
-//!
-//!     y = 2  # visibility constraint: test
-//!
-//! use(x)
-//! use(y)
-//! ```
-//! The static truthiness of the `test` condition can either be always-false, ambiguous, or
-//! always-true. Similarly, we have the same three options when evaluating a visibility constraint.
-//! This outcome determines the visibility of a definition: always-true means that the definition
-//! is definitely visible for a given use, always-false means that the definition is definitely
-//! not visible, and ambiguous means that we might see this definition or not. In the latter case,
-//! we need to consider both options during type inference and boundness analysis. For the example
-//! above, these are the possible type inference / boundness results for the uses of `x` and `y`:
-//!
-//! ```text
-//!       | `test` truthiness | `~test` truthiness | type of `x`     | boundness of `y` |
-//!       |-------------------|--------------------|-----------------|------------------|
-//!       | always false      | always true        | `Literal[1]`    | unbound          |
-//!       | ambiguous         | ambiguous          | `Literal[1, 2]` | possibly unbound |
-//!       | always true       | always false       | `Literal[2]`    | bound            |
-//! ```
-//!
-//! ### Sequential constraints (ternary AND)
-//!
-//! As we have seen above, visibility constraints can apply outside of a control flow element.
-//! So we need to consider the possibility that multiple constraints apply to the same binding.
-//! Here, we consider what happens if multiple `if`-statements lead to a sequence of constraints.
-//! Consider the following example:
-//! ```py
-//! x = 0
-//!
-//! if test1:
-//!     x = 1
-//!
-//! if test2:
-//!     x = 2
-//! ```
-//! The binding `x = 2` is easy to analyze. Its visibility corresponds to the truthiness of `test2`.
-//! For the `x = 1` binding, things are a bit more interesting. It is always visible if `test1` is
-//! always-true *and* `test2` is always-false. It is never visible if `test1` is always-false *or*
-//! `test2` is always-true. And it is ambiguous otherwise. This corresponds to a ternary *test1 AND
-//! ~test2* operation in three-valued Kleene logic [Kleene]:
-//!
-//! ```text
-//!       | AND          | always-false | ambiguous    | always-true  |
-//!       |--------------|--------------|--------------|--------------|
-//!       | always false | always-false | always-false | always-false |
-//!       | ambiguous    | always-false | ambiguous    | ambiguous    |
-//!       | always true  | always-false | ambiguous    | always-true  |
-//! ```
-//!
-//! The `x = 0` binding can be handled similarly, with the difference that both `test1` and `test2`
-//! are negated:
-//! ```py
-//! x = 0  # ~test1 AND ~test2
-//!
-//! if test1:
-//!     x = 1  # test1 AND ~test2
-//!
-//! if test2:
-//!     x = 2  # test2
-//! ```
-//!
-//! ### Merged constraints (ternary OR)
-//!
-//! Finally, we consider what happens in "parallel" control flow. Consider the following example
-//! where we have omitted the test condition for the outer `if` for clarity:
-//! ```py
-//! x = 0
-//!
-//! if <…>:
-//!     if test1:
-//!         x = 1
-//! else:
-//!     if test2:
-//!         x = 2
-//!
-//! use(x)
-//! ```
-//! At the usage of `x`, i.e. after control flow has been merged again, the visibility of the `x =
-//! 0` binding behaves as follows: the binding is always visible if `test1` is always-false *or*
-//! `test2` is always-false; and it is never visible if `test1` is always-true *and* `test2` is
-//! always-true. This corresponds to a ternary *OR* operation in Kleene logic:
-//!
-//! ```text
-//!       | OR           | always-false | ambiguous    | always-true  |
-//!       |--------------|--------------|--------------|--------------|
-//!       | always false | always-false | ambiguous    | always-true  |
-//!       | ambiguous    | ambiguous    | ambiguous    | always-true  |
-//!       | always true  | always-true  | always-true  | always-true  |
-//! ```
-//!
-//! Using this, we can annotate the visibility constraints for the example above:
-//! ```py
-//! x = 0  # ~test1 OR ~test2
-//!
-//! if <…>:
-//!     if test1:
-//!         x = 1  # test1
-//! else:
-//!     if test2:
-//!         x = 2  # test2
-//!
-//! use(x)
-//! ```
-//!
-//! ### Explicit ambiguity
-//!
-//! In some cases, we explicitly add a `VisibilityConstraint::Ambiguous` constraint to all bindings
-//! in a certain control flow path. We do this when branching on something that we can not (or
-//! intentionally do not want to) analyze statically. `for` loops are one example:
-//! ```py
-//! x = <unbound>
-//!
-//! for _ in range(2):
-//!    x = 1
-//! ```
-//! Here, we report an ambiguous visibility constraint before branching off. If we don't do this,
-//! the `x = <unbound>` binding would be considered unconditionally visible in the no-loop case.
-//! And since the other branch does not have the live `x = <unbound>` binding, we would incorrectly
-//! create a state where the `x = <unbound>` binding is always visible.
-//!
-//!
-//! ### Properties
-//!
-//! The ternary `AND` and `OR` operations have the property that `~a OR ~b = ~(a AND b)`. This
-//! means we could, in principle, get rid of either of these two to simplify the representation.
-//!
-//! However, we already apply negative constraints `~test1` and `~test2` to the "branches not
-//! taken" in the example above. This means that the tree-representation `~test1 OR ~test2` is much
-//! cheaper/shallower than basically creating `~(~(~test1) AND ~(~test2))`. Similarly, if we wanted
-//! to get rid of `AND`, we would also have to create additional nodes. So for performance reasons,
-//! there is a small "duplication" in the code between those two constraint types.
-//!
-//! [Kleene]: <https://en.wikipedia.org/wiki/Three-valued_logic#Kleene_and_Priest_logics>
-
-use ruff_index::IndexVec;
-
-use crate::semantic_index::ScopedVisibilityConstraintId;
-use crate::semantic_index::{
-    ast_ids::HasScopedExpressionId,
-    constraint::{Constraint, ConstraintNode, PatternConstraintKind},
-};
-use crate::types::{infer_expression_types, Truthiness};
-use crate::Db;
-
-/// The maximum depth of recursion when evaluating visibility constraints.
-///
-/// This is a performance optimization that prevents us from descending deeply in case of
-/// pathological cases. The actual limit here has been derived from performance testing on
-/// the `black` codebase. When increasing the limit beyond 32, we see a 5x runtime increase
-/// resulting from a few files with a lot of boolean expressions and `if`-statements.
-const MAX_RECURSION_DEPTH: usize = 24;
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub(crate) enum VisibilityConstraint<'db> {
-    AlwaysTrue,
-    Ambiguous,
-    VisibleIf(Constraint<'db>),
-    VisibleIfNot(ScopedVisibilityConstraintId),
-    KleeneAnd(ScopedVisibilityConstraintId, ScopedVisibilityConstraintId),
-    KleeneOr(ScopedVisibilityConstraintId, ScopedVisibilityConstraintId),
-}
-
-#[derive(Debug, PartialEq, Eq)]
-pub(crate) struct VisibilityConstraints<'db> {
-    constraints: IndexVec<ScopedVisibilityConstraintId, VisibilityConstraint<'db>>,
-}
-
-impl Default for VisibilityConstraints<'_> {
-    fn default() -> Self {
-        Self {
-            constraints: IndexVec::from_iter([VisibilityConstraint::AlwaysTrue]),
-        }
-    }
-}
-
-impl<'db> VisibilityConstraints<'db> {
-    pub(crate) fn add(
-        &mut self,
-        constraint: VisibilityConstraint<'db>,
-    ) -> ScopedVisibilityConstraintId {
-        self.constraints.push(constraint)
-    }
-
-    pub(crate) fn add_or_constraint(
-        &mut self,
-        a: ScopedVisibilityConstraintId,
-        b: ScopedVisibilityConstraintId,
-    ) -> ScopedVisibilityConstraintId {
-        match (&self.constraints[a], &self.constraints[b]) {
-            (_, VisibilityConstraint::VisibleIfNot(id)) if a == *id => {
-                ScopedVisibilityConstraintId::ALWAYS_TRUE
-            }
-            (VisibilityConstraint::VisibleIfNot(id), _) if *id == b => {
-                ScopedVisibilityConstraintId::ALWAYS_TRUE
-            }
-            _ => self.add(VisibilityConstraint::KleeneOr(a, b)),
-        }
-    }
-
-    pub(crate) fn add_and_constraint(
-        &mut self,
-        a: ScopedVisibilityConstraintId,
-        b: ScopedVisibilityConstraintId,
-    ) -> ScopedVisibilityConstraintId {
-        if a == ScopedVisibilityConstraintId::ALWAYS_TRUE {
-            b
-        } else if b == ScopedVisibilityConstraintId::ALWAYS_TRUE {
-            a
-        } else {
-            self.add(VisibilityConstraint::KleeneAnd(a, b))
-        }
-    }
-
-    /// Analyze the statically known visibility for a given visibility constraint.
-    pub(crate) fn evaluate(&self, db: &'db dyn Db, id: ScopedVisibilityConstraintId) -> Truthiness {
-        self.evaluate_impl(db, id, MAX_RECURSION_DEPTH)
-    }
-
-    fn evaluate_impl(
-        &self,
-        db: &'db dyn Db,
-        id: ScopedVisibilityConstraintId,
-        max_depth: usize,
-    ) -> Truthiness {
-        if max_depth == 0 {
-            return Truthiness::Ambiguous;
-        }
-
-        let visibility_constraint = &self.constraints[id];
-        match visibility_constraint {
-            VisibilityConstraint::AlwaysTrue => Truthiness::AlwaysTrue,
-            VisibilityConstraint::Ambiguous => Truthiness::Ambiguous,
-            VisibilityConstraint::VisibleIf(constraint) => Self::analyze_single(db, constraint),
-            VisibilityConstraint::VisibleIfNot(negated) => {
-                self.evaluate_impl(db, *negated, max_depth - 1).negate()
-            }
-            VisibilityConstraint::KleeneAnd(lhs, rhs) => {
-                let lhs = self.evaluate_impl(db, *lhs, max_depth - 1);
-
-                if lhs == Truthiness::AlwaysFalse {
-                    return Truthiness::AlwaysFalse;
-                }
-
-                let rhs = self.evaluate_impl(db, *rhs, max_depth - 1);
-
-                if rhs == Truthiness::AlwaysFalse {
-                    Truthiness::AlwaysFalse
-                } else if lhs == Truthiness::AlwaysTrue && rhs == Truthiness::AlwaysTrue {
-                    Truthiness::AlwaysTrue
-                } else {
-                    Truthiness::Ambiguous
-                }
-            }
-            VisibilityConstraint::KleeneOr(lhs_id, rhs_id) => {
-                let lhs = self.evaluate_impl(db, *lhs_id, max_depth - 1);
-
-                if lhs == Truthiness::AlwaysTrue {
-                    return Truthiness::AlwaysTrue;
-                }
-
-                let rhs = self.evaluate_impl(db, *rhs_id, max_depth - 1);
-
-                if rhs == Truthiness::AlwaysTrue {
-                    Truthiness::AlwaysTrue
-                } else if lhs == Truthiness::AlwaysFalse && rhs == Truthiness::AlwaysFalse {
-                    Truthiness::AlwaysFalse
-                } else {
-                    Truthiness::Ambiguous
-                }
-            }
-        }
-    }
-
-    fn analyze_single(db: &dyn Db, constraint: &Constraint) -> Truthiness {
-        match constraint.node {
-            ConstraintNode::Expression(test_expr) => {
-                let inference = infer_expression_types(db, test_expr);
-                let scope = test_expr.scope(db);
-                let ty =
-                    inference.expression_ty(test_expr.node_ref(db).scoped_expression_id(db, scope));
-
-                ty.bool(db).negate_if(!constraint.is_positive)
-            }
-            ConstraintNode::Pattern(inner) => match inner.kind(db) {
-                PatternConstraintKind::Value(value, guard) => {
-                    let subject_expression = inner.subject(db);
-                    let inference = infer_expression_types(db, *subject_expression);
-                    let scope = subject_expression.scope(db);
-                    let subject_ty = inference.expression_ty(
-                        subject_expression
-                            .node_ref(db)
-                            .scoped_expression_id(db, scope),
-                    );
-
-                    let inference = infer_expression_types(db, *value);
-                    let scope = value.scope(db);
-                    let value_ty =
-                        inference.expression_ty(value.node_ref(db).scoped_expression_id(db, scope));
-
-                    if subject_ty.is_single_valued(db) {
-                        let truthiness =
-                            Truthiness::from(subject_ty.is_equivalent_to(db, value_ty));
-
-                        if truthiness.is_always_true() && guard.is_some() {
-                            // Fall back to ambiguous, the guard might change the result.
-                            Truthiness::Ambiguous
-                        } else {
-                            truthiness
-                        }
-                    } else {
-                        Truthiness::Ambiguous
-                    }
-                }
-                PatternConstraintKind::Singleton(..) | PatternConstraintKind::Unsupported => {
-                    Truthiness::Ambiguous
-                }
-            },
-        }
-    }
-}

crates/red_knot_server/src/server/api.rs

@@ -91,11 +91,11 @@ fn background_request_task<'a, R: traits::BackgroundDocumentRequestHandler>(
         let db = match path {
             AnySystemPath::System(path) => {
                 match session.workspace_db_for_path(path.as_std_path()) {
-                    Some(db) => db.clone(),
-                    None => session.default_workspace_db().clone(),
+                    Some(db) => db.snapshot(),
+                    None => session.default_workspace_db().snapshot(),
                 }
             }
-            AnySystemPath::SystemVirtual(_) => session.default_workspace_db().clone(),
+            AnySystemPath::SystemVirtual(_) => session.default_workspace_db().snapshot(),
         };
 
         let Some(snapshot) = session.take_snapshot(url) else {

crates/red_knot_test/src/config.rs

@@ -9,7 +9,7 @@
 //! ```
 
 use anyhow::Context;
-use red_knot_python_semantic::{PythonPlatform, PythonVersion};
+use red_knot_python_semantic::PythonVersion;
 use serde::Deserialize;
 
 #[derive(Deserialize, Debug, Default, Clone)]
@@ -28,22 +28,13 @@ impl MarkdownTestConfig {
     pub(crate) fn python_version(&self) -> Option<PythonVersion> {
         self.environment.as_ref().and_then(|env| env.python_version)
     }
-
-    pub(crate) fn python_platform(&self) -> Option<PythonPlatform> {
-        self.environment
-            .as_ref()
-            .and_then(|env| env.python_platform.clone())
-    }
 }
 
 #[derive(Deserialize, Debug, Default, Clone)]
 #[serde(rename_all = "kebab-case", deny_unknown_fields)]
 pub(crate) struct Environment {
-    /// Target Python version to assume when resolving types.
+    /// Python version to assume when resolving types.
     pub(crate) python_version: Option<PythonVersion>,
-
-    /// Target platform to assume when resolving types.
-    pub(crate) python_platform: Option<PythonPlatform>,
 }
 
 #[derive(Deserialize, Debug, Clone)]

crates/red_knot_test/src/db.rs

@@ -1,7 +1,7 @@
-use red_knot_python_semantic::lint::{LintRegistry, RuleSelection};
+use red_knot_python_semantic::lint::RuleSelection;
 use red_knot_python_semantic::{
-    default_lint_registry, Db as SemanticDb, Program, ProgramSettings, PythonPlatform,
-    PythonVersion, SearchPathSettings,
+    default_lint_registry, Db as SemanticDb, Program, ProgramSettings, PythonVersion,
+    SearchPathSettings,
 };
 use ruff_db::files::{File, Files};
 use ruff_db::system::{DbWithTestSystem, System, SystemPath, SystemPathBuf, TestSystem};
@@ -9,7 +9,6 @@ use ruff_db::vendored::VendoredFileSystem;
 use ruff_db::{Db as SourceDb, Upcast};
 
 #[salsa::db]
-#[derive(Clone)]
 pub(crate) struct Db {
     workspace_root: SystemPathBuf,
     storage: salsa::Storage<Self>,
@@ -21,7 +20,7 @@ pub(crate) struct Db {
 
 impl Db {
     pub(crate) fn setup(workspace_root: SystemPathBuf) -> Self {
-        let rule_selection = RuleSelection::from_registry(default_lint_registry());
+        let rule_selection = RuleSelection::from_registry(&default_lint_registry());
 
         let db = Self {
             workspace_root,
@@ -40,7 +39,6 @@ impl Db {
             &db,
             &ProgramSettings {
                 python_version: PythonVersion::default(),
-                python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings::new(db.workspace_root.clone()),
             },
         )
@@ -97,10 +95,6 @@ impl SemanticDb for Db {
     fn rule_selection(&self) -> &RuleSelection {
         &self.rule_selection
     }
-
-    fn lint_registry(&self) -> &LintRegistry {
-        default_lint_registry()
-    }
 }
 
 #[salsa::db]