Separate TOC from the navigation

.github/workflows/ci.yaml

@@ -148,7 +148,7 @@ jobs:
       # sync, not just public items. Eventually we should do this for all
       # crates; for now add crates here as they are warning-clean to prevent
       # regression.
-      - run: cargo doc --no-deps -p red_knot_python_semantic -p red_knot -p red_knot_test -p ruff_db --document-private-items
+      - run: cargo doc --no-deps -p red_knot_python_semantic -p red_knot -p ruff_db --document-private-items
         env:
           # Setting RUSTDOCFLAGS because `cargo doc --check` isn't yet implemented (https://github.com/rust-lang/cargo/issues/10025).
           RUSTDOCFLAGS: "-D warnings"
@@ -518,8 +518,6 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
-        with:
-          python-version: "3.13"
       - name: "Add SSH key"
         if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
         uses: webfactory/ssh-agent@v0.9.0
@@ -527,15 +525,13 @@ jobs:
           ssh-private-key: ${{ secrets.MKDOCS_INSIDERS_SSH_KEY }}
       - name: "Install Rust toolchain"
         run: rustup show
-      - name: Install uv
-        uses: astral-sh/setup-uv@v3
       - uses: Swatinem/rust-cache@v2
       - name: "Install Insiders dependencies"
         if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
-        run: uv pip install -r docs/requirements-insiders.txt --system
+        run: pip install -r docs/requirements-insiders.txt
       - name: "Install dependencies"
         if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS != 'true' }}
-        run: uv pip install -r docs/requirements.txt --system
+        run: pip install -r docs/requirements.txt
       - name: "Update README File"
         run: python scripts/transform_readme.py --target mkdocs
       - name: "Generate docs"
@@ -612,7 +608,7 @@ jobs:
           just test
 
   benchmarks:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     needs: determine_changes
     if: ${{ github.repository == 'astral-sh/ruff' && (needs.determine_changes.outputs.code == 'true' || github.ref == 'refs/heads/main') }}
     timeout-minutes: 20

.github/workflows/release.yml

@@ -1,5 +1,3 @@
-# This file was autogenerated by cargo-dist: https://opensource.axo.dev/cargo-dist/
-#
 # Copyright 2022-2024, axodotdev
 # SPDX-License-Identifier: MIT or Apache-2.0
 #
@@ -66,7 +64,7 @@ jobs:
         # we specify bash to get pipefail; it guards against the `curl` command
         # failing. otherwise `sh` won't catch that `curl` returned non-0
         shell: bash
-        run: "curl --proto '=https' --tlsv1.2 -LsSf https://github.com/axodotdev/cargo-dist/releases/download/v0.22.1/cargo-dist-installer.sh | sh"
+        run: "curl --proto '=https' --tlsv1.2 -LsSf https://github.com/axodotdev/cargo-dist/releases/download/v0.18.0/cargo-dist-installer.sh | sh"
       - name: Cache cargo-dist
         uses: actions/upload-artifact@v4
         with:

.github/workflows/sync_typeshed.yaml

@@ -37,13 +37,13 @@ jobs:
       - name: Sync typeshed
         id: sync
         run: |
-          rm -rf ruff/crates/red_knot_vendored/vendor/typeshed
-          mkdir ruff/crates/red_knot_vendored/vendor/typeshed
-          cp typeshed/README.md ruff/crates/red_knot_vendored/vendor/typeshed
-          cp typeshed/LICENSE ruff/crates/red_knot_vendored/vendor/typeshed
-          cp -r typeshed/stdlib ruff/crates/red_knot_vendored/vendor/typeshed/stdlib
-          rm -rf ruff/crates/red_knot_vendored/vendor/typeshed/stdlib/@tests
-          git -C typeshed rev-parse HEAD > ruff/crates/red_knot_vendored/vendor/typeshed/source_commit.txt
+          rm -rf ruff/crates/red_knot_python_semantic/vendor/typeshed
+          mkdir ruff/crates/red_knot_python_semantic/vendor/typeshed
+          cp typeshed/README.md ruff/crates/red_knot_python_semantic/vendor/typeshed
+          cp typeshed/LICENSE ruff/crates/red_knot_python_semantic/vendor/typeshed
+          cp -r typeshed/stdlib ruff/crates/red_knot_python_semantic/vendor/typeshed/stdlib
+          rm -rf ruff/crates/red_knot_python_semantic/vendor/typeshed/stdlib/@tests
+          git -C typeshed rev-parse HEAD > ruff/crates/red_knot_python_semantic/vendor/typeshed/source_commit.txt
       - name: Commit the changes
         id: commit
         if: ${{ steps.sync.outcome == 'success' }}

.pre-commit-config.yaml

@@ -2,7 +2,7 @@ fail_fast: true
 
 exclude: |
   (?x)^(
-    crates/red_knot_vendored/vendor/.*|
+    crates/red_knot_python_semantic/vendor/.*|
     crates/red_knot_workspace/resources/.*|
     crates/ruff_linter/resources/.*|
     crates/ruff_linter/src/rules/.*/snapshots/.*|
@@ -17,7 +17,7 @@ exclude: |
 
 repos:
   - repo: https://github.com/abravalheri/validate-pyproject
-    rev: v0.20.2
+    rev: v0.19
     hooks:
       - id: validate-pyproject
 
@@ -28,7 +28,6 @@ repos:
         additional_dependencies:
           - mdformat-mkdocs
           - mdformat-admon
-          - mdformat-footnote
         exclude: |
           (?x)^(
             docs/formatter/black\.md
@@ -36,7 +35,7 @@ repos:
           )$
 
   - repo: https://github.com/igorshubovych/markdownlint-cli
-    rev: v0.42.0
+    rev: v0.41.0
     hooks:
       - id: markdownlint-fix
         exclude: |
@@ -46,7 +45,7 @@ repos:
           )$
 
   - repo: https://github.com/crate-ci/typos
-    rev: v1.25.0
+    rev: v1.24.3
     hooks:
       - id: typos
 
@@ -60,7 +59,7 @@ repos:
         pass_filenames: false # This makes it a lot faster
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.6.9
+    rev: v0.6.3
     hooks:
       - id: ruff-format
       - id: ruff
@@ -69,8 +68,8 @@ repos:
         require_serial: true
 
   # Prettier
-  - repo: https://github.com/rbubley/mirrors-prettier
-    rev: v3.3.3
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: v3.1.0
     hooks:
       - id: prettier
         types: [yaml]

CHANGELOG.md

@@ -1,164 +1,5 @@
 # Changelog
 
-## 0.6.9
-
-### Preview features
-
-- Fix codeblock dynamic line length calculation for indented docstring examples ([#13523](https://github.com/astral-sh/ruff/pull/13523))
-- \[`refurb`\] Mark `FURB118` fix as unsafe ([#13613](https://github.com/astral-sh/ruff/pull/13613))
-
-### Rule changes
-
-- \[`pydocstyle`\] Don't raise `D208` when last line is non-empty ([#13372](https://github.com/astral-sh/ruff/pull/13372))
-- \[`pylint`\] Preserve trivia (i.e. comments) in `PLR5501` autofix ([#13573](https://github.com/astral-sh/ruff/pull/13573))
-
-### Configuration
-
-- \[`pyflakes`\] Add `allow-unused-imports` setting for `unused-import` rule (`F401`) ([#13601](https://github.com/astral-sh/ruff/pull/13601))
-
-### Bug fixes
-
-- Support ruff discovery in pip build environments ([#13591](https://github.com/astral-sh/ruff/pull/13591))
-- \[`flake8-bugbear`\] Avoid short circuiting `B017` for multiple context managers ([#13609](https://github.com/astral-sh/ruff/pull/13609))
-- \[`pylint`\] Do not offer an invalid fix for `PLR1716` when the comparisons contain parenthesis ([#13527](https://github.com/astral-sh/ruff/pull/13527))
-- \[`pyupgrade`\] Fix `UP043` to apply to `collections.abc.Generator` and `collections.abc.AsyncGenerator` ([#13611](https://github.com/astral-sh/ruff/pull/13611))
-- \[`refurb`\] Fix handling of slices in tuples for `FURB118`, e.g., `x[:, 1]` ([#13518](https://github.com/astral-sh/ruff/pull/13518))
-
-### Documentation
-
-- Update GitHub Action link to `astral-sh/ruff-action` ([#13551](https://github.com/astral-sh/ruff/pull/13551))
-
-## 0.6.8
-
-### Preview features
-
-- Remove unnecessary parentheses around `match case` clauses ([#13510](https://github.com/astral-sh/ruff/pull/13510))
-- Parenthesize overlong `if` guards in `match..case` clauses ([#13513](https://github.com/astral-sh/ruff/pull/13513))
-- Detect basic wildcard imports in `ruff analyze graph` ([#13486](https://github.com/astral-sh/ruff/pull/13486))
-- \[`pylint`\] Implement `boolean-chained-comparison` (`R1716`) ([#13435](https://github.com/astral-sh/ruff/pull/13435))
-
-### Rule changes
-
-- \[`lake8-simplify`\] Detect `SIM910` when using variadic keyword arguments, i.e., `**kwargs` ([#13503](https://github.com/astral-sh/ruff/pull/13503))
-- \[`pyupgrade`\] Avoid false negatives with non-reference shadowed bindings of loop variables (`UP028`) ([#13504](https://github.com/astral-sh/ruff/pull/13504))
-
-### Bug fixes
-
-- Detect tuples bound to variadic positional arguments i.e. `*args` ([#13512](https://github.com/astral-sh/ruff/pull/13512))
-- Exit gracefully on broken pipe errors ([#13485](https://github.com/astral-sh/ruff/pull/13485))
-- Avoid panic when analyze graph hits broken pipe ([#13484](https://github.com/astral-sh/ruff/pull/13484))
-
-### Performance
-
-- Reuse `BTreeSets` in module resolver ([#13440](https://github.com/astral-sh/ruff/pull/13440))
-- Skip traversal for non-compound statements ([#13441](https://github.com/astral-sh/ruff/pull/13441))
-
-## 0.6.7
-
-### Preview features
-
-- Add Python version support to ruff analyze CLI ([#13426](https://github.com/astral-sh/ruff/pull/13426))
-- Add `exclude` support to `ruff analyze` ([#13425](https://github.com/astral-sh/ruff/pull/13425))
-- Fix parentheses around return type annotations ([#13381](https://github.com/astral-sh/ruff/pull/13381))
-
-### Rule changes
-
-- \[`pycodestyle`\] Fix: Don't autofix if the first line ends in a question mark? (D400) ([#13399](https://github.com/astral-sh/ruff/pull/13399))
-
-### Bug fixes
-
-- Respect `lint.exclude` in ruff check `--add-noqa` ([#13427](https://github.com/astral-sh/ruff/pull/13427))
-
-### Performance
-
-- Avoid tracking module resolver files in Salsa ([#13437](https://github.com/astral-sh/ruff/pull/13437))
-- Use `forget` for module resolver database ([#13438](https://github.com/astral-sh/ruff/pull/13438))
-
-## 0.6.6
-
-### Preview features
-
-- \[`refurb`\] Skip `slice-to-remove-prefix-or-suffix` (`FURB188`) when non-trivial slice steps are present ([#13405](https://github.com/astral-sh/ruff/pull/13405))
-- Add a subcommand to generate dependency graphs ([#13402](https://github.com/astral-sh/ruff/pull/13402))
-
-### Formatter
-
-- Fix placement of inline parameter comments ([#13379](https://github.com/astral-sh/ruff/pull/13379))
-
-### Server
-
-- Fix off-by one error in the `LineIndex::offset` calculation ([#13407](https://github.com/astral-sh/ruff/pull/13407))
-
-### Bug fixes
-
-- \[`fastapi`\] Respect FastAPI aliases in route definitions ([#13394](https://github.com/astral-sh/ruff/pull/13394))
-- \[`pydocstyle`\] Respect word boundaries when detecting function signature in docs ([#13388](https://github.com/astral-sh/ruff/pull/13388))
-
-### Documentation
-
-- Add backlinks to rule overview linter ([#13368](https://github.com/astral-sh/ruff/pull/13368))
-- Fix documentation for editor vim plugin ALE ([#13348](https://github.com/astral-sh/ruff/pull/13348))
-- Fix rendering of `FURB188` docs ([#13406](https://github.com/astral-sh/ruff/pull/13406))
-
-## 0.6.5
-
-### Preview features
-
-- \[`pydoclint`\] Ignore `DOC201` when function name is "**new**" ([#13300](https://github.com/astral-sh/ruff/pull/13300))
-- \[`refurb`\] Implement `slice-to-remove-prefix-or-suffix` (`FURB188`) ([#13256](https://github.com/astral-sh/ruff/pull/13256))
-
-### Rule changes
-
-- \[`eradicate`\] Ignore script-comments with multiple end-tags (`ERA001`) ([#13283](https://github.com/astral-sh/ruff/pull/13283))
-- \[`pyflakes`\] Improve error message for `UndefinedName` when a builtin was added in a newer version than specified in Ruff config (`F821`) ([#13293](https://github.com/astral-sh/ruff/pull/13293))
-
-### Server
-
-- Add support for extensionless Python files for server ([#13326](https://github.com/astral-sh/ruff/pull/13326))
-- Fix configuration inheritance for configurations specified in the LSP settings ([#13285](https://github.com/astral-sh/ruff/pull/13285))
-
-### Bug fixes
-
-- \[`ruff`\] Handle unary operators in `decimal-from-float-literal` (`RUF032`) ([#13275](https://github.com/astral-sh/ruff/pull/13275))
-
-### CLI
-
-- Only include rules with diagnostics in SARIF metadata ([#13268](https://github.com/astral-sh/ruff/pull/13268))
-
-### Playground
-
-- Add "Copy as pyproject.toml/ruff.toml" and "Paste from TOML" ([#13328](https://github.com/astral-sh/ruff/pull/13328))
-- Fix errors not shown for restored snippet on page load ([#13262](https://github.com/astral-sh/ruff/pull/13262))
-
-## 0.6.4
-
-### Preview features
-
-- \[`flake8-builtins`\] Use dynamic builtins list based on Python version ([#13172](https://github.com/astral-sh/ruff/pull/13172))
-- \[`pydoclint`\] Permit yielding `None` in `DOC402` and `DOC403` ([#13148](https://github.com/astral-sh/ruff/pull/13148))
-- \[`pylint`\] Update diagnostic message for `PLW3201` ([#13194](https://github.com/astral-sh/ruff/pull/13194))
-- \[`ruff`\] Implement `post-init-default` (`RUF033`) ([#13192](https://github.com/astral-sh/ruff/pull/13192))
-- \[`ruff`\] Implement useless if-else (`RUF034`) ([#13218](https://github.com/astral-sh/ruff/pull/13218))
-
-### Rule changes
-
-- \[`flake8-pyi`\] Respect `pep8_naming.classmethod-decorators` settings when determining if a method is a classmethod in `custom-type-var-return-type` (`PYI019`) ([#13162](https://github.com/astral-sh/ruff/pull/13162))
-- \[`flake8-pyi`\] Teach various rules that annotations might be stringized ([#12951](https://github.com/astral-sh/ruff/pull/12951))
-- \[`pylint`\] Avoid `no-self-use` for `attrs`-style validators ([#13166](https://github.com/astral-sh/ruff/pull/13166))
-- \[`pylint`\] Recurse into subscript subexpressions when searching for list/dict lookups (`PLR1733`, `PLR1736`) ([#13186](https://github.com/astral-sh/ruff/pull/13186))
-- \[`pyupgrade`\] Detect `aiofiles.open` calls in `UP015` ([#13173](https://github.com/astral-sh/ruff/pull/13173))
-- \[`pyupgrade`\] Mark `sys.version_info[0] < 3` and similar comparisons as outdated (`UP036`) ([#13175](https://github.com/astral-sh/ruff/pull/13175))
-
-### CLI
-
-- Enrich messages of SARIF results ([#13180](https://github.com/astral-sh/ruff/pull/13180))
-- Handle singular case for incompatible rules warning in `ruff format` output ([#13212](https://github.com/astral-sh/ruff/pull/13212))
-
-### Bug fixes
-
-- \[`pydocstyle`\] Improve heuristics for detecting Google-style docstrings ([#13142](https://github.com/astral-sh/ruff/pull/13142))
-- \[`refurb`\] Treat `sep` arguments with effects as unsafe removals (`FURB105`) ([#13165](https://github.com/astral-sh/ruff/pull/13165))
-
 ## 0.6.3
 
 ### Preview features

CONTRIBUTING.md

@@ -29,14 +29,16 @@ You'll also need [Insta](https://insta.rs/docs/) to update snapshot tests:
 cargo install cargo-insta
 ```
 
-You'll need [uv](https://docs.astral.sh/uv/getting-started/installation/) (or `pipx` and `pip`) to
-run Python utility commands.
+And you'll need pre-commit to run some validation checks:
+
+```shell
+pipx install pre-commit  # or `pip install pre-commit` if you have a virtualenv
+```
 
 You can optionally install pre-commit hooks to automatically run the validation checks
 when making a commit:
 
 ```shell
-uv tool install pre-commit
 pre-commit install
 ```
 
@@ -64,7 +66,7 @@ and that it passes both the lint and test validation checks:
 ```shell
 cargo clippy --workspace --all-targets --all-features -- -D warnings  # Rust linting
 RUFF_UPDATE_SCHEMA=1 cargo test  # Rust testing and updating ruff.schema.json
-uvx pre-commit run --all-files --show-diff-on-failure  # Rust and Python formatting, Markdown and Python linting, etc.
+pre-commit run --all-files --show-diff-on-failure  # Rust and Python formatting, Markdown and Python linting, etc.
 ```
 
 These checks will run on GitHub Actions when you open your pull request, but running them locally
@@ -265,20 +267,26 @@ To preview any changes to the documentation locally:
 
 1. Install the [Rust toolchain](https://www.rust-lang.org/tools/install).
 
+1. Install MkDocs and Material for MkDocs with:
+
+    ```shell
+    pip install -r docs/requirements.txt
+    ```
+
 1. Generate the MkDocs site with:
 
     ```shell
-    uv run --no-project --isolated --with-requirements docs/requirements.txt scripts/generate_mkdocs.py
+    python scripts/generate_mkdocs.py
     ```
 
 1. Run the development server with:
 
     ```shell
     # For contributors.
-    uvx --with-requirements docs/requirements.txt -- mkdocs serve -f mkdocs.public.yml
+    mkdocs serve -f mkdocs.public.yml
 
     # For members of the Astral org, which has access to MkDocs Insiders via sponsorship.
-    uvx --with-requirements docs/requirements-insiders.txt -- mkdocs serve -f mkdocs.insiders.yml
+    mkdocs serve -f mkdocs.insiders.yml
     ```
 
 The documentation should then be available locally at
@@ -360,8 +368,9 @@ GitHub Actions will run your changes against a number of real-world projects fro
 report on any linter or formatter differences. You can also run those checks locally via:
 
 ```shell
-uvx --from ./python/ruff-ecosystem ruff-ecosystem check ruff "./target/debug/ruff"
-uvx --from ./python/ruff-ecosystem ruff-ecosystem format ruff "./target/debug/ruff"
+pip install -e ./python/ruff-ecosystem
+ruff-ecosystem check ruff "./target/debug/ruff"
+ruff-ecosystem format ruff "./target/debug/ruff"
 ```
 
 See the [ruff-ecosystem package](https://github.com/astral-sh/ruff/tree/main/python/ruff-ecosystem) for more details.

Cargo.toml

@@ -14,10 +14,9 @@ license = "MIT"
 [workspace.dependencies]
 ruff = { path = "crates/ruff" }
 ruff_cache = { path = "crates/ruff_cache" }
-ruff_db = { path = "crates/ruff_db", default-features = false }
+ruff_db = { path = "crates/ruff_db" }
 ruff_diagnostics = { path = "crates/ruff_diagnostics" }
 ruff_formatter = { path = "crates/ruff_formatter" }
-ruff_graph = { path = "crates/ruff_graph" }
 ruff_index = { path = "crates/ruff_index" }
 ruff_linter = { path = "crates/ruff_linter" }
 ruff_macros = { path = "crates/ruff_macros" }
@@ -34,18 +33,15 @@ ruff_python_trivia = { path = "crates/ruff_python_trivia" }
 ruff_server = { path = "crates/ruff_server" }
 ruff_source_file = { path = "crates/ruff_source_file" }
 ruff_text_size = { path = "crates/ruff_text_size" }
-red_knot_vendored = { path = "crates/red_knot_vendored" }
 ruff_workspace = { path = "crates/ruff_workspace" }
 
 red_knot_python_semantic = { path = "crates/red_knot_python_semantic" }
 red_knot_server = { path = "crates/red_knot_server" }
-red_knot_test = { path = "crates/red_knot_test" }
-red_knot_workspace = { path = "crates/red_knot_workspace", default-features = false }
+red_knot_workspace = { path = "crates/red_knot_workspace" }
 
 aho-corasick = { version = "1.1.3" }
 annotate-snippets = { version = "0.9.2", features = ["color"] }
 anyhow = { version = "1.0.80" }
-assert_fs = { version = "1.1.0" }
 argfile = { version = "0.2.0" }
 bincode = { version = "1.3.3" }
 bitflags = { version = "2.5.0" }
@@ -72,11 +68,7 @@ fern = { version = "0.6.1" }
 filetime = { version = "0.2.23" }
 glob = { version = "0.3.1" }
 globset = { version = "0.4.14" }
-globwalk = { version = "0.9.1" }
-hashbrown = { version = "0.15.0", default-features = false, features = [
-    "raw-entry",
-    "inline-more",
-] }
+hashbrown = "0.14.3"
 ignore = { version = "0.4.22" }
 imara-diff = { version = "0.1.5" }
 imperative = { version = "1.0.4" }
@@ -94,7 +86,7 @@ libcst = { version = "1.1.0", default-features = false }
 log = { version = "0.4.17" }
 lsp-server = { version = "0.7.6" }
 lsp-types = { git = "https://github.com/astral-sh/lsp-types.git", rev = "3512a9f", features = [
-    "proposed",
+  "proposed",
 ] }
 matchit = { version = "0.8.1" }
 memchr = { version = "2.7.1" }
@@ -115,9 +107,8 @@ quote = { version = "1.0.23" }
 rand = { version = "0.8.5" }
 rayon = { version = "1.10.0" }
 regex = { version = "1.10.2" }
-rstest = { version = "0.22.0", default-features = false }
 rustc-hash = { version = "2.0.0" }
-salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "b14be5c0392f4c55eca60b92e457a35549372382" }
+salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "f608ff8b24f07706492027199f51132244034f29" }
 schemars = { version = "0.8.16" }
 seahash = { version = "4.1.0" }
 serde = { version = "1.0.197", features = ["derive"] }
@@ -125,7 +116,7 @@ serde-wasm-bindgen = { version = "0.6.4" }
 serde_json = { version = "1.0.113" }
 serde_test = { version = "1.0.152" }
 serde_with = { version = "3.6.0", default-features = false, features = [
-    "macros",
+  "macros",
 ] }
 shellexpand = { version = "3.0.0" }
 similar = { version = "2.4.0", features = ["inline"] }
@@ -142,10 +133,7 @@ toml = { version = "0.8.11" }
 tracing = { version = "0.1.40" }
 tracing-flame = { version = "0.2.0" }
 tracing-indicatif = { version = "0.3.6" }
-tracing-subscriber = { version = "0.3.18", default-features = false, features = [
-    "env-filter",
-    "fmt",
-] }
+tracing-subscriber = { version = "0.3.18", default-features = false, features = ["env-filter", "fmt"] }
 tracing-tree = { version = "0.4.0" }
 typed-arena = { version = "2.0.2" }
 unic-ucd-category = { version = "0.9" }
@@ -156,10 +144,10 @@ unicode-normalization = { version = "0.1.23" }
 ureq = { version = "2.9.6" }
 url = { version = "2.5.0" }
 uuid = { version = "1.6.1", features = [
-    "v4",
-    "fast-rng",
-    "macro-diagnostics",
-    "js",
+  "v4",
+  "fast-rng",
+  "macro-diagnostics",
+  "js",
 ] }
 walkdir = { version = "2.3.2" }
 wasm-bindgen = { version = "0.2.92" }
@@ -170,10 +158,7 @@ zip = { version = "0.6.6", default-features = false }
 [workspace.lints.rust]
 unsafe_code = "warn"
 unreachable_pub = "warn"
-unexpected_cfgs = { level = "warn", check-cfg = [
-    "cfg(fuzzing)",
-    "cfg(codspeed)",
-] }
+unexpected_cfgs = { level = "warn", check-cfg = ["cfg(fuzzing)", "cfg(codspeed)"] }
 
 [workspace.lints.clippy]
 pedantic = { level = "warn", priority = -2 }
@@ -245,9 +230,9 @@ inherits = "release"
 # Config for 'cargo dist'
 [workspace.metadata.dist]
 # The preferred cargo-dist version to use in CI (Cargo.toml SemVer syntax)
-cargo-dist-version = "0.22.1"
+cargo-dist-version = "0.18.0"
 # CI backends to support
-ci = "github"
+ci = ["github"]
 # The installers to generate for each app
 installers = ["shell", "powershell"]
 # The archive format to use for windows builds (defaults .zip)
@@ -256,33 +241,33 @@ windows-archive = ".zip"
 unix-archive = ".tar.gz"
 # Target platforms to build apps for (Rust target-triple syntax)
 targets = [
-    "aarch64-apple-darwin",
-    "aarch64-pc-windows-msvc",
-    "aarch64-unknown-linux-gnu",
-    "aarch64-unknown-linux-musl",
-    "arm-unknown-linux-musleabihf",
-    "armv7-unknown-linux-gnueabihf",
-    "armv7-unknown-linux-musleabihf",
-    "i686-pc-windows-msvc",
-    "i686-unknown-linux-gnu",
-    "i686-unknown-linux-musl",
-    "powerpc64-unknown-linux-gnu",
-    "powerpc64le-unknown-linux-gnu",
-    "s390x-unknown-linux-gnu",
-    "x86_64-apple-darwin",
-    "x86_64-pc-windows-msvc",
-    "x86_64-unknown-linux-gnu",
-    "x86_64-unknown-linux-musl",
+  "aarch64-apple-darwin",
+  "aarch64-pc-windows-msvc",
+  "aarch64-unknown-linux-gnu",
+  "aarch64-unknown-linux-musl",
+  "arm-unknown-linux-musleabihf",
+  "armv7-unknown-linux-gnueabihf",
+  "armv7-unknown-linux-musleabihf",
+  "i686-pc-windows-msvc",
+  "i686-unknown-linux-gnu",
+  "i686-unknown-linux-musl",
+  "powerpc64-unknown-linux-gnu",
+  "powerpc64le-unknown-linux-gnu",
+  "s390x-unknown-linux-gnu",
+  "x86_64-apple-darwin",
+  "x86_64-pc-windows-msvc",
+  "x86_64-unknown-linux-gnu",
+  "x86_64-unknown-linux-musl",
 ]
 # Whether to auto-include files like READMEs, LICENSEs, and CHANGELOGs (default true)
 auto-includes = false
 # Whether cargo-dist should create a GitHub Release or use an existing draft
 create-release = true
-# Which actions to run on pull requests
+# Publish jobs to run in CI
 pr-run-mode = "skip"
 # Whether CI should trigger releases with dispatches instead of tag pushes
 dispatch-releases = true
-# Which phase cargo-dist should use to create the GitHub release
+# The stage during which the GitHub Release should be created
 github-release = "announce"
 # Whether CI should include auto-generated code to build local artifacts
 build-local-artifacts = false
@@ -290,15 +275,9 @@ build-local-artifacts = false
 local-artifacts-jobs = ["./build-binaries", "./build-docker"]
 # Publish jobs to run in CI
 publish-jobs = ["./publish-pypi", "./publish-wasm"]
-# Post-announce jobs to run in CI
-post-announce-jobs = [
-    "./notify-dependents",
-    "./publish-docs",
-    "./publish-playground",
-]
+# Announcement jobs to run in CI
+post-announce-jobs = ["./notify-dependents", "./publish-docs", "./publish-playground"]
 # Custom permissions for GitHub Jobs
 github-custom-job-permissions = { "build-docker" = { packages = "write", contents = "read" }, "publish-wasm" = { contents = "read", id-token = "write", packages = "write" } }
 # Whether to install an updater program
 install-updater = false
-# Path that installers should place binaries in
-install-path = "CARGO_HOME"

README.md

@@ -136,8 +136,8 @@ 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/0.6.9/install.sh | sh
-powershell -c "irm https://astral.sh/ruff/0.6.9/install.ps1 | iex"
+curl -LsSf https://astral.sh/ruff/0.6.3/install.sh | sh
+powershell -c "irm https://astral.sh/ruff/0.6.3/install.ps1 | iex"
 ```
 
 You can also install Ruff via [Homebrew](https://formulae.brew.sh/formula/ruff), [Conda](https://anaconda.org/conda-forge/ruff),
@@ -170,7 +170,7 @@ 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: v0.6.9
+  rev: v0.6.3
   hooks:
     # Run the linter.
     - id: ruff
@@ -182,7 +182,7 @@ Ruff can also be used as a [pre-commit](https://pre-commit.com/) hook via [`ruff
 Ruff can also be used as a [VS Code extension](https://github.com/astral-sh/ruff-vscode) or with [various other editors](https://docs.astral.sh/ruff/editors/setup).
 
 Ruff can also be used as a [GitHub Action](https://github.com/features/actions) via
-[`ruff-action`](https://github.com/astral-sh/ruff-action):
+[`ruff-action`](https://github.com/chartboost/ruff-action):
 
 ```yaml
 name: Ruff
@@ -192,7 +192,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: astral-sh/ruff-action@v1
+      - uses: chartboost/ruff-action@v1
 ```
 
 ### Configuration<a id="configuration"></a>

_typos.toml

@@ -1,6 +1,6 @@
 [files]
 # https://github.com/crate-ci/typos/issues/868
-extend-exclude = ["crates/red_knot_vendored/vendor/**/*", "**/resources/**/*", "**/snapshots/**/*"]
+extend-exclude = ["crates/red_knot_python_semantic/vendor/**/*", "**/resources/**/*", "**/snapshots/**/*"]
 
 [default.extend-words]
 "arange" = "arange"  # e.g. `numpy.arange`
@@ -8,7 +8,7 @@ hel = "hel"
 whos = "whos"
 spawnve = "spawnve"
 ned = "ned"
-pn = "pn"  # `import panel as pn` is a thing
+pn = "pn"  # `import panel as pd` is a thing
 poit = "poit"
 BA = "BA" # acronym for "Bad Allowed", used in testing.
 jod = "jod" # e.g., `jod-thread`

crates/red_knot/Cargo.toml

@@ -13,8 +13,9 @@ license.workspace = true
 
 [dependencies]
 red_knot_python_semantic = { workspace = true }
-red_knot_workspace = { workspace = true, features = ["zstd"] }
+red_knot_workspace = { workspace = true }
 red_knot_server = { workspace = true }
+
 ruff_db = { workspace = true, features = ["os", "cache"] }
 
 anyhow = { workspace = true }

crates/red_knot/src/main.rs

@@ -160,7 +160,7 @@ fn run() -> anyhow::Result<ExitStatus> {
         SystemPathBuf::from_path_buf(cwd)
             .map_err(|path| {
                 anyhow!(
-                    "The current working directory `{}` contains non-Unicode characters. Red Knot only supports Unicode paths.",
+                    "The current working directory '{}' contains non-unicode characters. Red Knot only supports unicode paths.",
                     path.display()
                 )
             })?
@@ -174,7 +174,7 @@ fn run() -> anyhow::Result<ExitStatus> {
                 Ok(SystemPath::absolute(cwd, &cli_base_path))
             } else {
                 Err(anyhow!(
-                    "Provided current-directory path `{cwd}` is not a directory"
+                    "Provided current-directory path '{cwd}' is not a directory."
                 ))
             }
         })

crates/red_knot/tests/file_watching.rs

@@ -42,14 +42,14 @@ impl TestCase {
 
     fn stop_watch(&mut self) -> Vec<watch::ChangeEvent> {
         self.try_stop_watch(Duration::from_secs(10))
-            .expect("Expected watch changes but observed none")
+            .expect("Expected watch changes but observed none.")
     }
 
     fn try_stop_watch(&mut self, timeout: Duration) -> Option<Vec<watch::ChangeEvent>> {
         let watcher = self
             .watcher
             .take()
-            .expect("Cannot call `stop_watch` more than once");
+            .expect("Cannot call `stop_watch` more than once.");
 
         let mut all_events = self
             .changes_receiver
@@ -72,7 +72,7 @@ impl TestCase {
     #[cfg(unix)]
     fn take_watch_changes(&self) -> Vec<watch::ChangeEvent> {
         self.try_take_watch_changes(Duration::from_secs(10))
-            .expect("Expected watch changes but observed none")
+            .expect("Expected watch changes but observed none.")
     }
 
     fn try_take_watch_changes(&self, timeout: Duration) -> Option<Vec<watch::ChangeEvent>> {
@@ -150,14 +150,14 @@ where
             let absolute_path = workspace_path.join(relative_path);
             if let Some(parent) = absolute_path.parent() {
                 std::fs::create_dir_all(parent).with_context(|| {
-                    format!("Failed to create parent directory for file `{relative_path}`")
+                    format!("Failed to create parent directory for file '{relative_path}'.",)
                 })?;
             }
 
             let mut file = std::fs::File::create(absolute_path.as_std_path())
-                .with_context(|| format!("Failed to open file `{relative_path}`"))?;
+                .with_context(|| format!("Failed to open file '{relative_path}'"))?;
             file.write_all(content.as_bytes())
-                .with_context(|| format!("Failed to write to file `{relative_path}`"))?;
+                .with_context(|| format!("Failed to write to file '{relative_path}'"))?;
             file.sync_data()?;
         }
 
@@ -194,7 +194,7 @@ where
 
     let root_path = SystemPath::from_std_path(temp_dir.path()).ok_or_else(|| {
         anyhow!(
-            "Temporary directory `{}` is not a valid UTF-8 path.",
+            "Temp directory '{}' is not a valid UTF-8 path.",
             temp_dir.path().display()
         )
     })?;
@@ -209,7 +209,7 @@ where
     let workspace_path = root_path.join("workspace");
 
     std::fs::create_dir_all(workspace_path.as_std_path())
-        .with_context(|| format!("Failed to create workspace directory `{workspace_path}`"))?;
+        .with_context(|| format!("Failed to create workspace directory '{workspace_path}'",))?;
 
     setup_files
         .setup(&root_path, &workspace_path)
@@ -233,7 +233,7 @@ where
         }))
     {
         std::fs::create_dir_all(path.as_std_path())
-            .with_context(|| format!("Failed to create search path `{path}`"))?;
+            .with_context(|| format!("Failed to create search path '{path}'"))?;
     }
 
     let configuration = Configuration {
@@ -501,10 +501,7 @@ fn directory_moved_to_workspace() -> anyhow::Result<()> {
         .with_context(|| "Failed to create __init__.py")?;
     std::fs::write(a_original_path.as_std_path(), "").with_context(|| "Failed to create a.py")?;
 
-    let sub_a_module = resolve_module(
-        case.db().upcast(),
-        &ModuleName::new_static("sub.a").unwrap(),
-    );
+    let sub_a_module = resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap());
 
     assert_eq!(sub_a_module, None);
     assert_eq!(
@@ -528,11 +525,7 @@ fn directory_moved_to_workspace() -> anyhow::Result<()> {
         .expect("a.py to exist");
 
     // `import sub.a` should now resolve
-    assert!(resolve_module(
-        case.db().upcast(),
-        &ModuleName::new_static("sub.a").unwrap()
-    )
-    .is_some());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_some());
 
     assert_eq!(
         case.collect_package_files(&case.workspace_path("bar.py")),
@@ -551,11 +544,7 @@ fn directory_moved_to_trash() -> anyhow::Result<()> {
     ])?;
     let bar = case.system_file(case.workspace_path("bar.py")).unwrap();
 
-    assert!(resolve_module(
-        case.db().upcast(),
-        &ModuleName::new_static("sub.a").unwrap()
-    )
-    .is_some());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_some());
 
     let sub_path = case.workspace_path("sub");
     let init_file = case
@@ -580,11 +569,7 @@ fn directory_moved_to_trash() -> anyhow::Result<()> {
     case.apply_changes(changes);
 
     // `import sub.a` should no longer resolve
-    assert!(resolve_module(
-        case.db().upcast(),
-        &ModuleName::new_static("sub.a").unwrap()
-    )
-    .is_none());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_none());
 
     assert!(!init_file.exists(case.db()));
     assert!(!a_file.exists(case.db()));
@@ -607,14 +592,10 @@ fn directory_renamed() -> anyhow::Result<()> {
 
     let bar = case.system_file(case.workspace_path("bar.py")).unwrap();
 
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_some());
     assert!(resolve_module(
         case.db().upcast(),
-        &ModuleName::new_static("sub.a").unwrap()
-    )
-    .is_some());
-    assert!(resolve_module(
-        case.db().upcast(),
-        &ModuleName::new_static("foo.baz").unwrap()
+        ModuleName::new_static("foo.baz").unwrap()
     )
     .is_none());
 
@@ -642,15 +623,11 @@ fn directory_renamed() -> anyhow::Result<()> {
     case.apply_changes(changes);
 
     // `import sub.a` should no longer resolve
-    assert!(resolve_module(
-        case.db().upcast(),
-        &ModuleName::new_static("sub.a").unwrap()
-    )
-    .is_none());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_none());
     // `import foo.baz` should now resolve
     assert!(resolve_module(
         case.db().upcast(),
-        &ModuleName::new_static("foo.baz").unwrap()
+        ModuleName::new_static("foo.baz").unwrap()
     )
     .is_some());
 
@@ -688,11 +665,7 @@ fn directory_deleted() -> anyhow::Result<()> {
 
     let bar = case.system_file(case.workspace_path("bar.py")).unwrap();
 
-    assert!(resolve_module(
-        case.db().upcast(),
-        &ModuleName::new_static("sub.a").unwrap()
-    )
-    .is_some());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_some(),);
 
     let sub_path = case.workspace_path("sub");
 
@@ -715,11 +688,7 @@ fn directory_deleted() -> anyhow::Result<()> {
     case.apply_changes(changes);
 
     // `import sub.a` should no longer resolve
-    assert!(resolve_module(
-        case.db().upcast(),
-        &ModuleName::new_static("sub.a").unwrap()
-    )
-    .is_none());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("sub.a").unwrap()).is_none());
 
     assert!(!init_file.exists(case.db()));
     assert!(!a_file.exists(case.db()));
@@ -741,7 +710,7 @@ fn search_path() -> anyhow::Result<()> {
     let site_packages = case.root_path().join("site_packages");
 
     assert_eq!(
-        resolve_module(case.db(), &ModuleName::new("a").unwrap()),
+        resolve_module(case.db(), ModuleName::new("a").unwrap()),
         None
     );
 
@@ -751,7 +720,7 @@ fn search_path() -> anyhow::Result<()> {
 
     case.apply_changes(changes);
 
-    assert!(resolve_module(case.db().upcast(), &ModuleName::new_static("a").unwrap()).is_some());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("a").unwrap()).is_some());
     assert_eq!(
         case.collect_package_files(&case.workspace_path("bar.py")),
         &[case.system_file(case.workspace_path("bar.py")).unwrap()]
@@ -767,7 +736,7 @@ fn add_search_path() -> anyhow::Result<()> {
     let site_packages = case.workspace_path("site_packages");
     std::fs::create_dir_all(site_packages.as_std_path())?;
 
-    assert!(resolve_module(case.db().upcast(), &ModuleName::new_static("a").unwrap()).is_none());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("a").unwrap()).is_none());
 
     // Register site-packages as a search path.
     case.update_search_path_settings(SearchPathConfiguration {
@@ -782,7 +751,7 @@ fn add_search_path() -> anyhow::Result<()> {
 
     case.apply_changes(changes);
 
-    assert!(resolve_module(case.db().upcast(), &ModuleName::new_static("a").unwrap()).is_some());
+    assert!(resolve_module(case.db().upcast(), ModuleName::new_static("a").unwrap()).is_some());
 
     Ok(())
 }
@@ -836,7 +805,7 @@ fn changed_versions_file() -> anyhow::Result<()> {
 
     // Unset the custom typeshed directory.
     assert_eq!(
-        resolve_module(case.db(), &ModuleName::new("os").unwrap()),
+        resolve_module(case.db(), ModuleName::new("os").unwrap()),
         None
     );
 
@@ -851,7 +820,7 @@ fn changed_versions_file() -> anyhow::Result<()> {
 
     case.apply_changes(changes);
 
-    assert!(resolve_module(case.db(), &ModuleName::new("os").unwrap()).is_some());
+    assert!(resolve_module(case.db(), ModuleName::new("os").unwrap()).is_some());
 
     Ok(())
 }
@@ -1075,7 +1044,7 @@ mod unix {
 
         let baz = resolve_module(
             case.db().upcast(),
-            &ModuleName::new_static("bar.baz").unwrap(),
+            ModuleName::new_static("bar.baz").unwrap(),
         )
         .expect("Expected bar.baz to exist in site-packages.");
         let baz_workspace = case.workspace_path("bar/baz.py");
@@ -1156,7 +1125,7 @@ mod unix {
 
         let baz = resolve_module(
             case.db().upcast(),
-            &ModuleName::new_static("bar.baz").unwrap(),
+            ModuleName::new_static("bar.baz").unwrap(),
         )
         .expect("Expected bar.baz to exist in site-packages.");
         let bar_baz = case.workspace_path("bar/baz.py");
@@ -1260,7 +1229,7 @@ mod unix {
 
         let baz = resolve_module(
             case.db().upcast(),
-            &ModuleName::new_static("bar.baz").unwrap(),
+            ModuleName::new_static("bar.baz").unwrap(),
         )
         .expect("Expected bar.baz to exist in site-packages.");
         let baz_site_packages_path =

crates/red_knot_python_semantic/Cargo.toml

@@ -24,7 +24,7 @@ bitflags = { workspace = true }
 camino = { workspace = true }
 compact_str = { workspace = true }
 countme = { workspace = true }
-itertools = { workspace = true}
+once_cell = { workspace = true }
 ordermap = { workspace = true }
 salsa = { workspace = true }
 thiserror = { workspace = true }
@@ -33,19 +33,21 @@ rustc-hash = { workspace = true }
 hashbrown = { workspace = true }
 smallvec = { workspace = true }
 static_assertions = { workspace = true }
-test-case = { workspace = true }
-memchr = { workspace = true }
+
+[build-dependencies]
+path-slash = { workspace = true }
+walkdir = { workspace = true }
+zip = { workspace = true, features = ["zstd", "deflate"] }
 
 [dev-dependencies]
 ruff_db = { workspace = true, features = ["os", "testing"] }
 ruff_python_parser = { workspace = true }
-red_knot_test = { workspace = true }
-red_knot_vendored = { workspace = true }
 
 anyhow = { workspace = true }
 insta = { workspace = true }
-rstest = { workspace = true }
 tempfile = { workspace = true }
+walkdir = { workspace = true }
+zip = { workspace = true }
 
 [lints]
 workspace = true

crates/red_knot_python_semantic/README.md

@@ -1,5 +1,9 @@
-# Vendored types for the stdlib
+# Red Knot
 
-This crate vendors [typeshed](https://github.com/python/typeshed)'s stubs for the standard library. The vendored stubs can be found in `crates/red_knot_vendored/vendor/typeshed`. The file `crates/red_knot_vendored/vendor/typeshed/source_commit.txt` tells you the typeshed commit that our vendored stdlib stubs currently correspond to.
+Semantic analysis for the red-knot project.
+
+## Vendored types for the stdlib
+
+This crate vendors [typeshed](https://github.com/python/typeshed)'s stubs for the standard library. The vendored stubs can be found in `crates/red_knot_python_semantic/vendor/typeshed`. The file `crates/red_knot_python_semantic/vendor/typeshed/source_commit.txt` tells you the typeshed commit that our vendored stdlib stubs currently correspond to.
 
 The typeshed stubs are updated every two weeks via an automated PR using the `sync_typeshed.yaml` workflow in the `.github/workflows` directory. This workflow can also be triggered at any time via [workflow dispatch](https://docs.github.com/en/actions/using-workflows/manually-running-a-workflow#running-a-workflow).

crates/red_knot_python_semantic/build.rs

@@ -1,4 +1,87 @@
-/// Rebuild the crate if a test file is added or removed from
-pub fn main() {
-    println!("cargo:rerun-if-changed=resources/mdtest");
+//! Build script to package our vendored typeshed files
+//! into a zip archive that can be included in the Ruff binary.
+//!
+//! This script should be automatically run at build time
+//! whenever the script itself changes, or whenever any files
+//! in `crates/red_knot_python_semantic/vendor/typeshed` change.
+
+use std::fs::File;
+use std::path::Path;
+
+use path_slash::PathExt;
+use zip::result::ZipResult;
+use zip::write::{FileOptions, ZipWriter};
+use zip::CompressionMethod;
+
+const TYPESHED_SOURCE_DIR: &str = "vendor/typeshed";
+const TYPESHED_ZIP_LOCATION: &str = "/zipped_typeshed.zip";
+
+/// Recursively zip the contents of an entire directory.
+///
+/// This routine is adapted from a recipe at
+/// <https://github.com/zip-rs/zip-old/blob/5d0f198124946b7be4e5969719a7f29f363118cd/examples/write_dir.rs>
+fn zip_dir(directory_path: &str, writer: File) -> ZipResult<File> {
+    let mut zip = ZipWriter::new(writer);
+
+    // Use deflated compression for WASM builds because compiling `zstd-sys` requires clang
+    // [source](https://github.com/gyscos/zstd-rs/wiki/Compile-for-WASM) which complicates the build
+    // by a lot. Deflated compression is slower but it shouldn't matter much for the WASM use case
+    // (WASM itself is already slower than a native build for a specific platform).
+    // We can't use `#[cfg(...)]` here because the target-arch in a build script is the
+    // architecture of the system running the build script and not the architecture of the build-target.
+    // That's why we use the `TARGET` environment variable here.
+    let method = if std::env::var("TARGET").unwrap().contains("wasm32") {
+        CompressionMethod::Deflated
+    } else {
+        CompressionMethod::Zstd
+    };
+
+    let options = FileOptions::default()
+        .compression_method(method)
+        .unix_permissions(0o644);
+
+    for entry in walkdir::WalkDir::new(directory_path) {
+        let dir_entry = entry.unwrap();
+        let absolute_path = dir_entry.path();
+        let normalized_relative_path = absolute_path
+            .strip_prefix(Path::new(directory_path))
+            .unwrap()
+            .to_slash()
+            .expect("Unexpected non-utf8 typeshed path!");
+
+        // Write file or directory explicitly
+        // Some unzip tools unzip files with directory paths correctly, some do not!
+        if absolute_path.is_file() {
+            println!("adding file {absolute_path:?} as {normalized_relative_path:?} ...");
+            zip.start_file(normalized_relative_path, options)?;
+            let mut f = File::open(absolute_path)?;
+            std::io::copy(&mut f, &mut zip).unwrap();
+        } else if !normalized_relative_path.is_empty() {
+            // Only if not root! Avoids path spec / warning
+            // and mapname conversion failed error on unzip
+            println!("adding dir {absolute_path:?} as {normalized_relative_path:?} ...");
+            zip.add_directory(normalized_relative_path, options)?;
+        }
+    }
+    zip.finish()
+}
+
+fn main() {
+    println!("cargo:rerun-if-changed={TYPESHED_SOURCE_DIR}");
+    assert!(
+        Path::new(TYPESHED_SOURCE_DIR).is_dir(),
+        "Where is typeshed?"
+    );
+    let out_dir = std::env::var("OUT_DIR").unwrap();
+
+    // N.B. Deliberately using `format!()` instead of `Path::join()` here,
+    // so that we use `/` as a path separator on all platforms.
+    // That enables us to load the typeshed zip at compile time in `module.rs`
+    // (otherwise we'd have to dynamically determine the exact path to the typeshed zip
+    // based on the default path separator for the specific platform we're on,
+    // which can't be done at compile time.)
+    let zipped_typeshed_location = format!("{out_dir}{TYPESHED_ZIP_LOCATION}");
+
+    let zipped_typeshed = File::create(zipped_typeshed_location).unwrap();
+    zip_dir(TYPESHED_SOURCE_DIR, zipped_typeshed).unwrap();
 }

crates/red_knot_python_semantic/resources/README.md

@@ -1,4 +0,0 @@
-Markdown files within the `mdtest/` subdirectory are tests of type inference and type checking;
-executed by the `tests/mdtest.rs` integration test.
-
-See `crates/red_knot_test/README.md` for documentation of this test format.

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

@@ -1,25 +0,0 @@
-# Assignment with annotations
-
-## Annotation only transparent to local inference
-
-```py
-x = 1
-x: int
-y = x
-
-reveal_type(y)  # revealed: Literal[1]
-```
-
-## Violates own annotation
-
-```py
-x: int = 'foo' # error: [invalid-assignment] "Object of type `Literal["foo"]` is not assignable to `int`"
-
-```
-
-## Violates previous annotation
-
-```py
-x: int
-x = 'foo'  # error: [invalid-assignment] "Object of type `Literal["foo"]` is not assignable to `int`"
-```

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

@@ -1,9 +0,0 @@
-# Multi-target assignment
-
-## Basic
-
-```py
-x = y = 1
-reveal_type(x)  # revealed: Literal[1]
-reveal_type(y)  # revealed: Literal[1]
-```

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

@@ -1,32 +0,0 @@
-# Unbound
-
-## Maybe unbound
-
-```py
-if flag:
-    y = 3
-x = y
-reveal_type(x)  # revealed: Unbound | Literal[3]
-```
-
-## Unbound
-
-```py
-x = foo; foo = 1
-reveal_type(x)  # revealed: Unbound
-```
-
-## Unbound class variable
-
-Class variables can reference global variables unless overridden within the class scope.
-
-```py
-x = 1
-class C:
-    y = x
-    if flag:
-        x = 2
-
-reveal_type(C.x) # revealed: Unbound | Literal[2]
-reveal_type(C.y) # revealed: Literal[1]
-```

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

@@ -1,17 +0,0 @@
-# Walrus operator
-
-## Basic
-
-```py
-x = (y := 1) + 1
-reveal_type(x)  # revealed: Literal[2]
-reveal_type(y)  # revealed: Literal[1]
-```
-
-## Walrus self-addition
-
-```py
-x = 0
-(x := x + 1)
-reveal_type(x)  # revealed: Literal[1]
-```

crates/red_knot_python_semantic/resources/mdtest/attributes.md

@@ -1,15 +0,0 @@
-# Class attributes
-
-## Union of attributes
-
-```py
-if flag:
-    class C:
-        x = 1
-else:
-    class C:
-        x = 2
-
-y = C.x
-reveal_type(y)  # revealed: Literal[1, 2]
-```

crates/red_knot_python_semantic/resources/mdtest/binary/integers.md

@@ -1,36 +0,0 @@
-## Binary operations on integers
-
-## Basic Arithmetic
-
-```py
-a = 2 + 1
-b = a - 4
-c = a * b
-d = c // 3
-e = c / 3
-f = 5 % 3
-
-reveal_type(a)  # revealed: Literal[3]
-reveal_type(b)  # revealed: Literal[-1]
-reveal_type(c)  # revealed: Literal[-3]
-reveal_type(d)  # revealed: Literal[-1]
-reveal_type(e)  # revealed: float
-reveal_type(f)  # revealed: Literal[2]
-```
-
-## Division by Zero
-
-```py
-# TODO: `a` should be `int` and `e` should be `float` once we support inference.
-a = 1 / 0  # error: "Cannot divide object of type `Literal[1]` by zero"
-b = 2 // 0  # error: "Cannot floor divide object of type `Literal[2]` by zero"
-c = 3 % 0  # error: "Cannot reduce object of type `Literal[3]` modulo zero"
-d = int() / 0  # error: "Cannot divide object of type `int` by zero"
-e = 1.0 / 0  # error: "Cannot divide object of type `float` by zero"
-
-reveal_type(a)  # revealed: float
-reveal_type(b)  # revealed: int
-reveal_type(c)  # revealed: int
-reveal_type(d)  # revealed: @Todo
-reveal_type(e)  # revealed: @Todo
-```

crates/red_knot_python_semantic/resources/mdtest/call/callable_instance.md

@@ -1,21 +0,0 @@
-# Callable instance
-
-## Dunder call
-
-```py
-class Multiplier:
-    def __init__(self, factor: float):
-        self.factor = factor
-
-    def __call__(self, number: float) -> float:
-        return number * self.factor
-
-a = Multiplier(2.0)(3.0)
-
-class Unit: ...
-
-b = Unit()(3.0) # error: "Object of type `Unit` is not callable"
-
-reveal_type(a) # revealed: float
-reveal_type(b) # revealed: Unknown
-```

crates/red_knot_python_semantic/resources/mdtest/call/constructor.md

@@ -1,8 +0,0 @@
-# Constructor
-
-```py
-class Foo: ...
-
-x = Foo()
-reveal_type(x)  # revealed: Foo
-```

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

@@ -1,51 +0,0 @@
-# Call expression
-
-## Simple
-
-```py
-def get_int() -> int:
-    return 42
-
-x = get_int()
-reveal_type(x)  # revealed: int
-```
-
-## Async
-
-```py
-async def get_int_async() -> int:
-    return 42
-
-x = get_int_async()
-
-# TODO: we don't yet support `types.CoroutineType`, should be generic `Coroutine[Any, Any, int]`
-reveal_type(x)  # revealed: @Todo
-```
-
-## Decorated
-
-```py
-from typing import Callable
-
-def foo() -> int:
-    return 42
-
-def decorator(func) -> Callable[[], int]:
-    return foo
-
-@decorator
-def bar() -> str:
-    return 'bar'
-
-x = bar()
-
-# TODO: should reveal `int`, as the decorator replaces `bar` with `foo`
-reveal_type(x)  # revealed: @Todo
-```
-
-## Invalid callable
-
-```py
-nonsense = 123
-x = nonsense()  # error: "Object of type `Literal[123]` is not callable"
-```

crates/red_knot_python_semantic/resources/mdtest/call/union.md

@@ -1,74 +0,0 @@
-# Unions in calls
-
-## Union of return types
-
-```py
-if flag:
-    def f() -> int:
-        return 1
-else:
-    def f() -> str:
-        return 'foo'
-
-x = f()
-reveal_type(x)  # revealed: int | str
-```
-
-## Calling with an unknown union
-
-```py
-from nonexistent import f # error: [unresolved-import] "Cannot resolve import `nonexistent`"
-
-if flag:
-    def f() -> int:
-        return 1
-
-x = f()
-reveal_type(x)  # revealed: Unknown | int
-```
-
-## Non-callable elements in a union
-
-Calling a union with a non-callable element should emit a diagnostic.
-
-```py
-if flag:
-    f = 1
-else:
-    def f() -> int:
-        return 1
-
-x = f()  # error: "Object of type `Literal[1] | Literal[f]` is not callable (due to union element `Literal[1]`)"
-reveal_type(x)  # revealed: Unknown | int
-```
-
-## Multiple non-callable elements in a union
-
-Calling a union with multiple non-callable elements should mention all of them in the diagnostic.
-
-```py
-if flag:
-    f = 1
-elif flag2:
-    f = 'foo'
-else:
-    def f() -> int:
-        return 1
-
-x = f()  # error: "Object of type `Literal[1] | Literal["foo"] | Literal[f]` is not callable (due to union elements Literal[1], Literal["foo"])"
-reveal_type(x)  # revealed: Unknown | int
-```
-
-## All non-callable union elements
-
-Calling a union with no callable elements can emit a simpler diagnostic.
-
-```py
-if flag:
-    f = 1
-else:
-    f = 'foo'
-
-x = f()  # error: "Object of type `Literal[1] | Literal["foo"]` is not callable"
-reveal_type(x)  # revealed: Unknown
-```

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

@@ -1,43 +0,0 @@
-### Comparison: Byte literals
-
-These tests assert that we infer precise `Literal` types for comparisons between objects
-inferred as having `Literal` bytes types:
-
-```py
-reveal_type(b"abc" == b"abc")  # revealed: Literal[True]
-reveal_type(b"abc" == b"ab")   # revealed: Literal[False]
-
-reveal_type(b"abc" != b"abc")  # revealed: Literal[False]
-reveal_type(b"abc" != b"ab")   # revealed: Literal[True]
-
-reveal_type(b"abc" < b"abd")   # revealed: Literal[True]
-reveal_type(b"abc" < b"abb")   # revealed: Literal[False]
-
-reveal_type(b"abc" <= b"abc")  # revealed: Literal[True]
-reveal_type(b"abc" <= b"abb")  # revealed: Literal[False]
-
-reveal_type(b"abc" > b"abd")   # revealed: Literal[False]
-reveal_type(b"abc" > b"abb")   # revealed: Literal[True]
-
-reveal_type(b"abc" >= b"abc")  # revealed: Literal[True]
-reveal_type(b"abc" >= b"abd")  # revealed: Literal[False]
-
-reveal_type(b"" in b"")                      # revealed: Literal[True]
-reveal_type(b"" in b"abc")                   # revealed: Literal[True]
-reveal_type(b"abc" in b"")                   # revealed: Literal[False]
-reveal_type(b"ab" in b"abc")                 # revealed: Literal[True]
-reveal_type(b"abc" in b"abc")                # revealed: Literal[True]
-reveal_type(b"d" in b"abc")                  # revealed: Literal[False]
-reveal_type(b"ac" in b"abc")                 # revealed: Literal[False]
-reveal_type(b"\x81\x82" in b"\x80\x81\x82")  # revealed: Literal[True]
-reveal_type(b"\x82\x83" in b"\x80\x81\x82")  # revealed: Literal[False]
-
-reveal_type(b"ab" not in b"abc")             # revealed: Literal[False]
-reveal_type(b"ac" not in b"abc")             # revealed: Literal[True]
-
-reveal_type(b"abc" is b"abc")      # revealed: bool
-reveal_type(b"abc" is b"ab")       # revealed: Literal[False]
-
-reveal_type(b"abc" is not b"abc")  # revealed: bool
-reveal_type(b"abc" is not b"ab")   # revealed: Literal[True]
-```

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

@@ -1,41 +0,0 @@
-# Comparing integers
-
-## Integer literals
-
-```py
-a = 1 == 1 == True
-b = 1 == 1 == 2 == 4
-c = False < True <= 2 < 3 != 6
-d = 1 < 1
-e = 1 > 1
-f = 1 is 1
-g = 1 is not 1
-h = 1 is 2
-i = 1 is not 7
-j = 1 <= "" and 0 < 1
-
-reveal_type(a)  # revealed: Literal[True]
-reveal_type(b)  # revealed: Literal[False]
-reveal_type(c)  # revealed: Literal[True]
-reveal_type(d)  # revealed: Literal[False]
-reveal_type(e)  # revealed: Literal[False]
-reveal_type(f)  # revealed: bool
-reveal_type(g)  # revealed: bool
-reveal_type(h)  # revealed: Literal[False]
-reveal_type(i)  # revealed: Literal[True]
-reveal_type(j)  # revealed: @Todo | Literal[True]
-```
-
-## Integer instance
-
-```py
-# TODO: implement lookup of `__eq__` on typeshed `int` stub.
-def int_instance() -> int: ...
-a = 1 == int_instance()
-b = 9 < int_instance()
-c = int_instance() < int_instance()
-
-reveal_type(a)  # revealed: @Todo
-reveal_type(b)  # revealed: bool
-reveal_type(c)  # revealed: bool
-```

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

@@ -1,37 +0,0 @@
-# Non boolean returns
-
-Walking through examples:
-
-- `a = A() < B() < C()`
-
-    1. `A() < B() and B() < C()` - split in N comparison
-    1. `A()` and `B()`              - evaluate outcome types
-    1. `bool` and `bool`            - evaluate truthiness
-    1. `A | B`                    - union of "first true" types
-
-- `b = 0 < 1 < A() < 3`
-
-    1. `0 < 1 and 1 < A() and A() < 3` - split in N comparison
-    1. `True` and `bool` and `A` - evaluate outcome types
-    1. `True` and `bool` and `bool` - evaluate truthiness
-    1. `bool | A` - union of "true" types
-
-- `c = 10 < 0 < A() < B() < C()` short-circuit to False
-
-```py
-from __future__ import annotations
-class A:
-    def __lt__(self, other) -> A: ...
-class B:
-    def __lt__(self, other) -> B: ...
-class C:
-    def __lt__(self, other) -> C: ...
-
-a = A() < B() < C()
-b = 0 < 1 < A() < 3
-c = 10 < 0 < A() < B() < C()
-
-reveal_type(a)  # revealed: A | B
-reveal_type(b)  # revealed: bool | A
-reveal_type(c)  # revealed: Literal[False]
-```

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

@@ -1,29 +0,0 @@
-# Comparing strings
-
-## String literals
-
-```py
-def str_instance() -> str: ...
-a = "abc" == "abc"
-b = "ab_cd" <= "ab_ce"
-c = "abc" in "ab cd"
-d = "" not in "hello"
-e = "--" is "--"
-f = "A" is "B"
-g = "--" is not "--"
-h = "A" is not "B"
-i = str_instance() < "..."
-# ensure we're not comparing the interned salsa symbols, which compare by order of declaration.
-j = "ab" < "ab_cd"
-
-reveal_type(a)  # revealed: Literal[True]
-reveal_type(b)  # revealed: Literal[True]
-reveal_type(c)  # revealed: Literal[False]
-reveal_type(d)  # revealed: Literal[False]
-reveal_type(e)  # revealed: bool
-reveal_type(f)  # revealed: Literal[False]
-reveal_type(g)  # revealed: bool
-reveal_type(h)  # revealed: Literal[True]
-reveal_type(i)  # revealed: bool
-reveal_type(j)  # revealed: Literal[True]
-```

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

@@ -1,15 +0,0 @@
-# Unsupported operators
-
-```py
-a = 1 in 7      # error: "Operator `in` is not supported for types `Literal[1]` and `Literal[7]`"
-b = 0 not in 10 # error: "Operator `not in` is not supported for types `Literal[0]` and `Literal[10]`"
-c = object() < 5 # error: "Operator `<` is not supported for types `object` and `Literal[5]`"
-# TODO should error, need to check if __lt__ signature is valid for right operand
-d = 5 < object()
-
-reveal_type(a)  # revealed: bool
-reveal_type(b)  # revealed: bool
-reveal_type(c)  # revealed: Unknown
-# TODO: should be `Unknown`
-reveal_type(d)  # revealed: bool
-```

crates/red_knot_python_semantic/resources/mdtest/conditional/if_expression.md

@@ -1,35 +0,0 @@
-# If expressions
-
-## Simple if-expression
-
-```py
-x = 1 if flag else 2
-reveal_type(x)  # revealed: Literal[1, 2]
-```
-
-## If-expression with walrus operator
-
-```py
-y = 0
-z = 0
-x = (y := 1) if flag else (z := 2)
-a = y
-b = z
-reveal_type(x)  # revealed: Literal[1, 2]
-reveal_type(a)  # revealed: Literal[0, 1]
-reveal_type(b)  # revealed: Literal[0, 2]
-```
-
-## Nested if-expression
-
-```py
-x = 1 if flag else 2 if flag2 else 3
-reveal_type(x)  # revealed: Literal[1, 2, 3]
-```
-
-## None
-
-```py
-x = 1 if flag else None
-reveal_type(x)  # revealed: Literal[1] | None
-```

crates/red_knot_python_semantic/resources/mdtest/conditional/if_statement.md

@@ -1,97 +0,0 @@
-# If statements
-
-## Simple if
-
-```py
-y = 1
-y = 2
-
-if flag:
-    y = 3
-
-x = y
-
-reveal_type(x)  # revealed: Literal[2, 3]
-```
-
-## Simple if-elif-else
-
-```py
-y = 1
-y = 2
-if flag:
-    y = 3
-elif flag2:
-    y = 4
-else:
-    r = y
-    y = 5
-    s = y
-x = y
-reveal_type(x)  # revealed: Literal[3, 4, 5]
-reveal_type(r)  # revealed: Unbound | Literal[2]
-reveal_type(s)  # revealed: Unbound | Literal[5]
-```
-
-## Single symbol across if-elif-else
-
-```py
-if flag:
-    y = 1
-elif flag2:
-    y = 2
-else:
-    y = 3
-reveal_type(y)  # revealed: Literal[1, 2, 3]
-```
-
-## if-elif-else without else assignment
-
-```py
-y = 0
-if flag:
-    y = 1
-elif flag2:
-    y = 2
-else:
-    pass
-reveal_type(y)  # revealed: Literal[0, 1, 2]
-```
-
-## if-elif-else with intervening assignment
-
-```py
-y = 0
-if flag:
-    y = 1
-    z = 3
-elif flag2:
-    y = 2
-else:
-    pass
-reveal_type(y)  # revealed: Literal[0, 1, 2]
-```
-
-## Nested if statement
-
-```py
-y = 0
-if flag:
-    if flag2:
-        y = 1
-reveal_type(y)  # revealed: Literal[0, 1]
-```
-
-## if-elif without else
-
-```py
-y = 1
-y = 2
-if flag:
-    y = 3
-elif flag2:
-    y = 4
-x = y
-
-reveal_type(x)  # revealed: Literal[2, 3, 4]
-```

crates/red_knot_python_semantic/resources/mdtest/conditional/match.md

@@ -1,39 +0,0 @@
-# Pattern matching
-
-## With wildcard
-
-```py
-match 0:
-    case 1:
-        y = 2
-    case _:
-        y = 3
-
-reveal_type(y)  # revealed: Literal[2, 3]
-```
-
-## Without wildcard
-
-```py
-match 0:
-    case 1:
-        y = 2
-    case 2:
-        y = 3
-
-reveal_type(y)  # revealed: Unbound | Literal[2, 3]
-```
-
-## Basic match
-
-```py
-y = 1
-y = 2
-match 0:
-    case 1:
-        y = 3
-    case 2:
-        y = 4
-
-reveal_type(y)  # revealed: Literal[2, 3, 4]
-```

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

@@ -1,39 +0,0 @@
-# Errors while declaring
-
-## Violates previous assignment
-
-```py
-x = 1
-x: str  # error: [invalid-declaration] "Cannot declare type `str` for inferred type `Literal[1]`"
-```
-
-## Incompatible declarations
-
-```py
-if flag:
-    x: str
-else:
-    x: int
-x = 1  # error: [conflicting-declarations] "Conflicting declared types for `x`: str, int"
-```
-
-## Partial declarations
-
-```py
-if flag:
-    x: int
-x = 1  # error: [conflicting-declarations] "Conflicting declared types for `x`: Unknown, int"
-```
-
-## Incompatible declarations with bad assignment
-
-```py
-if flag:
-    x: str
-else:
-    x: int
-
-# error: [conflicting-declarations]
-# error: [invalid-assignment]
-x = b'foo'
-```

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

@@ -1,55 +0,0 @@
-# Exception Handling
-
-## Single Exception
-
-```py
-import re
-try:
-    x
-except NameError as e:
-    reveal_type(e)  # revealed: NameError
-except re.error as f:
-    reveal_type(f)  # revealed: error
-```
-
-## Unknown type in except handler does not cause spurious diagnostic
-
-```py
-from nonexistent_module import foo # error: [unresolved-import]
-
-try:
-    x
-except foo as e:
-    reveal_type(foo)  # revealed: Unknown
-    reveal_type(e)  # revealed: Unknown
-```
-
-## Multiple Exceptions in a Tuple
-
-```py
-EXCEPTIONS = (AttributeError, TypeError)
-
-try:
-    x
-except (RuntimeError, OSError) as e:
-    reveal_type(e)  # revealed: RuntimeError | OSError
-except EXCEPTIONS as f:
-    reveal_type(f)  # revealed: AttributeError | TypeError
-```
-
-## Dynamic exception types
-
-```py
-def foo(x: type[AttributeError], y: tuple[type[OSError], type[RuntimeError]], z: tuple[type[BaseException], ...]):
-    try:
-        w
-    except x as e:
-        # TODO: should be `AttributeError`
-        reveal_type(e)  # revealed: @Todo
-    except y as f:
-        # TODO: should be `OSError | RuntimeError`
-        reveal_type(f)  # revealed: @Todo
-    except z as g:
-        # TODO: should be `BaseException`
-        reveal_type(g)  # revealed: @Todo
-```

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

@@ -1,32 +0,0 @@
-# Except star
-
-TODO(Alex): Once we support `sys.version_info` branches, we can set `--target-version=py311` in these tests and the inferred type will just be `BaseExceptionGroup`
-
-## Except\* with BaseException
-
-```py
-try:
-    x
-except* BaseException as e:
-    reveal_type(e)  # revealed: Unknown | BaseExceptionGroup
-```
-
-## Except\* with specific exception
-
-```py
-try:
-    x
-except* OSError as e:
-    # TODO(Alex): more precise would be `ExceptionGroup[OSError]`
-    reveal_type(e)  # revealed: Unknown | BaseExceptionGroup
-```
-
-## Except\* with multiple exceptions
-
-```py
-try:
-    x
-except* (TypeError, AttributeError) as e:
-    #TODO(Alex): more precise would be `ExceptionGroup[TypeError | AttributeError]`.
-    reveal_type(e)  # revealed: Unknown | BaseExceptionGroup
-```

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

@@ -1,151 +0,0 @@
-# Expressions
-
-## OR
-
-```py
-def foo() -> str:
-    pass
-
-a = True or False
-b = 'x' or 'y' or 'z'
-c = '' or 'y' or 'z'
-d = False or 'z'
-e = False or True
-f = False or False
-g = foo() or False
-h = foo() or True
-
-reveal_type(a)  # revealed: Literal[True]
-reveal_type(b)  # revealed: Literal["x"]
-reveal_type(c)  # revealed: Literal["y"]
-reveal_type(d)  # revealed: Literal["z"]
-reveal_type(e)  # revealed: Literal[True]
-reveal_type(f)  # revealed: Literal[False]
-reveal_type(g)  # revealed: str | Literal[False]
-reveal_type(h)  # revealed: str | Literal[True]
-```
-
-## AND
-
-```py
-def foo() -> str:
-    pass
-
-a = True and False
-b = False and True
-c = foo() and False
-d = foo() and True
-e = 'x' and 'y' and 'z'
-f = 'x' and 'y' and ''
-g = '' and 'y'
-
-reveal_type(a)  # revealed: Literal[False]
-reveal_type(b)  # revealed: Literal[False]
-reveal_type(c)  # revealed: str | Literal[False]
-reveal_type(d)  # revealed: str | Literal[True]
-reveal_type(e)  # revealed: Literal["z"]
-reveal_type(f)  # revealed: Literal[""]
-reveal_type(g)  # revealed: Literal[""]
-```
-
-## Simple function calls to bool
-
-```py
-def returns_bool() -> bool:
-    return True
-
-if returns_bool():
-    x = True
-else:
-    x = False
-
-reveal_type(x)  # revealed: bool
-```
-
-## Complex
-
-```py
-def foo() -> str:
-    pass
-
-a = "x" and "y" or "z"
-b = "x" or "y" and "z"
-c = "" and "y" or "z"
-d = "" or "y" and "z"
-e = "x" and "y" or ""
-f = "x" or "y" and ""
-
-reveal_type(a)  # revealed: Literal["y"]
-reveal_type(b)  # revealed: Literal["x"]
-reveal_type(c)  # revealed: Literal["z"]
-reveal_type(d)  # revealed: Literal["z"]
-reveal_type(e)  # revealed: Literal["y"]
-reveal_type(f)  # revealed: Literal["x"]
-```
-
-## `bool()` function
-
-## Evaluates to builtin
-
-```py path=a.py
-redefined_builtin_bool = bool
-
-def my_bool(x)-> bool: pass
-```
-
-```py
-from a import redefined_builtin_bool, my_bool
-a = redefined_builtin_bool(0)
-b = my_bool(0)
-
-reveal_type(a)  # revealed: Literal[False]
-reveal_type(b)  # revealed: bool
-```
-
-## Truthy values
-
-```py
-a = bool(1)
-b = bool((0,))
-c = bool("NON EMPTY")
-d = bool(True)
-
-def foo(): pass
-e = bool(foo)
-
-reveal_type(a)  # revealed: Literal[True]
-reveal_type(b)  # revealed: Literal[True]
-reveal_type(c)  # revealed: Literal[True]
-reveal_type(d)  # revealed: Literal[True]
-reveal_type(e)  # revealed: Literal[True]
-```
-
-## Falsy values
-
-```py
-a = bool(0)
-b = bool(())
-c = bool(None)
-d = bool("")
-e = bool(False)
-f = bool()
-
-reveal_type(a)  # revealed: Literal[False]
-reveal_type(b)  # revealed: Literal[False]
-reveal_type(c)  # revealed: Literal[False]
-reveal_type(d)  # revealed: Literal[False]
-reveal_type(e)  # revealed: Literal[False]
-reveal_type(f)  # revealed: Literal[False]
-```
-
-## Ambiguous values
-
-```py
-a = bool([])
-b = bool({})
-c = bool(set())
-
-reveal_type(a)  # revealed: bool
-reveal_type(b)  # revealed: bool
-reveal_type(c)  # revealed: bool
-```

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

@@ -1,23 +0,0 @@
-# Structures
-
-## Class import following
-
-```py
-from b import C as D; E = D
-reveal_type(E) # revealed: Literal[C]
-```
-
-```py path=b.py
-class C: pass
-```
-
-## Module member resolution
-
-```py
-import b; D = b.C
-reveal_type(D) # revealed: Literal[C]
-```
-
-```py path=b.py
-class C: pass
-```

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

@@ -1,6 +0,0 @@
-# Importing builtin module
-
-```py
-import builtins; x = builtins.copyright
-reveal_type(x) # revealed: Literal[copyright]
-```

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

@@ -1,42 +0,0 @@
-# Conditional imports
-
-## Reimport
-
-```py path=c.py
-def f(): ...
-```
-
-```py path=b.py
-if flag:
-    from c import f
-else:
-    def f(): ...
-```
-
-```py
-# TODO we should not emit this error
-from b import f # error: [invalid-assignment] "Object of type `Literal[f, f]` is not assignable to `Literal[f, f]`"
-# TODO: We should disambiguate in such cases, showing `Literal[b.f, c.f]`.
-reveal_type(f)  # revealed: Literal[f, f]
-```
-
-## Reimport with stub declaration
-
-When we have a declared type in one path and only an inferred-from-definition type in the other, we
-should still be able to unify those:
-
-```py path=c.pyi
-x: int
-```
-
-```py path=b.py
-if flag:
-    from c import x
-else:
-    x = 1
-```
-
-```py
-from b import x
-reveal_type(x)  # revealed: int
-```

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

@@ -1,47 +0,0 @@
-# Unresolved Imports
-
-## Unresolved import statement
-
-```py
-import bar # error: "Cannot resolve import `bar`"
-```
-
-## Unresolved import from statement
-
-```py
-from bar import baz # error: "Cannot resolve import `bar`"
-```
-
-## Unresolved import from resolved module
-
-```py path=a.py
-```
-
-```py
-from a import thing # error: "Module `a` has no member `thing`"
-```
-
-## Resolved import of symbol from unresolved import
-
-```py path=a.py
-import foo as foo # error: "Cannot resolve import `foo`"
-```
-
-Importing the unresolved import into a second file should not trigger an additional "unresolved
-import" violation:
-
-```py
-from a import foo
-```
-
-## No implicit shadowing error
-
-```py path=b.py
-x: int
-```
-
-```py
-from b import x
-
-x = 'foo'  # error: "Object of type `Literal["foo"]"
-```

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

@@ -1,133 +0,0 @@
-# Relative
-
-## Non-existent
-
-```py path=package/__init__.py
-```
-
-```py path=package/bar.py
-from .foo import X # error: [unresolved-import]
-reveal_type(X)  # revealed: Unknown
-```
-
-## Simple
-
-```py path=package/__init__.py
-```
-
-```py path=package/foo.py
-X = 42
-```
-
-```py path=package/bar.py
-from .foo import X
-reveal_type(X)  # revealed: Literal[42]
-```
-
-## Dotted
-
-```py path=package/__init__.py
-```
-
-```py path=package/foo/bar/baz.py
-X = 42
-```
-
-```py path=package/bar.py
-from .foo.bar.baz import X
-reveal_type(X)  # revealed: Literal[42]
-```
-
-## Bare to package
-
-```py path=package/__init__.py
-X = 42
-```
-
-```py path=package/bar.py
-from . import X
-reveal_type(X)  # revealed: Literal[42]
-```
-
-## Non-existent + bare to package
-
-```py path=package/bar.py
-from . import X # error: [unresolved-import]
-reveal_type(X)  # revealed: Unknown
-```
-
-## Dunder init
-
-```py path=package/__init__.py
-from .foo import X
-reveal_type(X)  # revealed: Literal[42]
-```
-
-```py path=package/foo.py
-X = 42
-```
-
-## Non-existent + dunder init
-
-```py path=package/__init__.py
-from .foo import X # error: [unresolved-import]
-reveal_type(X)     # revealed: Unknown
-```
-
-## Long relative import
-
-```py path=package/__init__.py
-```
-
-```py path=package/foo.py
-X = 42
-```
-
-```py path=package/subpackage/subsubpackage/bar.py
-from ...foo import X
-reveal_type(X)  # revealed: Literal[42]
-```
-
-## Unbound symbol
-
-```py path=package/__init__.py
-```
-
-```py path=package/foo.py
-x
-```
-
-```py path=package/bar.py
-from .foo import x # error: [unresolved-import]
-reveal_type(x)     # revealed: Unknown
-```
-
-## Bare to module
-
-```py path=package/__init__.py
-```
-
-```py path=package/foo.py
-X = 42
-```
-
-```py path=package/bar.py
-# TODO: support submodule imports
-from . import foo  # error: [unresolved-import]
-y = foo.X
-
-# TODO: should be `Literal[42]`
-reveal_type(y)     # revealed: Unknown
-```
-
-## Non-existent + bare to module
-
-```py path=package/__init__.py
-```
-
-```py path=package/bar.py
-# TODO: submodule imports possibly not supported right now?
-from . import foo  # error: [unresolved-import]
-
-reveal_type(foo)   # revealed: Unknown
-```

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

@@ -1,25 +0,0 @@
-# Stubs
-
-## Import from stub declaration
-
-```py
-from b import x
-y = x
-reveal_type(y)  # revealed: int
-```
-
-```py path=b.pyi
-x: int
-```
-
-## Import from non-stub with declaration and definition
-
-```py
-from b import x
-y = x
-reveal_type(y)  # revealed: int
-```
-
-```py path=b.py
-x: int = 1
-```

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

@@ -1,8 +0,0 @@
-# Boolean literals
-
-```py
-x = True
-y = False
-reveal_type(x)  # revealed: Literal[True]
-reveal_type(y)  # revealed: Literal[False]
-```

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

@@ -1,8 +0,0 @@
-# Dictionaries
-
-## Empty dictionary
-
-```py
-x = {}
-reveal_type(x)  # revealed: dict
-```

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

@@ -1,8 +0,0 @@
-# Lists
-
-## Empty list
-
-```py
-x = []
-reveal_type(x)  # revealed: list
-```

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

@@ -1,8 +0,0 @@
-# Sets
-
-## Basic set
-
-```py
-x = {1, 2}
-reveal_type(x)  # revealed: set
-```

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

@@ -1,20 +0,0 @@
-# Tuples
-
-## Empty tuple
-
-```py
-x = ()
-reveal_type(x)  # revealed: tuple[()]
-```
-
-## Heterogeneous tuple
-
-```py
-x = (1, 'a')
-y = (1, (2, 3))
-z = (x, 2)
-
-reveal_type(x)  # revealed: tuple[Literal[1], Literal["a"]]
-reveal_type(y)  # revealed: tuple[Literal[1], tuple[Literal[2], Literal[3]]]
-reveal_type(z)  # revealed: tuple[tuple[Literal[1], Literal["a"]], Literal[2]]
-```

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

@@ -1,7 +0,0 @@
-# Complex literals
-
-## Complex numbers
-
-```py
-reveal_type(2j)  # revealed: complex
-```

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

@@ -1,44 +0,0 @@
-# f-strings
-
-## Expression
-
-```py
-x = 0
-y = str()
-z = False
-
-a = f'hello'
-b = f'h {x}'
-c = 'one ' f'single ' f'literal'
-d = 'first ' f'second({b})' f' third'
-e = f'-{y}-'
-f = f'-{y}-' f'--' '--'
-g = f'{z} == {False} is {True}'
-
-reveal_type(a)  # revealed: Literal["hello"]
-reveal_type(b)  # revealed: Literal["h 0"]
-reveal_type(c)  # revealed: Literal["one single literal"]
-reveal_type(d)  # revealed: Literal["first second(h 0) third"]
-reveal_type(e)  # revealed: str
-reveal_type(f)  # revealed: str
-reveal_type(g)  # revealed: Literal["False == False is True"]
-```
-
-## Conversion Flags
-
-```py
-string = 'hello'
-a = f'{string!r}'
-
-# TODO: should be `Literal["'hello'"]`
-reveal_type(a)  # revealed: str
-```
-
-## Format Specifiers
-
-```py
-a = f'{1:02}'
-
-# TODO: should be `Literal["01"]`
-reveal_type(a)  # revealed: str
-```

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

@@ -1,7 +0,0 @@
-# Float literals
-
-## Basic
-
-```py
-reveal_type(1.0)  # revealed: float
-```

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

@@ -1,56 +0,0 @@
-# Integer literals
-
-## Literals
-
-We can infer an integer literal type:
-
-```py
-reveal_type(1)  # revealed: Literal[1]
-```
-
-## Variable
-
-```py
-x = 1
-reveal_type(x)  # revealed: Literal[1]
-```
-
-## Overflow
-
-We only track integer literals within the range of an i64:
-
-```py
-reveal_type(9223372036854775808)  # revealed: int
-```
-
-## Big int
-
-We don't support big integer literals; we just infer `int` type instead:
-
-```py
-x = 10_000_000_000_000_000_000
-reveal_type(x)  # revealed: int
-```
-
-## Negated
-
-```py
-x = -1
-y = -1234567890987654321
-z = --987
-reveal_type(x)  # revealed: Literal[-1]
-reveal_type(y)  # revealed: Literal[-1234567890987654321]
-reveal_type(z)  # revealed: Literal[987]
-```
-
-## Floats
-
-```py
-reveal_type(1.0)  # revealed: float
-```
-
-## Complex
-
-```py
-reveal_type(2j)  # revealed: complex
-```

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

@@ -1,26 +0,0 @@
-# String literals
-
-## Simple
-
-```py
-w = "Hello"
-x = 'world'
-y = "Guten " + 'tag'
-z = 'bon ' + "jour"
-
-reveal_type(w)  # revealed: Literal["Hello"]
-reveal_type(x)  # revealed: Literal["world"]
-reveal_type(y)  # revealed: Literal["Guten tag"]
-reveal_type(z)  # revealed: Literal["bon jour"]
-```
-
-## Nested Quotes
-
-```py
-x = 'I say "hello" to you'
-y = "You say \"hey\" back"
-z = 'No "closure here'
-reveal_type(x)  # revealed: Literal["I say \"hello\" to you"]
-reveal_type(y)  # revealed: Literal["You say \"hey\" back"]
-reveal_type(z)  # revealed: Literal["No \"closure here"]
-```

crates/red_knot_python_semantic/resources/mdtest/loops/async_for_loops.md

@@ -1,41 +0,0 @@
-# Async
-
-Async `for` loops do not work according to the synchronous iteration protocol.
-
-## Invalid async for loop
-
-```py
-async def foo():
-    class Iterator:
-        def __next__(self) -> int:
-            return 42
-
-    class Iterable:
-        def __iter__(self) -> Iterator:
-            return Iterator()
-
-    async for x in Iterator():
-        pass
-
-    # TODO
-    reveal_type(x)  # revealed: Unbound | @Todo
-```
-
-## Basic async for loop
-
-```py
-async def foo():
-    class IntAsyncIterator:
-        async def __anext__(self) -> int:
-            return 42
-
-    class IntAsyncIterable:
-        def __aiter__(self) -> IntAsyncIterator:
-            return IntAsyncIterator()
-
-    #TODO(Alex): async iterables/iterators!
-    async for x in IntAsyncIterable():
-        pass
-
-    reveal_type(x)  # revealed: Unbound | @Todo
-```

crates/red_knot_python_semantic/resources/mdtest/loops/for_loop.md

@@ -1,134 +0,0 @@
-# For loops
-
-## Basic `for` loop
-
-```py
-class IntIterator:
-    def __next__(self) -> int:
-        return 42
-
-class IntIterable:
-    def __iter__(self) -> IntIterator:
-        return IntIterator()
-
-for x in IntIterable():
-    pass
-
-reveal_type(x)  # revealed: Unbound | int
-```
-
-## With previous definition
-
-```py
-class IntIterator:
-    def __next__(self) -> int:
-        return 42
-
-class IntIterable:
-    def __iter__(self) -> IntIterator:
-        return IntIterator()
-
-x = 'foo'
-
-for x in IntIterable():
-    pass
-
-reveal_type(x)  # revealed: Literal["foo"] | int
-```
-
-## With `else` (no break)
-
-```py
-class IntIterator:
-    def __next__(self) -> int:
-        return 42
-
-class IntIterable:
-    def __iter__(self) -> IntIterator:
-        return IntIterator()
-
-for x in IntIterable():
-    pass
-else:
-    x = 'foo'
-
-reveal_type(x)  # revealed: Literal["foo"]
-```
-
-## May `break`
-
-```py
-class IntIterator:
-    def __next__(self) -> int:
-        return 42
-
-class IntIterable:
-    def __iter__(self) -> IntIterator:
-        return IntIterator()
-
-for x in IntIterable():
-    if x > 5:
-        break
-else:
-    x = 'foo'
-
-reveal_type(x)  # revealed: int | Literal["foo"]
-```
-
-## With old-style iteration protocol
-
-```py
-class OldStyleIterable:
-    def __getitem__(self, key: int) -> int:
-        return 42
-
-for x in OldStyleIterable():
-    pass
-
-reveal_type(x)  # revealed: Unbound | int
-```
-
-## With heterogeneous tuple
-
-```py
-for x in (1, 'a', b'foo'):
-    pass
-
-reveal_type(x)  # revealed: Unbound | Literal[1] | Literal["a"] | Literal[b"foo"]
-```
-
-## With non-callable iterator
-
-```py
-class NotIterable:
-    if flag:
-        __iter__ = 1
-    else:
-        __iter__ = None
-
-for x in NotIterable(): # error: "Object of type `NotIterable` is not iterable"
-    pass
-
-reveal_type(x)  # revealed: Unbound | Unknown
-```
-
-## Invalid iterable
-
-```py
-nonsense = 123
-for x in nonsense: # error: "Object of type `Literal[123]` is not iterable"
-    pass
-```
-
-## New over old style iteration protocol
-
-```py
-class NotIterable:
-    def __getitem__(self, key: int) -> int:
-        return 42
-
-    __iter__ = None
-
-for x in NotIterable(): # error: "Object of type `NotIterable` is not iterable"
-    pass
-```

crates/red_knot_python_semantic/resources/mdtest/loops/iterators.md

@@ -1,18 +0,0 @@
-# Iterators
-
-## Yield must be iterable
-
-```py
-class NotIterable: pass
-
-class Iterator:
-    def __next__(self) -> int:
-        return 42
-
-class Iterable:
-    def __iter__(self) -> Iterator: ...
-
-def generator_function():
-    yield from Iterable()
-    yield from NotIterable() # error: "Object of type `NotIterable` is not iterable"
-```

crates/red_knot_python_semantic/resources/mdtest/loops/while_loop.md

@@ -1,43 +0,0 @@
-# While loops
-
-## Basic While Loop
-
-```py
-x = 1
-while flag:
-    x = 2
-
-reveal_type(x)  # revealed: Literal[1, 2]
-```
-
-## While with else (no break)
-
-```py
-x = 1
-while flag:
-    x = 2
-else:
-    y = x
-    x = 3
-
-reveal_type(x)  # revealed: Literal[3]
-reveal_type(y)  # revealed: Literal[1, 2]
-```
-
-## While with Else (may break)
-
-```py
-x = 1
-y = 0
-while flag:
-    x = 2
-    if flag2:
-        y = 4
-        break
-else:
-    y = x
-    x = 3
-
-reveal_type(x)  # revealed: Literal[2, 3]
-reveal_type(y)  # revealed: Literal[1, 2, 4]
-```

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

@@ -1,29 +0,0 @@
-# Narrowing for `is` conditionals
-
-## `is None`
-
-```py
-x = None if flag else 1
-
-if x is None:
-    # TODO the following should be simplified to 'None'
-    reveal_type(x)  # revealed: None | Literal[1] & None
-
-reveal_type(x)  # revealed: None | Literal[1]
-```
-
-## `is` for other types
-
-```py
-class A:
-    ...
-
-x = A()
-y = x if flag else None
-
-if y is x:
-    # TODO the following should be simplified to 'A'
-    reveal_type(y)  # revealed: A | None & A
-
-reveal_type(y)  # revealed: A | None
-```

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

@@ -1,40 +0,0 @@
-# Narrowing for `is not` conditionals
-
-## `is not None`
-
-The type guard removes `None` from the union type:
-
-```py
-x = None if flag else 1
-
-if x is not None:
-    reveal_type(x)  # revealed: Literal[1]
-
-reveal_type(x)  # revealed: None | Literal[1]
-```
-
-## `is not` for other singleton types
-
-```py
-x = True if flag else False
-reveal_type(x)  # revealed: bool
-
-if x is not False:
-    # TODO the following should be `Literal[True]`
-    reveal_type(x)  # revealed: bool & ~Literal[False]
-```
-
-## `is not` for non-singleton types
-
-Non-singleton types should *not* narrow the type: two instances of a
-non-singleton class may occupy different addresses in memory even if
-they compare equal.
-
-```py
-x = [1]
-y = [1]
-
-if x is not y:
-    # TODO: should include type parameter: list[int]
-    reveal_type(x)  # revealed: list
-```

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

@@ -1,17 +0,0 @@
-# Narrowing for `match` statements
-
-## Single `match` pattern
-
-```py
-x = None if flag else 1
-reveal_type(x)  # revealed: None | Literal[1]
-
-y = 0
-
-match x:
-    case None:
-        y = x
-
-# TODO intersection simplification: should be just Literal[0] | None
-reveal_type(y)  # revealed: Literal[0] | None | Literal[1] & None
-```

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

@@ -1,9 +0,0 @@
-# `is not None` narrowing
-
-```py
-x = None if flag else 1
-if x is not None:
-    reveal_type(x)  # revealed: Literal[1]
-
-reveal_type(x)  # revealed: None | Literal[1]
-```

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

@@ -1,17 +0,0 @@
-# Classes shadowing
-
-## Implicit error
-
-```py
-class C: pass
-C = 1 # error: "Implicit shadowing of class `C`; annotate to make it explicit if this is intentional"
-```
-
-## Explicit
-
-No diagnostic is raised in the case of explicit shadowing:
-
-```py
-class C: pass
-C: int = 1
-```

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

@@ -1,24 +0,0 @@
-# Function shadowing
-
-## Parameter
-
-Parameter `x` of type `str` is shadowed and reassigned with a new `int` value inside the function. No diagnostics should be generated.
-
-```py path=a.py
-def f(x: str):
-    x: int = int(x)
-```
-
-## Implicit error
-
-```py path=a.py
-def f(): pass
-f = 1 # error: "Implicit shadowing of function `f`; annotate to make it explicit if this is intentional"
-```
-
-## Explicit shadowing
-
-```py path=a.py
-def f(): pass
-f: int = 1
-```

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

@@ -1,11 +0,0 @@
-# Shadwing declaration
-
-## Shadow after incompatible declarations is OK
-
-```py
-if flag:
-    x: str
-else:
-    x: int
-x: bytes = b'foo'
-```

crates/red_knot_python_semantic/resources/mdtest/stubs/class.md

@@ -1,10 +0,0 @@
-# Class defenitions in stubs
-
-## Cyclical class definition
-
-In type stubs, classes can reference themselves in their base class definitions. For example, in `typeshed`, we have `class str(Sequence[str]): ...`.
-
-```py path=a.pyi
-class C(C): ...
-reveal_type(C)  # revealed: Literal[C]
-```

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

@@ -1,15 +0,0 @@
-# Bytes subscript
-
-## Simple
-
-```py
-w = b'red' b'knot'
-x = b'hello'
-y = b'world' + b'!'
-z = b'\xff\x00'
-
-reveal_type(w)  # revealed: Literal[b"redknot"]
-reveal_type(x)  # revealed: Literal[b"hello"]
-reveal_type(y)  # revealed: Literal[b"world!"]
-reveal_type(z)  # revealed: Literal[b"\xff\x00"]
-```

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

@@ -1,92 +0,0 @@
-# Class subscript
-
-## Class getitem unbound
-
-```py
-class NotSubscriptable: pass
-a = NotSubscriptable[0]  # error: "Cannot subscript object of type `Literal[NotSubscriptable]` with no `__class_getitem__` method"
-```
-
-## Class getitem
-
-```py
-class Identity:
-    def __class_getitem__(cls, item: int) -> str:
-        return item
-
-a = Identity[0]  
-reveal_type(a) # revealed: str
-```
-
-## Class getitem union
-
-```py
-flag = True
-
-class Identity:
-    if flag:
-        def __class_getitem__(cls, item: int) -> str:
-            return item
-    else:
-        def __class_getitem__(cls, item: int) -> int:
-            return item
-
-a = Identity[0]  
-reveal_type(a) # revealed: str | int
-```
-
-## Class getitem with class union
-
-```py
-flag = True
-
-class Identity1:
-    def __class_getitem__(cls, item: int) -> str:
-        return item
-
-class Identity2:
-    def __class_getitem__(cls, item: int) -> int:
-        return item
-
-if flag:
-    a = Identity1
-else:
-    a = Identity2
-
-b = a[0]
-reveal_type(a) # revealed: Literal[Identity1, Identity2]
-reveal_type(b) # revealed: str | int
-```
-
-## Class getitem with unbound method union
-
-```py
-flag = True
-
-if flag:
-    class Identity:
-        def __class_getitem__(self, x: int) -> str:
-            pass
-else:
-    class Identity: pass
-
-a = Identity[42] # error: [call-non-callable] "Method `__class_getitem__` of type `Literal[__class_getitem__] | Unbound` is not callable on object of type `Literal[Identity, Identity]`" 
-reveal_type(a) # revealed: str | Unknown 
-```
-
-## TODO: Class getitem non-class union
-
-```py
-flag = True
-
-if flag:
-    class Identity:
-        def __class_getitem__(self, x: int) -> str:
-            pass
-else:
-    Identity = 1
-
-a = Identity[42] # error: "Cannot subscript object of type `Literal[Identity] | Literal[1]` with no `__getitem__` method"
-# TODO: should _probably_ emit `str | Unknown` 
-reveal_type(a) # revealed: Unknown 
-```

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

@@ -1,45 +0,0 @@
-# Instance subscript
-
-## Getitem unbound
-
-```py
-class NotSubscriptable: pass
-a = NotSubscriptable()[0]  # error: "Cannot subscript object of type `NotSubscriptable` with no `__getitem__` method"
-```
-
-## Getitem not callable
-
-```py
-class NotSubscriptable:
-    __getitem__ = None
-
-a = NotSubscriptable()[0]  # error: "Method `__getitem__` of type `None` is not callable on object of type `NotSubscriptable`"
-```
-
-## Valid getitem
-
-```py
-class Identity:
-    def __getitem__(self, index: int) -> int:
-        return index
-
-a = Identity()[0]  
-reveal_type(a) # revealed: int
-```
-
-## Getitem union
-
-```py
-flag = True
-
-class Identity:
-    if flag:
-        def __getitem__(self, index: int) -> int:
-            return index
-    else:
-        def __getitem__(self, index: int) -> str:
-            return str(index)
-
-a = Identity()[0]  
-reveal_type(a) # revealed: int | str
-```

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

@@ -1,32 +0,0 @@
-# Subscript on strings
-
-## Simple
-
-```py
-s = 'abcde'
-
-a = s[0]
-b = s[1]
-c = s[-1]
-d = s[-2]
-e = s[8]        # error: [index-out-of-bounds] "Index 8 is out of bounds for string `Literal["abcde"]` with length 5"
-f = s[-8]       # error: [index-out-of-bounds] "Index -8 is out of bounds for string `Literal["abcde"]` with length 5"
-
-reveal_type(a)  # revealed: Literal["a"]
-reveal_type(b)  # revealed: Literal["b"]
-reveal_type(c)  # revealed: Literal["e"]
-reveal_type(d)  # revealed: Literal["d"]
-reveal_type(e)  # revealed: Unknown
-reveal_type(f)  # revealed: Unknown
-```
-
-## Function return
-
-```py
-def add(x: int, y: int) -> int:
-    return x + y
-
-a = 'abcde'[add(0, 1)]
-# TODO: Support overloads... Should be `str`
-reveal_type(a)  # revealed: @Todo
-```

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

@@ -1,21 +0,0 @@
-# Tuple subscripts
-
-## Basic
-
-```py
-t = (1, 'a', 'b')
-
-a = t[0]
-b = t[1]
-c = t[-1]
-d = t[-2]
-e = t[4]        # error: [index-out-of-bounds]
-f = t[-4]       # error: [index-out-of-bounds]
-
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: Literal["a"]
-reveal_type(c)  # revealed: Literal["b"]
-reveal_type(d)  # revealed: Literal["a"]
-reveal_type(e)  # revealed: Unknown
-reveal_type(f)  # revealed: Unknown
-```

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

@@ -1,37 +0,0 @@
-# Unary Operations
-
-## Unary Addition
-
-```py
-a = +0
-b = +1
-c = +True
-
-reveal_type(a)  # revealed: Literal[0]
-reveal_type(b)  # revealed: Literal[1]
-reveal_type(c)  # revealed: Literal[1]
-```
-
-## Unary Subtraction
-
-```py
-a = -0
-b = -1
-c = -True
-
-reveal_type(a)  # revealed: Literal[0]
-reveal_type(b)  # revealed: Literal[-1]
-reveal_type(c)  # revealed: Literal[-1]
-```
-
-## Unary Bitwise Inversion
-
-```py
-a = ~0
-b = ~1
-c = ~True
-
-reveal_type(a) # revealed: Literal[-1] 
-reveal_type(b) # revealed: Literal[-2]
-reveal_type(c) # revealed: Literal[-2]
-```

crates/red_knot_python_semantic/resources/mdtest/unary/not.md

@@ -1,149 +0,0 @@
-# Unary not
-
-## None
-
-```py
-a = not None
-b = not not None
-reveal_type(a)  # revealed: Literal[True]
-reveal_type(b)  # revealed: Literal[False]
-```
-
-## Function
-
-```py
-from typing import reveal_type
-
-def f():
-    return 1
-
-a = not f
-b = not reveal_type
-
-reveal_type(a)  # revealed: Literal[False]
-# TODO Unknown should not be part of the type of typing.reveal_type
-# reveal_type(b)  revealed: Literal[False]
-```
-
-## Module
-
-```py
-import b; import warnings
-
-x = not b
-z = not warnings
-
-reveal_type(x)  # revealed: Literal[False]
-reveal_type(z)  # revealed: Literal[False]
-```
-
-```py path=b.py
-y = 1
-```
-
-## Union
-
-```py
-if flag:
-    p = 1
-    q = 3.3
-    r = "hello"
-    s = "world"
-    t = 0
-else:
-    p = "hello"
-    q = 4
-    r = ""
-    s = 0
-    t = ""
-
-a = not p
-b = not q
-c = not r
-d = not s
-e = not t
-
-reveal_type(a)  # revealed: Literal[False]
-reveal_type(b)  # revealed: bool
-reveal_type(c)  # revealed: bool
-reveal_type(d)  # revealed: bool
-reveal_type(e)  # revealed: Literal[True]
-```
-
-## Integer literal
-
-```py
-a = not 1
-b = not 1234567890987654321
-e = not 0
-x = not -1
-y = not -1234567890987654321
-z = not --987
-
-reveal_type(a)  # revealed: Literal[False]
-reveal_type(b)  # revealed: Literal[False]
-reveal_type(e)  # revealed: Literal[True]
-reveal_type(x)  # revealed: Literal[False]
-reveal_type(y)  # revealed: Literal[False]
-reveal_type(z)  # revealed: Literal[False]
-```
-
-## Boolean literal
-
-```py
-w = True
-x = False
-y = not w
-z = not x
-
-reveal_type(w)  # revealed: Literal[True]
-reveal_type(x)  # revealed: Literal[False]
-reveal_type(y)  # revealed: Literal[False]
-reveal_type(z)  # revealed: Literal[True]
-```
-
-## String literal
-
-```py
-a = not "hello"
-b = not ""
-c = not "0"
-d = not "hello" + "world"
-
-reveal_type(a)  # revealed: Literal[False]
-reveal_type(b)  # revealed: Literal[True]
-reveal_type(c)  # revealed: Literal[False]
-reveal_type(d)  # revealed: Literal[False]
-```
-
-## Bytes literal
-
-```py
-a = not b"hello"
-b = not b""
-c = not b"0"
-d = not b"hello" + b"world"
-
-reveal_type(a)  # revealed: Literal[False]
-reveal_type(b)  # revealed: Literal[True]
-reveal_type(c)  # revealed: Literal[False]
-reveal_type(d)  # revealed: Literal[False]
-```
-
-## Tuple
-
-```py
-a = not (1,)
-b = not (1, 2)
-c = not (1, 2, 3)
-d = not ()
-e = not ("hello",)
-f = not (1, "hello")
-
-reveal_type(a)  # revealed: Literal[False]
-reveal_type(b)  # revealed: Literal[False]
-reveal_type(c)  # revealed: Literal[False]
-reveal_type(d)  # revealed: Literal[True]
-reveal_type(e)  # revealed: Literal[False]
-reveal_type(f)  # revealed: Literal[False]
-```

crates/red_knot_python_semantic/resources/mdtest/unpacking.md

@@ -1,273 +0,0 @@
-# Unpacking
-
-## Tuple
-
-### Simple tuple
-
-```py
-(a, b, c) = (1, 2, 3)
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: Literal[2]
-reveal_type(c)  # revealed: Literal[3]
-```
-
-### Simple list
-
-```py
-[a, b, c] = (1, 2, 3)
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: Literal[2]
-reveal_type(c)  # revealed: Literal[3]
-```
-
-### Simple mixed
-
-```py
-[a, (b, c), d] = (1, (2, 3), 4)
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: Literal[2]
-reveal_type(c)  # revealed: Literal[3]
-reveal_type(d)  # revealed: Literal[4]
-```
-
-### Multiple assignment
-
-```py
-a, b = c = 1, 2
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: Literal[2]
-reveal_type(c)  # revealed: tuple[Literal[1], Literal[2]]
-```
-
-### Nested tuple with unpacking
-
-```py
-(a, (b, c), d) = (1, (2, 3), 4)
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: Literal[2]
-reveal_type(c)  # revealed: Literal[3]
-reveal_type(d)  # revealed: Literal[4]
-```
-
-### Nested tuple without unpacking
-
-```py
-(a, b, c) = (1, (2, 3), 4)
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: tuple[Literal[2], Literal[3]]
-reveal_type(c)  # revealed: Literal[4]
-```
-
-### Uneven unpacking (1)
-
-```py
-# 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]
-reveal_type(c)  # revealed: Unknown
-```
-
-### Uneven unpacking (2)
-
-```py
-# 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]
-```
-
-### Starred expression (1)
-
-```py
-# TODO: Add diagnostic (need more values to unpack)
-# TODO: Remove 'not-iterable' diagnostic
-[a, *b, c, d] = (1, 2)  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: Literal[1]
-# TODO: Should be list[Any] once support for assigning to starred expression is added
-reveal_type(b)  # revealed: @Todo
-reveal_type(c)  # revealed: Literal[2]
-reveal_type(d)  # revealed: Unknown
-```
-
-### Starred expression (2)
-
-```py
-[a, *b, c] = (1, 2)  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: Literal[1]
-# TODO: Should be list[Any] once support for assigning to starred expression is added
-reveal_type(b)  # revealed: @Todo
-reveal_type(c)  # revealed: Literal[2]
-```
-
-### Starred expression (3)
-
-```py
-# TODO: Remove 'not-iterable' diagnostic
-[a, *b, c] = (1, 2, 3)  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: Literal[1]
-# TODO: Should be list[int] once support for assigning to starred expression is added
-reveal_type(b)  # revealed: @Todo
-reveal_type(c)  # revealed: Literal[3]
-```
-
-### Starred expression (4)
-
-```py
-# TODO: Remove 'not-iterable' diagnostic
-[a, *b, c, d] = (1, 2, 3, 4, 5, 6)  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: Literal[1]
-# TODO: Should be list[int] once support for assigning to starred expression is added
-reveal_type(b)  # revealed: @Todo
-reveal_type(c)  # revealed: Literal[5]
-reveal_type(d)  # revealed: Literal[6]
-```
-
-### Starred expression (5)
-
-```py
-# TODO: Remove 'not-iterable' diagnostic
-[a, b, *c] = (1, 2, 3, 4)  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: Literal[2]
-# TODO: Should be list[int] once support for assigning to starred expression is added
-reveal_type(c)  # revealed: @Todo
-```
-
-### Non-iterable unpacking
-
-TODO: Remove duplicate diagnostics. This is happening because for a sequence-like
-assignment target, multiple definitions are created and the inference engine runs
-on each of them which results in duplicate diagnostics.
-
-```py
-# error: "Object of type `Literal[1]` is not iterable"
-# error: "Object of type `Literal[1]` is not iterable"
-a, b = 1
-reveal_type(a)  # revealed: Unknown
-reveal_type(b)  # revealed: Unknown
-```
-
-### Custom iterator unpacking
-
-```py
-class Iterator:
-    def __next__(self) -> int:
-        return 42
-
-
-class Iterable:
-    def __iter__(self) -> Iterator:
-        return Iterator()
-
-
-(a, b) = Iterable()
-reveal_type(a)  # revealed: int
-reveal_type(b)  # revealed: int
-```
-
-### Custom iterator unpacking nested
-
-```py
-class Iterator:
-    def __next__(self) -> int:
-        return 42
-
-
-class Iterable:
-    def __iter__(self) -> Iterator:
-        return Iterator()
-
-
-(a, (b, c), d) = (1, Iterable(), 2)
-reveal_type(a)  # revealed: Literal[1]
-reveal_type(b)  # revealed: int
-reveal_type(c)  # revealed: int
-reveal_type(d)  # revealed: Literal[2]
-```
-
-## String
-
-### Simple unpacking
-
-```py
-a, b = 'ab'
-reveal_type(a)  # revealed: LiteralString
-reveal_type(b)  # revealed: LiteralString
-```
-
-### Uneven unpacking (1)
-
-```py
-# TODO: Add diagnostic (there aren't enough values to unpack)
-a, b, c = 'ab'
-reveal_type(a)  # revealed: LiteralString
-reveal_type(b)  # revealed: LiteralString
-reveal_type(c)  # revealed: Unknown
-```
-
-### Uneven unpacking (2)
-
-```py
-# TODO: Add diagnostic (too many values to unpack)
-a, b = 'abc'
-reveal_type(a)  # revealed: LiteralString
-reveal_type(b)  # revealed: LiteralString
-```
-
-### Starred expression (1)
-
-```py
-# TODO: Add diagnostic (need more values to unpack)
-# TODO: Remove 'not-iterable' diagnostic
-(a, *b, c, d) = "ab"  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: LiteralString
-# TODO: Should be list[LiteralString] once support for assigning to starred expression is added
-reveal_type(b)  # revealed: @Todo
-reveal_type(c)  # revealed: LiteralString
-reveal_type(d)  # revealed: Unknown
-```
-
-### Starred expression (2)
-
-```py
-(a, *b, c) = "ab"  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: LiteralString
-# TODO: Should be list[Any] once support for assigning to starred expression is added
-reveal_type(b)  # revealed: @Todo
-reveal_type(c)  # revealed: LiteralString
-```
-
-### Starred expression (3)
-
-```py
-# TODO: Remove 'not-iterable' diagnostic
-(a, *b, c) = "abc"  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: LiteralString
-# TODO: Should be list[LiteralString] once support for assigning to starred expression is added
-reveal_type(b)  # revealed: @Todo
-reveal_type(c)  # revealed: LiteralString
-```
-
-### Starred expression (4)
-
-```py
-# TODO: Remove 'not-iterable' diagnostic
-(a, *b, c, d) = "abcdef"  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: LiteralString
-# TODO: Should be list[LiteralString] once support for assigning to starred expression is added
-reveal_type(b)  # revealed: @Todo
-reveal_type(c)  # revealed: LiteralString
-reveal_type(d)  # revealed: LiteralString
-```
-
-### Starred expression (5)
-
-```py
-# TODO: Remove 'not-iterable' diagnostic
-(a, b, *c) = "abcd"  # error: "Object of type `None` is not iterable"
-reveal_type(a)  # revealed: LiteralString
-reveal_type(b)  # revealed: LiteralString
-# TODO: Should be list[int] once support for assigning to starred expression is added
-reveal_type(c)  # revealed: @Todo
-```

crates/red_knot_python_semantic/src/builtins.rs

@@ -0,0 +1,16 @@
+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::Db;
+
+/// Salsa query to get the builtins scope.
+///
+/// Can return None if a custom typeshed is used that is missing `builtins.pyi`.
+#[salsa::tracked]
+pub(crate) fn builtins_scope(db: &dyn Db) -> Option<ScopeId<'_>> {
+    let builtins_name =
+        ModuleName::new_static("builtins").expect("Expected 'builtins' to be a valid module name");
+    let builtins_file = resolve_module(db, builtins_name)?.file();
+    Some(global_scope(db, builtins_file))
+}

crates/red_knot_python_semantic/src/db.rs

@@ -11,6 +11,7 @@ pub trait Db: SourceDb + Upcast<dyn SourceDb> {
 pub(crate) mod tests {
     use std::sync::Arc;
 
+    use crate::module_resolver::vendored_typeshed_stubs;
     use ruff_db::files::{File, Files};
     use ruff_db::system::{DbWithTestSystem, System, TestSystem};
     use ruff_db::vendored::VendoredFileSystem;
@@ -32,7 +33,7 @@ pub(crate) mod tests {
             Self {
                 storage: salsa::Storage::default(),
                 system: TestSystem::default(),
-                vendored: red_knot_vendored::file_system().clone(),
+                vendored: vendored_typeshed_stubs().clone(),
                 events: std::sync::Arc::default(),
                 files: Files::default(),
             }

crates/red_knot_python_semantic/src/lib.rs

@@ -4,12 +4,13 @@ use rustc_hash::FxHasher;
 
 pub use db::Db;
 pub use module_name::ModuleName;
-pub use module_resolver::{resolve_module, system_module_search_paths, Module};
+pub use module_resolver::{resolve_module, system_module_search_paths, vendored_typeshed_stubs};
 pub use program::{Program, ProgramSettings, SearchPathSettings, SitePackages};
 pub use python_version::PythonVersion;
 pub use semantic_model::{HasTy, SemanticModel};
 
 pub mod ast_node_ref;
+mod builtins;
 mod db;
 mod module_name;
 mod module_resolver;
@@ -19,7 +20,7 @@ mod python_version;
 pub mod semantic_index;
 mod semantic_model;
 pub(crate) mod site_packages;
-mod stdlib;
 pub mod types;
 
 type FxOrderSet<V> = ordermap::set::OrderSet<V, BuildHasherDefault<FxHasher>>;
+type FxOrderMap<K, V> = ordermap::map::OrderMap<K, V, BuildHasherDefault<FxHasher>>;

crates/red_knot_python_semantic/src/module_resolver/mod.rs

@@ -1,9 +1,10 @@
 use std::iter::FusedIterator;
 
-pub use module::Module;
+pub(crate) use module::Module;
 pub use resolver::resolve_module;
 pub(crate) use resolver::{file_to_module, SearchPaths};
 use ruff_db::system::SystemPath;
+pub use typeshed::vendored_typeshed_stubs;
 
 use crate::module_resolver::resolver::search_paths;
 use crate::Db;

crates/red_knot_python_semantic/src/module_resolver/path.rs

@@ -59,10 +59,6 @@ impl ModulePath {
         self.relative_path.push(component);
     }
 
-    pub(crate) fn pop(&mut self) -> bool {
-        self.relative_path.pop()
-    }
-
     #[must_use]
     pub(super) fn is_directory(&self, resolver: &ResolverContext) -> bool {
         let ModulePath {

crates/red_knot_python_semantic/src/module_resolver/resolver.rs

@@ -1,23 +1,22 @@
+use rustc_hash::{FxBuildHasher, FxHashSet};
 use std::borrow::Cow;
 use std::iter::FusedIterator;
-
-use rustc_hash::{FxBuildHasher, FxHashSet};
+use std::ops::Deref;
 
 use ruff_db::files::{File, FilePath, FileRootKind};
 use ruff_db::system::{DirectoryEntry, System, SystemPath, SystemPathBuf};
 use ruff_db::vendored::{VendoredFileSystem, VendoredPath};
 
+use super::module::{Module, ModuleKind};
+use super::path::{ModulePath, SearchPath, SearchPathValidationError};
 use crate::db::Db;
 use crate::module_name::ModuleName;
 use crate::module_resolver::typeshed::{vendored_typeshed_versions, TypeshedVersions};
 use crate::site_packages::VirtualEnvironment;
 use crate::{Program, PythonVersion, SearchPathSettings, SitePackages};
 
-use super::module::{Module, ModuleKind};
-use super::path::{ModulePath, SearchPath, SearchPathValidationError};
-
 /// Resolves a module name to a module.
-pub fn resolve_module(db: &dyn Db, module_name: &ModuleName) -> Option<Module> {
+pub fn resolve_module(db: &dyn Db, module_name: ModuleName) -> Option<Module> {
     let interned_name = ModuleNameIngredient::new(db, module_name);
 
     resolve_module_query(db, interned_name)
@@ -36,14 +35,14 @@ pub(crate) fn resolve_module_query<'db>(
     let _span = tracing::trace_span!("resolve_module", %name).entered();
 
     let Some((search_path, module_file, kind)) = resolve_name(db, name) else {
-        tracing::debug!("Module `{name}` not found in search paths");
+        tracing::debug!("Module '{name}' not found in the search paths.");
         return None;
     };
 
     let module = Module::new(name.clone(), kind, search_path, module_file);
 
     tracing::trace!(
-        "Resolved module `{name}` to `{path}`",
+        "Resolved module '{name}' to '{path}'.",
         path = module_file.path(db)
     );
 
@@ -103,7 +102,7 @@ pub(crate) fn file_to_module(db: &dyn Db, file: File) -> Option<Module> {
     // If it doesn't, then that means that multiple modules have the same name in different
     // root paths, but that the module corresponding to `path` is in a lower priority search path,
     // in which case we ignore it.
-    let module = resolve_module(db, &module_name)?;
+    let module = resolve_module(db, module_name)?;
 
     if file == module.file() {
         Some(module)
@@ -137,7 +136,7 @@ pub(crate) struct SearchPaths {
     /// for the first `site-packages` path
     site_packages: Vec<SearchPath>,
 
-    typeshed_versions: TypeshedVersions,
+    typeshed_versions: ResolvedTypeshedVersions,
 }
 
 impl SearchPaths {
@@ -203,11 +202,11 @@ impl SearchPaths {
 
             let search_path = SearchPath::custom_stdlib(db, &custom_typeshed)?;
 
-            (parsed, search_path)
+            (ResolvedTypeshedVersions::Custom(parsed), search_path)
         } else {
             tracing::debug!("Using vendored stdlib");
             (
-                vendored_typeshed_versions(db),
+                ResolvedTypeshedVersions::Vendored(vendored_typeshed_versions()),
                 SearchPath::vendored_stdlib(),
             )
         };
@@ -280,6 +279,23 @@ impl SearchPaths {
     }
 }
 
+#[derive(Debug, PartialEq, Eq)]
+enum ResolvedTypeshedVersions {
+    Vendored(&'static TypeshedVersions),
+    Custom(TypeshedVersions),
+}
+
+impl Deref for ResolvedTypeshedVersions {
+    type Target = TypeshedVersions;
+
+    fn deref(&self) -> &Self::Target {
+        match self {
+            ResolvedTypeshedVersions::Vendored(versions) => versions,
+            ResolvedTypeshedVersions::Custom(versions) => versions,
+        }
+    }
+}
+
 /// Collect all dynamic search paths. For each `site-packages` path:
 /// - Collect that `site-packages` path
 /// - Collect any search paths listed in `.pth` files in that `site-packages` directory
@@ -324,7 +340,7 @@ pub(crate) fn dynamic_resolution_paths(db: &dyn Db) -> Vec<SearchPath> {
 
         let site_packages_root = files
             .root(db.upcast(), site_packages_dir)
-            .expect("Site-package root to have been created");
+            .expect("Site-package root to have been created.");
 
         // This query needs to be re-executed each time a `.pth` file
         // is added, modified or removed from the `site-packages` directory.
@@ -553,16 +569,24 @@ fn resolve_name(db: &dyn Db, name: &ModuleName) -> Option<(SearchPath, File, Mod
 
                 package_path.push(module_name);
 
-                // Check for a regular package first (highest priority)
-                package_path.push("__init__");
-                if let Some(regular_package) = resolve_file_module(&package_path, &resolver_state) {
-                    return Some((search_path.clone(), regular_package, ModuleKind::Package));
+                // Must be a `__init__.pyi` or `__init__.py` or it isn't a package.
+                let kind = if package_path.is_directory(&resolver_state) {
+                    package_path.push("__init__");
+                    ModuleKind::Package
+                } else {
+                    ModuleKind::Module
+                };
+
+                // TODO Implement full https://peps.python.org/pep-0561/#type-checker-module-resolution-order resolution
+                if let Some(stub) = package_path.with_pyi_extension().to_file(&resolver_state) {
+                    return Some((search_path.clone(), stub, kind));
                 }
 
-                // Check for a file module next
-                package_path.pop();
-                if let Some(file_module) = resolve_file_module(&package_path, &resolver_state) {
-                    return Some((search_path.clone(), file_module, ModuleKind::Module));
+                if let Some(module) = package_path
+                    .with_py_extension()
+                    .and_then(|path| path.to_file(&resolver_state))
+                {
+                    return Some((search_path.clone(), module, kind));
                 }
 
                 // For regular packages, don't search the next search path. All files of that
@@ -583,23 +607,6 @@ fn resolve_name(db: &dyn Db, name: &ModuleName) -> Option<(SearchPath, File, Mod
     None
 }
 
-/// If `module` exists on disk with either a `.pyi` or `.py` extension,
-/// return the [`File`] corresponding to that path.
-///
-/// `.pyi` files take priority, as they always have priority when
-/// resolving modules.
-fn resolve_file_module(module: &ModulePath, resolver_state: &ResolverContext) -> Option<File> {
-    // Stubs have precedence over source files
-    module
-        .with_pyi_extension()
-        .to_file(resolver_state)
-        .or_else(|| {
-            module
-                .with_py_extension()
-                .and_then(|path| path.to_file(resolver_state))
-        })
-}
-
 fn resolve_package<'a, 'db, I>(
     module_search_path: &SearchPath,
     components: I,
@@ -626,10 +633,7 @@ where
 
         if is_regular_package {
             in_namespace_package = false;
-        } else if package_path.is_directory(resolver_state)
-            // Pure modules hide namespace packages with the same name
-            && resolve_file_module(&package_path, resolver_state).is_none()
-        {
+        } else if package_path.is_directory(resolver_state) {
             // A directory without an `__init__.py` is a namespace package, continue with the next folder.
             in_namespace_package = true;
         } else if in_namespace_package {
@@ -728,11 +732,11 @@ mod tests {
             .build();
 
         let foo_module_name = ModuleName::new_static("foo").unwrap();
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
+        let foo_module = resolve_module(&db, foo_module_name.clone()).unwrap();
 
         assert_eq!(
             Some(&foo_module),
-            resolve_module(&db, &foo_module_name).as_ref()
+            resolve_module(&db, foo_module_name.clone()).as_ref()
         );
 
         assert_eq!("foo", foo_module.name());
@@ -755,7 +759,7 @@ mod tests {
             .build();
 
         let builtins_module_name = ModuleName::new_static("builtins").unwrap();
-        let builtins = resolve_module(&db, &builtins_module_name).expect("builtins to resolve");
+        let builtins = resolve_module(&db, builtins_module_name).expect("builtins to resolve");
 
         assert_eq!(builtins.file().path(&db), &stdlib.join("builtins.pyi"));
     }
@@ -776,7 +780,7 @@ mod tests {
             .build();
 
         let builtins_module_name = ModuleName::new_static("builtins").unwrap();
-        let builtins = resolve_module(&db, &builtins_module_name).expect("builtins to resolve");
+        let builtins = resolve_module(&db, builtins_module_name).expect("builtins to resolve");
 
         assert_eq!(builtins.file().path(&db), &stdlib.join("builtins.pyi"));
     }
@@ -794,11 +798,11 @@ mod tests {
             .build();
 
         let functools_module_name = ModuleName::new_static("functools").unwrap();
-        let functools_module = resolve_module(&db, &functools_module_name).unwrap();
+        let functools_module = resolve_module(&db, functools_module_name.clone()).unwrap();
 
         assert_eq!(
             Some(&functools_module),
-            resolve_module(&db, &functools_module_name).as_ref()
+            resolve_module(&db, functools_module_name).as_ref()
         );
 
         assert_eq!(&stdlib, functools_module.search_path());
@@ -848,7 +852,7 @@ mod tests {
 
         let existing_modules = create_module_names(&["asyncio", "functools", "xml.etree"]);
         for module_name in existing_modules {
-            let resolved_module = resolve_module(&db, &module_name).unwrap_or_else(|| {
+            let resolved_module = resolve_module(&db, module_name.clone()).unwrap_or_else(|| {
                 panic!("Expected module {module_name} to exist in the mock stdlib")
             });
             let search_path = resolved_module.search_path();
@@ -901,7 +905,7 @@ mod tests {
 
         for module_name in nonexisting_modules {
             assert!(
-                resolve_module(&db, &module_name).is_none(),
+                resolve_module(&db, module_name.clone()).is_none(),
                 "Unexpectedly resolved a module for {module_name}"
             );
         }
@@ -944,7 +948,7 @@ mod tests {
         ]);
 
         for module_name in existing_modules {
-            let resolved_module = resolve_module(&db, &module_name).unwrap_or_else(|| {
+            let resolved_module = resolve_module(&db, module_name.clone()).unwrap_or_else(|| {
                 panic!("Expected module {module_name} to exist in the mock stdlib")
             });
             let search_path = resolved_module.search_path();
@@ -980,7 +984,7 @@ mod tests {
         let nonexisting_modules = create_module_names(&["importlib", "xml", "xml.etree"]);
         for module_name in nonexisting_modules {
             assert!(
-                resolve_module(&db, &module_name).is_none(),
+                resolve_module(&db, module_name.clone()).is_none(),
                 "Unexpectedly resolved a module for {module_name}"
             );
         }
@@ -1002,11 +1006,11 @@ mod tests {
             .build();
 
         let functools_module_name = ModuleName::new_static("functools").unwrap();
-        let functools_module = resolve_module(&db, &functools_module_name).unwrap();
+        let functools_module = resolve_module(&db, functools_module_name.clone()).unwrap();
 
         assert_eq!(
             Some(&functools_module),
-            resolve_module(&db, &functools_module_name).as_ref()
+            resolve_module(&db, functools_module_name).as_ref()
         );
         assert_eq!(&src, functools_module.search_path());
         assert_eq!(ModuleKind::Module, functools_module.kind());
@@ -1026,7 +1030,7 @@ mod tests {
             .build();
 
         let pydoc_data_topics_name = ModuleName::new_static("pydoc_data.topics").unwrap();
-        let pydoc_data_topics = resolve_module(&db, &pydoc_data_topics_name).unwrap();
+        let pydoc_data_topics = resolve_module(&db, pydoc_data_topics_name).unwrap();
 
         assert_eq!("pydoc_data.topics", pydoc_data_topics.name());
         assert_eq!(pydoc_data_topics.search_path(), &stdlib);
@@ -1043,7 +1047,7 @@ mod tests {
             .build();
 
         let foo_path = src.join("foo/__init__.py");
-        let foo_module = resolve_module(&db, &ModuleName::new_static("foo").unwrap()).unwrap();
+        let foo_module = resolve_module(&db, ModuleName::new_static("foo").unwrap()).unwrap();
 
         assert_eq!("foo", foo_module.name());
         assert_eq!(&src, foo_module.search_path());
@@ -1070,7 +1074,7 @@ mod tests {
 
         let TestCase { db, src, .. } = TestCaseBuilder::new().with_src_files(SRC).build();
 
-        let foo_module = resolve_module(&db, &ModuleName::new_static("foo").unwrap()).unwrap();
+        let foo_module = resolve_module(&db, ModuleName::new_static("foo").unwrap()).unwrap();
         let foo_init_path = src.join("foo/__init__.py");
 
         assert_eq!(&src, foo_module.search_path());
@@ -1087,32 +1091,13 @@ mod tests {
         );
     }
 
-    #[test]
-    fn single_file_takes_priority_over_namespace_package() {
-        //const SRC: &[FileSpec] = &[("foo.py", "x = 1")];
-        const SRC: &[FileSpec] = &[("foo.py", "x = 1"), ("foo/bar.py", "x = 2")];
-
-        let TestCase { db, src, .. } = TestCaseBuilder::new().with_src_files(SRC).build();
-
-        let foo_module_name = ModuleName::new_static("foo").unwrap();
-        let foo_bar_module_name = ModuleName::new_static("foo.bar").unwrap();
-
-        // `foo.py` takes priority over the `foo` namespace package
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
-        assert_eq!(foo_module.file().path(&db), &src.join("foo.py"));
-
-        // `foo.bar` isn't recognised as a module
-        let foo_bar_module = resolve_module(&db, &foo_bar_module_name);
-        assert_eq!(foo_bar_module, None);
-    }
-
     #[test]
     fn typing_stub_over_module() {
         const SRC: &[FileSpec] = &[("foo.py", "print('Hello, world!')"), ("foo.pyi", "x: int")];
 
         let TestCase { db, src, .. } = TestCaseBuilder::new().with_src_files(SRC).build();
 
-        let foo = resolve_module(&db, &ModuleName::new_static("foo").unwrap()).unwrap();
+        let foo = resolve_module(&db, ModuleName::new_static("foo").unwrap()).unwrap();
         let foo_stub = src.join("foo.pyi");
 
         assert_eq!(&src, foo.search_path());
@@ -1136,7 +1121,7 @@ mod tests {
         let TestCase { db, src, .. } = TestCaseBuilder::new().with_src_files(SRC).build();
 
         let baz_module =
-            resolve_module(&db, &ModuleName::new_static("foo.bar.baz").unwrap()).unwrap();
+            resolve_module(&db, ModuleName::new_static("foo.bar.baz").unwrap()).unwrap();
         let baz_path = src.join("foo/bar/baz.py");
 
         assert_eq!(&src, baz_module.search_path());
@@ -1175,14 +1160,14 @@ mod tests {
         let one_module_name = ModuleName::new_static("parent.child.one").unwrap();
         let one_module_path = FilePath::System(src.join("parent/child/one.py"));
         assert_eq!(
-            resolve_module(&db, &one_module_name),
+            resolve_module(&db, one_module_name),
             path_to_module(&db, &one_module_path)
         );
 
         let two_module_name = ModuleName::new_static("parent.child.two").unwrap();
         let two_module_path = FilePath::System(site_packages.join("parent/child/two.py"));
         assert_eq!(
-            resolve_module(&db, &two_module_name),
+            resolve_module(&db, two_module_name),
             path_to_module(&db, &two_module_path)
         );
     }
@@ -1215,12 +1200,12 @@ mod tests {
 
         let one_module_path = FilePath::System(src.join("parent/child/one.py"));
         let one_module_name =
-            resolve_module(&db, &ModuleName::new_static("parent.child.one").unwrap());
+            resolve_module(&db, ModuleName::new_static("parent.child.one").unwrap());
         assert_eq!(one_module_name, path_to_module(&db, &one_module_path));
 
         assert_eq!(
             None,
-            resolve_module(&db, &ModuleName::new_static("parent.child.two").unwrap())
+            resolve_module(&db, ModuleName::new_static("parent.child.two").unwrap())
         );
     }
 
@@ -1236,7 +1221,7 @@ mod tests {
             .with_site_packages_files(&[("foo.py", "")])
             .build();
 
-        let foo_module = resolve_module(&db, &ModuleName::new_static("foo").unwrap()).unwrap();
+        let foo_module = resolve_module(&db, ModuleName::new_static("foo").unwrap()).unwrap();
         let foo_src_path = src.join("foo.py");
 
         assert_eq!(&src, foo_module.search_path());
@@ -1301,8 +1286,8 @@ mod tests {
         )
         .context("Invalid program settings")?;
 
-        let foo_module = resolve_module(&db, &ModuleName::new_static("foo").unwrap()).unwrap();
-        let bar_module = resolve_module(&db, &ModuleName::new_static("bar").unwrap()).unwrap();
+        let foo_module = resolve_module(&db, ModuleName::new_static("foo").unwrap()).unwrap();
+        let bar_module = resolve_module(&db, ModuleName::new_static("bar").unwrap()).unwrap();
 
         assert_ne!(foo_module, bar_module);
 
@@ -1337,7 +1322,7 @@ mod tests {
             .build();
 
         let foo_module_name = ModuleName::new_static("foo").unwrap();
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
+        let foo_module = resolve_module(&db, foo_module_name.clone()).unwrap();
 
         let bar_path = src.join("bar.py");
         let bar = system_path_to_file(&db, &bar_path).expect("bar.py to exist");
@@ -1351,7 +1336,7 @@ mod tests {
         // Re-query the foo module. The foo module should still be cached because `bar.py` isn't relevant
         // for resolving `foo`.
 
-        let foo_module2 = resolve_module(&db, &foo_module_name);
+        let foo_module2 = resolve_module(&db, foo_module_name);
 
         assert!(!db
             .take_salsa_events()
@@ -1368,14 +1353,14 @@ mod tests {
         let foo_path = src.join("foo.py");
 
         let foo_module_name = ModuleName::new_static("foo").unwrap();
-        assert_eq!(resolve_module(&db, &foo_module_name), None);
+        assert_eq!(resolve_module(&db, foo_module_name.clone()), None);
 
         // Now write the foo file
         db.write_file(&foo_path, "x = 1")?;
 
         let foo_file = system_path_to_file(&db, &foo_path).expect("foo.py to exist");
 
-        let foo_module = resolve_module(&db, &foo_module_name).expect("Foo module to resolve");
+        let foo_module = resolve_module(&db, foo_module_name).expect("Foo module to resolve");
         assert_eq!(foo_file, foo_module.file());
 
         Ok(())
@@ -1389,7 +1374,7 @@ mod tests {
         let TestCase { mut db, src, .. } = TestCaseBuilder::new().with_src_files(SRC).build();
 
         let foo_module_name = ModuleName::new_static("foo").unwrap();
-        let foo_module = resolve_module(&db, &foo_module_name).expect("foo module to exist");
+        let foo_module = resolve_module(&db, foo_module_name.clone()).expect("foo module to exist");
         let foo_init_path = src.join("foo/__init__.py");
 
         assert_eq!(&foo_init_path, foo_module.file().path(&db));
@@ -1401,7 +1386,7 @@ mod tests {
         File::sync_path(&mut db, &foo_init_path);
         File::sync_path(&mut db, foo_init_path.parent().unwrap());
 
-        let foo_module = resolve_module(&db, &foo_module_name).expect("Foo module to resolve");
+        let foo_module = resolve_module(&db, foo_module_name).expect("Foo module to resolve");
         assert_eq!(&src.join("foo.py"), foo_module.file().path(&db));
 
         Ok(())
@@ -1427,7 +1412,7 @@ mod tests {
         let functools_module_name = ModuleName::new_static("functools").unwrap();
         let stdlib_functools_path = stdlib.join("functools.pyi");
 
-        let functools_module = resolve_module(&db, &functools_module_name).unwrap();
+        let functools_module = resolve_module(&db, functools_module_name.clone()).unwrap();
         assert_eq!(functools_module.search_path(), &stdlib);
         assert_eq!(
             Ok(functools_module.file()),
@@ -1440,7 +1425,7 @@ mod tests {
         let site_packages_functools_path = site_packages.join("functools.py");
         db.write_file(&site_packages_functools_path, "f: int")
             .unwrap();
-        let functools_module = resolve_module(&db, &functools_module_name).unwrap();
+        let functools_module = resolve_module(&db, functools_module_name.clone()).unwrap();
         let events = db.take_salsa_events();
         assert_function_query_was_not_run(
             &db,
@@ -1473,7 +1458,7 @@ mod tests {
             .build();
 
         let functools_module_name = ModuleName::new_static("functools").unwrap();
-        let functools_module = resolve_module(&db, &functools_module_name).unwrap();
+        let functools_module = resolve_module(&db, functools_module_name.clone()).unwrap();
         assert_eq!(functools_module.search_path(), &stdlib);
         assert_eq!(
             Ok(functools_module.file()),
@@ -1484,7 +1469,7 @@ mod tests {
         // since first-party files take higher priority in module resolution:
         let src_functools_path = src.join("functools.py");
         db.write_file(&src_functools_path, "FOO: int").unwrap();
-        let functools_module = resolve_module(&db, &functools_module_name).unwrap();
+        let functools_module = resolve_module(&db, functools_module_name.clone()).unwrap();
         assert_eq!(functools_module.search_path(), &src);
         assert_eq!(
             Ok(functools_module.file()),
@@ -1515,7 +1500,7 @@ mod tests {
         let functools_module_name = ModuleName::new_static("functools").unwrap();
         let src_functools_path = src.join("functools.py");
 
-        let functools_module = resolve_module(&db, &functools_module_name).unwrap();
+        let functools_module = resolve_module(&db, functools_module_name.clone()).unwrap();
         assert_eq!(functools_module.search_path(), &src);
         assert_eq!(
             Ok(functools_module.file()),
@@ -1528,7 +1513,7 @@ mod tests {
             .remove_file(&src_functools_path)
             .unwrap();
         File::sync_path(&mut db, &src_functools_path);
-        let functools_module = resolve_module(&db, &functools_module_name).unwrap();
+        let functools_module = resolve_module(&db, functools_module_name.clone()).unwrap();
         assert_eq!(functools_module.search_path(), &stdlib);
         assert_eq!(
             Ok(functools_module.file()),
@@ -1550,8 +1535,8 @@ mod tests {
         let foo_module_name = ModuleName::new_static("foo").unwrap();
         let foo_bar_module_name = ModuleName::new_static("foo.bar").unwrap();
 
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
-        let foo_bar_module = resolve_module(&db, &foo_bar_module_name).unwrap();
+        let foo_module = resolve_module(&db, foo_module_name.clone()).unwrap();
+        let foo_bar_module = resolve_module(&db, foo_bar_module_name.clone()).unwrap();
 
         assert_eq!(
             foo_module.file().path(&db),
@@ -1579,11 +1564,11 @@ mod tests {
 
         // Lines with leading whitespace in `.pth` files do not parse:
         let foo_module_name = ModuleName::new_static("foo").unwrap();
-        assert_eq!(resolve_module(&db, &foo_module_name), None);
+        assert_eq!(resolve_module(&db, foo_module_name), None);
 
         // Lines with trailing whitespace in `.pth` files do:
         let bar_module_name = ModuleName::new_static("bar").unwrap();
-        let bar_module = resolve_module(&db, &bar_module_name).unwrap();
+        let bar_module = resolve_module(&db, bar_module_name.clone()).unwrap();
         assert_eq!(
             bar_module.file().path(&db),
             &FilePath::system("/y/src/bar.py")
@@ -1602,7 +1587,7 @@ mod tests {
             .build();
 
         let foo_module_name = ModuleName::new_static("foo").unwrap();
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
+        let foo_module = resolve_module(&db, foo_module_name.clone()).unwrap();
 
         assert_eq!(
             foo_module.file().path(&db),
@@ -1650,10 +1635,10 @@ not_a_directory
         let b_module_name = ModuleName::new_static("b").unwrap();
         let spam_module_name = ModuleName::new_static("spam").unwrap();
 
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
-        let a_module = resolve_module(&db, &a_module_name).unwrap();
-        let b_module = resolve_module(&db, &b_module_name).unwrap();
-        let spam_module = resolve_module(&db, &spam_module_name).unwrap();
+        let foo_module = resolve_module(&db, foo_module_name.clone()).unwrap();
+        let a_module = resolve_module(&db, a_module_name.clone()).unwrap();
+        let b_module = resolve_module(&db, b_module_name.clone()).unwrap();
+        let spam_module = resolve_module(&db, spam_module_name.clone()).unwrap();
 
         assert_eq!(
             foo_module.file().path(&db),
@@ -1681,14 +1666,14 @@ not_a_directory
         let foo_module_name = ModuleName::new_static("foo").unwrap();
         let bar_module_name = ModuleName::new_static("bar").unwrap();
 
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
+        let foo_module = resolve_module(&db, foo_module_name).unwrap();
         assert_eq!(
             foo_module.file().path(&db),
             &FilePath::system("/x/src/foo.py")
         );
 
         db.clear_salsa_events();
-        let bar_module = resolve_module(&db, &bar_module_name).unwrap();
+        let bar_module = resolve_module(&db, bar_module_name).unwrap();
         assert_eq!(
             bar_module.file().path(&db),
             &FilePath::system("/y/src/bar.py")
@@ -1713,7 +1698,7 @@ not_a_directory
         db.write_files(x_directory).unwrap();
 
         let foo_module_name = ModuleName::new_static("foo").unwrap();
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
+        let foo_module = resolve_module(&db, foo_module_name.clone()).unwrap();
         assert_eq!(
             foo_module.file().path(&db),
             &FilePath::system("/x/src/foo.py")
@@ -1725,7 +1710,7 @@ not_a_directory
 
         File::sync_path(&mut db, &site_packages.join("_foo.pth"));
 
-        assert_eq!(resolve_module(&db, &foo_module_name), None);
+        assert_eq!(resolve_module(&db, foo_module_name.clone()), None);
     }
 
     #[test]
@@ -1740,7 +1725,7 @@ not_a_directory
         db.write_files(x_directory).unwrap();
 
         let foo_module_name = ModuleName::new_static("foo").unwrap();
-        let foo_module = resolve_module(&db, &foo_module_name).unwrap();
+        let foo_module = resolve_module(&db, foo_module_name.clone()).unwrap();
         let src_path = SystemPathBuf::from("/x/src");
         assert_eq!(
             foo_module.file().path(&db),
@@ -1753,7 +1738,7 @@ not_a_directory
         db.memory_file_system().remove_directory(&src_path).unwrap();
         File::sync_path(&mut db, &src_path.join("foo.py"));
         File::sync_path(&mut db, &src_path);
-        assert_eq!(resolve_module(&db, &foo_module_name), None);
+        assert_eq!(resolve_module(&db, foo_module_name.clone()), None);
     }
 
     #[test]
@@ -1812,7 +1797,7 @@ not_a_directory
         // The editable installs discovered from the `.pth` file in the first `site-packages` directory
         // take precedence over the second `site-packages` directory...
         let a_module_name = ModuleName::new_static("a").unwrap();
-        let a_module = resolve_module(&db, &a_module_name).unwrap();
+        let a_module = resolve_module(&db, a_module_name.clone()).unwrap();
         assert_eq!(a_module.file().path(&db), &editable_install_location);
 
         db.memory_file_system()
@@ -1823,7 +1808,7 @@ not_a_directory
         // ...But now that the `.pth` file in the first `site-packages` directory has been deleted,
         // the editable install no longer exists, so the module now resolves to the file in the
         // second `site-packages` directory
-        let a_module = resolve_module(&db, &a_module_name).unwrap();
+        let a_module = resolve_module(&db, a_module_name).unwrap();
         assert_eq!(a_module.file().path(&db), &system_site_packages_location);
     }
 }

crates/red_knot_python_semantic/src/module_resolver/typeshed/mod.rs

@@ -0,0 +1,8 @@
+pub use self::vendored::vendored_typeshed_stubs;
+pub(super) use self::versions::{
+    typeshed_versions, vendored_typeshed_versions, TypeshedVersions, TypeshedVersionsParseError,
+    TypeshedVersionsQueryResult,
+};
+
+mod vendored;
+mod versions;

crates/red_knot_python_semantic/src/module_resolver/typeshed/vendored.rs

@@ -6,7 +6,7 @@ use ruff_db::vendored::VendoredFileSystem;
 // Luckily this crate will fail to build if this file isn't available at build time.
 static TYPESHED_ZIP_BYTES: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/zipped_typeshed.zip"));
 
-pub fn file_system() -> &'static VendoredFileSystem {
+pub fn vendored_typeshed_stubs() -> &'static VendoredFileSystem {
     static VENDORED_TYPESHED_STUBS: Lazy<VendoredFileSystem> =
         Lazy::new(|| VendoredFileSystem::new_static(TYPESHED_ZIP_BYTES).unwrap());
     &VENDORED_TYPESHED_STUBS
@@ -42,7 +42,7 @@ mod tests {
     #[test]
     fn typeshed_vfs_consistent_with_vendored_stubs() {
         let vendored_typeshed_dir = Path::new("vendor/typeshed").canonicalize().unwrap();
-        let vendored_typeshed_stubs = file_system();
+        let vendored_typeshed_stubs = vendored_typeshed_stubs();
 
         let mut empty_iterator = true;
         for entry in walkdir::WalkDir::new(&vendored_typeshed_dir).min_depth(1) {

crates/red_knot_python_semantic/src/module_resolver/typeshed/versions.rs

@@ -4,19 +4,25 @@ use std::num::{NonZeroU16, NonZeroUsize};
 use std::ops::{RangeFrom, RangeInclusive};
 use std::str::FromStr;
 
+use once_cell::sync::Lazy;
 use rustc_hash::FxHashMap;
 
+use super::vendored::vendored_typeshed_stubs;
 use crate::db::Db;
 use crate::module_name::ModuleName;
 use crate::{Program, PythonVersion};
 
-pub(in crate::module_resolver) fn vendored_typeshed_versions(db: &dyn Db) -> TypeshedVersions {
+static VENDORED_VERSIONS: Lazy<TypeshedVersions> = Lazy::new(|| {
     TypeshedVersions::from_str(
-        &db.vendored()
+        &vendored_typeshed_stubs()
             .read_to_string("stdlib/VERSIONS")
-            .expect("The vendored typeshed stubs should contain a VERSIONS file"),
+            .unwrap(),
     )
-    .expect("The VERSIONS file in the vendored typeshed stubs should be well-formed")
+    .unwrap()
+});
+
+pub(crate) fn vendored_typeshed_versions() -> &'static TypeshedVersions {
+    &VENDORED_VERSIONS
 }
 
 pub(crate) fn typeshed_versions(db: &dyn Db) -> &TypeshedVersions {
@@ -326,8 +332,6 @@ mod tests {
 
     use insta::assert_snapshot;
 
-    use crate::db::tests::TestDb;
-
     use super::*;
 
     const TYPESHED_STDLIB_DIR: &str = "stdlib";
@@ -349,9 +353,12 @@ mod tests {
 
     #[test]
     fn can_parse_vendored_versions_file() {
-        let db = TestDb::new();
+        let versions_data = include_str!(concat!(
+            env!("CARGO_MANIFEST_DIR"),
+            "/vendor/typeshed/stdlib/VERSIONS"
+        ));
 
-        let versions = vendored_typeshed_versions(&db);
+        let versions = TypeshedVersions::from_str(versions_data).unwrap();
         assert!(versions.len() > 100);
         assert!(versions.len() < 1000);
 
@@ -388,10 +395,9 @@ mod tests {
 
     #[test]
     fn typeshed_versions_consistent_with_vendored_stubs() {
-        let db = TestDb::new();
-        let vendored_typeshed_versions = vendored_typeshed_versions(&db);
-        let vendored_typeshed_dir =
-            Path::new(env!("CARGO_MANIFEST_DIR")).join("../red_knot_vendored/vendor/typeshed");
+        const VERSIONS_DATA: &str = include_str!("../../../vendor/typeshed/stdlib/VERSIONS");
+        let vendored_typeshed_dir = Path::new("vendor/typeshed").canonicalize().unwrap();
+        let vendored_typeshed_versions = TypeshedVersions::from_str(VERSIONS_DATA).unwrap();
 
         let mut empty_iterator = true;
 

crates/red_knot_python_semantic/src/python_version.rs

@@ -54,13 +54,6 @@ impl TryFrom<(&str, &str)> for PythonVersion {
     }
 }
 
-impl From<(u8, u8)> for PythonVersion {
-    fn from(value: (u8, u8)) -> Self {
-        let (major, minor) = value;
-        Self { major, minor }
-    }
-}
-
 impl fmt::Display for PythonVersion {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let PythonVersion { major, minor } = self;

crates/red_knot_python_semantic/src/semantic_index.rs

@@ -1,7 +1,7 @@
 use std::iter::FusedIterator;
 use std::sync::Arc;
 
-use rustc_hash::{FxBuildHasher, FxHashMap};
+use rustc_hash::FxHashMap;
 use salsa::plumbing::AsId;
 
 use ruff_db::files::File;
@@ -21,17 +21,14 @@ use crate::Db;
 
 pub mod ast_ids;
 mod builder;
-pub(crate) mod constraint;
 pub mod definition;
 pub mod expression;
 pub mod symbol;
 mod use_def;
 
-pub(crate) use self::use_def::{
-    BindingWithConstraints, BindingWithConstraintsIterator, DeclarationsIterator,
-};
+pub(crate) use self::use_def::{DefinitionWithConstraints, DefinitionWithConstraintsIterator};
 
-type SymbolMap = hashbrown::HashMap<ScopedSymbolId, (), FxBuildHasher>;
+type SymbolMap = hashbrown::HashMap<ScopedSymbolId, (), ()>;
 
 /// Returns the semantic index for `file`.
 ///
@@ -115,9 +112,6 @@ pub(crate) struct SemanticIndex<'db> {
     /// Note: We should not depend on this map when analysing other files or
     /// changing a file invalidates all dependents.
     ast_ids: IndexVec<FileScopeId, AstIds>,
-
-    /// Flags about the global scope (code usage impacting inference)
-    has_future_annotations: bool,
 }
 
 impl<'db> SemanticIndex<'db> {
@@ -218,12 +212,6 @@ impl<'db> SemanticIndex<'db> {
     pub(crate) fn node_scope(&self, node: NodeWithScopeRef) -> FileScopeId {
         self.scopes_by_node[&node.node_key()]
     }
-
-    /// Checks if there is an import of `__future__.annotations` in the global scope, which affects
-    /// the logic for type inference.
-    pub(super) fn has_future_annotations(&self) -> bool {
-        self.has_future_annotations
-    }
 }
 
 pub struct AncestorsIter<'a> {
@@ -337,16 +325,16 @@ mod tests {
     use crate::Db;
 
     impl UseDefMap<'_> {
-        fn first_public_binding(&self, symbol: ScopedSymbolId) -> Option<Definition<'_>> {
-            self.public_bindings(symbol)
+        fn first_public_definition(&self, symbol: ScopedSymbolId) -> Option<Definition<'_>> {
+            self.public_definitions(symbol)
                 .next()
-                .map(|constrained_binding| constrained_binding.binding)
+                .map(|constrained_definition| constrained_definition.definition)
         }
 
-        fn first_binding_at_use(&self, use_id: ScopedUseId) -> Option<Definition<'_>> {
-            self.bindings_at_use(use_id)
+        fn first_use_definition(&self, use_id: ScopedUseId) -> Option<Definition<'_>> {
+            self.use_definitions(use_id)
                 .next()
-                .map(|constrained_binding| constrained_binding.binding)
+                .map(|constrained_definition| constrained_definition.definition)
         }
     }
 
@@ -408,8 +396,8 @@ mod tests {
         let foo = global_table.symbol_id_by_name("foo").unwrap();
 
         let use_def = use_def_map(&db, scope);
-        let binding = use_def.first_public_binding(foo).unwrap();
-        assert!(matches!(binding.kind(&db), DefinitionKind::Import(_)));
+        let definition = use_def.first_public_definition(foo).unwrap();
+        assert!(matches!(definition.node(&db), DefinitionKind::Import(_)));
     }
 
     #[test]
@@ -438,19 +426,22 @@ mod tests {
         assert!(
             global_table
                 .symbol_by_name("foo")
-                .is_some_and(|symbol| { symbol.is_bound() && !symbol.is_used() }),
+                .is_some_and(|symbol| { symbol.is_defined() && !symbol.is_used() }),
             "symbols that are defined get the defined flag"
         );
 
         let use_def = use_def_map(&db, scope);
-        let binding = use_def
-            .first_public_binding(
+        let definition = use_def
+            .first_public_definition(
                 global_table
                     .symbol_id_by_name("foo")
                     .expect("symbol to exist"),
             )
             .unwrap();
-        assert!(matches!(binding.kind(&db), DefinitionKind::ImportFrom(_)));
+        assert!(matches!(
+            definition.node(&db),
+            DefinitionKind::ImportFrom(_)
+        ));
     }
 
     #[test]
@@ -463,14 +454,17 @@ mod tests {
         assert!(
             global_table
                 .symbol_by_name("foo")
-                .is_some_and(|symbol| { !symbol.is_bound() && symbol.is_used() }),
-            "a symbol used but not bound in a scope should have only the used flag"
+                .is_some_and(|symbol| { !symbol.is_defined() && symbol.is_used() }),
+            "a symbol used but not defined in a scope should have only the used flag"
         );
         let use_def = use_def_map(&db, scope);
-        let binding = use_def
-            .first_public_binding(global_table.symbol_id_by_name("x").expect("symbol exists"))
+        let definition = use_def
+            .first_public_definition(global_table.symbol_id_by_name("x").expect("symbol exists"))
             .unwrap();
-        assert!(matches!(binding.kind(&db), DefinitionKind::Assignment(_)));
+        assert!(matches!(
+            definition.node(&db),
+            DefinitionKind::Assignment(_)
+        ));
     }
 
     #[test]
@@ -482,12 +476,12 @@ mod tests {
         assert_eq!(names(&global_table), vec!["x"]);
 
         let use_def = use_def_map(&db, scope);
-        let binding = use_def
-            .first_public_binding(global_table.symbol_id_by_name("x").unwrap())
+        let definition = use_def
+            .first_public_definition(global_table.symbol_id_by_name("x").unwrap())
             .unwrap();
 
         assert!(matches!(
-            binding.kind(&db),
+            definition.node(&db),
             DefinitionKind::AugmentedAssignment(_)
         ));
     }
@@ -520,10 +514,13 @@ y = 2
         assert_eq!(names(&class_table), vec!["x"]);
 
         let use_def = index.use_def_map(class_scope_id);
-        let binding = use_def
-            .first_public_binding(class_table.symbol_id_by_name("x").expect("symbol exists"))
+        let definition = use_def
+            .first_public_definition(class_table.symbol_id_by_name("x").expect("symbol exists"))
             .unwrap();
-        assert!(matches!(binding.kind(&db), DefinitionKind::Assignment(_)));
+        assert!(matches!(
+            definition.node(&db),
+            DefinitionKind::Assignment(_)
+        ));
     }
 
     #[test]
@@ -553,14 +550,17 @@ y = 2
         assert_eq!(names(&function_table), vec!["x"]);
 
         let use_def = index.use_def_map(function_scope_id);
-        let binding = use_def
-            .first_public_binding(
+        let definition = use_def
+            .first_public_definition(
                 function_table
                     .symbol_id_by_name("x")
                     .expect("symbol exists"),
             )
             .unwrap();
-        assert!(matches!(binding.kind(&db), DefinitionKind::Assignment(_)));
+        assert!(matches!(
+            definition.node(&db),
+            DefinitionKind::Assignment(_)
+        ));
     }
 
     #[test]
@@ -592,27 +592,27 @@ def f(a: str, /, b: str, c: int = 1, *args, d: int = 2, **kwargs):
 
         let use_def = index.use_def_map(function_scope_id);
         for name in ["a", "b", "c", "d"] {
-            let binding = use_def
-                .first_public_binding(
+            let definition = use_def
+                .first_public_definition(
                     function_table
                         .symbol_id_by_name(name)
                         .expect("symbol exists"),
                 )
                 .unwrap();
             assert!(matches!(
-                binding.kind(&db),
+                definition.node(&db),
                 DefinitionKind::ParameterWithDefault(_)
             ));
         }
         for name in ["args", "kwargs"] {
-            let binding = use_def
-                .first_public_binding(
+            let definition = use_def
+                .first_public_definition(
                     function_table
                         .symbol_id_by_name(name)
                         .expect("symbol exists"),
                 )
                 .unwrap();
-            assert!(matches!(binding.kind(&db), DefinitionKind::Parameter(_)));
+            assert!(matches!(definition.node(&db), DefinitionKind::Parameter(_)));
         }
     }
 
@@ -640,19 +640,23 @@ def f(a: str, /, b: str, c: int = 1, *args, d: int = 2, **kwargs):
 
         let use_def = index.use_def_map(lambda_scope_id);
         for name in ["a", "b", "c", "d"] {
-            let binding = use_def
-                .first_public_binding(lambda_table.symbol_id_by_name(name).expect("symbol exists"))
+            let definition = use_def
+                .first_public_definition(
+                    lambda_table.symbol_id_by_name(name).expect("symbol exists"),
+                )
                 .unwrap();
             assert!(matches!(
-                binding.kind(&db),
+                definition.node(&db),
                 DefinitionKind::ParameterWithDefault(_)
             ));
         }
         for name in ["args", "kwargs"] {
-            let binding = use_def
-                .first_public_binding(lambda_table.symbol_id_by_name(name).expect("symbol exists"))
+            let definition = use_def
+                .first_public_definition(
+                    lambda_table.symbol_id_by_name(name).expect("symbol exists"),
+                )
                 .unwrap();
-            assert!(matches!(binding.kind(&db), DefinitionKind::Parameter(_)));
+            assert!(matches!(definition.node(&db), DefinitionKind::Parameter(_)));
         }
     }
 
@@ -690,15 +694,15 @@ def f(a: str, /, b: str, c: int = 1, *args, d: int = 2, **kwargs):
 
         let use_def = index.use_def_map(comprehension_scope_id);
         for name in ["x", "y"] {
-            let binding = use_def
-                .first_public_binding(
+            let definition = use_def
+                .first_public_definition(
                     comprehension_symbol_table
                         .symbol_id_by_name(name)
                         .expect("symbol exists"),
                 )
                 .unwrap();
             assert!(matches!(
-                binding.kind(&db),
+                definition.node(&db),
                 DefinitionKind::Comprehension(_)
             ));
         }
@@ -737,8 +741,8 @@ def f(a: str, /, b: str, c: int = 1, *args, d: int = 2, **kwargs):
         let element_use_id =
             element.scoped_use_id(&db, comprehension_scope_id.to_scope_id(&db, file));
 
-        let binding = use_def.first_binding_at_use(element_use_id).unwrap();
-        let DefinitionKind::Comprehension(comprehension) = binding.kind(&db) else {
+        let definition = use_def.first_use_definition(element_use_id).unwrap();
+        let DefinitionKind::Comprehension(comprehension) = definition.node(&db) else {
             panic!("expected generator definition")
         };
         let target = comprehension.target();
@@ -817,10 +821,12 @@ with item1 as x, item2 as y:
 
         let use_def = index.use_def_map(FileScopeId::global());
         for name in ["x", "y"] {
-            let binding = use_def
-                .first_public_binding(global_table.symbol_id_by_name(name).expect("symbol exists"))
-                .expect("Expected with item definition for {name}");
-            assert!(matches!(binding.kind(&db), DefinitionKind::WithItem(_)));
+            let Some(definition) = use_def.first_public_definition(
+                global_table.symbol_id_by_name(name).expect("symbol exists"),
+            ) else {
+                panic!("Expected with item definition for {name}");
+            };
+            assert!(matches!(definition.node(&db), DefinitionKind::WithItem(_)));
         }
     }
 
@@ -840,10 +846,12 @@ with context() as (x, y):
 
         let use_def = index.use_def_map(FileScopeId::global());
         for name in ["x", "y"] {
-            let binding = use_def
-                .first_public_binding(global_table.symbol_id_by_name(name).expect("symbol exists"))
-                .expect("Expected with item definition for {name}");
-            assert!(matches!(binding.kind(&db), DefinitionKind::WithItem(_)));
+            let Some(definition) = use_def.first_public_definition(
+                global_table.symbol_id_by_name(name).expect("symbol exists"),
+            ) else {
+                panic!("Expected with item definition for {name}");
+            };
+            assert!(matches!(definition.node(&db), DefinitionKind::WithItem(_)));
         }
     }
 
@@ -880,14 +888,14 @@ def func():
         assert_eq!(names(&func2_table), vec!["y"]);
 
         let use_def = index.use_def_map(FileScopeId::global());
-        let binding = use_def
-            .first_public_binding(
+        let definition = use_def
+            .first_public_definition(
                 global_table
                     .symbol_id_by_name("func")
                     .expect("symbol exists"),
             )
             .unwrap();
-        assert!(matches!(binding.kind(&db), DefinitionKind::Function(_)));
+        assert!(matches!(definition.node(&db), DefinitionKind::Function(_)));
     }
 
     #[test]
@@ -955,7 +963,7 @@ class C[T]:
         assert!(
             ann_table
                 .symbol_by_name("T")
-                .is_some_and(|s| s.is_bound() && !s.is_used()),
+                .is_some_and(|s| s.is_defined() && !s.is_used()),
             "type parameters are defined by the scope that introduces them"
         );
 
@@ -987,14 +995,14 @@ class C[T]:
         };
         let x_use_id = x_use_expr_name.scoped_use_id(&db, scope);
         let use_def = use_def_map(&db, scope);
-        let binding = use_def.first_binding_at_use(x_use_id).unwrap();
-        let DefinitionKind::Assignment(assignment) = binding.kind(&db) else {
+        let definition = use_def.first_use_definition(x_use_id).unwrap();
+        let DefinitionKind::Assignment(assignment) = definition.node(&db) else {
             panic!("should be an assignment definition")
         };
         let ast::Expr::NumberLiteral(ast::ExprNumberLiteral {
             value: ast::Number::Int(num),
             ..
-        }) = assignment.value()
+        }) = &*assignment.assignment().value
         else {
             panic!("should be a number literal")
         };
@@ -1036,7 +1044,7 @@ class C[T]:
         }
 
         let TestCase { db, file } = test_case(
-            r"
+            r#"
 class Test:
     def foo():
         def bar():
@@ -1045,7 +1053,7 @@ class Test:
         pass
 
 def x():
-    pass",
+    pass"#,
         );
 
         let index = semantic_index(&db, file);
@@ -1118,10 +1126,12 @@ match subject:
             ("k", 0),
             ("l", 1),
         ] {
-            let binding = use_def
-                .first_public_binding(global_table.symbol_id_by_name(name).expect("symbol exists"))
+            let definition = use_def
+                .first_public_definition(
+                    global_table.symbol_id_by_name(name).expect("symbol exists"),
+                )
                 .expect("Expected with item definition for {name}");
-            if let DefinitionKind::MatchPattern(pattern) = binding.kind(&db) {
+            if let DefinitionKind::MatchPattern(pattern) = definition.node(&db) {
                 assert_eq!(pattern.index(), expected_index);
             } else {
                 panic!("Expected match pattern definition for {name}");
@@ -1148,10 +1158,12 @@ match 1:
 
         let use_def = use_def_map(&db, global_scope_id);
         for (name, expected_index) in [("first", 0), ("second", 0)] {
-            let binding = use_def
-                .first_public_binding(global_table.symbol_id_by_name(name).expect("symbol exists"))
+            let definition = use_def
+                .first_public_definition(
+                    global_table.symbol_id_by_name(name).expect("symbol exists"),
+                )
                 .expect("Expected with item definition for {name}");
-            if let DefinitionKind::MatchPattern(pattern) = binding.kind(&db) {
+            if let DefinitionKind::MatchPattern(pattern) = definition.node(&db) {
                 assert_eq!(pattern.index(), expected_index);
             } else {
                 panic!("Expected match pattern definition for {name}");
@@ -1168,11 +1180,11 @@ match 1:
         assert_eq!(&names(&global_table), &["a", "x"]);
 
         let use_def = use_def_map(&db, scope);
-        let binding = use_def
-            .first_public_binding(global_table.symbol_id_by_name("x").unwrap())
+        let definition = use_def
+            .first_public_definition(global_table.symbol_id_by_name("x").unwrap())
             .unwrap();
 
-        assert!(matches!(binding.kind(&db), DefinitionKind::For(_)));
+        assert!(matches!(definition.node(&db), DefinitionKind::For(_)));
     }
 
     #[test]
@@ -1184,15 +1196,15 @@ match 1:
         assert_eq!(&names(&global_table), &["a", "x", "y"]);
 
         let use_def = use_def_map(&db, scope);
-        let x_binding = use_def
-            .first_public_binding(global_table.symbol_id_by_name("x").unwrap())
+        let x_definition = use_def
+            .first_public_definition(global_table.symbol_id_by_name("x").unwrap())
             .unwrap();
-        let y_binding = use_def
-            .first_public_binding(global_table.symbol_id_by_name("y").unwrap())
+        let y_definition = use_def
+            .first_public_definition(global_table.symbol_id_by_name("y").unwrap())
             .unwrap();
 
-        assert!(matches!(x_binding.kind(&db), DefinitionKind::For(_)));
-        assert!(matches!(y_binding.kind(&db), DefinitionKind::For(_)));
+        assert!(matches!(x_definition.node(&db), DefinitionKind::For(_)));
+        assert!(matches!(y_definition.node(&db), DefinitionKind::For(_)));
     }
 
     #[test]
@@ -1204,10 +1216,10 @@ match 1:
         assert_eq!(&names(&global_table), &["e", "a", "b", "c", "d"]);
 
         let use_def = use_def_map(&db, scope);
-        let binding = use_def
-            .first_public_binding(global_table.symbol_id_by_name("a").unwrap())
+        let definition = use_def
+            .first_public_definition(global_table.symbol_id_by_name("a").unwrap())
             .unwrap();
 
-        assert!(matches!(binding.kind(&db), DefinitionKind::For(_)));
+        assert!(matches!(definition.node(&db), DefinitionKind::For(_)));
     }
 }

crates/red_knot_python_semantic/src/semantic_index/builder.rs

@@ -19,18 +19,14 @@ use crate::semantic_index::definition::{
 };
 use crate::semantic_index::expression::Expression;
 use crate::semantic_index::symbol::{
-    FileScopeId, NodeWithScopeKey, NodeWithScopeRef, Scope, ScopeId, ScopedSymbolId,
+    FileScopeId, NodeWithScopeKey, NodeWithScopeRef, Scope, ScopeId, ScopedSymbolId, SymbolFlags,
     SymbolTableBuilder,
 };
 use crate::semantic_index::use_def::{FlowSnapshot, UseDefMapBuilder};
 use crate::semantic_index::SemanticIndex;
 use crate::Db;
 
-use super::constraint::{Constraint, PatternConstraint};
-use super::definition::{
-    AssignmentKind, DefinitionCategory, ExceptHandlerDefinitionNodeRef,
-    MatchPatternDefinitionNodeRef, WithItemDefinitionNodeRef,
-};
+use super::definition::{MatchPatternDefinitionNodeRef, WithItemDefinitionNodeRef};
 
 pub(super) struct SemanticIndexBuilder<'db> {
     // Builder state
@@ -45,9 +41,6 @@ pub(super) struct SemanticIndexBuilder<'db> {
     /// Flow states at each `break` in the current loop.
     loop_break_states: Vec<FlowSnapshot>,
 
-    /// Flags about the file's global scope
-    has_future_annotations: bool,
-
     // Semantic Index fields
     scopes: IndexVec<FileScopeId, Scope>,
     scope_ids_by_scope: IndexVec<FileScopeId, ScopeId<'db>>,
@@ -71,8 +64,6 @@ impl<'db> SemanticIndexBuilder<'db> {
             current_match_case: None,
             loop_break_states: vec![],
 
-            has_future_annotations: false,
-
             scopes: IndexVec::new(),
             symbol_tables: IndexVec::new(),
             ast_ids: IndexVec::new(),
@@ -174,95 +165,49 @@ impl<'db> SemanticIndexBuilder<'db> {
         self.current_use_def_map_mut().merge(state);
     }
 
-    fn add_symbol(&mut self, name: Name) -> ScopedSymbolId {
-        let (symbol_id, added) = self.current_symbol_table().add_symbol(name);
+    fn add_or_update_symbol(&mut self, name: Name, flags: SymbolFlags) -> ScopedSymbolId {
+        let symbol_table = self.current_symbol_table();
+        let (symbol_id, added) = symbol_table.add_or_update_symbol(name, flags);
         if added {
-            self.current_use_def_map_mut().add_symbol(symbol_id);
+            let use_def_map = self.current_use_def_map_mut();
+            use_def_map.add_symbol(symbol_id);
         }
         symbol_id
     }
 
-    fn mark_symbol_bound(&mut self, id: ScopedSymbolId) {
-        self.current_symbol_table().mark_symbol_bound(id);
-    }
-
-    fn mark_symbol_used(&mut self, id: ScopedSymbolId) {
-        self.current_symbol_table().mark_symbol_used(id);
-    }
-
     fn add_definition<'a>(
         &mut self,
         symbol: ScopedSymbolId,
         definition_node: impl Into<DefinitionNodeRef<'a>>,
     ) -> Definition<'db> {
         let definition_node: DefinitionNodeRef<'_> = definition_node.into();
-        #[allow(unsafe_code)]
-        // SAFETY: `definition_node` is guaranteed to be a child of `self.module`
-        let kind = unsafe { definition_node.into_owned(self.module.clone()) };
-        let category = kind.category();
         let definition = Definition::new(
             self.db,
             self.file,
             self.current_scope(),
             symbol,
-            kind,
+            #[allow(unsafe_code)]
+            unsafe {
+                definition_node.into_owned(self.module.clone())
+            },
             countme::Count::default(),
         );
 
-        let existing_definition = self
-            .definitions_by_node
+        self.definitions_by_node
             .insert(definition_node.key(), definition);
-        debug_assert_eq!(existing_definition, None);
-
-        if category.is_binding() {
-            self.mark_symbol_bound(symbol);
-        }
-
-        let use_def = self.current_use_def_map_mut();
-        match category {
-            DefinitionCategory::DeclarationAndBinding => {
-                use_def.record_declaration_and_binding(symbol, definition);
-            }
-            DefinitionCategory::Declaration => use_def.record_declaration(symbol, definition),
-            DefinitionCategory::Binding => use_def.record_binding(symbol, definition),
-        }
+        self.current_use_def_map_mut()
+            .record_definition(symbol, definition);
 
         definition
     }
 
-    fn add_expression_constraint(&mut self, constraint_node: &ast::Expr) -> Expression<'db> {
+    fn add_constraint(&mut self, constraint_node: &ast::Expr) -> Expression<'db> {
         let expression = self.add_standalone_expression(constraint_node);
-        self.current_use_def_map_mut()
-            .record_constraint(Constraint::Expression(expression));
+        self.current_use_def_map_mut().record_constraint(expression);
 
         expression
     }
 
-    fn add_pattern_constraint(
-        &mut self,
-        subject: &ast::Expr,
-        pattern: &ast::Pattern,
-    ) -> 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,
-            pattern,
-            countme::Count::default(),
-        );
-        self.current_use_def_map_mut()
-            .record_constraint(Constraint::Pattern(pattern_constraint));
-        pattern_constraint
-    }
-
     /// Record an expression that needs to be a Salsa ingredient, because we need to infer its type
     /// standalone (type narrowing tests, RHS of an assignment.)
     fn add_standalone_expression(&mut self, expression_node: &ast::Expr) -> Expression<'db> {
@@ -307,13 +252,10 @@ impl<'db> SemanticIndexBuilder<'db> {
                         ..
                     }) => (name, &None, default),
                 };
-                let symbol = self.add_symbol(name.id.clone());
-                // TODO create Definition for PEP 695 typevars
-                // note that the "bound" on the typevar is a totally different thing than whether
-                // or not a name is "bound" by a typevar declaration; the latter is always true.
-                self.mark_symbol_bound(symbol);
-                if let Some(bounds) = bound {
-                    self.visit_expr(bounds);
+                // TODO create Definition for typevars
+                self.add_or_update_symbol(name.id.clone(), SymbolFlags::IS_DEFINED);
+                if let Some(bound) = bound {
+                    self.visit_expr(bound);
                 }
                 if let Some(default) = default {
                     self.visit_expr(default);
@@ -330,23 +272,11 @@ impl<'db> SemanticIndexBuilder<'db> {
         nested_scope
     }
 
-    /// This method does several things:
-    /// - It pushes a new scope onto the stack for visiting
-    ///   a list/dict/set comprehension or generator expression
-    /// - Inside that scope, it visits a list of [`Comprehension`] nodes,
-    ///   assumed to be the "generators" that compose a comprehension
-    ///   (that is, the `for x in y` and `for y in z` parts of `x for x in y for y in z`).
-    /// - Inside that scope, it also calls a closure for visiting the outer `elt`
-    ///   of a list/dict/set comprehension or generator expression
-    /// - It then pops the new scope off the stack
+    /// Visit a list of [`Comprehension`] nodes, assumed to be the "generators" that compose a
+    /// comprehension (that is, the `for x in y` and `for y in z` parts of `x for x in y for y in z`.)
     ///
     /// [`Comprehension`]: ast::Comprehension
-    fn with_generators_scope(
-        &mut self,
-        scope: NodeWithScopeRef,
-        generators: &'db [ast::Comprehension],
-        visit_outer_elt: impl FnOnce(&mut Self),
-    ) {
+    fn visit_generators(&mut self, scope: NodeWithScopeRef, generators: &'db [ast::Comprehension]) {
         let mut generators_iter = generators.iter();
 
         let Some(generator) = generators_iter.next() else {
@@ -385,13 +315,11 @@ impl<'db> SemanticIndexBuilder<'db> {
                 self.visit_expr(expr);
             }
         }
-
-        visit_outer_elt(self);
-        self.pop_scope();
     }
 
     fn declare_parameter(&mut self, parameter: AnyParameterRef) {
-        let symbol = self.add_symbol(parameter.name().id().clone());
+        let symbol =
+            self.add_or_update_symbol(parameter.name().id().clone(), SymbolFlags::IS_DEFINED);
 
         let definition = self.add_definition(symbol, parameter);
 
@@ -399,11 +327,10 @@ impl<'db> SemanticIndexBuilder<'db> {
             // Insert a mapping from the parameter to the same definition.
             // This ensures that calling `HasTy::ty` on the inner parameter returns
             // a valid type (and doesn't panic)
-            let existing_definition = self.definitions_by_node.insert(
+            self.definitions_by_node.insert(
                 DefinitionNodeRef::from(AnyParameterRef::Variadic(&with_default.parameter)).key(),
                 definition,
             );
-            debug_assert_eq!(existing_definition, None);
         }
     }
 
@@ -455,7 +382,6 @@ impl<'db> SemanticIndexBuilder<'db> {
             scopes_by_expression: self.scopes_by_expression,
             scopes_by_node: self.scopes_by_node,
             use_def_maps,
-            has_future_annotations: self.has_future_annotations,
         }
     }
 }
@@ -503,7 +429,8 @@ where
                 // The symbol for the function name itself has to be evaluated
                 // at the end to match the runtime evaluation of parameter defaults
                 // and return-type annotations.
-                let symbol = self.add_symbol(function_def.name.id.clone());
+                let symbol = self
+                    .add_or_update_symbol(function_def.name.id.clone(), SymbolFlags::IS_DEFINED);
                 self.add_definition(symbol, function_def);
             }
             ast::Stmt::ClassDef(class) => {
@@ -511,7 +438,8 @@ where
                     self.visit_decorator(decorator);
                 }
 
-                let symbol = self.add_symbol(class.name.id.clone());
+                let symbol =
+                    self.add_or_update_symbol(class.name.id.clone(), SymbolFlags::IS_DEFINED);
                 self.add_definition(symbol, class);
 
                 self.with_type_params(
@@ -537,7 +465,7 @@ where
                         Name::new(alias.name.id.split('.').next().unwrap())
                     };
 
-                    let symbol = self.add_symbol(symbol_name);
+                    let symbol = self.add_or_update_symbol(symbol_name, SymbolFlags::IS_DEFINED);
                     self.add_definition(symbol, alias);
                 }
             }
@@ -549,16 +477,8 @@ where
                         &alias.name.id
                     };
 
-                    // Look for imports `from __future__ import annotations`, ignore `as ...`
-                    // We intentionally don't enforce the rules about location of `__future__`
-                    // imports here, we assume the user's intent was to apply the `__future__`
-                    // import, so we still check using it (and will also emit a diagnostic about a
-                    // miss-placed `__future__` import.)
-                    self.has_future_annotations |= alias.name.id == "annotations"
-                        && node.module.as_deref() == Some("__future__");
-
-                    let symbol = self.add_symbol(symbol_name.clone());
-
+                    let symbol =
+                        self.add_or_update_symbol(symbol_name.clone(), SymbolFlags::IS_DEFINED);
                     self.add_definition(symbol, ImportFromDefinitionNodeRef { node, alias_index });
                 }
             }
@@ -566,25 +486,15 @@ where
                 debug_assert!(self.current_assignment.is_none());
                 self.visit_expr(&node.value);
                 self.add_standalone_expression(&node.value);
-                for (target_index, target) in node.targets.iter().enumerate() {
-                    let kind = match target {
-                        ast::Expr::List(_) | ast::Expr::Tuple(_) => Some(AssignmentKind::Sequence),
-                        ast::Expr::Name(_) => Some(AssignmentKind::Name),
-                        _ => None,
-                    };
-                    if let Some(kind) = kind {
-                        self.current_assignment = Some(CurrentAssignment::Assign {
-                            assignment: node,
-                            target_index,
-                            kind,
-                        });
-                    }
+                self.current_assignment = Some(node.into());
+                for target in &node.targets {
                     self.visit_expr(target);
-                    self.current_assignment = None;
                 }
+                self.current_assignment = None;
             }
             ast::Stmt::AnnAssign(node) => {
                 debug_assert!(self.current_assignment.is_none());
+                // TODO deferred annotation visiting
                 self.visit_expr(&node.annotation);
                 if let Some(value) = &node.value {
                     self.visit_expr(value);
@@ -610,7 +520,7 @@ where
             ast::Stmt::If(node) => {
                 self.visit_expr(&node.test);
                 let pre_if = self.flow_snapshot();
-                self.add_expression_constraint(&node.test);
+                self.add_constraint(&node.test);
                 self.visit_body(&node.body);
                 let mut post_clauses: Vec<FlowSnapshot> = vec![];
                 for clause in &node.elif_else_clauses {
@@ -635,23 +545,14 @@ where
                     self.flow_merge(pre_if);
                 }
             }
-            ast::Stmt::While(ast::StmtWhile {
-                test,
-                body,
-                orelse,
-                range: _,
-            }) => {
-                self.visit_expr(test);
+            ast::Stmt::While(node) => {
+                self.visit_expr(&node.test);
 
                 let pre_loop = self.flow_snapshot();
 
                 // Save aside any break states from an outer loop
                 let saved_break_states = std::mem::take(&mut self.loop_break_states);
-
-                // TODO: definitions created inside the body should be fully visible
-                // to other statements/expressions inside the body --Alex/Carl
-                self.visit_body(body);
-
+                self.visit_body(&node.body);
                 // Get the break states from the body of this loop, and restore the saved outer
                 // ones.
                 let break_states =
@@ -660,7 +561,7 @@ 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);
-                self.visit_body(orelse);
+                self.visit_body(&node.orelse);
 
                 // Breaking out of a while loop bypasses the `else` clause, so merge in the break
                 // states after visiting `else`.
@@ -694,35 +595,15 @@ where
                     orelse,
                 },
             ) => {
+                // TODO add control flow similar to `ast::Stmt::While` above
                 self.add_standalone_expression(iter);
                 self.visit_expr(iter);
-
-                let pre_loop = self.flow_snapshot();
-                let saved_break_states = std::mem::take(&mut self.loop_break_states);
-
                 debug_assert!(self.current_assignment.is_none());
                 self.current_assignment = Some(for_stmt.into());
                 self.visit_expr(target);
                 self.current_assignment = None;
-
-                // TODO: Definitions created by loop variables
-                // (and definitions created inside the body)
-                // are fully visible to other statements/expressions inside the body --Alex/Carl
                 self.visit_body(body);
-
-                let break_states =
-                    std::mem::replace(&mut self.loop_break_states, saved_break_states);
-
-                // 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);
                 self.visit_body(orelse);
-
-                // Breaking out of a `for` loop bypasses the `else` clause, so merge in the break
-                // states after visiting `else`.
-                for break_state in break_states {
-                    self.flow_merge(break_state);
-                }
             }
             ast::Stmt::Match(ast::StmtMatch {
                 subject,
@@ -731,74 +612,9 @@ where
             }) => {
                 self.add_standalone_expression(subject);
                 self.visit_expr(subject);
-
-                let after_subject = self.flow_snapshot();
-                let Some((first, remaining)) = cases.split_first() else {
-                    return;
-                };
-                self.add_pattern_constraint(subject, &first.pattern);
-                self.visit_match_case(first);
-
-                let mut post_case_snapshots = vec![];
-                for case in remaining {
-                    post_case_snapshots.push(self.flow_snapshot());
-                    self.flow_restore(after_subject.clone());
-                    self.add_pattern_constraint(subject, &case.pattern);
+                for case in cases {
                     self.visit_match_case(case);
                 }
-                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())
-                {
-                    self.flow_merge(after_subject);
-                }
-            }
-            ast::Stmt::Try(ast::StmtTry {
-                body,
-                handlers,
-                orelse,
-                finalbody,
-                is_star,
-                range: _,
-            }) => {
-                self.visit_body(body);
-
-                for except_handler in handlers {
-                    let ast::ExceptHandler::ExceptHandler(except_handler) = except_handler;
-                    let ast::ExceptHandlerExceptHandler {
-                        name: symbol_name,
-                        type_: handled_exceptions,
-                        body: handler_body,
-                        range: _,
-                    } = except_handler;
-
-                    if let Some(handled_exceptions) = handled_exceptions {
-                        self.visit_expr(handled_exceptions);
-                    }
-
-                    // If `handled_exceptions` above was `None`, it's something like `except as e:`,
-                    // which is invalid syntax. However, it's still pretty obvious here that the user
-                    // *wanted* `e` to be bound, so we should still create a definition here nonetheless.
-                    if let Some(symbol_name) = symbol_name {
-                        let symbol = self.add_symbol(symbol_name.id.clone());
-
-                        self.add_definition(
-                            symbol,
-                            DefinitionNodeRef::ExceptHandler(ExceptHandlerDefinitionNodeRef {
-                                handler: except_handler,
-                                is_star: *is_star,
-                            }),
-                        );
-                    }
-
-                    self.visit_body(handler_body);
-                }
-
-                self.visit_body(orelse);
-                self.visit_body(finalbody);
             }
             _ => {
                 walk_stmt(self, stmt);
@@ -813,31 +629,30 @@ where
 
         match expr {
             ast::Expr::Name(name_node @ ast::ExprName { id, ctx, .. }) => {
-                let (is_use, is_definition) = match (ctx, self.current_assignment) {
-                    (ast::ExprContext::Store, Some(CurrentAssignment::AugAssign(_))) => {
-                        // For augmented assignment, the target expression is also used.
-                        (true, true)
-                    }
-                    (ast::ExprContext::Load, _) => (true, false),
-                    (ast::ExprContext::Store, _) => (false, true),
-                    (ast::ExprContext::Del, _) => (false, true),
-                    (ast::ExprContext::Invalid, _) => (false, false),
+                let mut flags = match ctx {
+                    ast::ExprContext::Load => SymbolFlags::IS_USED,
+                    ast::ExprContext::Store => SymbolFlags::IS_DEFINED,
+                    ast::ExprContext::Del => SymbolFlags::IS_DEFINED,
+                    ast::ExprContext::Invalid => SymbolFlags::empty(),
                 };
-                let symbol = self.add_symbol(id.clone());
-                if is_definition {
+                if matches!(
+                    self.current_assignment,
+                    Some(CurrentAssignment::AugAssign(_))
+                ) && !ctx.is_invalid()
+                {
+                    // For augmented assignment, the target expression is also used, so we should
+                    // record that as a use.
+                    flags |= SymbolFlags::IS_USED;
+                }
+                let symbol = self.add_or_update_symbol(id.clone(), flags);
+                if flags.contains(SymbolFlags::IS_DEFINED) {
                     match self.current_assignment {
-                        Some(CurrentAssignment::Assign {
-                            assignment,
-                            target_index,
-                            kind,
-                        }) => {
+                        Some(CurrentAssignment::Assign(assignment)) => {
                             self.add_definition(
                                 symbol,
                                 AssignmentDefinitionNodeRef {
                                     assignment,
-                                    target_index,
-                                    name: name_node,
-                                    kind,
+                                    target: name_node,
                                 },
                             );
                         }
@@ -853,7 +668,6 @@ where
                                 ForStmtDefinitionNodeRef {
                                     iterable: &node.iter,
                                     target: name_node,
-                                    is_async: node.is_async,
                                 },
                             );
                         }
@@ -870,7 +684,6 @@ where
                                     iterable: &node.iter,
                                     target: name_node,
                                     first,
-                                    is_async: node.is_async,
                                 },
                             );
                         }
@@ -887,8 +700,7 @@ where
                     }
                 }
 
-                if is_use {
-                    self.mark_symbol_used(symbol);
+                if flags.contains(SymbolFlags::IS_USED) {
                     let use_id = self.current_ast_ids().record_use(expr);
                     self.current_use_def_map_mut().record_use(symbol, use_id);
                 }
@@ -925,7 +737,6 @@ where
                 }
 
                 self.visit_expr(lambda.body.as_ref());
-                self.pop_scope();
             }
             ast::Expr::If(ast::ExprIf {
                 body, test, orelse, ..
@@ -946,33 +757,30 @@ where
                     elt, generators, ..
                 },
             ) => {
-                self.with_generators_scope(
+                self.visit_generators(
                     NodeWithScopeRef::ListComprehension(list_comprehension),
                     generators,
-                    |builder| builder.visit_expr(elt),
                 );
+                self.visit_expr(elt);
             }
             ast::Expr::SetComp(
                 set_comprehension @ ast::ExprSetComp {
                     elt, generators, ..
                 },
             ) => {
-                self.with_generators_scope(
+                self.visit_generators(
                     NodeWithScopeRef::SetComprehension(set_comprehension),
                     generators,
-                    |builder| builder.visit_expr(elt),
                 );
+                self.visit_expr(elt);
             }
             ast::Expr::Generator(
                 generator @ ast::ExprGenerator {
                     elt, generators, ..
                 },
             ) => {
-                self.with_generators_scope(
-                    NodeWithScopeRef::GeneratorExpression(generator),
-                    generators,
-                    |builder| builder.visit_expr(elt),
-                );
+                self.visit_generators(NodeWithScopeRef::GeneratorExpression(generator), generators);
+                self.visit_expr(elt);
             }
             ast::Expr::DictComp(
                 dict_comprehension @ ast::ExprDictComp {
@@ -982,19 +790,28 @@ where
                     ..
                 },
             ) => {
-                self.with_generators_scope(
+                self.visit_generators(
                     NodeWithScopeRef::DictComprehension(dict_comprehension),
                     generators,
-                    |builder| {
-                        builder.visit_expr(key);
-                        builder.visit_expr(value);
-                    },
                 );
+                self.visit_expr(key);
+                self.visit_expr(value);
             }
             _ => {
                 walk_expr(self, expr);
             }
         }
+
+        if matches!(
+            expr,
+            ast::Expr::Lambda(_)
+                | ast::Expr::ListComp(_)
+                | ast::Expr::SetComp(_)
+                | ast::Expr::Generator(_)
+                | ast::Expr::DictComp(_)
+        ) {
+            self.pop_scope();
+        }
     }
 
     fn visit_parameters(&mut self, parameters: &'ast ast::Parameters) {
@@ -1023,7 +840,7 @@ where
             range: _,
         }) = pattern
         {
-            let symbol = self.add_symbol(name.id().clone());
+            let symbol = self.add_or_update_symbol(name.id().clone(), SymbolFlags::IS_DEFINED);
             let state = self.current_match_case.as_ref().unwrap();
             self.add_definition(
                 symbol,
@@ -1044,7 +861,7 @@ where
             rest: Some(name), ..
         }) = pattern
         {
-            let symbol = self.add_symbol(name.id().clone());
+            let symbol = self.add_or_update_symbol(name.id().clone(), SymbolFlags::IS_DEFINED);
             let state = self.current_match_case.as_ref().unwrap();
             self.add_definition(
                 symbol,
@@ -1062,11 +879,7 @@ where
 
 #[derive(Copy, Clone, Debug)]
 enum CurrentAssignment<'a> {
-    Assign {
-        assignment: &'a ast::StmtAssign,
-        target_index: usize,
-        kind: AssignmentKind,
-    },
+    Assign(&'a ast::StmtAssign),
     AnnAssign(&'a ast::StmtAnnAssign),
     AugAssign(&'a ast::StmtAugAssign),
     For(&'a ast::StmtFor),
@@ -1078,6 +891,12 @@ enum CurrentAssignment<'a> {
     WithItem(&'a ast::WithItem),
 }
 
+impl<'a> From<&'a ast::StmtAssign> for CurrentAssignment<'a> {
+    fn from(value: &'a ast::StmtAssign) -> Self {
+        Self::Assign(value)
+    }
+}
+
 impl<'a> From<&'a ast::StmtAnnAssign> for CurrentAssignment<'a> {
     fn from(value: &'a ast::StmtAnnAssign) -> Self {
         Self::AnnAssign(value)

crates/red_knot_python_semantic/src/semantic_index/constraint.rs

@@ -1,39 +0,0 @@
-use ruff_db::files::File;
-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};
-
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub(crate) enum Constraint<'db> {
-    Expression(Expression<'db>),
-    Pattern(PatternConstraint<'db>),
-}
-
-#[salsa::tracked]
-pub(crate) struct PatternConstraint<'db> {
-    #[id]
-    pub(crate) file: File,
-
-    #[id]
-    pub(crate) file_scope: FileScopeId,
-
-    #[no_eq]
-    #[return_ref]
-    pub(crate) subject: AstNodeRef<ast::Expr>,
-
-    #[no_eq]
-    #[return_ref]
-    pub(crate) pattern: AstNodeRef<ast::Pattern>,
-
-    #[no_eq]
-    count: countme::Count<PatternConstraint<'static>>,
-}
-
-impl<'db> PatternConstraint<'db> {
-    pub(crate) fn scope(self, db: &'db dyn Db) -> ScopeId<'db> {
-        self.file_scope(db).to_scope_id(db, self.file(db))
-    }
-}

crates/red_knot_python_semantic/src/semantic_index/definition.rs

@@ -3,7 +3,6 @@ use ruff_db::parsed::ParsedModule;
 use ruff_python_ast as ast;
 
 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::Db;
@@ -24,7 +23,7 @@ pub struct Definition<'db> {
 
     #[no_eq]
     #[return_ref]
-    pub(crate) kind: DefinitionKind,
+    pub(crate) node: DefinitionKind,
 
     #[no_eq]
     count: countme::Count<Definition<'static>>,
@@ -34,26 +33,6 @@ impl<'db> Definition<'db> {
     pub(crate) fn scope(self, db: &'db dyn Db) -> ScopeId<'db> {
         self.file_scope(db).to_scope_id(db, self.file(db))
     }
-
-    pub(crate) fn category(self, db: &'db dyn Db) -> DefinitionCategory {
-        self.kind(db).category()
-    }
-
-    pub(crate) fn is_declaration(self, db: &'db dyn Db) -> bool {
-        self.kind(db).category().is_declaration()
-    }
-
-    pub(crate) fn is_binding(self, db: &'db dyn Db) -> bool {
-        self.kind(db).category().is_binding()
-    }
-
-    /// Return true if this is a symbol was defined in the `typing` or `typing_extensions` modules
-    pub(crate) fn is_typing_definition(self, db: &'db dyn Db) -> bool {
-        file_to_module(db, self.file(db)).is_some_and(|module| {
-            module.search_path().is_standard_library()
-                && matches!(&**module.name(), "typing" | "typing_extensions")
-        })
-    }
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -71,7 +50,6 @@ pub(crate) enum DefinitionNodeRef<'a> {
     Parameter(ast::AnyParameterRef<'a>),
     WithItem(WithItemDefinitionNodeRef<'a>),
     MatchPattern(MatchPatternDefinitionNodeRef<'a>),
-    ExceptHandler(ExceptHandlerDefinitionNodeRef<'a>),
 }
 
 impl<'a> From<&'a ast::StmtFunctionDef> for DefinitionNodeRef<'a> {
@@ -161,9 +139,7 @@ pub(crate) struct ImportFromDefinitionNodeRef<'a> {
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct AssignmentDefinitionNodeRef<'a> {
     pub(crate) assignment: &'a ast::StmtAssign,
-    pub(crate) target_index: usize,
-    pub(crate) name: &'a ast::ExprName,
-    pub(crate) kind: AssignmentKind,
+    pub(crate) target: &'a ast::ExprName,
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -176,13 +152,6 @@ pub(crate) struct WithItemDefinitionNodeRef<'a> {
 pub(crate) struct ForStmtDefinitionNodeRef<'a> {
     pub(crate) iterable: &'a ast::Expr,
     pub(crate) target: &'a ast::ExprName,
-    pub(crate) is_async: bool,
-}
-
-#[derive(Copy, Clone, Debug)]
-pub(crate) struct ExceptHandlerDefinitionNodeRef<'a> {
-    pub(crate) handler: &'a ast::ExceptHandlerExceptHandler,
-    pub(crate) is_star: bool,
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -190,7 +159,6 @@ pub(crate) struct ComprehensionDefinitionNodeRef<'a> {
     pub(crate) iterable: &'a ast::Expr,
     pub(crate) target: &'a ast::ExprName,
     pub(crate) first: bool,
-    pub(crate) is_async: bool,
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -226,42 +194,32 @@ impl DefinitionNodeRef<'_> {
             DefinitionNodeRef::NamedExpression(named) => {
                 DefinitionKind::NamedExpression(AstNodeRef::new(parsed, named))
             }
-            DefinitionNodeRef::Assignment(AssignmentDefinitionNodeRef {
-                assignment,
-                target_index,
-                name,
-                kind,
-            }) => DefinitionKind::Assignment(AssignmentDefinitionKind {
-                assignment: AstNodeRef::new(parsed.clone(), assignment),
-                target_index,
-                name: AstNodeRef::new(parsed, name),
-                kind,
-            }),
+            DefinitionNodeRef::Assignment(AssignmentDefinitionNodeRef { assignment, target }) => {
+                DefinitionKind::Assignment(AssignmentDefinitionKind {
+                    assignment: AstNodeRef::new(parsed.clone(), assignment),
+                    target: AstNodeRef::new(parsed, target),
+                })
+            }
             DefinitionNodeRef::AnnotatedAssignment(assign) => {
                 DefinitionKind::AnnotatedAssignment(AstNodeRef::new(parsed, assign))
             }
             DefinitionNodeRef::AugmentedAssignment(augmented_assignment) => {
                 DefinitionKind::AugmentedAssignment(AstNodeRef::new(parsed, augmented_assignment))
             }
-            DefinitionNodeRef::For(ForStmtDefinitionNodeRef {
-                iterable,
-                target,
-                is_async,
-            }) => DefinitionKind::For(ForStmtDefinitionKind {
-                iterable: AstNodeRef::new(parsed.clone(), iterable),
-                target: AstNodeRef::new(parsed, target),
-                is_async,
-            }),
+            DefinitionNodeRef::For(ForStmtDefinitionNodeRef { iterable, target }) => {
+                DefinitionKind::For(ForStmtDefinitionKind {
+                    iterable: AstNodeRef::new(parsed.clone(), iterable),
+                    target: AstNodeRef::new(parsed, target),
+                })
+            }
             DefinitionNodeRef::Comprehension(ComprehensionDefinitionNodeRef {
                 iterable,
                 target,
                 first,
-                is_async,
             }) => DefinitionKind::Comprehension(ComprehensionDefinitionKind {
                 iterable: AstNodeRef::new(parsed.clone(), iterable),
                 target: AstNodeRef::new(parsed, target),
                 first,
-                is_async,
             }),
             DefinitionNodeRef::Parameter(parameter) => match parameter {
                 ast::AnyParameterRef::Variadic(parameter) => {
@@ -286,13 +244,6 @@ impl DefinitionNodeRef<'_> {
                 identifier: AstNodeRef::new(parsed, identifier),
                 index,
             }),
-            DefinitionNodeRef::ExceptHandler(ExceptHandlerDefinitionNodeRef {
-                handler,
-                is_star,
-            }) => DefinitionKind::ExceptHandler(ExceptHandlerDefinitionKind {
-                handler: AstNodeRef::new(parsed.clone(), handler),
-                is_star,
-            }),
         }
     }
 
@@ -307,16 +258,13 @@ impl DefinitionNodeRef<'_> {
             Self::NamedExpression(node) => node.into(),
             Self::Assignment(AssignmentDefinitionNodeRef {
                 assignment: _,
-                target_index: _,
-                name,
-                kind: _,
-            }) => name.into(),
+                target,
+            }) => target.into(),
             Self::AnnotatedAssignment(node) => node.into(),
             Self::AugmentedAssignment(node) => node.into(),
             Self::For(ForStmtDefinitionNodeRef {
                 iterable: _,
                 target,
-                is_async: _,
             }) => target.into(),
             Self::Comprehension(ComprehensionDefinitionNodeRef { target, .. }) => target.into(),
             Self::Parameter(node) => match node {
@@ -327,46 +275,10 @@ impl DefinitionNodeRef<'_> {
             Self::MatchPattern(MatchPatternDefinitionNodeRef { identifier, .. }) => {
                 identifier.into()
             }
-            Self::ExceptHandler(ExceptHandlerDefinitionNodeRef { handler, .. }) => handler.into(),
         }
     }
 }
 
-#[derive(Clone, Copy, Debug)]
-pub(crate) enum DefinitionCategory {
-    /// A Definition which binds a value to a name (e.g. `x = 1`).
-    Binding,
-    /// A Definition which declares the upper-bound of acceptable types for this name (`x: int`).
-    Declaration,
-    /// A Definition which both declares a type and binds a value (e.g. `x: int = 1`).
-    DeclarationAndBinding,
-}
-
-impl DefinitionCategory {
-    /// True if this definition establishes a "declared type" for the symbol.
-    ///
-    /// If so, any assignments reached by this definition are in error if they assign a value of a
-    /// type not assignable to the declared type.
-    ///
-    /// Annotations establish a declared type. So do function and class definitions, and imports.
-    pub(crate) fn is_declaration(self) -> bool {
-        matches!(
-            self,
-            DefinitionCategory::Declaration | DefinitionCategory::DeclarationAndBinding
-        )
-    }
-
-    /// True if this definition assigns a value to the symbol.
-    ///
-    /// False only for annotated assignments without a RHS.
-    pub(crate) fn is_binding(self) -> bool {
-        matches!(
-            self,
-            DefinitionCategory::Binding | DefinitionCategory::DeclarationAndBinding
-        )
-    }
-}
-
 #[derive(Clone, Debug)]
 pub enum DefinitionKind {
     Import(AstNodeRef<ast::Alias>),
@@ -383,52 +295,6 @@ pub enum DefinitionKind {
     ParameterWithDefault(AstNodeRef<ast::ParameterWithDefault>),
     WithItem(WithItemDefinitionKind),
     MatchPattern(MatchPatternDefinitionKind),
-    ExceptHandler(ExceptHandlerDefinitionKind),
-}
-
-impl DefinitionKind {
-    pub(crate) fn category(&self) -> DefinitionCategory {
-        match self {
-            // functions, classes, and imports always bind, and we consider them declarations
-            DefinitionKind::Function(_)
-            | DefinitionKind::Class(_)
-            | DefinitionKind::Import(_)
-            | DefinitionKind::ImportFrom(_) => DefinitionCategory::DeclarationAndBinding,
-            // a parameter always binds a value, but is only a declaration if annotated
-            DefinitionKind::Parameter(parameter) => {
-                if parameter.annotation.is_some() {
-                    DefinitionCategory::DeclarationAndBinding
-                } else {
-                    DefinitionCategory::Binding
-                }
-            }
-            // presence of a default is irrelevant, same logic as for a no-default parameter
-            DefinitionKind::ParameterWithDefault(parameter_with_default) => {
-                if parameter_with_default.parameter.annotation.is_some() {
-                    DefinitionCategory::DeclarationAndBinding
-                } else {
-                    DefinitionCategory::Binding
-                }
-            }
-            // annotated assignment is always a declaration, only a binding if there is a RHS
-            DefinitionKind::AnnotatedAssignment(ann_assign) => {
-                if ann_assign.value.is_some() {
-                    DefinitionCategory::DeclarationAndBinding
-                } else {
-                    DefinitionCategory::Declaration
-                }
-            }
-            // all of these bind values without declaring a type
-            DefinitionKind::NamedExpression(_)
-            | DefinitionKind::Assignment(_)
-            | DefinitionKind::AugmentedAssignment(_)
-            | DefinitionKind::For(_)
-            | DefinitionKind::Comprehension(_)
-            | DefinitionKind::WithItem(_)
-            | DefinitionKind::MatchPattern(_)
-            | DefinitionKind::ExceptHandler(_) => DefinitionCategory::Binding,
-        }
-    }
 }
 
 #[derive(Clone, Debug)]
@@ -454,7 +320,6 @@ pub struct ComprehensionDefinitionKind {
     iterable: AstNodeRef<ast::Expr>,
     target: AstNodeRef<ast::ExprName>,
     first: bool,
-    is_async: bool,
 }
 
 impl ComprehensionDefinitionKind {
@@ -469,10 +334,6 @@ impl ComprehensionDefinitionKind {
     pub(crate) fn is_first(&self) -> bool {
         self.first
     }
-
-    pub(crate) fn is_async(&self) -> bool {
-        self.is_async
-    }
 }
 
 #[derive(Clone, Debug)]
@@ -494,34 +355,17 @@ impl ImportFromDefinitionKind {
 #[derive(Clone, Debug)]
 pub struct AssignmentDefinitionKind {
     assignment: AstNodeRef<ast::StmtAssign>,
-    target_index: usize,
-    name: AstNodeRef<ast::ExprName>,
-    kind: AssignmentKind,
+    target: AstNodeRef<ast::ExprName>,
 }
 
 impl AssignmentDefinitionKind {
-    pub(crate) fn value(&self) -> &ast::Expr {
-        &self.assignment.node().value
+    pub(crate) fn assignment(&self) -> &ast::StmtAssign {
+        self.assignment.node()
     }
 
-    pub(crate) fn target(&self) -> &ast::Expr {
-        &self.assignment.node().targets[self.target_index]
+    pub(crate) fn target(&self) -> &ast::ExprName {
+        self.target.node()
     }
-
-    pub(crate) fn name(&self) -> &ast::ExprName {
-        self.name.node()
-    }
-
-    pub(crate) fn kind(&self) -> AssignmentKind {
-        self.kind
-    }
-}
-
-/// The kind of assignment target expression.
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum AssignmentKind {
-    Sequence,
-    Name,
 }
 
 #[derive(Clone, Debug)]
@@ -544,7 +388,6 @@ impl WithItemDefinitionKind {
 pub struct ForStmtDefinitionKind {
     iterable: AstNodeRef<ast::Expr>,
     target: AstNodeRef<ast::ExprName>,
-    is_async: bool,
 }
 
 impl ForStmtDefinitionKind {
@@ -555,30 +398,6 @@ impl ForStmtDefinitionKind {
     pub(crate) fn target(&self) -> &ast::ExprName {
         self.target.node()
     }
-
-    pub(crate) fn is_async(&self) -> bool {
-        self.is_async
-    }
-}
-
-#[derive(Clone, Debug)]
-pub struct ExceptHandlerDefinitionKind {
-    handler: AstNodeRef<ast::ExceptHandlerExceptHandler>,
-    is_star: bool,
-}
-
-impl ExceptHandlerDefinitionKind {
-    pub(crate) fn node(&self) -> &ast::ExceptHandlerExceptHandler {
-        self.handler.node()
-    }
-
-    pub(crate) fn handled_exceptions(&self) -> Option<&ast::Expr> {
-        self.node().type_.as_deref()
-    }
-
-    pub(crate) fn is_star(&self) -> bool {
-        self.is_star
-    }
 }
 
 #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
@@ -649,9 +468,3 @@ impl From<&ast::Identifier> for DefinitionNodeKey {
         Self(NodeKey::from_node(identifier))
     }
 }
-
-impl From<&ast::ExceptHandlerExceptHandler> for DefinitionNodeKey {
-    fn from(handler: &ast::ExceptHandlerExceptHandler) -> Self {
-        Self(NodeKey::from_node(handler))
-    }
-}

crates/red_knot_python_semantic/src/semantic_index/symbol.rs

@@ -44,16 +44,16 @@ impl Symbol {
     }
 
     /// Is the symbol defined in its containing scope?
-    pub fn is_bound(&self) -> bool {
-        self.flags.contains(SymbolFlags::IS_BOUND)
+    pub fn is_defined(&self) -> bool {
+        self.flags.contains(SymbolFlags::IS_DEFINED)
     }
 }
 
 bitflags! {
     #[derive(Copy, Clone, Debug, Eq, PartialEq)]
-    struct SymbolFlags: u8 {
+    pub(super) struct SymbolFlags: u8 {
         const IS_USED         = 1 << 0;
-        const IS_BOUND      = 1 << 1;
+        const IS_DEFINED      = 1 << 1;
         /// TODO: This flag is not yet set by anything
         const MARKED_GLOBAL   = 1 << 2;
         /// TODO: This flag is not yet set by anything
@@ -272,7 +272,11 @@ impl SymbolTableBuilder {
         }
     }
 
-    pub(super) fn add_symbol(&mut self, name: Name) -> (ScopedSymbolId, bool) {
+    pub(super) fn add_or_update_symbol(
+        &mut self,
+        name: Name,
+        flags: SymbolFlags,
+    ) -> (ScopedSymbolId, bool) {
         let hash = SymbolTable::hash_name(&name);
         let entry = self
             .table
@@ -281,9 +285,15 @@ impl SymbolTableBuilder {
             .from_hash(hash, |id| self.table.symbols[*id].name() == &name);
 
         match entry {
-            RawEntryMut::Occupied(entry) => (*entry.key(), false),
+            RawEntryMut::Occupied(entry) => {
+                let symbol = &mut self.table.symbols[*entry.key()];
+                symbol.insert_flags(flags);
+
+                (*entry.key(), false)
+            }
             RawEntryMut::Vacant(entry) => {
-                let symbol = Symbol::new(name);
+                let mut symbol = Symbol::new(name);
+                symbol.insert_flags(flags);
 
                 let id = self.table.symbols.push(symbol);
                 entry.insert_with_hasher(hash, id, (), |id| {
@@ -294,14 +304,6 @@ impl SymbolTableBuilder {
         }
     }
 
-    pub(super) fn mark_symbol_bound(&mut self, id: ScopedSymbolId) {
-        self.table.symbols[id].insert_flags(SymbolFlags::IS_BOUND);
-    }
-
-    pub(super) fn mark_symbol_used(&mut self, id: ScopedSymbolId) {
-        self.table.symbols[id].insert_flags(SymbolFlags::IS_USED);
-    }
-
     pub(super) fn finish(mut self) -> SymbolTable {
         self.table.shrink_to_fit();
         self.table

crates/red_knot_python_semantic/src/semantic_index/use_def.rs

@@ -1,79 +1,5 @@
-//! First, some terminology:
-//!
-//! * A "binding" gives a new value to a variable. This includes many different Python statements
-//!   (assignment statements of course, but also imports, `def` and `class` statements, `as`
-//!   clauses in `with` and `except` statements, match patterns, and others) and even one
-//!   expression kind (named expressions). It notably does not include annotated assignment
-//!   statements without a right-hand side value; these do not assign any new value to the
-//!   variable. We consider function parameters to be bindings as well, since (from the perspective
-//!   of the function's internal scope), a function parameter begins the scope bound to a value.
-//!
-//! * A "declaration" establishes an upper bound type for the values that a variable may be
-//!   permitted to take on. Annotated assignment statements (with or without an RHS value) are
-//!   declarations; annotated function parameters are also declarations. We consider `def` and
-//!   `class` statements to also be declarations, so as to prohibit accidentally shadowing them.
-//!
-//! Annotated assignments with a right-hand side, and annotated function parameters, are both
-//! bindings and declarations.
-//!
-//! We use [`Definition`] as the universal term (and Salsa tracked struct) encompassing both
-//! bindings and declarations. (This sacrifices a bit of type safety in exchange for improved
-//! performance via fewer Salsa tracked structs and queries, since most declarations -- typed
-//! parameters and annotated assignments with RHS -- are both bindings and declarations.)
-//!
-//! At any given use of a variable, we can ask about both its "declared type" and its "inferred
-//! type". These may be different, but the inferred type must always be assignable to the declared
-//! type; that is, the declared type is always wider, and the inferred type may be more precise. If
-//! we see an invalid assignment, we emit a diagnostic and abandon our inferred type, deferring to
-//! the declared type (this allows an explicit annotation to override bad inference, without a
-//! cast), maintaining the invariant.
-//!
-//! The **inferred type** represents the most precise type we believe encompasses all possible
-//! values for the variable at a given use. It is based on a union of the bindings which can reach
-//! that use through some control flow path, and the narrowing constraints that control flow must
-//! have passed through between the binding and the use. For example, in this code:
-//!
-//! ```python
-//! x = 1 if flag else None
-//! if x is not None:
-//!     use(x)
-//! ```
-//!
-//! For the use of `x` on the third line, the inferred type should be `Literal[1]`. This is based
-//! on the binding on the first line, which assigns the type `Literal[1] | None`, and the narrowing
-//! constraint on the second line, which rules out the type `None`, since control flow must pass
-//! through this constraint to reach the use in question.
-//!
-//! The **declared type** represents the code author's declaration (usually through a type
-//! annotation) that a given variable should not be assigned any type outside the declared type. In
-//! our model, declared types are also control-flow-sensitive; we allow the code author to
-//! explicitly re-declare the same variable with a different type. So for a given binding of a
-//! variable, we will want to ask which declarations of that variable can reach that binding, in
-//! order to determine whether the binding is permitted, or should be a type error. For example:
-//!
-//! ```python
-//! from pathlib import Path
-//! def f(path: str):
-//!     path: Path = Path(path)
-//! ```
-//!
-//! In this function, the initial declared type of `path` is `str`, meaning that the assignment
-//! `path = Path(path)` would be a type error, since it assigns to `path` a value whose type is not
-//! assignable to `str`. This is the purpose of declared types: they prevent accidental assignment
-//! of the wrong type to a variable.
-//!
-//! But in some cases it is useful to "shadow" or "re-declare" a variable with a new type, and we
-//! permit this, as long as it is done with an explicit re-annotation. So `path: Path =
-//! Path(path)`, with the explicit `: Path` annotation, is permitted.
-//!
-//! The general rule is that whatever declaration(s) can reach a given binding determine the
-//! validity of that binding. If there is a path in which the symbol is not declared, that is a
-//! declaration of `Unknown`. If multiple declarations can reach a binding, we union them, but by
-//! default we also issue a type error, since this implicit union of declared types may hide an
-//! error.
-//!
-//! To support type inference, we build a map from each use of a symbol to the bindings live at
-//! that use, and the type narrowing constraints that apply to each binding.
+//! Build a map from each use of a symbol to the definitions visible from that use, and the
+//! type-narrowing constraints that apply to each definition.
 //!
 //! Let's take this code sample:
 //!
@@ -81,157 +7,148 @@
 //! x = 1
 //! x = 2
 //! y = x
-//! if flag:
+//! if y is not None:
 //!     x = 3
 //! else:
 //!     x = 4
 //! z = x
 //! ```
 //!
-//! In this snippet, we have four bindings of `x` (the statements assigning `1`, `2`, `3`, and `4`
-//! to it), and two uses of `x` (the `y = x` and `z = x` assignments). The first binding of `x`
-//! does not reach any use, because it's immediately replaced by the second binding, before any use
-//! happens. (A linter could thus flag the statement `x = 1` as likely superfluous.)
+//! In this snippet, we have four definitions of `x` (the statements assigning `1`, `2`, `3`,
+//! and `4` to it), and two uses of `x` (the `y = x` and `z = x` assignments). The first
+//! [`Definition`] of `x` is never visible to any use, because it's immediately replaced by the
+//! second definition, before any use happens. (A linter could thus flag the statement `x = 1`
+//! as likely superfluous.)
 //!
-//! The first use of `x` has one live binding: the assignment `x = 2`.
+//! The first use of `x` has one definition visible to it: the assignment `x = 2`.
 //!
 //! Things get a bit more complex when we have branches. We will definitely take either the `if` or
-//! the `else` branch. Thus, the second use of `x` has two live bindings: `x = 3` and `x = 4`. The
-//! `x = 2` assignment is no longer visible, because it must be replaced by either `x = 3` or `x =
-//! 4`, no matter which branch was taken. We don't know which branch was taken, so we must consider
-//! both bindings as live, which means eventually we would (in type inference) look at these two
-//! bindings and infer a type of `Literal[3, 4]` -- the union of `Literal[3]` and `Literal[4]` --
-//! for the second use of `x`.
+//! the `else` branch. Thus, the second use of `x` has two definitions visible to it: `x = 3` and
+//! `x = 4`. The `x = 2` definition is no longer visible, because it must be replaced by either `x
+//! = 3` or `x = 4`, no matter which branch was taken. We don't know which branch was taken, so we
+//! must consider both definitions as visible, which means eventually we would (in type inference)
+//! look at these two definitions and infer a type of `Literal[3, 4]` -- the union of `Literal[3]`
+//! and `Literal[4]` -- for the second use of `x`.
 //!
 //! So that's one question our use-def map needs to answer: given a specific use of a symbol, which
-//! binding(s) can reach that use. In [`AstIds`](crate::semantic_index::ast_ids::AstIds) we number
-//! all uses (that means a `Name` node with `Load` context) so we have a `ScopedUseId` to
-//! efficiently represent each use.
+//! definition(s) is/are visible from that use. In
+//! [`AstIds`](crate::semantic_index::ast_ids::AstIds) we number all uses (that means a `Name` node
+//! with `Load` context) so we have a `ScopedUseId` to efficiently represent each use.
 //!
-//! We also need to know, for a given definition of a symbol, what type narrowing constraints apply
+//! Another case we need to handle is when a symbol is referenced from a different scope (the most
+//! obvious example of this is an import). We call this "public" use of a symbol. So the other
+//! question we need to be able to answer is, what are the publicly-visible definitions of each
+//! symbol?
+//!
+//! Technically, public use of a symbol could also occur from any point in control flow of the
+//! scope where the symbol is defined (via inline imports and import cycles, in the case of an
+//! import, or via a function call partway through the local scope that ends up using a symbol from
+//! the scope via a global or nonlocal reference.) But modeling this fully accurately requires
+//! whole-program analysis that isn't tractable for an efficient incremental compiler, since it
+//! means a given symbol could have a different type every place it's referenced throughout the
+//! program, depending on the shape of arbitrarily-sized call/import graphs. So we follow other
+//! Python type-checkers in making the simplifying assumption that usually the scope will finish
+//! execution before its symbols are made visible to other scopes; for instance, most imports will
+//! import from a complete module, not a partially-executed module. (We may want to get a little
+//! smarter than this in the future, in particular for closures, but for now this is where we
+//! start.)
+//!
+//! So this means that the publicly-visible definitions of a symbol are the definitions still
+//! visible at the end of the scope; effectively we have an implicit "use" of every symbol at the
+//! end of the scope.
+//!
+//! We also need to know, for a given definition of a symbol, what type-narrowing constraints apply
 //! to it. For instance, in this code sample:
 //!
 //! ```python
 //! x = 1 if flag else None
 //! if x is not None:
-//!     use(x)
+//!     y = x
 //! ```
 //!
-//! At the use of `x`, the live binding of `x` is `1 if flag else None`, which would infer as the
-//! type `Literal[1] | None`. But the constraint `x is not None` dominates this use, which means we
-//! can rule out the possibility that `x` is `None` here, which should give us the type
-//! `Literal[1]` for this use.
-//!
-//! For declared types, we need to be able to answer the question "given a binding to a symbol,
-//! which declarations of that symbol can reach the binding?" This allows us to emit a diagnostic
-//! if the binding is attempting to bind a value of a type that is not assignable to the declared
-//! type for that symbol, at that point in control flow.
-//!
-//! We also need to know, given a declaration of a symbol, what the inferred type of that symbol is
-//! at that point. This allows us to emit a diagnostic in a case like `x = "foo"; x: int`. The
-//! binding `x = "foo"` occurs before the declaration `x: int`, so according to our
-//! control-flow-sensitive interpretation of declarations, the assignment is not an error. But the
-//! declaration is an error, since it would violate the "inferred type must be assignable to
-//! declared type" rule.
-//!
-//! Another case we need to handle is when a symbol is referenced from a different scope (for
-//! example, an import or a nonlocal reference). We call this "public" use of a symbol. For public
-//! use of a symbol, we prefer the declared type, if there are any declarations of that symbol; if
-//! not, we fall back to the inferred type. So we also need to know which declarations and bindings
-//! can reach the end of the scope.
-//!
-//! Technically, public use of a symbol could occur from any point in control flow of the scope
-//! where the symbol is defined (via inline imports and import cycles, in the case of an import, or
-//! via a function call partway through the local scope that ends up using a symbol from the scope
-//! via a global or nonlocal reference.) But modeling this fully accurately requires whole-program
-//! analysis that isn't tractable for an efficient analysis, since it means a given symbol could
-//! have a different type every place it's referenced throughout the program, depending on the
-//! shape of arbitrarily-sized call/import graphs. So we follow other Python type checkers in
-//! making the simplifying assumption that usually the scope will finish execution before its
-//! symbols are made visible to other scopes; for instance, most imports will import from a
-//! complete module, not a partially-executed module. (We may want to get a little smarter than
-//! this in the future for some closures, but for now this is where we start.)
+//! At the use of `x` in `y = x`, the visible definition of `x` is `1 if flag else None`, which
+//! would infer as the type `Literal[1] | None`. But the constraint `x is not None` dominates this
+//! use, which means we can rule out the possibility that `x` is `None` here, which should give us
+//! the type `Literal[1]` for this use.
 //!
 //! The data structure we build to answer these questions is the `UseDefMap`. It has a
-//! `bindings_by_use` vector of [`SymbolBindings`] indexed by [`ScopedUseId`], a
-//! `declarations_by_binding` vector of [`SymbolDeclarations`] indexed by [`ScopedDefinitionId`], a
-//! `bindings_by_declaration` vector of [`SymbolBindings`] indexed by [`ScopedDefinitionId`], and
-//! `public_bindings` and `public_definitions` vectors indexed by [`ScopedSymbolId`]. The values in
-//! each of these vectors are (in principle) a list of live bindings at that use/definition, or at
-//! the end of the scope for that symbol, with a list of the dominating constraints for each
-//! binding.
+//! `definitions_by_use` vector indexed by [`ScopedUseId`] and a `public_definitions` vector
+//! indexed by [`ScopedSymbolId`]. The values in each of these vectors are (in principle) a list of
+//! visible definitions at that use, or at the end of the scope for that symbol, with a list of the
+//! dominating constraints for each of those definitions.
 //!
 //! In order to avoid vectors-of-vectors-of-vectors and all the allocations that would entail, we
 //! don't actually store these "list of visible definitions" as a vector of [`Definition`].
-//! Instead, [`SymbolBindings`] and [`SymbolDeclarations`] are structs which use bit-sets to track
-//! definitions (and constraints, in the case of bindings) in terms of [`ScopedDefinitionId`] and
-//! [`ScopedConstraintId`], which are indices into the `all_definitions` and `all_constraints`
-//! indexvecs in the [`UseDefMap`].
+//! Instead, the values in `definitions_by_use` and `public_definitions` are a [`SymbolState`]
+//! struct which uses bit-sets to track definitions and constraints in terms of
+//! [`ScopedDefinitionId`] and [`ScopedConstraintId`], which are indices into the `all_definitions`
+//! and `all_constraints` 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.
 //!
-//! 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.
+//! The simplest way to model "unbound" would be as an actual [`Definition`] itself: the initial
+//! visible [`Definition`] for each symbol in a scope. But actually modeling it this way would
+//! unnecessarily increase the number of [`Definition`] that Salsa must track. Since "unbound" is a
+//! special definition 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 [`SymbolState`] struct. If this flag is `true`, it means the
+//! symbol/use really has one additional visible "definition", which is the unbound state. If this
+//! flag is `false`, it means we've eliminated the possibility of unbound: every path we've
+//! followed includes a definition for this symbol.
 //!
 //! To build a [`UseDefMap`], the [`UseDefMapBuilder`] is notified of each new use, definition, and
 //! constraint as they are encountered by the
 //! [`SemanticIndexBuilder`](crate::semantic_index::builder::SemanticIndexBuilder) AST visit. For
-//! each symbol, the builder tracks the `SymbolState` (`SymbolBindings` and `SymbolDeclarations`)
-//! for that symbol. When we hit a use or definition of a symbol, we record the necessary parts of
-//! the current state for that symbol that we need for that use or definition. When we reach the
-//! end of the scope, it records the state for each symbol as the public definitions of that
-//! symbol.
+//! each symbol, the builder tracks the `SymbolState` for that symbol. When we hit a use of a
+//! symbol, it records the current state for that symbol for that use. When we reach the 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 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.
+//! Let's walk through the above example. Initially we record for `x` that it has no visible
+//! definitions, and may be unbound. When we see `x = 1`, we record that as the sole visible
+//! definition of `x`, and flip `may_be_unbound` to `false`. Then we see `x = 2`, and it replaces
+//! `x = 1` as the sole visible definition of `x`. When we get to `y = x`, we record that the
+//! visible definitions 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,
-//! which we'll need later. Then we record `flag` as a possible constraint on the current binding
-//! (`x = 2`), and go ahead and visit the `if` body. When we see `x = 3`, it replaces `x = 2`
-//! (constrained by `flag`) as the sole live binding of `x`. At the end of the `if` body, we take
-//! another snapshot of the current symbol state; we'll call this the post-if-body snapshot.
+//! happen regardless. Then we take a pre-branch snapshot of the currently visible definitions for
+//! all symbols, which we'll need later. Then we record `flag` as a possible constraint on the
+//! currently visible definition (`x = 2`), and go ahead and visit the `if` body. When we see `x =
+//! 3`, it replaces `x = 2` (constrained by `flag`) as the sole visible definition of `x`. At the
+//! end of the `if` body, we take another snapshot of the currently-visible definitions; we'll call
+//! this the post-if-body snapshot.
 //!
 //! Now we need to visit the `else` clause. The conditions when entering the `else` clause should
 //! 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), then visit the `else` clause, where `x = 4` replaces `x = 2` as the sole live binding
-//! of `x`.
+//! using the snapshot we took previously (meaning we now have `x = 2` as the sole visible
+//! definition for `x` again), then visit the `else` clause, where `x = 4` replaces `x = 2` as the
+//! sole visible definition 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
 //! `else` branch, and we don't know which. So we need to "merge" our current builder state
-//! (reflecting the end-of-else state, with `x = 4` as the only live binding) with our post-if-body
-//! 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`.
+//! (reflecting the end-of-else state, with `x = 4` as the only visible definition) with our
+//! post-if-body snapshot (which has `x = 3` as the only visible definition). The result of this
+//! merge is that we now have two visible definitions of `x`: `x = 3` and `x = 4`.
 //!
 //! 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.
+//!
+//! (In the future we may have some other questions we want to answer as well, such as "is this
+//! definition used?", which will require tracking a bit more info in our map, e.g. a "used" bit
+//! for each [`Definition`] which is flipped to true when we record that definition for a use.)
 use self::symbol_state::{
-    BindingIdWithConstraintsIterator, ConstraintIdIterator, DeclarationIdIterator,
-    ScopedConstraintId, ScopedDefinitionId, SymbolBindings, SymbolDeclarations, SymbolState,
+    ConstraintIdIterator, DefinitionIdWithConstraintsIterator, ScopedConstraintId,
+    ScopedDefinitionId, SymbolState,
 };
 use crate::semantic_index::ast_ids::ScopedUseId;
 use crate::semantic_index::definition::Definition;
+use crate::semantic_index::expression::Expression;
 use crate::semantic_index::symbol::ScopedSymbolId;
 use ruff_index::IndexVec;
-use rustc_hash::FxHashMap;
-
-use super::constraint::Constraint;
 
 mod bitset;
 mod symbol_state;
@@ -242,135 +159,63 @@ pub(crate) struct UseDefMap<'db> {
     /// Array of [`Definition`] in this scope.
     all_definitions: IndexVec<ScopedDefinitionId, Definition<'db>>,
 
-    /// Array of [`Constraint`] in this scope.
-    all_constraints: IndexVec<ScopedConstraintId, Constraint<'db>>,
+    /// Array of constraints (as [`Expression`]) in this scope.
+    all_constraints: IndexVec<ScopedConstraintId, Expression<'db>>,
 
-    /// [`SymbolBindings`] reaching a [`ScopedUseId`].
-    bindings_by_use: IndexVec<ScopedUseId, SymbolBindings>,
-
-    /// [`SymbolBindings`] or [`SymbolDeclarations`] reaching a given [`Definition`].
-    ///
-    /// If the definition is a binding (only) -- `x = 1` for example -- then we need
-    /// [`SymbolDeclarations`] to know whether this binding is permitted by the live declarations.
-    ///
-    /// If the definition is a declaration (only) -- `x: int` for example -- then we need
-    /// [`SymbolBindings`] to know whether this declaration is consistent with the previously
-    /// inferred type.
-    ///
-    /// If the definition is both a declaration and a binding -- `x: int = 1` for example -- then
-    /// we don't actually need anything here, all we'll need to validate is that our own RHS is a
-    /// valid assignment to our own annotation.
-    definitions_by_definition: FxHashMap<Definition<'db>, SymbolDefinitions>,
+    /// [`SymbolState`] visible at a [`ScopedUseId`].
+    definitions_by_use: IndexVec<ScopedUseId, SymbolState>,
 
     /// [`SymbolState`] visible at end of scope for each symbol.
-    public_symbols: IndexVec<ScopedSymbolId, SymbolState>,
+    public_definitions: IndexVec<ScopedSymbolId, SymbolState>,
 }
 
 impl<'db> UseDefMap<'db> {
-    pub(crate) fn bindings_at_use(
+    pub(crate) fn use_definitions(
         &self,
         use_id: ScopedUseId,
-    ) -> BindingWithConstraintsIterator<'_, 'db> {
-        self.bindings_iterator(&self.bindings_by_use[use_id])
+    ) -> DefinitionWithConstraintsIterator<'_, 'db> {
+        DefinitionWithConstraintsIterator {
+            all_definitions: &self.all_definitions,
+            all_constraints: &self.all_constraints,
+            inner: self.definitions_by_use[use_id].visible_definitions(),
+        }
     }
 
     pub(crate) fn use_may_be_unbound(&self, use_id: ScopedUseId) -> bool {
-        self.bindings_by_use[use_id].may_be_unbound()
+        self.definitions_by_use[use_id].may_be_unbound()
     }
 
-    pub(crate) fn public_bindings(
+    pub(crate) fn public_definitions(
         &self,
         symbol: ScopedSymbolId,
-    ) -> BindingWithConstraintsIterator<'_, 'db> {
-        self.bindings_iterator(self.public_symbols[symbol].bindings())
+    ) -> DefinitionWithConstraintsIterator<'_, 'db> {
+        DefinitionWithConstraintsIterator {
+            all_definitions: &self.all_definitions,
+            all_constraints: &self.all_constraints,
+            inner: self.public_definitions[symbol].visible_definitions(),
+        }
     }
 
     pub(crate) fn public_may_be_unbound(&self, symbol: ScopedSymbolId) -> bool {
-        self.public_symbols[symbol].may_be_unbound()
+        self.public_definitions[symbol].may_be_unbound()
     }
-
-    pub(crate) fn bindings_at_declaration(
-        &self,
-        declaration: Definition<'db>,
-    ) -> BindingWithConstraintsIterator<'_, 'db> {
-        if let SymbolDefinitions::Bindings(bindings) = &self.definitions_by_definition[&declaration]
-        {
-            self.bindings_iterator(bindings)
-        } else {
-            unreachable!("Declaration has non-Bindings in definitions_by_definition");
-        }
-    }
-
-    pub(crate) fn declarations_at_binding(
-        &self,
-        binding: Definition<'db>,
-    ) -> DeclarationsIterator<'_, 'db> {
-        if let SymbolDefinitions::Declarations(declarations) =
-            &self.definitions_by_definition[&binding]
-        {
-            self.declarations_iterator(declarations)
-        } else {
-            unreachable!("Binding has non-Declarations in definitions_by_definition");
-        }
-    }
-
-    pub(crate) fn public_declarations(
-        &self,
-        symbol: ScopedSymbolId,
-    ) -> DeclarationsIterator<'_, 'db> {
-        let declarations = self.public_symbols[symbol].declarations();
-        self.declarations_iterator(declarations)
-    }
-
-    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,
-            inner: bindings.iter(),
-        }
-    }
-
-    fn declarations_iterator<'a>(
-        &'a self,
-        declarations: &'a SymbolDeclarations,
-    ) -> DeclarationsIterator<'a, 'db> {
-        DeclarationsIterator {
-            all_definitions: &self.all_definitions,
-            inner: declarations.iter(),
-            may_be_undeclared: declarations.may_be_undeclared(),
-        }
-    }
-}
-
-/// Either live bindings or live declarations for a symbol.
-#[derive(Debug, PartialEq, Eq)]
-enum SymbolDefinitions {
-    Bindings(SymbolBindings),
-    Declarations(SymbolDeclarations),
 }
 
 #[derive(Debug)]
-pub(crate) struct BindingWithConstraintsIterator<'map, 'db> {
+pub(crate) struct DefinitionWithConstraintsIterator<'map, 'db> {
     all_definitions: &'map IndexVec<ScopedDefinitionId, Definition<'db>>,
-    all_constraints: &'map IndexVec<ScopedConstraintId, Constraint<'db>>,
-    inner: BindingIdWithConstraintsIterator<'map>,
+    all_constraints: &'map IndexVec<ScopedConstraintId, Expression<'db>>,
+    inner: DefinitionIdWithConstraintsIterator<'map>,
 }
 
-impl<'map, 'db> Iterator for BindingWithConstraintsIterator<'map, 'db> {
-    type Item = BindingWithConstraints<'map, 'db>;
+impl<'map, 'db> Iterator for DefinitionWithConstraintsIterator<'map, 'db> {
+    type Item = DefinitionWithConstraints<'map, 'db>;
 
     fn next(&mut self) -> Option<Self::Item> {
         self.inner
             .next()
-            .map(|def_id_with_constraints| BindingWithConstraints {
-                binding: self.all_definitions[def_id_with_constraints.definition],
+            .map(|def_id_with_constraints| DefinitionWithConstraints {
+                definition: self.all_definitions[def_id_with_constraints.definition],
                 constraints: ConstraintsIterator {
                     all_constraints: self.all_constraints,
                     constraint_ids: def_id_with_constraints.constraint_ids,
@@ -379,20 +224,20 @@ impl<'map, 'db> Iterator for BindingWithConstraintsIterator<'map, 'db> {
     }
 }
 
-impl std::iter::FusedIterator for BindingWithConstraintsIterator<'_, '_> {}
+impl std::iter::FusedIterator for DefinitionWithConstraintsIterator<'_, '_> {}
 
-pub(crate) struct BindingWithConstraints<'map, 'db> {
-    pub(crate) binding: Definition<'db>,
+pub(crate) struct DefinitionWithConstraints<'map, 'db> {
+    pub(crate) definition: Definition<'db>,
     pub(crate) constraints: ConstraintsIterator<'map, 'db>,
 }
 
 pub(crate) struct ConstraintsIterator<'map, 'db> {
-    all_constraints: &'map IndexVec<ScopedConstraintId, Constraint<'db>>,
+    all_constraints: &'map IndexVec<ScopedConstraintId, Expression<'db>>,
     constraint_ids: ConstraintIdIterator<'map>,
 }
 
 impl<'map, 'db> Iterator for ConstraintsIterator<'map, 'db> {
-    type Item = Constraint<'db>;
+    type Item = Expression<'db>;
 
     fn next(&mut self) -> Option<Self::Item> {
         self.constraint_ids
@@ -403,50 +248,25 @@ impl<'map, 'db> Iterator for ConstraintsIterator<'map, 'db> {
 
 impl std::iter::FusedIterator for ConstraintsIterator<'_, '_> {}
 
-pub(crate) struct DeclarationsIterator<'map, 'db> {
-    all_definitions: &'map IndexVec<ScopedDefinitionId, Definition<'db>>,
-    inner: DeclarationIdIterator<'map>,
-    may_be_undeclared: bool,
-}
-
-impl DeclarationsIterator<'_, '_> {
-    pub(crate) fn may_be_undeclared(&self) -> bool {
-        self.may_be_undeclared
-    }
-}
-
-impl<'map, 'db> Iterator for DeclarationsIterator<'map, 'db> {
-    type Item = Definition<'db>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.inner.next().map(|def_id| self.all_definitions[def_id])
-    }
-}
-
-impl std::iter::FusedIterator for DeclarationsIterator<'_, '_> {}
-
 /// A snapshot of the definitions and constraints state at a particular point in control flow.
 #[derive(Clone, Debug)]
 pub(super) struct FlowSnapshot {
-    symbol_states: IndexVec<ScopedSymbolId, SymbolState>,
+    definitions_by_symbol: IndexVec<ScopedSymbolId, SymbolState>,
 }
 
 #[derive(Debug, Default)]
 pub(super) struct UseDefMapBuilder<'db> {
-    /// Append-only array of [`Definition`].
+    /// Append-only array of [`Definition`]; None is unbound.
     all_definitions: IndexVec<ScopedDefinitionId, Definition<'db>>,
 
-    /// Append-only array of [`Constraint`].
-    all_constraints: IndexVec<ScopedConstraintId, Constraint<'db>>,
+    /// Append-only array of constraints (as [`Expression`]).
+    all_constraints: IndexVec<ScopedConstraintId, Expression<'db>>,
 
-    /// Live bindings at each so-far-recorded use.
-    bindings_by_use: IndexVec<ScopedUseId, SymbolBindings>,
+    /// Visible definitions at each so-far-recorded use.
+    definitions_by_use: IndexVec<ScopedUseId, SymbolState>,
 
-    /// Live bindings or declarations for each so-far-recorded definition.
-    definitions_by_definition: FxHashMap<Definition<'db>, SymbolDefinitions>,
-
-    /// Currently live bindings and declarations for each symbol.
-    symbol_states: IndexVec<ScopedSymbolId, SymbolState>,
+    /// Currently visible definitions for each symbol.
+    definitions_by_symbol: IndexVec<ScopedSymbolId, SymbolState>,
 }
 
 impl<'db> UseDefMapBuilder<'db> {
@@ -455,104 +275,86 @@ impl<'db> UseDefMapBuilder<'db> {
     }
 
     pub(super) fn add_symbol(&mut self, symbol: ScopedSymbolId) {
-        let new_symbol = self.symbol_states.push(SymbolState::undefined());
+        let new_symbol = self.definitions_by_symbol.push(SymbolState::unbound());
         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(binding);
-        let symbol_state = &mut self.symbol_states[symbol];
-        self.definitions_by_definition.insert(
-            binding,
-            SymbolDefinitions::Declarations(symbol_state.declarations().clone()),
-        );
-        symbol_state.record_binding(def_id);
-    }
-
-    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_id);
-        }
-    }
-
-    pub(super) fn record_declaration(
-        &mut self,
-        symbol: ScopedSymbolId,
-        declaration: Definition<'db>,
-    ) {
-        let def_id = self.all_definitions.push(declaration);
-        let symbol_state = &mut self.symbol_states[symbol];
-        self.definitions_by_definition.insert(
-            declaration,
-            SymbolDefinitions::Bindings(symbol_state.bindings().clone()),
-        );
-        symbol_state.record_declaration(def_id);
-    }
-
-    pub(super) fn record_declaration_and_binding(
+    pub(super) fn record_definition(
         &mut self,
         symbol: ScopedSymbolId,
         definition: Definition<'db>,
     ) {
-        // We don't need to store anything in self.definitions_by_definition.
+        // We have a new definition of a symbol; this replaces any previous definitions in this
+        // path.
         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);
+        self.definitions_by_symbol[symbol] = SymbolState::with(def_id);
+    }
+
+    pub(super) fn record_constraint(&mut self, constraint: Expression<'db>) {
+        let constraint_id = self.all_constraints.push(constraint);
+        for definitions in &mut self.definitions_by_symbol {
+            definitions.add_constraint(constraint_id);
+        }
     }
 
     pub(super) fn record_use(&mut self, symbol: ScopedSymbolId, use_id: ScopedUseId) {
-        // We have a use of a symbol; clone the current bindings for that symbol, and record them
-        // as the live bindings for this use.
+        // We have a use of a symbol; clone the currently visible definitions for that symbol, and
+        // record them as the visible definitions for this use.
         let new_use = self
-            .bindings_by_use
-            .push(self.symbol_states[symbol].bindings().clone());
+            .definitions_by_use
+            .push(self.definitions_by_symbol[symbol].clone());
         debug_assert_eq!(use_id, new_use);
     }
 
     /// Take a snapshot of the current visible-symbols state.
     pub(super) fn snapshot(&self) -> FlowSnapshot {
         FlowSnapshot {
-            symbol_states: self.symbol_states.clone(),
+            definitions_by_symbol: self.definitions_by_symbol.clone(),
         }
     }
 
-    /// Restore the current builder symbols state to the given snapshot.
+    /// Restore the current builder visible-definitions state to the given snapshot.
     pub(super) fn restore(&mut self, snapshot: FlowSnapshot) {
-        // We never remove symbols from `symbol_states` (it's an IndexVec, and the symbol
+        // We never remove symbols from `definitions_by_symbol` (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.
-        let num_symbols = self.symbol_states.len();
-        debug_assert!(num_symbols >= snapshot.symbol_states.len());
+        let num_symbols = self.definitions_by_symbol.len();
+        debug_assert!(num_symbols >= snapshot.definitions_by_symbol.len());
 
         // Restore the current visible-definitions state to the given snapshot.
-        self.symbol_states = snapshot.symbol_states;
+        self.definitions_by_symbol = snapshot.definitions_by_symbol;
 
         // 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());
+        // snapshot, the correct state to fill them in with is "unbound".
+        self.definitions_by_symbol
+            .resize(num_symbols, SymbolState::unbound());
     }
 
     /// 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.
+    /// path to get here. The new visible-definitions state for each symbol should include
+    /// definitions from both the prior state and the snapshot.
     pub(super) fn merge(&mut self, snapshot: FlowSnapshot) {
-        // We never remove symbols from `symbol_states` (it's an IndexVec, and the symbol
+        // The tricky thing about merging two Ranges pointing into `all_definitions` is that if the
+        // two Ranges aren't already adjacent in `all_definitions`, we will have to copy at least
+        // one or the other of the ranges to the end of `all_definitions` so as to make them
+        // adjacent. We can't ever move things around in `all_definitions` because previously
+        // recorded uses may still have ranges pointing to any part of it; all we can do is append.
+        // It's possible we may end up with some old entries in `all_definitions` that nobody is
+        // pointing to, but that's OK.
+
+        // We never remove symbols from `definitions_by_symbol` (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.
-        debug_assert!(self.symbol_states.len() >= snapshot.symbol_states.len());
+        debug_assert!(self.definitions_by_symbol.len() >= snapshot.definitions_by_symbol.len());
 
-        let mut snapshot_definitions_iter = snapshot.symbol_states.into_iter();
-        for current in &mut self.symbol_states {
+        let mut snapshot_definitions_iter = snapshot.definitions_by_symbol.into_iter();
+        for current in &mut self.definitions_by_symbol {
             if let Some(snapshot) = snapshot_definitions_iter.next() {
                 current.merge(snapshot);
             } else {
-                // Symbol not present in snapshot, so it's unbound/undeclared from that path.
-                current.set_may_be_unbound();
-                current.set_may_be_undeclared();
+                // Symbol not present in snapshot, so it's unbound from that path.
+                current.add_unbound();
             }
         }
     }
@@ -560,16 +362,14 @@ impl<'db> UseDefMapBuilder<'db> {
     pub(super) fn finish(mut self) -> UseDefMap<'db> {
         self.all_definitions.shrink_to_fit();
         self.all_constraints.shrink_to_fit();
-        self.symbol_states.shrink_to_fit();
-        self.bindings_by_use.shrink_to_fit();
-        self.definitions_by_definition.shrink_to_fit();
+        self.definitions_by_symbol.shrink_to_fit();
+        self.definitions_by_use.shrink_to_fit();
 
         UseDefMap {
             all_definitions: self.all_definitions,
             all_constraints: self.all_constraints,
-            bindings_by_use: self.bindings_by_use,
-            public_symbols: self.symbol_states,
-            definitions_by_definition: self.definitions_by_definition,
+            definitions_by_use: self.definitions_by_use,
+            public_definitions: self.definitions_by_symbol,
         }
     }
 }

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

@@ -32,25 +32,17 @@ 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;
-        self.resize_blocks(num_blocks_needed as usize);
-    }
-
-    fn resize_blocks(&mut self, num_blocks_needed: usize) {
         match self {
             Self::Inline(blocks) => {
                 let mut vec = blocks.to_vec();
-                vec.resize(num_blocks_needed, 0);
+                vec.resize(num_blocks_needed as usize, 0);
                 *self = Self::Heap(vec);
             }
             Self::Heap(vec) => {
-                vec.resize(num_blocks_needed, 0);
+                vec.resize(num_blocks_needed as usize, 0);
             }
         }
     }
@@ -97,19 +89,6 @@ 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();
@@ -239,59 +218,6 @@ 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);
@@ -299,11 +225,4 @@ 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

@@ -1,13 +1,13 @@
-//! Track live bindings per symbol, applicable constraints per binding, and live declarations.
+//! Track visible definitions of a symbol, and applicable constraints per definition.
 //!
 //! These data structures operate entirely on scope-local newtype-indices for definitions and
 //! constraints, referring to their location in the `all_definitions` and `all_constraints`
 //! indexvecs in [`super::UseDefMapBuilder`].
 //!
-//! We need to track arbitrary associations between bindings and constraints, not just a single set
-//! of currently dominating constraints (where "dominating" means "control flow must have passed
-//! through it to reach this point"), because we can have dominating constraints that apply to some
-//! bindings but not others, as in this code:
+//! We need to track arbitrary associations between definitions and constraints, not just a single
+//! set of currently dominating constraints (where "dominating" means "control flow must have
+//! passed through it to reach this point"), because we can have dominating constraints that apply
+//! to some definitions but not others, as in this code:
 //!
 //! ```python
 //! x = 1 if flag else None
@@ -18,11 +18,11 @@
 //! ```
 //!
 //! The `x is not None` constraint dominates the final use of `x`, but it applies only to the first
-//! binding of `x`, not the second, so `None` is a possible value for `x`.
+//! definition of `x`, not the second, so `None` is a possible value for `x`.
 //!
-//! And we can't just track, for each binding, an index into a list of dominating constraints,
-//! either, because we can have bindings which are still visible, but subject to constraints that
-//! are no longer dominating, as in this code:
+//! And we can't just track, for each definition, an index into a list of dominating constraints,
+//! either, because we can have definitions which are still visible, but subject to constraints
+//! that are no longer dominating, as in this code:
 //!
 //! ```python
 //! x = 0
@@ -33,16 +33,13 @@
 //! ```
 //!
 //! From the point of view of the final use of `x`, the `x is not None` constraint no longer
-//! dominates, but it does dominate the `x = 1 if flag2 else None` binding, so we have to keep
+//! dominates, but it does dominate the `x = 1 if flag2 else None` definition, so we have to keep
 //! track of that.
 //!
 //! The data structures used here ([`BitSet`] and [`smallvec::SmallVec`]) optimize for keeping all
 //! data inline (avoiding lots of scattered allocations) in small-to-medium cases, and falling back
-//! to heap allocation to be able to scale to arbitrary numbers of live bindings and constraints
-//! when needed.
-//!
-//! Tracking live declarations is simpler, since constraints are not involved, but otherwise very
-//! similar to tracking live bindings.
+//! to heap allocation to be able to scale to arbitrary numbers of definitions and constraints when
+//! needed.
 use super::bitset::{BitSet, BitSetIterator};
 use ruff_index::newtype_index;
 use smallvec::SmallVec;
@@ -56,200 +53,93 @@ pub(super) struct ScopedDefinitionId;
 pub(super) struct ScopedConstraintId;
 
 /// Can reference this * 64 total definitions inline; more will fall back to the heap.
-const INLINE_BINDING_BLOCKS: usize = 3;
+const INLINE_DEFINITION_BLOCKS: usize = 3;
 
-/// A [`BitSet`] of [`ScopedDefinitionId`], representing live bindings of a symbol in a scope.
-type Bindings = BitSet<INLINE_BINDING_BLOCKS>;
-type BindingsIterator<'a> = BitSetIterator<'a, INLINE_BINDING_BLOCKS>;
-
-/// Can reference this * 64 total declarations inline; more will fall back to the heap.
-const INLINE_DECLARATION_BLOCKS: usize = 3;
-
-/// A [`BitSet`] of [`ScopedDefinitionId`], representing live declarations of a symbol in a scope.
-type Declarations = BitSet<INLINE_DECLARATION_BLOCKS>;
-type DeclarationsIterator<'a> = BitSetIterator<'a, INLINE_DECLARATION_BLOCKS>;
+/// A [`BitSet`] of [`ScopedDefinitionId`], representing visible definitions of a symbol in a scope.
+type Definitions = BitSet<INLINE_DEFINITION_BLOCKS>;
+type DefinitionsIterator<'a> = BitSetIterator<'a, INLINE_DEFINITION_BLOCKS>;
 
 /// Can reference this * 64 total constraints inline; more will fall back to the heap.
 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;
+/// Can keep inline this many visible definitions per symbol at a given time; more will go to heap.
+const INLINE_VISIBLE_DEFINITIONS_PER_SYMBOL: usize = 4;
 
-/// One [`BitSet`] of applicable [`ScopedConstraintId`] per live binding.
-type InlineConstraintArray = [BitSet<INLINE_CONSTRAINT_BLOCKS>; INLINE_BINDINGS_PER_SYMBOL];
+/// One [`BitSet`] of applicable [`ScopedConstraintId`] per visible definition.
+type InlineConstraintArray =
+    [BitSet<INLINE_CONSTRAINT_BLOCKS>; INLINE_VISIBLE_DEFINITIONS_PER_SYMBOL];
 type Constraints = SmallVec<InlineConstraintArray>;
 type ConstraintsIterator<'a> = std::slice::Iter<'a, BitSet<INLINE_CONSTRAINT_BLOCKS>>;
 type ConstraintsIntoIterator = smallvec::IntoIter<InlineConstraintArray>;
 
-/// Live declarations for a single symbol at some point in control flow.
+/// Visible definitions and narrowing constraints 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?
-    live_declarations: Declarations,
+pub(super) struct SymbolState {
+    /// [`BitSet`]: which [`ScopedDefinitionId`] are visible for this symbol?
+    visible_definitions: Definitions,
 
-    /// Could the symbol be un-declared at this point?
-    may_be_undeclared: bool,
-}
-
-impl SymbolDeclarations {
-    fn undeclared() -> Self {
-        Self {
-            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.may_be_undeclared = false;
-    }
-
-    /// 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 {
-            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 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?
-    live_bindings: Bindings,
-
-    /// For each live binding, which [`ScopedConstraintId`] apply?
+    /// For each definition, which [`ScopedConstraintId`] apply?
     ///
     /// This is a [`smallvec::SmallVec`] which should always have one [`BitSet`] of constraints per
-    /// binding in `live_bindings`.
+    /// definition in `visible_definitions`.
     constraints: Constraints,
 
     /// Could the symbol be unbound at this point?
     may_be_unbound: bool,
 }
 
-impl SymbolBindings {
-    fn unbound() -> Self {
+/// A single [`ScopedDefinitionId`] with an iterator of its applicable [`ScopedConstraintId`].
+#[derive(Debug)]
+pub(super) struct DefinitionIdWithConstraints<'a> {
+    pub(super) definition: ScopedDefinitionId,
+    pub(super) constraint_ids: ConstraintIdIterator<'a>,
+}
+
+impl SymbolState {
+    /// Return a new [`SymbolState`] representing an unbound symbol.
+    pub(super) fn unbound() -> Self {
         Self {
-            live_bindings: Bindings::default(),
+            visible_definitions: Definitions::default(),
             constraints: Constraints::default(),
             may_be_unbound: true,
         }
     }
 
+    /// Return a new [`SymbolState`] representing a symbol with a single visible definition.
+    pub(super) fn with(definition_id: ScopedDefinitionId) -> Self {
+        let mut constraints = Constraints::with_capacity(1);
+        constraints.push(BitSet::default());
+        Self {
+            visible_definitions: Definitions::with(definition_id.into()),
+            constraints,
+            may_be_unbound: false,
+        }
+    }
+
     /// Add Unbound as a possibility for this symbol.
-    fn set_may_be_unbound(&mut self) {
+    pub(super) fn add_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 = Constraints::with_capacity(1);
-        self.constraints.push(BitSet::default());
-        self.may_be_unbound = false;
-    }
-
-    /// Add given constraint to all live bindings.
-    pub(super) fn record_constraint(&mut self, constraint_id: ScopedConstraintId) {
+    /// Add given constraint to all currently-visible definitions.
+    pub(super) fn add_constraint(&mut self, constraint_id: ScopedConstraintId) {
         for bitset in &mut self.constraints {
             bitset.insert(constraint_id.into());
         }
     }
 
-    /// Iterate over currently live bindings for this symbol.
-    pub(super) fn iter(&self) -> BindingIdWithConstraintsIterator {
-        BindingIdWithConstraintsIterator {
-            definitions: self.live_bindings.iter(),
-            constraints: self.constraints.iter(),
-        }
-    }
-
-    pub(super) fn may_be_unbound(&self) -> bool {
-        self.may_be_unbound
-    }
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub(super) struct SymbolState {
-    declarations: SymbolDeclarations,
-    bindings: SymbolBindings,
-}
-
-impl SymbolState {
-    /// Return a new [`SymbolState`] representing an unbound, undeclared symbol.
-    pub(super) fn undefined() -> Self {
-        Self {
-            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) {
-        self.bindings.record_binding(binding_id);
-    }
-
-    /// Add given constraint to all live bindings.
-    pub(super) fn record_constraint(&mut self, constraint_id: ScopedConstraintId) {
-        self.bindings.record_constraint(constraint_id);
-    }
-
-    /// 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.
-    pub(super) fn record_declaration(&mut self, declaration_id: ScopedDefinitionId) {
-        self.declarations.record_declaration(declaration_id);
-    }
-
     /// Merge another [`SymbolState`] into this one.
     pub(super) fn merge(&mut self, b: SymbolState) {
         let mut a = Self {
-            bindings: SymbolBindings {
-                live_bindings: Bindings::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(),
-                may_be_undeclared: self.declarations.may_be_undeclared
-                    || b.declarations.may_be_undeclared,
-            },
+            visible_definitions: Definitions::default(),
+            constraints: Constraints::default(),
+            may_be_unbound: self.may_be_unbound || b.may_be_unbound,
         };
-
         std::mem::swap(&mut a, self);
-        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_defs_iter = a.visible_definitions.iter();
+        let mut b_defs_iter = b.visible_definitions.iter();
+        let mut a_constraints_iter = a.constraints.into_iter();
+        let mut b_constraints_iter = b.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();
@@ -262,7 +152,7 @@ impl SymbolState {
 
         // Helper to push `def`, with constraints in `constraints_iter`, onto `self`.
         let push = |def, constraints_iter: &mut ConstraintsIntoIterator, merged: &mut Self| {
-            merged.bindings.live_bindings.insert(def);
+            merged.visible_definitions.insert(def);
             // 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
@@ -271,7 +161,7 @@ impl SymbolState {
             let constraints = constraints_iter
                 .next()
                 .expect("definitions and constraints length mismatch");
-            merged.bindings.constraints.push(constraints);
+            merged.constraints.push(constraints);
         };
 
         loop {
@@ -301,8 +191,7 @@ impl SymbolState {
                         // 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.
-                        self.bindings
-                            .constraints
+                        self.constraints
                             .last_mut()
                             .unwrap()
                             .intersect(&a_constraints);
@@ -325,49 +214,40 @@ impl SymbolState {
         }
     }
 
-    pub(super) fn bindings(&self) -> &SymbolBindings {
-        &self.bindings
-    }
-
-    pub(super) fn declarations(&self) -> &SymbolDeclarations {
-        &self.declarations
+    /// Get iterator over visible definitions with constraints.
+    pub(super) fn visible_definitions(&self) -> DefinitionIdWithConstraintsIterator {
+        DefinitionIdWithConstraintsIterator {
+            definitions: self.visible_definitions.iter(),
+            constraints: self.constraints.iter(),
+        }
     }
 
     /// Could the symbol be unbound?
     pub(super) fn may_be_unbound(&self) -> bool {
-        self.bindings.may_be_unbound()
+        self.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).
+/// The default state of a symbol (if we've seen no definitions of it) is unbound.
 impl Default for SymbolState {
     fn default() -> Self {
-        SymbolState::undefined()
+        SymbolState::unbound()
     }
 }
 
-/// A single binding (as [`ScopedDefinitionId`]) with an iterator of its applicable
-/// [`ScopedConstraintId`].
 #[derive(Debug)]
-pub(super) struct BindingIdWithConstraints<'a> {
-    pub(super) definition: ScopedDefinitionId,
-    pub(super) constraint_ids: ConstraintIdIterator<'a>,
-}
-
-#[derive(Debug)]
-pub(super) struct BindingIdWithConstraintsIterator<'a> {
-    definitions: BindingsIterator<'a>,
+pub(super) struct DefinitionIdWithConstraintsIterator<'a> {
+    definitions: DefinitionsIterator<'a>,
     constraints: ConstraintsIterator<'a>,
 }
 
-impl<'a> Iterator for BindingIdWithConstraintsIterator<'a> {
-    type Item = BindingIdWithConstraints<'a>;
+impl<'a> Iterator for DefinitionIdWithConstraintsIterator<'a> {
+    type Item = DefinitionIdWithConstraints<'a>;
 
     fn next(&mut self) -> Option<Self::Item> {
         match (self.definitions.next(), self.constraints.next()) {
             (None, None) => None,
-            (Some(def), Some(constraints)) => Some(BindingIdWithConstraints {
+            (Some(def), Some(constraints)) => Some(DefinitionIdWithConstraints {
                 definition: ScopedDefinitionId::from_u32(def),
                 constraint_ids: ConstraintIdIterator {
                     wrapped: constraints.iter(),
@@ -379,7 +259,7 @@ impl<'a> Iterator for BindingIdWithConstraintsIterator<'a> {
     }
 }
 
-impl std::iter::FusedIterator for BindingIdWithConstraintsIterator<'_> {}
+impl std::iter::FusedIterator for DefinitionIdWithConstraintsIterator<'_> {}
 
 #[derive(Debug)]
 pub(super) struct ConstraintIdIterator<'a> {
@@ -396,193 +276,99 @@ impl Iterator for ConstraintIdIterator<'_> {
 
 impl std::iter::FusedIterator for ConstraintIdIterator<'_> {}
 
-#[derive(Debug)]
-pub(super) struct DeclarationIdIterator<'a> {
-    inner: DeclarationsIterator<'a>,
-}
-
-impl<'a> Iterator for DeclarationIdIterator<'a> {
-    type Item = ScopedDefinitionId;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.inner.next().map(ScopedDefinitionId::from_u32)
-    }
-}
-
-impl std::iter::FusedIterator for DeclarationIdIterator<'_> {}
-
 #[cfg(test)]
 mod tests {
     use super::{ScopedConstraintId, ScopedDefinitionId, SymbolState};
 
-    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| {
-                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);
-    }
-
-    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(ScopedDefinitionId::as_u32)
-            .collect::<Vec<_>>();
-        assert_eq!(actual, expected);
+    impl SymbolState {
+        pub(crate) fn assert(&self, may_be_unbound: bool, expected: &[&str]) {
+            assert_eq!(self.may_be_unbound(), may_be_unbound);
+            let actual = self
+                .visible_definitions()
+                .map(|def_id_with_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);
+        }
     }
 
     #[test]
     fn unbound() {
-        let sym = SymbolState::undefined();
+        let cd = SymbolState::unbound();
 
-        assert_bindings(&sym, true, &[]);
+        cd.assert(true, &[]);
     }
 
     #[test]
     fn with() {
-        let mut sym = SymbolState::undefined();
-        sym.record_binding(ScopedDefinitionId::from_u32(0));
+        let cd = SymbolState::with(ScopedDefinitionId::from_u32(0));
 
-        assert_bindings(&sym, false, &["0<>"]);
+        cd.assert(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();
+    fn add_unbound() {
+        let mut cd = SymbolState::with(ScopedDefinitionId::from_u32(0));
+        cd.add_unbound();
 
-        assert_bindings(&sym, true, &["0<>"]);
+        cd.assert(true, &["0<>"]);
     }
 
     #[test]
-    fn record_constraint() {
-        let mut sym = SymbolState::undefined();
-        sym.record_binding(ScopedDefinitionId::from_u32(0));
-        sym.record_constraint(ScopedConstraintId::from_u32(0));
+    fn add_constraint() {
+        let mut cd = SymbolState::with(ScopedDefinitionId::from_u32(0));
+        cd.add_constraint(ScopedConstraintId::from_u32(0));
 
-        assert_bindings(&sym, false, &["0<0>"]);
+        cd.assert(false, &["0<0>"]);
     }
 
     #[test]
     fn merge() {
         // merging the same definition with the same constraint keeps the constraint
-        let mut sym0a = SymbolState::undefined();
-        sym0a.record_binding(ScopedDefinitionId::from_u32(0));
-        sym0a.record_constraint(ScopedConstraintId::from_u32(0));
+        let mut cd0a = SymbolState::with(ScopedDefinitionId::from_u32(0));
+        cd0a.add_constraint(ScopedConstraintId::from_u32(0));
 
-        let mut sym0b = SymbolState::undefined();
-        sym0b.record_binding(ScopedDefinitionId::from_u32(0));
-        sym0b.record_constraint(ScopedConstraintId::from_u32(0));
+        let mut cd0b = SymbolState::with(ScopedDefinitionId::from_u32(0));
+        cd0b.add_constraint(ScopedConstraintId::from_u32(0));
 
-        sym0a.merge(sym0b);
-        let mut sym0 = sym0a;
-        assert_bindings(&sym0, false, &["0<0>"]);
+        cd0a.merge(cd0b);
+        let mut cd0 = cd0a;
+        cd0.assert(false, &["0<0>"]);
 
         // merging the same definition with differing constraints drops all constraints
-        let mut sym1a = SymbolState::undefined();
-        sym1a.record_binding(ScopedDefinitionId::from_u32(1));
-        sym1a.record_constraint(ScopedConstraintId::from_u32(1));
+        let mut cd1a = SymbolState::with(ScopedDefinitionId::from_u32(1));
+        cd1a.add_constraint(ScopedConstraintId::from_u32(1));
 
-        let mut sym1b = SymbolState::undefined();
-        sym1b.record_binding(ScopedDefinitionId::from_u32(1));
-        sym1b.record_constraint(ScopedConstraintId::from_u32(2));
+        let mut cd1b = SymbolState::with(ScopedDefinitionId::from_u32(1));
+        cd1b.add_constraint(ScopedConstraintId::from_u32(2));
 
-        sym1a.merge(sym1b);
-        let sym1 = sym1a;
-        assert_bindings(&sym1, false, &["1<>"]);
+        cd1a.merge(cd1b);
+        let cd1 = cd1a;
+        cd1.assert(false, &["1<>"]);
 
         // merging a constrained definition with unbound keeps both
-        let mut sym2a = SymbolState::undefined();
-        sym2a.record_binding(ScopedDefinitionId::from_u32(2));
-        sym2a.record_constraint(ScopedConstraintId::from_u32(3));
+        let mut cd2a = SymbolState::with(ScopedDefinitionId::from_u32(2));
+        cd2a.add_constraint(ScopedConstraintId::from_u32(3));
 
-        let sym2b = SymbolState::undefined();
+        let cd2b = SymbolState::unbound();
 
-        sym2a.merge(sym2b);
-        let sym2 = sym2a;
-        assert_bindings(&sym2, true, &["2<3>"]);
+        cd2a.merge(cd2b);
+        let cd2 = cd2a;
+        cd2.assert(true, &["2<3>"]);
 
         // merging different definitions keeps them each with their existing constraints
-        sym0.merge(sym2);
-        let sym = sym0;
-        assert_bindings(&sym, true, &["0<0>", "2<3>"]);
-    }
-
-    #[test]
-    fn no_declaration() {
-        let sym = SymbolState::undefined();
-
-        assert_declarations(&sym, true, &[]);
-    }
-
-    #[test]
-    fn record_declaration() {
-        let mut sym = SymbolState::undefined();
-        sym.record_declaration(ScopedDefinitionId::from_u32(1));
-
-        assert_declarations(&sym, false, &[1]);
-    }
-
-    #[test]
-    fn record_declaration_override() {
-        let mut sym = SymbolState::undefined();
-        sym.record_declaration(ScopedDefinitionId::from_u32(1));
-        sym.record_declaration(ScopedDefinitionId::from_u32(2));
-
-        assert_declarations(&sym, false, &[2]);
-    }
-
-    #[test]
-    fn record_declaration_merge() {
-        let mut sym = SymbolState::undefined();
-        sym.record_declaration(ScopedDefinitionId::from_u32(1));
-
-        let mut sym2 = SymbolState::undefined();
-        sym2.record_declaration(ScopedDefinitionId::from_u32(2));
-
-        sym.merge(sym2);
-
-        assert_declarations(&sym, false, &[1, 2]);
-    }
-
-    #[test]
-    fn record_declaration_merge_partial_undeclared() {
-        let mut sym = SymbolState::undefined();
-        sym.record_declaration(ScopedDefinitionId::from_u32(1));
-
-        let sym2 = SymbolState::undefined();
-
-        sym.merge(sym2);
-
-        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]);
+        cd0.merge(cd2);
+        let cd = cd0;
+        cd.assert(true, &["0<0>", "2<3>"]);
     }
 }

crates/red_knot_python_semantic/src/semantic_model.rs

@@ -8,7 +8,7 @@ use crate::module_name::ModuleName;
 use crate::module_resolver::{resolve_module, Module};
 use crate::semantic_index::ast_ids::HasScopedAstId;
 use crate::semantic_index::semantic_index;
-use crate::types::{binding_ty, global_symbol_ty, infer_scope_types, Type};
+use crate::types::{definition_ty, global_symbol_ty_by_name, infer_scope_types, Type};
 use crate::Db;
 
 pub struct SemanticModel<'db> {
@@ -35,12 +35,12 @@ impl<'db> SemanticModel<'db> {
         line_index(self.db.upcast(), self.file)
     }
 
-    pub fn resolve_module(&self, module_name: &ModuleName) -> Option<Module> {
+    pub fn resolve_module(&self, module_name: ModuleName) -> Option<Module> {
         resolve_module(self.db, module_name)
     }
 
     pub fn global_symbol_ty(&self, module: &Module, symbol_name: &str) -> Type<'db> {
-        global_symbol_ty(self.db, module.file(), symbol_name)
+        global_symbol_ty_by_name(self.db, module.file(), symbol_name)
     }
 }
 
@@ -147,24 +147,24 @@ impl HasTy for ast::Expr {
     }
 }
 
-macro_rules! impl_binding_has_ty {
+macro_rules! impl_definition_has_ty {
     ($ty: ty) => {
         impl HasTy for $ty {
             #[inline]
             fn ty<'db>(&self, model: &SemanticModel<'db>) -> Type<'db> {
                 let index = semantic_index(model.db, model.file);
-                let binding = index.definition(self);
-                binding_ty(model.db, binding)
+                let definition = index.definition(self);
+                definition_ty(model.db, definition)
             }
         }
     };
 }
 
-impl_binding_has_ty!(ast::StmtFunctionDef);
-impl_binding_has_ty!(ast::StmtClassDef);
-impl_binding_has_ty!(ast::Alias);
-impl_binding_has_ty!(ast::Parameter);
-impl_binding_has_ty!(ast::ParameterWithDefault);
+impl_definition_has_ty!(ast::StmtFunctionDef);
+impl_definition_has_ty!(ast::StmtClassDef);
+impl_definition_has_ty!(ast::Alias);
+impl_definition_has_ty!(ast::Parameter);
+impl_definition_has_ty!(ast::ParameterWithDefault);
 
 #[cfg(test)]
 mod tests {

crates/red_knot_python_semantic/src/site_packages.rs

@@ -192,7 +192,7 @@ impl VirtualEnvironment {
             } else {
                 tracing::warn!(
                     "Failed to resolve `sys.prefix` of the system Python installation \
-from the `home` value in the `pyvenv.cfg` file at `{}`. \
+from the `home` value in the `pyvenv.cfg` file at '{}'. \
 System site-packages will not be used for module resolution.",
                     venv_path.join("pyvenv.cfg")
                 );
@@ -426,7 +426,7 @@ impl Deref for SysPrefixPath {
 
 impl fmt::Display for SysPrefixPath {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "`sys.prefix` path `{}`", self.0)
+        write!(f, "`sys.prefix` path '{}'", self.0)
     }
 }
 
@@ -483,7 +483,7 @@ impl Deref for PythonHomePath {
 
 impl fmt::Display for PythonHomePath {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "`home` location `{}`", self.0)
+        write!(f, "`home` location '{}'", self.0)
     }
 }
 

crates/red_knot_python_semantic/src/stdlib.rs

@@ -1,87 +0,0 @@
-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::types::{global_symbol_ty, Type};
-use crate::Db;
-
-/// Enumeration of various core stdlib modules, for which we have dedicated Salsa queries.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-enum CoreStdlibModule {
-    Builtins,
-    Types,
-    Typeshed,
-    TypingExtensions,
-}
-
-impl CoreStdlibModule {
-    fn name(self) -> ModuleName {
-        let module_name = match self {
-            Self::Builtins => "builtins",
-            Self::Types => "types",
-            Self::Typeshed => "_typeshed",
-            Self::TypingExtensions => "typing_extensions",
-        };
-        ModuleName::new_static(module_name)
-            .unwrap_or_else(|| panic!("{module_name} should be a valid module name!"))
-    }
-}
-
-/// Lookup the type of `symbol` in a given core module
-///
-/// Returns `Unbound` if the given core module cannot be resolved for some reason
-fn core_module_symbol_ty<'db>(
-    db: &'db dyn Db,
-    core_module: CoreStdlibModule,
-    symbol: &str,
-) -> Type<'db> {
-    resolve_module(db, &core_module.name())
-        .map(|module| global_symbol_ty(db, module.file(), symbol))
-        .unwrap_or(Type::Unbound)
-}
-
-/// Lookup the type of `symbol` in the builtins namespace.
-///
-/// Returns `Unbound` if the `builtins` module isn't available for some reason.
-#[inline]
-pub(crate) fn builtins_symbol_ty<'db>(db: &'db dyn Db, symbol: &str) -> Type<'db> {
-    core_module_symbol_ty(db, CoreStdlibModule::Builtins, symbol)
-}
-
-/// Lookup the type of `symbol` in the `types` module namespace.
-///
-/// Returns `Unbound` if the `types` module isn't available for some reason.
-#[inline]
-pub(crate) fn types_symbol_ty<'db>(db: &'db dyn Db, symbol: &str) -> Type<'db> {
-    core_module_symbol_ty(db, CoreStdlibModule::Types, symbol)
-}
-
-/// Lookup the type of `symbol` in the `_typeshed` module namespace.
-///
-/// Returns `Unbound` if the `_typeshed` module isn't available for some reason.
-#[inline]
-pub(crate) fn typeshed_symbol_ty<'db>(db: &'db dyn Db, symbol: &str) -> Type<'db> {
-    core_module_symbol_ty(db, CoreStdlibModule::Typeshed, symbol)
-}
-
-/// Lookup the type of `symbol` in the `typing_extensions` module namespace.
-///
-/// Returns `Unbound` if the `typing_extensions` module isn't available for some reason.
-#[inline]
-pub(crate) fn typing_extensions_symbol_ty<'db>(db: &'db dyn Db, symbol: &str) -> Type<'db> {
-    core_module_symbol_ty(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: CoreStdlibModule) -> Option<ScopeId<'_>> {
-    resolve_module(db, &core_module.name()).map(|module| global_scope(db, module.file()))
-}
-
-/// Get the `builtins` module scope.
-///
-/// 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, CoreStdlibModule::Builtins)
-}

crates/red_knot_python_semantic/src/types/builder.rs

@@ -25,14 +25,15 @@
 //!   * No type in an intersection can be a supertype of any other type in the intersection (just
 //!     eliminate the supertype from the intersection).
 //!   * An intersection containing two non-overlapping types should simplify to [`Type::Never`].
+
 use crate::types::{IntersectionType, Type, UnionType};
 use crate::{Db, FxOrderSet};
-use smallvec::SmallVec;
+use ordermap::set::MutableValues;
 
-use super::KnownClass;
+use super::builtins_symbol_ty_by_name;
 
 pub(crate) struct UnionBuilder<'db> {
-    elements: Vec<Type<'db>>,
+    elements: FxOrderSet<Type<'db>>,
     db: &'db dyn Db,
 }
 
@@ -40,7 +41,7 @@ impl<'db> UnionBuilder<'db> {
     pub(crate) fn new(db: &'db dyn Db) -> Self {
         Self {
             db,
-            elements: vec![],
+            elements: FxOrderSet::default(),
         }
     }
 
@@ -48,70 +49,47 @@ impl<'db> UnionBuilder<'db> {
     pub(crate) fn add(mut self, ty: Type<'db>) -> Self {
         match ty {
             Type::Union(union) => {
-                let new_elements = union.elements(self.db);
-                self.elements.reserve(new_elements.len());
-                for element in new_elements {
-                    self = self.add(*element);
-                }
+                self.elements.extend(union.elements(self.db));
             }
             Type::Never => {}
             _ => {
-                let bool_pair = if let Type::BooleanLiteral(b) = ty {
-                    Some(Type::BooleanLiteral(!b))
-                } else {
-                    None
-                };
-
-                let mut to_add = ty;
-                let mut to_remove = SmallVec::<[usize; 2]>::new();
-                for (index, element) in self.elements.iter().enumerate() {
-                    if Some(*element) == bool_pair {
-                        to_add = KnownClass::Bool.to_instance(self.db);
-                        to_remove.push(index);
-                        // The type we are adding is a BooleanLiteral, which doesn't have any
-                        // subtypes. And we just found that the union already contained our
-                        // mirror-image BooleanLiteral, so it can't also contain bool or any
-                        // supertype of bool. Therefore, we are done.
-                        break;
-                    }
-                    if ty.is_subtype_of(self.db, *element) {
-                        return self;
-                    } else if element.is_subtype_of(self.db, ty) {
-                        to_remove.push(index);
-                    }
-                }
-
-                match to_remove[..] {
-                    [] => self.elements.push(to_add),
-                    [index] => self.elements[index] = to_add,
-                    _ => {
-                        let mut current_index = 0;
-                        let mut to_remove = to_remove.into_iter();
-                        let mut next_to_remove_index = to_remove.next();
-                        self.elements.retain(|_| {
-                            let retain = if Some(current_index) == next_to_remove_index {
-                                next_to_remove_index = to_remove.next();
-                                false
-                            } else {
-                                true
-                            };
-                            current_index += 1;
-                            retain
-                        });
-                        self.elements.push(to_add);
-                    }
-                }
+                self.elements.insert(ty);
             }
         }
 
         self
     }
 
-    pub(crate) fn build(self) -> Type<'db> {
+    /// Performs the following normalizations:
+    ///     - Replaces `Literal[True,False]` with `bool`.
+    ///     - TODO For enums `E` with members `X1`,...,`Xn`, replaces
+    ///     `Literal[E.X1,...,E.Xn]` with `E`.
+    fn simplify(&mut self) {
+        if let Some(true_index) = self.elements.get_index_of(&Type::BooleanLiteral(true)) {
+            if self.elements.contains(&Type::BooleanLiteral(false)) {
+                *self.elements.get_index_mut2(true_index).unwrap() =
+                    builtins_symbol_ty_by_name(self.db, "bool");
+                self.elements.remove(&Type::BooleanLiteral(false));
+            }
+        }
+    }
+
+    pub(crate) fn build(mut self) -> Type<'db> {
         match self.elements.len() {
             0 => Type::Never,
             1 => self.elements[0],
-            _ => Type::Union(UnionType::new(self.db, self.elements.into_boxed_slice())),
+            _ => {
+                self.simplify();
+
+                match self.elements.len() {
+                    0 => Type::Never,
+                    1 => self.elements[0],
+                    _ => {
+                        self.elements.shrink_to_fit();
+                        Type::Union(UnionType::new(self.db, self.elements))
+                    }
+                }
+            }
         }
     }
 }
@@ -194,12 +172,11 @@ impl<'db> IntersectionBuilder<'db> {
         if self.intersections.len() == 1 {
             self.intersections.pop().unwrap().build(self.db)
         } else {
-            UnionType::from_elements(
-                self.db,
-                self.intersections
-                    .into_iter()
-                    .map(|inner| inner.build(self.db)),
-            )
+            let mut builder = UnionBuilder::new(self.db);
+            for inner in self.intersections {
+                builder = builder.add(inner.build(self.db));
+            }
+            builder.build()
         }
     }
 }
@@ -217,7 +194,6 @@ impl<'db> InnerIntersectionBuilder<'db> {
 
     /// Adds a positive type to this intersection.
     fn add_positive(&mut self, db: &'db dyn Db, ty: Type<'db>) {
-        // TODO `Any`/`Unknown`/`Todo` actually should not self-cancel
         match ty {
             Type::Intersection(inter) => {
                 let pos = inter.positive(db);
@@ -237,7 +213,7 @@ impl<'db> InnerIntersectionBuilder<'db> {
 
     /// Adds a negative type to this intersection.
     fn add_negative(&mut self, db: &'db dyn Db, ty: Type<'db>) {
-        // TODO `Any`/`Unknown`/`Todo` actually should not self-cancel
+        // TODO Any/Unknown actually should not self-cancel
         match ty {
             Type::Intersection(intersection) => {
                 let pos = intersection.negative(db);
@@ -298,14 +274,20 @@ impl<'db> InnerIntersectionBuilder<'db> {
 
 #[cfg(test)]
 mod tests {
-    use super::{IntersectionBuilder, IntersectionType, Type, UnionType};
+    use super::{IntersectionBuilder, IntersectionType, Type, UnionBuilder, UnionType};
     use crate::db::tests::TestDb;
     use crate::program::{Program, SearchPathSettings};
     use crate::python_version::PythonVersion;
-    use crate::types::{KnownClass, UnionBuilder};
+    use crate::types::builtins_symbol_ty_by_name;
     use crate::ProgramSettings;
     use ruff_db::system::{DbWithTestSystem, SystemPathBuf};
 
+    impl<'db> UnionType<'db> {
+        fn elements_vec(self, db: &'db TestDb) -> Vec<Type<'db>> {
+            self.elements(db).into_iter().copied().collect()
+        }
+    }
+
     fn setup_db() -> TestDb {
         let db = TestDb::new();
 
@@ -331,16 +313,21 @@ mod tests {
         let db = setup_db();
         let t0 = Type::IntLiteral(0);
         let t1 = Type::IntLiteral(1);
-        let union = UnionType::from_elements(&db, [t0, t1]).expect_union();
+        let union = UnionBuilder::new(&db)
+            .add(t0)
+            .add(t1)
+            .build()
+            .expect_union();
 
-        assert_eq!(union.elements(&db), &[t0, t1]);
+        assert_eq!(union.elements_vec(&db), &[t0, t1]);
     }
 
     #[test]
     fn build_union_single() {
         let db = setup_db();
         let t0 = Type::IntLiteral(0);
-        let ty = UnionType::from_elements(&db, [t0]);
+        let ty = UnionBuilder::new(&db).add(t0).build();
+
         assert_eq!(ty, t0);
     }
 
@@ -348,6 +335,7 @@ mod tests {
     fn build_union_empty() {
         let db = setup_db();
         let ty = UnionBuilder::new(&db).build();
+
         assert_eq!(ty, Type::Never);
     }
 
@@ -355,25 +343,37 @@ mod tests {
     fn build_union_never() {
         let db = setup_db();
         let t0 = Type::IntLiteral(0);
-        let ty = UnionType::from_elements(&db, [t0, Type::Never]);
+        let ty = UnionBuilder::new(&db).add(t0).add(Type::Never).build();
+
         assert_eq!(ty, t0);
     }
 
     #[test]
     fn build_union_bool() {
         let db = setup_db();
-        let bool_instance_ty = KnownClass::Bool.to_instance(&db);
+        let bool_ty = builtins_symbol_ty_by_name(&db, "bool");
 
         let t0 = Type::BooleanLiteral(true);
         let t1 = Type::BooleanLiteral(true);
         let t2 = Type::BooleanLiteral(false);
         let t3 = Type::IntLiteral(17);
 
-        let union = UnionType::from_elements(&db, [t0, t1, t3]).expect_union();
-        assert_eq!(union.elements(&db), &[t0, t3]);
+        let union = UnionBuilder::new(&db)
+            .add(t0)
+            .add(t1)
+            .add(t3)
+            .build()
+            .expect_union();
+        assert_eq!(union.elements_vec(&db), &[t0, t3]);
+        let union = UnionBuilder::new(&db)
+            .add(t0)
+            .add(t1)
+            .add(t2)
+            .add(t3)
+            .build()
+            .expect_union();
 
-        let union = UnionType::from_elements(&db, [t0, t1, t2, t3]).expect_union();
-        assert_eq!(union.elements(&db), &[bool_instance_ty, t3]);
+        assert_eq!(union.elements_vec(&db), &[bool_ty, t3]);
     }
 
     #[test]
@@ -382,47 +382,14 @@ mod tests {
         let t0 = Type::IntLiteral(0);
         let t1 = Type::IntLiteral(1);
         let t2 = Type::IntLiteral(2);
-        let u1 = UnionType::from_elements(&db, [t0, t1]);
-        let union = UnionType::from_elements(&db, [u1, t2]).expect_union();
+        let u1 = UnionBuilder::new(&db).add(t0).add(t1).build();
+        let union = UnionBuilder::new(&db)
+            .add(u1)
+            .add(t2)
+            .build()
+            .expect_union();
 
-        assert_eq!(union.elements(&db), &[t0, t1, t2]);
-    }
-
-    #[test]
-    fn build_union_simplify_subtype() {
-        let db = setup_db();
-        let t0 = KnownClass::Str.to_instance(&db);
-        let t1 = Type::LiteralString;
-        let u0 = UnionType::from_elements(&db, [t0, t1]);
-        let u1 = UnionType::from_elements(&db, [t1, t0]);
-
-        assert_eq!(u0, t0);
-        assert_eq!(u1, t0);
-    }
-
-    #[test]
-    fn build_union_no_simplify_unknown() {
-        let db = setup_db();
-        let t0 = KnownClass::Str.to_instance(&db);
-        let t1 = Type::Unknown;
-        let u0 = UnionType::from_elements(&db, [t0, t1]);
-        let u1 = UnionType::from_elements(&db, [t1, t0]);
-
-        assert_eq!(u0.expect_union().elements(&db), &[t0, t1]);
-        assert_eq!(u1.expect_union().elements(&db), &[t1, t0]);
-    }
-
-    #[test]
-    fn build_union_subsume_multiple() {
-        let db = setup_db();
-        let str_ty = KnownClass::Str.to_instance(&db);
-        let int_ty = KnownClass::Int.to_instance(&db);
-        let object_ty = KnownClass::Object.to_instance(&db);
-        let unknown_ty = Type::Unknown;
-
-        let u0 = UnionType::from_elements(&db, [str_ty, unknown_ty, int_ty, object_ty]);
-
-        assert_eq!(u0.expect_union().elements(&db), &[unknown_ty, object_ty]);
+        assert_eq!(union.elements_vec(&db), &[t0, t1, t2]);
     }
 
     impl<'db> IntersectionType<'db> {
@@ -496,14 +463,14 @@ mod tests {
         let t0 = Type::IntLiteral(0);
         let t1 = Type::IntLiteral(1);
         let ta = Type::Any;
-        let u0 = UnionType::from_elements(&db, [t0, t1]);
+        let u0 = UnionBuilder::new(&db).add(t0).add(t1).build();
 
         let union = IntersectionBuilder::new(&db)
             .add_positive(ta)
             .add_positive(u0)
             .build()
             .expect_union();
-        let [Type::Intersection(i0), Type::Intersection(i1)] = union.elements(&db)[..] else {
+        let [Type::Intersection(i0), Type::Intersection(i1)] = union.elements_vec(&db)[..] else {
             panic!("expected a union of two intersections");
         };
         assert_eq!(i0.pos_vec(&db), &[ta, t0]);

crates/red_knot_python_semantic/src/types/display.rs

@@ -1,20 +1,19 @@
 //! Display implementations for types.
 
-use std::fmt::{self, Display, Formatter};
+use std::fmt::{Display, Formatter};
 
-use ruff_db::display::FormatterJoinExtension;
 use ruff_python_ast::str::Quote;
 use ruff_python_literal::escape::AsciiEscape;
 
 use crate::types::{IntersectionType, Type, UnionType};
-use crate::Db;
-use rustc_hash::FxHashMap;
+use crate::{Db, FxOrderMap};
 
 impl<'db> Type<'db> {
-    pub fn display(&self, db: &'db dyn Db) -> DisplayType {
+    pub fn display(&'db self, db: &'db dyn Db) -> DisplayType<'db> {
         DisplayType { ty: self, db }
     }
-    fn representation(self, db: &'db dyn Db) -> DisplayRepresentation<'db> {
+
+    fn representation(&'db self, db: &'db dyn Db) -> DisplayRepresentation<'db> {
         DisplayRepresentation { db, ty: self }
     }
 }
@@ -26,7 +25,7 @@ pub struct DisplayType<'db> {
 }
 
 impl Display for DisplayType<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         let representation = self.ty.representation(self.db);
         if matches!(
             self.ty,
@@ -37,16 +36,16 @@ impl Display for DisplayType<'_> {
                 | Type::Class(_)
                 | Type::Function(_)
         ) {
-            write!(f, "Literal[{representation}]")
+            write!(f, "Literal[{representation}]",)
         } else {
             representation.fmt(f)
         }
     }
 }
 
-impl fmt::Debug for DisplayType<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        Display::fmt(self, f)
+impl std::fmt::Debug for DisplayType<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Display::fmt(self, f)
     }
 }
 
@@ -54,21 +53,18 @@ impl fmt::Debug for DisplayType<'_> {
 /// `Literal[<repr>]` or `Literal[<repr1>, <repr2>]` for literal types or as `<repr>` for
 /// non literals
 struct DisplayRepresentation<'db> {
-    ty: Type<'db>,
+    ty: &'db Type<'db>,
     db: &'db dyn Db,
 }
 
-impl Display for DisplayRepresentation<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+impl std::fmt::Display for DisplayRepresentation<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self.ty {
             Type::Any => f.write_str("Any"),
             Type::Never => f.write_str("Never"),
             Type::Unknown => f.write_str("Unknown"),
             Type::Unbound => f.write_str("Unbound"),
             Type::None => f.write_str("None"),
-            // `[Type::Todo]`'s display should be explicit that is not a valid display of
-            // any other type
-            Type::Todo => f.write_str("@Todo"),
             Type::Module(file) => {
                 write!(f, "<module '{:?}'>", file.path(self.db))
             }
@@ -78,8 +74,8 @@ impl Display for DisplayRepresentation<'_> {
             Type::Function(function) => f.write_str(function.name(self.db)),
             Type::Union(union) => union.display(self.db).fmt(f),
             Type::Intersection(intersection) => intersection.display(self.db).fmt(f),
-            Type::IntLiteral(n) => n.fmt(f),
-            Type::BooleanLiteral(boolean) => f.write_str(if boolean { "True" } else { "False" }),
+            Type::IntLiteral(n) => write!(f, "{n}"),
+            Type::BooleanLiteral(boolean) => f.write_str(if *boolean { "True" } else { "False" }),
             Type::StringLiteral(string) => {
                 write!(f, r#""{}""#, string.value(self.db).replace('"', r#"\""#))
             }
@@ -90,16 +86,6 @@ impl Display for DisplayRepresentation<'_> {
 
                 escape.bytes_repr().write(f)
             }
-            Type::Tuple(tuple) => {
-                f.write_str("tuple[")?;
-                let elements = tuple.elements(self.db);
-                if elements.is_empty() {
-                    f.write_str("()")?;
-                } else {
-                    elements.display(self.db).fmt(f)?;
-                }
-                f.write_str("]")
-            }
         }
     }
 }
@@ -116,11 +102,11 @@ struct DisplayUnionType<'db> {
 }
 
 impl Display for DisplayUnionType<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         let elements = self.ty.elements(self.db);
 
         // Group literal types by kind.
-        let mut grouped_literals = FxHashMap::default();
+        let mut grouped_literals = FxOrderMap::default();
 
         for element in elements {
             if let Ok(literal_kind) = LiteralTypeKind::try_from(*element) {
@@ -131,26 +117,42 @@ impl Display for DisplayUnionType<'_> {
             }
         }
 
-        let mut join = f.join(" | ");
+        let mut first = true;
 
-        for element in elements {
-            if let Ok(literal_kind) = LiteralTypeKind::try_from(*element) {
+        // Print all types, but write all literals together (while preserving their position).
+        for ty in elements {
+            if let Ok(literal_kind) = LiteralTypeKind::try_from(*ty) {
                 let Some(mut literals) = grouped_literals.remove(&literal_kind) else {
                     continue;
                 };
+
+                if !first {
+                    f.write_str(" | ")?;
+                };
+
+                f.write_str("Literal[")?;
+
                 if literal_kind == LiteralTypeKind::IntLiteral {
                     literals.sort_unstable_by_key(|ty| ty.expect_int_literal());
                 }
-                join.entry(&DisplayLiteralGroup {
-                    literals,
-                    db: self.db,
-                });
-            } else {
-                join.entry(&element.display(self.db));
-            }
-        }
 
-        join.finish()?;
+                for (i, literal_ty) in literals.iter().enumerate() {
+                    if i > 0 {
+                        f.write_str(", ")?;
+                    }
+                    literal_ty.representation(self.db).fmt(f)?;
+                }
+                f.write_str("]")?;
+            } else {
+                if !first {
+                    f.write_str(" | ")?;
+                };
+
+                ty.display(self.db).fmt(f)?;
+            }
+
+            first = false;
+        }
 
         debug_assert!(grouped_literals.is_empty());
 
@@ -158,24 +160,9 @@ impl Display for DisplayUnionType<'_> {
     }
 }
 
-impl fmt::Debug for DisplayUnionType<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        Display::fmt(self, f)
-    }
-}
-
-struct DisplayLiteralGroup<'db> {
-    literals: Vec<Type<'db>>,
-    db: &'db dyn Db,
-}
-
-impl Display for DisplayLiteralGroup<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        f.write_str("Literal[")?;
-        f.join(", ")
-            .entries(self.literals.iter().map(|ty| ty.representation(self.db)))
-            .finish()?;
-        f.write_str("]")
+impl std::fmt::Debug for DisplayUnionType<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Display::fmt(self, f)
     }
 }
 
@@ -215,77 +202,31 @@ struct DisplayIntersectionType<'db> {
 }
 
 impl Display for DisplayIntersectionType<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        let tys = self
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        let mut first = true;
+        for (neg, ty) in self
             .ty
             .positive(self.db)
             .iter()
-            .map(|&ty| DisplayMaybeNegatedType {
-                ty,
-                db: self.db,
-                negated: false,
-            })
-            .chain(
-                self.ty
-                    .negative(self.db)
-                    .iter()
-                    .map(|&ty| DisplayMaybeNegatedType {
-                        ty,
-                        db: self.db,
-                        negated: true,
-                    }),
-            );
-        f.join(" & ").entries(tys).finish()
-    }
-}
-
-impl fmt::Debug for DisplayIntersectionType<'_> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        Display::fmt(self, f)
-    }
-}
-
-struct DisplayMaybeNegatedType<'db> {
-    ty: Type<'db>,
-    db: &'db dyn Db,
-    negated: bool,
-}
-
-impl<'db> Display for DisplayMaybeNegatedType<'db> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        if self.negated {
-            f.write_str("~")?;
+            .map(|ty| (false, ty))
+            .chain(self.ty.negative(self.db).iter().map(|ty| (true, ty)))
+        {
+            if !first {
+                f.write_str(" & ")?;
+            };
+            first = false;
+            if neg {
+                f.write_str("~")?;
+            };
+            write!(f, "{}", ty.display(self.db))?;
         }
-        self.ty.display(self.db).fmt(f)
+        Ok(())
     }
 }
 
-pub(crate) trait TypeArrayDisplay<'db> {
-    fn display(&self, db: &'db dyn Db) -> DisplayTypeArray;
-}
-
-impl<'db> TypeArrayDisplay<'db> for Box<[Type<'db>]> {
-    fn display(&self, db: &'db dyn Db) -> DisplayTypeArray {
-        DisplayTypeArray { types: self, db }
-    }
-}
-
-impl<'db> TypeArrayDisplay<'db> for Vec<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,
-}
-
-impl<'db> Display for DisplayTypeArray<'_, 'db> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        f.join(", ")
-            .entries(self.types.iter().map(|ty| ty.display(self.db)))
-            .finish()
+impl std::fmt::Debug for DisplayIntersectionType<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Display::fmt(self, f)
     }
 }
 
@@ -295,7 +236,9 @@ mod tests {
     use ruff_db::system::{DbWithTestSystem, SystemPathBuf};
 
     use crate::db::tests::TestDb;
-    use crate::types::{global_symbol_ty, BytesLiteralType, StringLiteralType, Type, UnionType};
+    use crate::types::{
+        global_symbol_ty_by_name, BytesLiteralType, StringLiteralType, Type, UnionBuilder,
+    };
     use crate::{Program, ProgramSettings, PythonVersion, SearchPathSettings};
 
     fn setup_db() -> TestDb {
@@ -335,25 +278,28 @@ mod tests {
             class B: ...
             ",
         )?;
-        let mod_file = system_path_to_file(&db, "src/main.py").expect("file to exist");
+        let mod_file = system_path_to_file(&db, "src/main.py").expect("Expected file to exist.");
 
-        let union_elements = &[
+        let vec: Vec<Type<'_>> = vec![
             Type::Unknown,
             Type::IntLiteral(-1),
-            global_symbol_ty(&db, mod_file, "A"),
-            Type::StringLiteral(StringLiteralType::new(&db, "A")),
-            Type::BytesLiteral(BytesLiteralType::new(&db, [0u8].as_slice())),
-            Type::BytesLiteral(BytesLiteralType::new(&db, [7u8].as_slice())),
+            global_symbol_ty_by_name(&db, mod_file, "A"),
+            Type::StringLiteral(StringLiteralType::new(&db, Box::from("A"))),
+            Type::BytesLiteral(BytesLiteralType::new(&db, Box::from([0]))),
+            Type::BytesLiteral(BytesLiteralType::new(&db, Box::from([7]))),
             Type::IntLiteral(0),
             Type::IntLiteral(1),
-            Type::StringLiteral(StringLiteralType::new(&db, "B")),
-            global_symbol_ty(&db, mod_file, "foo"),
-            global_symbol_ty(&db, mod_file, "bar"),
-            global_symbol_ty(&db, mod_file, "B"),
+            Type::StringLiteral(StringLiteralType::new(&db, Box::from("B"))),
+            global_symbol_ty_by_name(&db, mod_file, "foo"),
+            global_symbol_ty_by_name(&db, mod_file, "bar"),
+            global_symbol_ty_by_name(&db, mod_file, "B"),
             Type::BooleanLiteral(true),
             Type::None,
         ];
-        let union = UnionType::from_elements(&db, union_elements).expect_union();
+        let builder = vec.iter().fold(UnionBuilder::new(&db), |builder, literal| {
+            builder.add(*literal)
+        });
+        let union = builder.build().expect_union();
         let display = format!("{}", union.display(&db));
         assert_eq!(
             display,