Bump version to v0.4.9 (#11872)

## Summary

This PR makes the `ruff_db` a required crate for `ruff_python_semantic`.

Refer
https://github.com/astral-sh/ruff/actions/runs/9516626143/job/26233307158?pr=11872

## Test Plan

1. `maturin sdist --out dist`
2. `tar -xf dist/ruff-0.4.8.tar.gz --directory=dist/ruff-0.4.8`
3. `pip install dist/ruff-0.4.8.tar.gz` works

.cargo/config.toml

@@ -1,3 +1,10 @@
 [alias]
 dev = "run --package ruff_dev --bin ruff_dev"
 benchmark = "bench -p ruff_benchmark --bench linter --bench formatter --"
+
+# statically link the C runtime so the executable does not depend on
+# that shared/dynamic library.
+#
+# See: https://github.com/astral-sh/ruff/issues/11503
+[target.'cfg(all(target_env="msvc", target_os = "windows"))']
+rustflags = ["-C", "target-feature=+crt-static"]

.github/CODEOWNERS

@@ -15,3 +15,6 @@
 
 # Script for fuzzing the parser
 /scripts/fuzz-parser/ @AlexWaygood
+
+# red-knot
+/crates/red_knot/ @carljm @MichaReiser

.github/renovate.json5

@@ -41,6 +41,13 @@
       description: "Disable PRs updating GitHub runners (e.g. 'runs-on: macos-14')",
       enabled: false,
     },
+    {
+      // Disable updates of `zip-rs`; intentionally pinned for now due to ownership change
+      // See: https://github.com/astral-sh/uv/issues/3642
+      matchPackagePatterns: ["zip"],
+      matchManagers: ["cargo"],
+      enabled: false,
+    },
     {
       groupName: "pre-commit dependencies",
       matchManagers: ["pre-commit"],

.github/workflows/ci.yaml

@@ -167,6 +167,9 @@ jobs:
       - uses: Swatinem/rust-cache@v2
       - name: "Run tests"
         shell: bash
+        env:
+          # Workaround for <https://github.com/nextest-rs/nextest/issues/1493>.
+          RUSTUP_WINDOWS_PATH_ADD_BIN: 1
         run: |
           cargo nextest run --all-features --profile ci
           cargo test --all-features --doc
@@ -209,6 +212,38 @@ jobs:
       - name: "Build"
         run: cargo build --release --locked
 
+  cargo-build-msrv:
+    name: "cargo build (msrv)"
+    runs-on: ubuntu-latest
+    needs: determine_changes
+    if: ${{ needs.determine_changes.outputs.code == 'true' || github.ref == 'refs/heads/main' }}
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@v4
+      - uses: SebRollen/toml-action@v1.2.0
+        id: msrv
+        with:
+          file: "Cargo.toml"
+          field: "workspace.package.rust-version"
+      - name: "Install Rust toolchain"
+        run: rustup default ${{ steps.msrv.outputs.value }}
+      - name: "Install mold"
+        uses: rui314/setup-mold@v1
+      - name: "Install cargo nextest"
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-nextest
+      - name: "Install cargo insta"
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-insta
+      - uses: Swatinem/rust-cache@v2
+      - name: "Run tests"
+        shell: bash
+        env:
+          NEXTEST_PROFILE: "ci"
+        run: cargo +${{ steps.msrv.outputs.value }} insta test --all-features --unreferenced reject --test-runner nextest
+
   cargo-fuzz:
     name: "cargo fuzz"
     runs-on: ubuntu-latest
@@ -303,7 +338,7 @@ jobs:
           name: ruff
           path: target/debug
 
-      - uses: dawidd6/action-download-artifact@v3
+      - uses: dawidd6/action-download-artifact@v5
         name: Download baseline Ruff binary
         with:
           name: ruff

.github/workflows/docs.yaml

@@ -47,7 +47,7 @@ jobs:
         run: mkdocs build --strict -f mkdocs.public.yml
       - name: "Deploy to Cloudflare Pages"
         if: ${{ env.CF_API_TOKEN_EXISTS == 'true' }}
-        uses: cloudflare/wrangler-action@v3.5.0
+        uses: cloudflare/wrangler-action@v3.6.1
         with:
           apiToken: ${{ secrets.CF_API_TOKEN }}
           accountId: ${{ secrets.CF_ACCOUNT_ID }}

.github/workflows/playground.yaml

@@ -40,7 +40,7 @@ jobs:
         working-directory: playground
       - name: "Deploy to Cloudflare Pages"
         if: ${{ env.CF_API_TOKEN_EXISTS == 'true' }}
-        uses: cloudflare/wrangler-action@v3.5.0
+        uses: cloudflare/wrangler-action@v3.6.1
         with:
           apiToken: ${{ secrets.CF_API_TOKEN }}
           accountId: ${{ secrets.CF_ACCOUNT_ID }}

.github/workflows/pr-comment.yaml

@@ -17,7 +17,7 @@ jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-      - uses: dawidd6/action-download-artifact@v3
+      - uses: dawidd6/action-download-artifact@v5
         name: Download pull request number
         with:
           name: pr-number
@@ -32,7 +32,7 @@ jobs:
             echo "pr-number=$(<pr-number)" >> $GITHUB_OUTPUT
           fi
 
-      - uses: dawidd6/action-download-artifact@v3
+      - uses: dawidd6/action-download-artifact@v5
         name: "Download ecosystem results"
         id: download-ecosystem-result
         if: steps.pr-number.outputs.pr-number

.github/workflows/release.yaml

@@ -163,6 +163,9 @@ jobs:
         with:
           target: ${{ matrix.platform.target }}
           args: --release --locked --out dist
+        env:
+          # aarch64 build fails, see https://github.com/PyO3/maturin/issues/2110
+          XWIN_VERSION: 16
       - name: "Test wheel"
         if: ${{ !startsWith(matrix.platform.target, 'aarch64') }}
         shell: bash

.pre-commit-config.yaml

@@ -14,7 +14,7 @@ exclude: |
 
 repos:
   - repo: https://github.com/abravalheri/validate-pyproject
-    rev: v0.17
+    rev: v0.18
     hooks:
       - id: validate-pyproject
 
@@ -32,7 +32,7 @@ repos:
           )$
 
   - repo: https://github.com/igorshubovych/markdownlint-cli
-    rev: v0.40.0
+    rev: v0.41.0
     hooks:
       - id: markdownlint-fix
         exclude: |
@@ -42,7 +42,7 @@ repos:
           )$
 
   - repo: https://github.com/crate-ci/typos
-    rev: v1.21.0
+    rev: v1.22.3
     hooks:
       - id: typos
 
@@ -56,7 +56,7 @@ repos:
         pass_filenames: false # This makes it a lot faster
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.4.4
+    rev: v0.4.8
     hooks:
       - id: ruff-format
       - id: ruff

.vscode/extensions.json

@@ -0,0 +1,5 @@
+{
+    "recommendations": [
+        "rust-lang.rust-analyzer"
+    ]
+}

.vscode/settings.json

@@ -0,0 +1,6 @@
+{
+    "rust-analyzer.check.extraArgs": [
+        "--all-features"
+    ],
+    "rust-analyzer.check.command": "clippy",
+}

CHANGELOG.md

@@ -1,5 +1,196 @@
 # Changelog
 
+## 0.4.9
+
+### Preview features
+
+- \[`pylint`\] Implement `consider-dict-items` (`C0206`) ([#11688](https://github.com/astral-sh/ruff/pull/11688))
+- \[`refurb`\] Implement `repeated-global` (`FURB154`) ([#11187](https://github.com/astral-sh/ruff/pull/11187))
+
+### Rule changes
+
+- \[`pycodestyle`\] Adapt fix for `E203` to work identical to `ruff format` ([#10999](https://github.com/astral-sh/ruff/pull/10999))
+
+### Formatter
+
+- Fix formatter instability for lines only consisting of zero-width characters ([#11748](https://github.com/astral-sh/ruff/pull/11748))
+
+### Server
+
+- Add supported commands in server capabilities ([#11850](https://github.com/astral-sh/ruff/pull/11850))
+- Use real file path when available in `ruff server` ([#11800](https://github.com/astral-sh/ruff/pull/11800))
+- Improve error message when a command is run on an unavailable document ([#11823](https://github.com/astral-sh/ruff/pull/11823))
+- Introduce the `ruff.printDebugInformation` command ([#11831](https://github.com/astral-sh/ruff/pull/11831))
+- Tracing system now respects log level and trace level, with options to log to a file ([#11747](https://github.com/astral-sh/ruff/pull/11747))
+
+### CLI
+
+- Handle non-printable characters in diff view ([#11687](https://github.com/astral-sh/ruff/pull/11687))
+
+### Bug fixes
+
+- \[`refurb`\] Avoid suggesting starmap when arguments are used outside call (`FURB140`) ([#11830](https://github.com/astral-sh/ruff/pull/11830))
+- \[`flake8-bugbear`\] Avoid panic in `B909` when checking large loop blocks ([#11772](https://github.com/astral-sh/ruff/pull/11772))
+- \[`refurb`\] Fix misbehavior of `operator.itemgetter` when getter param is a tuple (`FURB118`) ([#11774](https://github.com/astral-sh/ruff/pull/11774))
+
+## 0.4.8
+
+### Performance
+
+- Linter performance has been improved by around 10% on some microbenchmarks by refactoring the lexer and parser to maintain synchronicity between them ([#11457](https://github.com/astral-sh/ruff/pull/11457))
+
+### Preview features
+
+- \[`flake8-bugbear`\] Implement `return-in-generator` (`B901`) ([#11644](https://github.com/astral-sh/ruff/pull/11644))
+- \[`flake8-pyi`\] Implement `PYI063` ([#11699](https://github.com/astral-sh/ruff/pull/11699))
+- \[`pygrep_hooks`\] Check blanket ignores via file-level pragmas (`PGH004`) ([#11540](https://github.com/astral-sh/ruff/pull/11540))
+
+### Rule changes
+
+- \[`pyupgrade`\] Update `UP035` for Python 3.13 and the latest version of `typing_extensions` ([#11693](https://github.com/astral-sh/ruff/pull/11693))
+- \[`numpy`\] Update `NPY001` rule for NumPy 2.0 ([#11735](https://github.com/astral-sh/ruff/pull/11735))
+
+### Server
+
+- Formatting a document with syntax problems no longer spams a visible error popup ([#11745](https://github.com/astral-sh/ruff/pull/11745))
+
+### CLI
+
+- Add RDJson support for `--output-format` flag ([#11682](https://github.com/astral-sh/ruff/pull/11682))
+
+### Bug fixes
+
+- \[`pyupgrade`\] Write empty string in lieu of panic when fixing `UP032` ([#11696](https://github.com/astral-sh/ruff/pull/11696))
+- \[`flake8-simplify`\] Simplify double negatives in `SIM103` ([#11684](https://github.com/astral-sh/ruff/pull/11684))
+- Ensure the expression generator adds a newline before `type` statements ([#11720](https://github.com/astral-sh/ruff/pull/11720))
+- Respect per-file ignores for blanket and redirected noqa rules ([#11728](https://github.com/astral-sh/ruff/pull/11728))
+
+## 0.4.7
+
+### Preview features
+
+- \[`flake8-pyi`\] Implement `PYI064` ([#11325](https://github.com/astral-sh/ruff/pull/11325))
+- \[`flake8-pyi`\] Implement `PYI066` ([#11541](https://github.com/astral-sh/ruff/pull/11541))
+- \[`flake8-pyi`\] Implement `PYI057` ([#11486](https://github.com/astral-sh/ruff/pull/11486))
+- \[`pyflakes`\] Enable `F822` in `__init__.py` files by default ([#11370](https://github.com/astral-sh/ruff/pull/11370))
+
+### Formatter
+
+- Fix incorrect placement of trailing stub function comments ([#11632](https://github.com/astral-sh/ruff/pull/11632))
+
+### Server
+
+- Respect file exclusions in `ruff server` ([#11590](https://github.com/astral-sh/ruff/pull/11590))
+- Add support for documents not exist on disk ([#11588](https://github.com/astral-sh/ruff/pull/11588))
+- Add Vim and Kate setup guide for `ruff server` ([#11615](https://github.com/astral-sh/ruff/pull/11615))
+
+### Bug fixes
+
+- Avoid removing newlines between docstring headers and rST blocks ([#11609](https://github.com/astral-sh/ruff/pull/11609))
+- Infer indentation with imports when logical indent is absent ([#11608](https://github.com/astral-sh/ruff/pull/11608))
+- Use char index rather than position for indent slice ([#11645](https://github.com/astral-sh/ruff/pull/11645))
+- \[`flake8-comprehension`\] Strip parentheses around generators in `C400` ([#11607](https://github.com/astral-sh/ruff/pull/11607))
+- Mark `repeated-isinstance-calls` as unsafe on Python 3.10 and later ([#11622](https://github.com/astral-sh/ruff/pull/11622))
+
+## 0.4.6
+
+### Breaking changes
+
+- Use project-relative paths when calculating GitLab fingerprints ([#11532](https://github.com/astral-sh/ruff/pull/11532))
+- Bump minimum supported Windows version to Windows 10 ([#11613](https://github.com/astral-sh/ruff/pull/11613))
+
+### Preview features
+
+- \[`flake8-async`\] Sleep with >24 hour interval should usually sleep forever (`ASYNC116`) ([#11498](https://github.com/astral-sh/ruff/pull/11498))
+
+### Rule changes
+
+- \[`numpy`\] Add missing functions to NumPy 2.0 migration rule ([#11528](https://github.com/astral-sh/ruff/pull/11528))
+- \[`mccabe`\] Consider irrefutable pattern similar to `if .. else` for `C901` ([#11565](https://github.com/astral-sh/ruff/pull/11565))
+- Consider `match`-`case` statements for `C901`, `PLR0912`, and `PLR0915` ([#11521](https://github.com/astral-sh/ruff/pull/11521))
+- Remove empty strings when converting to f-string (`UP032`) ([#11524](https://github.com/astral-sh/ruff/pull/11524))
+- \[`flake8-bandit`\] `request-without-timeout` should warn for `requests.request` ([#11548](https://github.com/astral-sh/ruff/pull/11548))
+- \[`flake8-self`\] Ignore sunder accesses in `flake8-self` rules ([#11546](https://github.com/astral-sh/ruff/pull/11546))
+- \[`pyupgrade`\] Lint for `TypeAliasType` usages (`UP040`) ([#11530](https://github.com/astral-sh/ruff/pull/11530))
+
+### Server
+
+- Respect excludes in `ruff server` configuration discovery ([#11551](https://github.com/astral-sh/ruff/pull/11551))
+- Use default settings if initialization options is empty or not provided ([#11566](https://github.com/astral-sh/ruff/pull/11566))
+- `ruff server` correctly treats `.pyi` files as stub files ([#11535](https://github.com/astral-sh/ruff/pull/11535))
+- `ruff server` searches for configuration in parent directories ([#11537](https://github.com/astral-sh/ruff/pull/11537))
+- `ruff server`: An empty code action filter no longer returns notebook source actions ([#11526](https://github.com/astral-sh/ruff/pull/11526))
+
+### Bug fixes
+
+- \[`flake8-logging-format`\] Fix autofix title in `logging-warn` (`G010`) ([#11514](https://github.com/astral-sh/ruff/pull/11514))
+- \[`refurb`\] Avoid recommending `operator.itemgetter` with dependence on lambda arguments ([#11574](https://github.com/astral-sh/ruff/pull/11574))
+- \[`flake8-simplify`\] Avoid recommending context manager in `__enter__` implementations ([#11575](https://github.com/astral-sh/ruff/pull/11575))
+- Create intermediary directories for `--output-file` ([#11550](https://github.com/astral-sh/ruff/pull/11550))
+- Propagate reads on global variables ([#11584](https://github.com/astral-sh/ruff/pull/11584))
+- Treat all `singledispatch` arguments as runtime-required ([#11523](https://github.com/astral-sh/ruff/pull/11523))
+
+## 0.4.5
+
+### Ruff's language server is now in Beta
+
+`v0.4.5` marks the official Beta release of `ruff server`, an integrated language server built into Ruff.
+`ruff server` supports the same feature set as `ruff-lsp`, powering linting, formatting, and
+code fixes in Ruff's editor integrations -- but with superior performance and
+no installation required. We'd love your feedback!
+
+You can enable `ruff server` in the [VS Code extension](https://github.com/astral-sh/ruff-vscode?tab=readme-ov-file#enabling-the-rust-based-language-server) today.
+
+To read more about this exciting milestone, check out our [blog post](https://astral.sh/blog/ruff-v0.4.5)!
+
+### Rule changes
+
+- \[`flake8-future-annotations`\] Reword `future-rewritable-type-annotation` (`FA100`) message ([#11381](https://github.com/astral-sh/ruff/pull/11381))
+- \[`isort`\] Expanded the set of standard-library modules to include `_string`, etc. ([#11374](https://github.com/astral-sh/ruff/pull/11374))
+- \[`pycodestyle`\] Consider soft keywords for `E27` rules ([#11446](https://github.com/astral-sh/ruff/pull/11446))
+- \[`pyflakes`\] Recommend adding unused import bindings to `__all__` ([#11314](https://github.com/astral-sh/ruff/pull/11314))
+- \[`pyflakes`\] Update documentation and deprecate `ignore_init_module_imports` ([#11436](https://github.com/astral-sh/ruff/pull/11436))
+- \[`pyupgrade`\] Mark quotes as unnecessary for non-evaluated annotations ([#11485](https://github.com/astral-sh/ruff/pull/11485))
+
+### Formatter
+
+- Avoid multiline quotes warning with `quote-style = preserve` ([#11490](https://github.com/astral-sh/ruff/pull/11490))
+
+### Server
+
+- Support Jupyter Notebook files ([#11206](https://github.com/astral-sh/ruff/pull/11206))
+- Support `noqa` comment code actions ([#11276](https://github.com/astral-sh/ruff/pull/11276))
+- Fix automatic configuration reloading ([#11492](https://github.com/astral-sh/ruff/pull/11492))
+- Fix several issues with configuration in Neovim and Helix ([#11497](https://github.com/astral-sh/ruff/pull/11497))
+
+### CLI
+
+- Add `--output-format` as a CLI option for `ruff config` ([#11438](https://github.com/astral-sh/ruff/pull/11438))
+
+### Bug fixes
+
+- Avoid `PLE0237` for property with setter ([#11377](https://github.com/astral-sh/ruff/pull/11377))
+- Avoid `TCH005` for `if` stmt with `elif`/`else` block ([#11376](https://github.com/astral-sh/ruff/pull/11376))
+- Avoid flagging `__future__` annotations as required for non-evaluated type annotations ([#11414](https://github.com/astral-sh/ruff/pull/11414))
+- Check for ruff executable in 'bin' directory as installed by 'pip install --target'. ([#11450](https://github.com/astral-sh/ruff/pull/11450))
+- Sort edits prior to deduplicating in quotation fix ([#11452](https://github.com/astral-sh/ruff/pull/11452))
+- Treat escaped newline as valid sequence ([#11465](https://github.com/astral-sh/ruff/pull/11465))
+- \[`flake8-pie`\] Preserve parentheses in `unnecessary-dict-kwargs` ([#11372](https://github.com/astral-sh/ruff/pull/11372))
+- \[`pylint`\] Ignore `__slots__` with dynamic values ([#11488](https://github.com/astral-sh/ruff/pull/11488))
+- \[`pylint`\] Remove `try` body from branch counting ([#11487](https://github.com/astral-sh/ruff/pull/11487))
+- \[`refurb`\] Respect operator precedence in `FURB110` ([#11464](https://github.com/astral-sh/ruff/pull/11464))
+
+### Documentation
+
+- Add `--preview` to the README ([#11395](https://github.com/astral-sh/ruff/pull/11395))
+- Add Python 3.13 to list of allowed Python versions ([#11411](https://github.com/astral-sh/ruff/pull/11411))
+- Simplify Neovim setup documentation ([#11489](https://github.com/astral-sh/ruff/pull/11489))
+- Update CONTRIBUTING.md to reflect the new parser ([#11434](https://github.com/astral-sh/ruff/pull/11434))
+- Update server documentation with new migration guide ([#11499](https://github.com/astral-sh/ruff/pull/11499))
+- \[`pycodestyle`\] Clarify motivation for `E713` and `E714` ([#11483](https://github.com/astral-sh/ruff/pull/11483))
+- \[`pyflakes`\] Update docs to describe WAI behavior (F541) ([#11362](https://github.com/astral-sh/ruff/pull/11362))
+- \[`pylint`\] Clearly indicate what is counted as a branch ([#11423](https://github.com/astral-sh/ruff/pull/11423))
+
 ## 0.4.4
 
 ### Preview features
@@ -74,6 +265,10 @@
 - Avoid allocations for isort module names ([#11251](https://github.com/astral-sh/ruff/pull/11251))
 - Build a separate ARM wheel for macOS ([#11149](https://github.com/astral-sh/ruff/pull/11149))
 
+### Windows
+
+- Increase the minimum requirement to Windows 10.
+
 ## 0.4.2
 
 ### Rule changes

CONTRIBUTING.md

@@ -101,6 +101,8 @@ pre-commit run --all-files --show-diff-on-failure  # Rust and Python formatting,
 These checks will run on GitHub Actions when you open your pull request, but running them locally
 will save you time and expedite the merge process.
 
+If you're using VS Code, you can also install the recommended [rust-analyzer](https://marketplace.visualstudio.com/items?itemName=rust-lang.rust-analyzer) extension to get these checks while editing.
+
 Note that many code changes also require updating the snapshot tests, which is done interactively
 after running `cargo test` like so:
 

Cargo.toml

@@ -4,7 +4,7 @@ resolver = "2"
 
 [workspace.package]
 edition = "2021"
-rust-version = "1.71"
+rust-version = "1.75"
 homepage = "https://docs.astral.sh/ruff"
 documentation = "https://docs.astral.sh/ruff"
 repository = "https://github.com/astral-sh/ruff"
@@ -14,6 +14,7 @@ license = "MIT"
 [workspace.dependencies]
 ruff = { path = "crates/ruff" }
 ruff_cache = { path = "crates/ruff_cache" }
+ruff_db = { path = "crates/ruff_db" }
 ruff_diagnostics = { path = "crates/ruff_diagnostics" }
 ruff_formatter = { path = "crates/ruff_formatter" }
 ruff_index = { path = "crates/ruff_index" }
@@ -42,6 +43,7 @@ bincode = { version = "1.3.3" }
 bitflags = { version = "2.5.0" }
 bstr = { version = "1.9.1" }
 cachedir = { version = "0.3.1" }
+camino = { version = "1.1.7" }
 chrono = { version = "0.4.35", default-features = false, features = ["clock"] }
 clap = { version = "4.5.3", features = ["derive"] }
 clap_complete_command = { version = "0.5.1" }
@@ -62,7 +64,6 @@ filetime = { version = "0.2.23" }
 glob = { version = "0.3.1" }
 globset = { version = "0.4.14" }
 hashbrown = "0.14.3"
-hexf-parse = { version = "0.2.1" }
 ignore = { version = "0.4.22" }
 imara-diff = { version = "0.1.5" }
 imperative = { version = "1.0.4" }
@@ -73,15 +74,16 @@ insta = { version = "1.35.1", feature = ["filters", "glob"] }
 insta-cmd = { version = "0.6.0" }
 is-macro = { version = "0.3.5" }
 is-wsl = { version = "0.4.0" }
-itertools = { version = "0.12.1" }
+itertools = { version = "0.13.0" }
 js-sys = { version = "0.3.69" }
 jod-thread = { version = "0.1.2" }
-lexical-parse-float = { version = "0.8.0", features = ["format"] }
 libc = { version = "0.2.153" }
 libcst = { version = "1.1.0", default-features = false }
 log = { version = "0.4.17" }
 lsp-server = { version = "0.7.6" }
-lsp-types = { version = "0.95.0", features = ["proposed"] }
+lsp-types = { git = "https://github.com/astral-sh/lsp-types.git", rev = "3512a9f", features = [
+  "proposed",
+] }
 matchit = { version = "0.8.1" }
 memchr = { version = "2.7.1" }
 mimalloc = { version = "0.1.39" }
@@ -101,15 +103,17 @@ quote = { version = "1.0.23" }
 rand = { version = "0.8.5" }
 rayon = { version = "1.10.0" }
 regex = { version = "1.10.2" }
-result-like = { version = "0.5.0" }
 rustc-hash = { version = "1.1.0" }
+salsa = { git = "https://github.com/salsa-rs/salsa.git", package = "salsa-2022", rev = "05b4e3ebdcdc47730cdd359e7e97fb2470527279" }
 schemars = { version = "0.8.16" }
 seahash = { version = "4.1.0" }
 serde = { version = "1.0.197", features = ["derive"] }
 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"] }
+serde_with = { version = "3.6.0", default-features = false, features = [
+  "macros",
+] }
 shellexpand = { version = "3.0.0" }
 similar = { version = "2.4.0", features = ["inline"] }
 smallvec = { version = "1.13.2" }
@@ -134,11 +138,17 @@ unicode_names2 = { version = "1.2.2" }
 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"] }
+uuid = { version = "1.6.1", features = [
+  "v4",
+  "fast-rng",
+  "macro-diagnostics",
+  "js",
+] }
 walkdir = { version = "2.3.2" }
 wasm-bindgen = { version = "0.2.92" }
 wasm-bindgen-test = { version = "0.3.42" }
 wild = { version = "2" }
+zip = { version = "0.6.6", default-features = false, features = ["zstd"] }
 
 [workspace.lints.rust]
 unsafe_code = "warn"

README.md

@@ -28,7 +28,7 @@ An extremely fast Python linter and code formatter, written in Rust.
 - ⚡️ 10-100x faster than existing linters (like Flake8) and formatters (like Black)
 - 🐍 Installable via `pip`
 - 🛠️ `pyproject.toml` support
-- 🤝 Python 3.12 compatibility
+- 🤝 Python 3.13 compatibility
 - ⚖️ Drop-in parity with [Flake8](https://docs.astral.sh/ruff/faq/#how-does-ruff-compare-to-flake8), isort, and Black
 - 📦 Built-in caching, to avoid re-analyzing unchanged files
 - 🔧 Fix support, for automatic error correction (e.g., automatically remove unused imports)
@@ -152,7 +152,7 @@ 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: v0.4.4
+  rev: v0.4.9
   hooks:
     # Run the linter.
     - id: ruff
@@ -408,6 +408,7 @@ Ruff is used by a number of major open-source projects and companies, including:
 - [Dagster](https://github.com/dagster-io/dagster)
 - Databricks ([MLflow](https://github.com/mlflow/mlflow))
 - [FastAPI](https://github.com/tiangolo/fastapi)
+- [Godot](https://github.com/godotengine/godot)
 - [Gradio](https://github.com/gradio-app/gradio)
 - [Great Expectations](https://github.com/great-expectations/great_expectations)
 - [HTTPX](https://github.com/encode/httpx)
@@ -433,6 +434,7 @@ Ruff is used by a number of major open-source projects and companies, including:
 - Modern Treasury ([Python SDK](https://github.com/Modern-Treasury/modern-treasury-python))
 - Mozilla ([Firefox](https://github.com/mozilla/gecko-dev))
 - [Mypy](https://github.com/python/mypy)
+- [Nautobot](https://github.com/nautobot/nautobot)
 - Netflix ([Dispatch](https://github.com/Netflix/dispatch))
 - [Neon](https://github.com/neondatabase/neon)
 - [Nokia](https://nokia.com/)
@@ -467,6 +469,7 @@ Ruff is used by a number of major open-source projects and companies, including:
 - [Sphinx](https://github.com/sphinx-doc/sphinx)
 - [Stable Baselines3](https://github.com/DLR-RM/stable-baselines3)
 - [Starlette](https://github.com/encode/starlette)
+- [Streamlit](https://github.com/streamlit/streamlit)
 - [The Algorithms](https://github.com/TheAlgorithms/Python)
 - [Vega-Altair](https://github.com/altair-viz/altair)
 - WordPress ([Openverse](https://github.com/WordPress/openverse))

crates/red_knot/Cargo.toml

@@ -14,6 +14,7 @@ license.workspace = true
 [dependencies]
 ruff_python_parser = { workspace = true }
 ruff_python_ast = { workspace = true }
+ruff_python_stdlib = { workspace = true }
 ruff_text_size = { workspace = true }
 ruff_index = { workspace = true }
 ruff_notebook = { workspace = true }
@@ -25,6 +26,7 @@ ctrlc = { version = "3.4.4" }
 dashmap = { workspace = true }
 hashbrown = { workspace = true }
 indexmap = { workspace = true }
+is-macro = { workspace = true }
 notify = { workspace = true }
 parking_lot = { workspace = true }
 rayon = { workspace = true }
@@ -33,9 +35,14 @@ smol_str = { version = "0.2.1" }
 tracing = { workspace = true }
 tracing-subscriber = { workspace = true }
 tracing-tree = { workspace = true }
+zip = { workspace = true }
+
+[build-dependencies]
+zip = { workspace = true }
+walkdir = { workspace = true }
 
 [dev-dependencies]
-textwrap = { version = "0.16.1" }
+insta = { workspace = true }
 tempfile = { workspace = true }
 
 [lints]

crates/red_knot/build.rs

@@ -0,0 +1,73 @@
+//! 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/vendor/typeshed` change.
+
+use std::fs::File;
+use std::path::Path;
+
+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);
+
+    let options = FileOptions::default()
+        .compression_method(CompressionMethod::Zstd)
+        .unix_permissions(0o644);
+
+    for entry in walkdir::WalkDir::new(directory_path) {
+        let dir_entry = entry.unwrap();
+        let relative_path = dir_entry.path();
+        let name = relative_path
+            .strip_prefix(Path::new(directory_path))
+            .unwrap()
+            .to_str()
+            .expect("Unexpected non-utf8 typeshed path!");
+
+        // Write file or directory explicitly
+        // Some unzip tools unzip files with directory paths correctly, some do not!
+        if relative_path.is_file() {
+            println!("adding file {relative_path:?} as {name:?} ...");
+            zip.start_file(name, options)?;
+            let mut f = File::open(relative_path)?;
+            std::io::copy(&mut f, &mut zip).unwrap();
+        } else if !name.is_empty() {
+            // Only if not root! Avoids path spec / warning
+            // and mapname conversion failed error on unzip
+            println!("adding dir {relative_path:?} as {name:?} ...");
+            zip.add_directory(name, 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/src/ast_ids.rs

@@ -6,8 +6,8 @@ use std::marker::PhantomData;
 use rustc_hash::FxHashMap;
 
 use ruff_index::{Idx, IndexVec};
-use ruff_python_ast::visitor::preorder;
-use ruff_python_ast::visitor::preorder::{PreorderVisitor, TraversalSignal};
+use ruff_python_ast::visitor::source_order;
+use ruff_python_ast::visitor::source_order::{SourceOrderVisitor, TraversalSignal};
 use ruff_python_ast::{
     AnyNodeRef, AstNode, ExceptHandler, ExceptHandlerExceptHandler, Expr, MatchCase, ModModule,
     NodeKind, Parameter, Stmt, StmtAnnAssign, StmtAssign, StmtAugAssign, StmtClassDef,
@@ -91,9 +91,9 @@ impl AstIds {
         while let Some(deferred) = visitor.deferred.pop() {
             match deferred {
                 DeferredNode::FunctionDefinition(def) => {
-                    def.visit_preorder(&mut visitor);
+                    def.visit_source_order(&mut visitor);
                 }
-                DeferredNode::ClassDefinition(def) => def.visit_preorder(&mut visitor),
+                DeferredNode::ClassDefinition(def) => def.visit_source_order(&mut visitor),
             }
         }
 
@@ -182,7 +182,7 @@ impl<'a> AstIdsVisitor<'a> {
     }
 }
 
-impl<'a> PreorderVisitor<'a> for AstIdsVisitor<'a> {
+impl<'a> SourceOrderVisitor<'a> for AstIdsVisitor<'a> {
     fn visit_stmt(&mut self, stmt: &'a Stmt) {
         match stmt {
             Stmt::FunctionDef(def) => {
@@ -226,14 +226,14 @@ impl<'a> PreorderVisitor<'a> for AstIdsVisitor<'a> {
             Stmt::IpyEscapeCommand(_) => {}
         }
 
-        preorder::walk_stmt(self, stmt);
+        source_order::walk_stmt(self, stmt);
     }
 
     fn visit_expr(&mut self, _expr: &'a Expr) {}
 
     fn visit_parameter(&mut self, parameter: &'a Parameter) {
         self.create_id(parameter);
-        preorder::walk_parameter(self, parameter);
+        source_order::walk_parameter(self, parameter);
     }
 
     fn visit_except_handler(&mut self, except_handler: &'a ExceptHandler) {
@@ -243,17 +243,17 @@ impl<'a> PreorderVisitor<'a> for AstIdsVisitor<'a> {
             }
         }
 
-        preorder::walk_except_handler(self, except_handler);
+        source_order::walk_except_handler(self, except_handler);
     }
 
     fn visit_with_item(&mut self, with_item: &'a WithItem) {
         self.create_id(with_item);
-        preorder::walk_with_item(self, with_item);
+        source_order::walk_with_item(self, with_item);
     }
 
     fn visit_match_case(&mut self, match_case: &'a MatchCase) {
         self.create_id(match_case);
-        preorder::walk_match_case(self, match_case);
+        source_order::walk_match_case(self, match_case);
     }
 
     fn visit_type_param(&mut self, type_param: &'a TypeParam) {
@@ -275,10 +275,7 @@ pub struct TypedNodeKey<N: AstNode> {
 
 impl<N: AstNode> TypedNodeKey<N> {
     pub fn from_node(node: &N) -> Self {
-        let inner = NodeKey {
-            kind: node.as_any_node_ref().kind(),
-            range: node.range(),
-        };
+        let inner = NodeKey::from_node(node.as_any_node_ref());
         Self {
             inner,
             _marker: PhantomData,
@@ -312,7 +309,7 @@ struct FindNodeKeyVisitor<'a> {
     result: Option<AnyNodeRef<'a>>,
 }
 
-impl<'a> PreorderVisitor<'a> for FindNodeKeyVisitor<'a> {
+impl<'a> SourceOrderVisitor<'a> for FindNodeKeyVisitor<'a> {
     fn enter_node(&mut self, node: AnyNodeRef<'a>) -> TraversalSignal {
         if self.result.is_some() {
             return TraversalSignal::Skip;
@@ -352,6 +349,12 @@ pub struct NodeKey {
 }
 
 impl NodeKey {
+    pub fn from_node(node: AnyNodeRef) -> Self {
+        NodeKey {
+            kind: node.kind(),
+            range: node.range(),
+        }
+    }
     pub fn resolve<'a>(&self, root: AnyNodeRef<'a>) -> Option<AnyNodeRef<'a>> {
         // We need to do a binary search here. Only traverse into a node if the range is withint the node
         let mut visitor = FindNodeKeyVisitor {

crates/red_knot/src/db.rs

@@ -9,9 +9,9 @@ use crate::files::FileId;
 use crate::lint::{LintSemanticStorage, LintSyntaxStorage};
 use crate::module::ModuleResolver;
 use crate::parse::ParsedStorage;
+use crate::semantic::SemanticIndexStorage;
+use crate::semantic::TypeStore;
 use crate::source::SourceStorage;
-use crate::symbols::SymbolTablesStorage;
-use crate::types::TypeStore;
 
 mod jars;
 mod query;
@@ -125,7 +125,7 @@ pub struct SourceJar {
 #[derive(Debug, Default)]
 pub struct SemanticJar {
     pub module_resolver: ModuleResolver,
-    pub symbol_tables: SymbolTablesStorage,
+    pub semantic_indices: SemanticIndexStorage,
     pub type_store: TypeStore,
 }
 

crates/red_knot/src/lib.rs

@@ -17,9 +17,9 @@ pub mod lint;
 pub mod module;
 mod parse;
 pub mod program;
+mod semantic;
 pub mod source;
-mod symbols;
-mod types;
+pub mod typeshed_versions;
 pub mod watch;
 
 pub(crate) type FxDashMap<K, V> = dashmap::DashMap<K, V, BuildHasherDefault<FxHasher>>;

crates/red_knot/src/lint.rs

@@ -5,17 +5,18 @@ use std::time::Duration;
 
 use ruff_python_ast::visitor::Visitor;
 use ruff_python_ast::{ModModule, StringLiteral};
+use ruff_python_parser::Parsed;
 
 use crate::cache::KeyValueCache;
 use crate::db::{LintDb, LintJar, QueryResult};
 use crate::files::FileId;
-use crate::module::ModuleName;
-use crate::parse::{parse, Parsed};
-use crate::source::{source_text, Source};
-use crate::symbols::{
-    resolve_global_symbol, symbol_table, Definition, GlobalSymbolId, SymbolId, SymbolTable,
+use crate::module::{resolve_module, ModuleName};
+use crate::parse::parse;
+use crate::semantic::{infer_definition_type, infer_symbol_public_type, Type};
+use crate::semantic::{
+    resolve_global_symbol, semantic_index, Definition, GlobalSymbolId, SemanticIndex, SymbolId,
 };
-use crate::types::{infer_definition_type, infer_symbol_type, Type};
+use crate::source::{source_text, Source};
 
 #[tracing::instrument(level = "debug", skip(db))]
 pub(crate) fn lint_syntax(db: &dyn LintDb, file_id: FileId) -> QueryResult<Diagnostics> {
@@ -40,7 +41,7 @@ pub(crate) fn lint_syntax(db: &dyn LintDb, file_id: FileId) -> QueryResult<Diagn
         let parsed = parse(db.upcast(), *file_id)?;
 
         if parsed.errors().is_empty() {
-            let ast = parsed.ast();
+            let ast = parsed.syntax();
 
             let mut visitor = SyntaxLintVisitor {
                 diagnostics,
@@ -81,13 +82,13 @@ pub(crate) fn lint_semantic(db: &dyn LintDb, file_id: FileId) -> QueryResult<Dia
     storage.get(&file_id, |file_id| {
         let source = source_text(db.upcast(), *file_id)?;
         let parsed = parse(db.upcast(), *file_id)?;
-        let symbols = symbol_table(db.upcast(), *file_id)?;
+        let semantic_index = semantic_index(db.upcast(), *file_id)?;
 
         let context = SemanticLintContext {
             file_id: *file_id,
             source,
-            parsed,
-            symbols,
+            parsed: &parsed,
+            semantic_index,
             db,
             diagnostics: RefCell::new(Vec::new()),
         };
@@ -101,17 +102,17 @@ pub(crate) fn lint_semantic(db: &dyn LintDb, file_id: FileId) -> QueryResult<Dia
 
 fn lint_unresolved_imports(context: &SemanticLintContext) -> QueryResult<()> {
     // TODO: Consider iterating over the dependencies (imports) only instead of all definitions.
-    for (symbol, definition) in context.symbols().all_definitions() {
+    for (symbol, definition) in context.semantic_index().symbol_table().all_definitions() {
         match definition {
             Definition::Import(import) => {
-                let ty = context.infer_symbol_type(symbol)?;
+                let ty = context.infer_symbol_public_type(symbol)?;
 
                 if ty.is_unknown() {
                     context.push_diagnostic(format!("Unresolved module {}", import.module));
                 }
             }
             Definition::ImportFrom(import) => {
-                let ty = context.infer_symbol_type(symbol)?;
+                let ty = context.infer_symbol_public_type(symbol)?;
 
                 if ty.is_unknown() {
                     let module_name = import.module().map(Deref::deref).unwrap_or_default();
@@ -144,16 +145,14 @@ fn lint_bad_overrides(context: &SemanticLintContext) -> QueryResult<()> {
     // TODO we should have a special marker on the real typing module (from typeshed) so if you
     // have your own "typing" module in your project, we don't consider it THE typing module (and
     // same for other stdlib modules that our lint rules care about)
-    let Some(typing_override) =
-        resolve_global_symbol(context.db.upcast(), ModuleName::new("typing"), "override")?
-    else {
+    let Some(typing_override) = context.resolve_global_symbol("typing", "override")? else {
         // TODO once we bundle typeshed, this should be unreachable!()
         return Ok(());
     };
 
     // TODO we should maybe index definitions by type instead of iterating all, or else iterate all
     // just once, match, and branch to all lint rules that care about a type of definition
-    for (symbol, definition) in context.symbols().all_definitions() {
+    for (symbol, definition) in context.semantic_index().symbol_table().all_definitions() {
         if !matches!(definition, Definition::FunctionDef(_)) {
             continue;
         }
@@ -194,8 +193,8 @@ fn lint_bad_overrides(context: &SemanticLintContext) -> QueryResult<()> {
 pub struct SemanticLintContext<'a> {
     file_id: FileId,
     source: Source,
-    parsed: Parsed,
-    symbols: Arc<SymbolTable>,
+    parsed: &'a Parsed<ModModule>,
+    semantic_index: Arc<SemanticIndex>,
     db: &'a dyn LintDb,
     diagnostics: RefCell<Vec<String>>,
 }
@@ -209,16 +208,16 @@ impl<'a> SemanticLintContext<'a> {
         self.file_id
     }
 
-    pub fn ast(&self) -> &ModModule {
-        self.parsed.ast()
+    pub fn ast(&self) -> &'a ModModule {
+        self.parsed.syntax()
     }
 
-    pub fn symbols(&self) -> &SymbolTable {
-        &self.symbols
+    pub fn semantic_index(&self) -> &SemanticIndex {
+        &self.semantic_index
     }
 
-    pub fn infer_symbol_type(&self, symbol_id: SymbolId) -> QueryResult<Type> {
-        infer_symbol_type(
+    pub fn infer_symbol_public_type(&self, symbol_id: SymbolId) -> QueryResult<Type> {
+        infer_symbol_public_type(
             self.db.upcast(),
             GlobalSymbolId {
                 file_id: self.file_id,
@@ -234,6 +233,18 @@ impl<'a> SemanticLintContext<'a> {
     pub fn extend_diagnostics(&mut self, diagnostics: impl IntoIterator<Item = String>) {
         self.diagnostics.get_mut().extend(diagnostics);
     }
+
+    pub fn resolve_global_symbol(
+        &self,
+        module: &str,
+        symbol_name: &str,
+    ) -> QueryResult<Option<GlobalSymbolId>> {
+        let Some(module) = resolve_module(self.db.upcast(), ModuleName::new(module))? else {
+            return Ok(None);
+        };
+
+        resolve_global_symbol(self.db.upcast(), module, symbol_name)
+    }
 }
 
 #[derive(Debug)]

crates/red_knot/src/main.rs

@@ -12,7 +12,7 @@ use tracing_subscriber::{Layer, Registry};
 use tracing_tree::time::Uptime;
 
 use red_knot::db::{HasJar, ParallelDatabase, QueryError, SourceDb, SourceJar};
-use red_knot::module::{set_module_search_paths, ModuleSearchPath, ModuleSearchPathKind};
+use red_knot::module::{set_module_search_paths, ModuleResolutionInputs};
 use red_knot::program::check::ExecutionMode;
 use red_knot::program::{FileWatcherChange, Program};
 use red_knot::watch::FileWatcher;
@@ -44,12 +44,17 @@ fn main() -> anyhow::Result<()> {
     let workspace_folder = entry_point.parent().unwrap();
     let workspace = Workspace::new(workspace_folder.to_path_buf());
 
-    let workspace_search_path = ModuleSearchPath::new(
-        workspace.root().to_path_buf(),
-        ModuleSearchPathKind::FirstParty,
-    );
+    let workspace_search_path = workspace.root().to_path_buf();
+
+    let search_paths = ModuleResolutionInputs {
+        extra_paths: vec![],
+        workspace_root: workspace_search_path,
+        site_packages: None,
+        custom_typeshed: None,
+    };
+
     let mut program = Program::new(workspace);
-    set_module_search_paths(&mut program, vec![workspace_search_path]);
+    set_module_search_paths(&mut program, search_paths);
 
     let entry_id = program.file_id(entry_point);
     program.workspace_mut().open_file(entry_id);

crates/red_knot/src/module.rs

@@ -9,14 +9,18 @@ use smol_str::SmolStr;
 
 use crate::db::{QueryResult, SemanticDb, SemanticJar};
 use crate::files::FileId;
-use crate::symbols::Dependency;
+use crate::semantic::Dependency;
 use crate::FxDashMap;
 
-/// ID uniquely identifying a module.
+/// Representation of a Python module.
+///
+/// The inner type wrapped by this struct is a unique identifier for the module
+/// that is used by the struct's methods to lazily query information about the module.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 pub struct Module(u32);
 
 impl Module {
+    /// Return the absolute name of the module (e.g. `foo.bar`)
     pub fn name(&self, db: &dyn SemanticDb) -> QueryResult<ModuleName> {
         let jar: &SemanticJar = db.jar()?;
         let modules = &jar.module_resolver;
@@ -24,6 +28,7 @@ impl Module {
         Ok(modules.modules.get(self).unwrap().name.clone())
     }
 
+    /// Return the path to the source code that defines this module
     pub fn path(&self, db: &dyn SemanticDb) -> QueryResult<ModulePath> {
         let jar: &SemanticJar = db.jar()?;
         let modules = &jar.module_resolver;
@@ -31,6 +36,7 @@ impl Module {
         Ok(modules.modules.get(self).unwrap().path.clone())
     }
 
+    /// Determine whether this module is a single-file module or a package
     pub fn kind(&self, db: &dyn SemanticDb) -> QueryResult<ModuleKind> {
         let jar: &SemanticJar = db.jar()?;
         let modules = &jar.module_resolver;
@@ -38,6 +44,16 @@ impl Module {
         Ok(modules.modules.get(self).unwrap().kind)
     }
 
+    /// Attempt to resolve a dependency of this module to an absolute [`ModuleName`].
+    ///
+    /// A dependency could be either absolute (e.g. the `foo` dependency implied by `from foo import bar`)
+    /// or relative to this module (e.g. the `.foo` dependency implied by `from .foo import bar`)
+    ///
+    /// - Returns an error if the query failed.
+    /// - Returns `Ok(None)` if the query succeeded,
+    ///   but the dependency refers to a module that does not exist.
+    /// - Returns `Ok(Some(ModuleName))` if the query succeeded,
+    ///   and the dependency refers to a module that exists.
     pub fn resolve_dependency(
         &self,
         db: &dyn SemanticDb,
@@ -87,7 +103,8 @@ impl Module {
 
 /// A module name, e.g. `foo.bar`.
 ///
-/// Always normalized to the absolute form (never a relative module name).
+/// Always normalized to the absolute form
+/// (never a relative module name, i.e., never `.foo`).
 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 pub struct ModuleName(smol_str::SmolStr);
 
@@ -124,10 +141,13 @@ impl ModuleName {
         Some(Self(name))
     }
 
+    /// An iterator over the components of the module name:
+    /// `foo.bar.baz` -> `foo`, `bar`, `baz`
     pub fn components(&self) -> impl DoubleEndedIterator<Item = &str> {
         self.0.split('.')
     }
 
+    /// The name of this module's immediate parent, if it has a parent
     pub fn parent(&self) -> Option<ModuleName> {
         let (_, parent) = self.0.rsplit_once('.')?;
 
@@ -159,9 +179,10 @@ impl std::fmt::Display for ModuleName {
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 pub enum ModuleKind {
+    /// A single-file module (e.g. `foo.py` or `foo.pyi`)
     Module,
 
-    /// A python package (a `__init__.py` or `__init__.pyi` file)
+    /// A python package (`foo/__init__.py` or `foo/__init__.pyi`)
     Package,
 }
 
@@ -181,10 +202,12 @@ impl ModuleSearchPath {
         }
     }
 
+    /// Determine whether this is a first-party, third-party or standard-library search path
     pub fn kind(&self) -> ModuleSearchPathKind {
         self.inner.kind
     }
 
+    /// Return the location of the search path on the file system
     pub fn path(&self) -> &Path {
         &self.inner.path
     }
@@ -202,22 +225,31 @@ struct ModuleSearchPathInner {
     kind: ModuleSearchPathKind,
 }
 
-#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
+/// Enumeration of the different kinds of search paths type checkers are expected to support.
+///
+/// N.B. Although we don't implement `Ord` for this enum, they are ordered in terms of the
+/// priority that we want to give these modules when resolving them.
+/// This is roughly [the order given in the typing spec], but typeshed's stubs
+/// for the standard library are moved higher up to match Python's semantics at runtime.
+///
+/// [the order given in the typing spec]: https://typing.readthedocs.io/en/latest/spec/distributing.html#import-resolution-ordering
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, is_macro::Is)]
 pub enum ModuleSearchPathKind {
-    // Project dependency
+    /// "Extra" paths provided by the user in a config file, env var or CLI flag.
+    /// E.g. mypy's `MYPYPATH` env var, or pyright's `stubPath` configuration setting
+    Extra,
+
+    /// Files in the project we're directly being invoked on
     FirstParty,
 
-    // e.g. site packages
-    ThirdParty,
-
-    // e.g. built-in modules, typeshed
+    /// The `stdlib` directory of typeshed (either vendored or custom)
     StandardLibrary,
-}
 
-impl ModuleSearchPathKind {
-    pub const fn is_first_party(self) -> bool {
-        matches!(self, Self::FirstParty)
-    }
+    /// Stubs or runtime modules installed in site-packages
+    SitePackagesThirdParty,
+
+    /// Vendored third-party stubs from typeshed
+    VendoredThirdParty,
 }
 
 #[derive(Debug, Eq, PartialEq)]
@@ -231,9 +263,11 @@ pub struct ModuleData {
 // Queries
 //////////////////////////////////////////////////////
 
-/// Resolves a module name to a module id
-/// TODO: This would not work with Salsa because `ModuleName` isn't an ingredient and, therefore, cannot be used as part of a query.
-///  For this to work with salsa, it would be necessary to intern all `ModuleName`s.
+/// Resolves a module name to a module.
+///
+/// TODO: This would not work with Salsa because `ModuleName` isn't an ingredient
+/// and, therefore, cannot be used as part of a query.
+/// For this to work with salsa, it would be necessary to intern all `ModuleName`s.
 #[tracing::instrument(level = "debug", skip(db))]
 pub fn resolve_module(db: &dyn SemanticDb, name: ModuleName) -> QueryResult<Option<Module>> {
     let jar: &SemanticJar = db.jar()?;
@@ -255,7 +289,7 @@ pub fn resolve_module(db: &dyn SemanticDb, name: ModuleName) -> QueryResult<Opti
             let file_id = db.file_id(&normalized);
             let path = ModulePath::new(root_path.clone(), file_id);
 
-            let id = Module(
+            let module = Module(
                 modules
                     .next_module_id
                     .fetch_add(1, std::sync::atomic::Ordering::Relaxed),
@@ -263,7 +297,7 @@ pub fn resolve_module(db: &dyn SemanticDb, name: ModuleName) -> QueryResult<Opti
 
             modules
                 .modules
-                .insert(id, Arc::from(ModuleData { name, path, kind }));
+                .insert(module, Arc::from(ModuleData { name, path, kind }));
 
             // A path can map to multiple modules because of symlinks:
             // ```
@@ -272,33 +306,33 @@ pub fn resolve_module(db: &dyn SemanticDb, name: ModuleName) -> QueryResult<Opti
             // ```
             // Here, both `foo` and `bar` resolve to the same module but through different paths.
             // That's why we need to insert the absolute path and not the normalized path here.
-            let absolute_id = if absolute_path == normalized {
+            let absolute_file_id = if absolute_path == normalized {
                 file_id
             } else {
                 db.file_id(&absolute_path)
             };
 
-            modules.by_file.insert(absolute_id, id);
+            modules.by_file.insert(absolute_file_id, module);
 
-            entry.insert_entry(id);
+            entry.insert_entry(module);
 
-            Ok(Some(id))
+            Ok(Some(module))
         }
     }
 }
 
-/// Resolves the module id for the given path.
+/// Resolves the module for the given path.
 ///
-/// Returns `None` if the path is not a module in `sys.path`.
+/// Returns `None` if the path is not a module locatable via `sys.path`.
 #[tracing::instrument(level = "debug", skip(db))]
 pub fn path_to_module(db: &dyn SemanticDb, path: &Path) -> QueryResult<Option<Module>> {
     let file = db.file_id(path);
     file_to_module(db, file)
 }
 
-/// Resolves the module id for the file with the given id.
+/// Resolves the module for the file with the given id.
 ///
-/// Returns `None` if the file is not a module in `sys.path`.
+/// Returns `None` if the file is not a module locatable via `sys.path`.
 #[tracing::instrument(level = "debug", skip(db))]
 pub fn file_to_module(db: &dyn SemanticDb, file: FileId) -> QueryResult<Option<Module>> {
     let jar: &SemanticJar = db.jar()?;
@@ -325,12 +359,12 @@ pub fn file_to_module(db: &dyn SemanticDb, file: FileId) -> QueryResult<Option<M
 
     // Resolve the module name to see if Python would resolve the name to the same path.
     // If it doesn't, then that means that multiple modules have the same in different
-    // root paths, but that the module corresponding to the past path is in a lower priority path,
+    // root paths, but that the module corresponding to the past path is in a lower priority search path,
     // in which case we ignore it.
-    let Some(module_id) = resolve_module(db, module_name)? else {
+    let Some(module) = resolve_module(db, module_name)? else {
         return Ok(None);
     };
-    let module_path = module_id.path(db)?;
+    let module_path = module.path(db)?;
 
     if module_path.root() == &root_path {
         let Ok(normalized) = path.canonicalize() else {
@@ -350,7 +384,7 @@ pub fn file_to_module(db: &dyn SemanticDb, file: FileId) -> QueryResult<Option<M
         }
 
         // Path has been inserted by `resolved`
-        Ok(Some(module_id))
+        Ok(Some(module))
     } else {
         // This path is for a module with the same name but in a module search path with a lower priority.
         // Ignore it.
@@ -363,25 +397,100 @@ pub fn file_to_module(db: &dyn SemanticDb, file: FileId) -> QueryResult<Option<M
 //////////////////////////////////////////////////////
 
 /// Changes the module search paths to `search_paths`.
-pub fn set_module_search_paths(db: &mut dyn SemanticDb, search_paths: Vec<ModuleSearchPath>) {
+pub fn set_module_search_paths(db: &mut dyn SemanticDb, search_paths: ModuleResolutionInputs) {
     let jar: &mut SemanticJar = db.jar_mut();
 
-    jar.module_resolver = ModuleResolver::new(search_paths);
+    jar.module_resolver = ModuleResolver::new(search_paths.into_ordered_search_paths());
 }
 
-/// Adds a module to the resolver.
+/// Struct for holding the various paths that are put together
+/// to create an `OrderedSearchPatsh` instance
+///
+/// - `extra_paths` is a list of user-provided paths
+///   that should take first priority in the module resolution.
+///   Examples in other type checkers are mypy's MYPYPATH environment variable,
+///   or pyright's stubPath configuration setting.
+/// - `workspace_root` is the root of the workspace,
+///   used for finding first-party modules
+/// - `site-packages` is the path to the user's `site-packages` directory,
+///   where third-party packages from ``PyPI`` are installed
+/// - `custom_typeshed` is a path to standard-library typeshed stubs.
+///   Currently this has to be a directory that exists on disk.
+///   (TODO: fall back to vendored stubs if no custom directory is provided.)
+#[derive(Debug)]
+pub struct ModuleResolutionInputs {
+    pub extra_paths: Vec<PathBuf>,
+    pub workspace_root: PathBuf,
+    pub site_packages: Option<PathBuf>,
+    pub custom_typeshed: Option<PathBuf>,
+}
+
+impl ModuleResolutionInputs {
+    /// Implementation of PEP 561's module resolution order
+    /// (with some small, deliberate, differences)
+    fn into_ordered_search_paths(self) -> OrderedSearchPaths {
+        let ModuleResolutionInputs {
+            extra_paths,
+            workspace_root,
+            site_packages,
+            custom_typeshed,
+        } = self;
+
+        OrderedSearchPaths(
+            extra_paths
+                .into_iter()
+                .map(|path| ModuleSearchPath::new(path, ModuleSearchPathKind::Extra))
+                .chain(std::iter::once(ModuleSearchPath::new(
+                    workspace_root,
+                    ModuleSearchPathKind::FirstParty,
+                )))
+                // TODO fallback to vendored typeshed stubs if no custom typeshed directory is provided by the user
+                .chain(custom_typeshed.into_iter().map(|path| {
+                    ModuleSearchPath::new(
+                        path.join(TYPESHED_STDLIB_DIRECTORY),
+                        ModuleSearchPathKind::StandardLibrary,
+                    )
+                }))
+                .chain(site_packages.into_iter().map(|path| {
+                    ModuleSearchPath::new(path, ModuleSearchPathKind::SitePackagesThirdParty)
+                }))
+                // TODO vendor typeshed's third-party stubs as well as the stdlib and fallback to them as a final step
+                .collect(),
+        )
+    }
+}
+
+const TYPESHED_STDLIB_DIRECTORY: &str = "stdlib";
+
+/// A resolved module resolution order, implementing PEP 561
+/// (with some small, deliberate differences)
+#[derive(Clone, Debug, Default, Eq, PartialEq)]
+struct OrderedSearchPaths(Vec<ModuleSearchPath>);
+
+impl Deref for OrderedSearchPaths {
+    type Target = [ModuleSearchPath];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+/// Adds a module located at `path` to the resolver.
 ///
 /// Returns `None` if the path doesn't resolve to a module.
 ///
-/// Returns `Some` with the id of the module and the ids of the modules that need re-resolving
-/// because they were part of a namespace package and might now resolve differently.
+/// Returns `Some(module, other_modules)`, where `module` is the resolved module
+/// with file location `path`, and `other_modules` is a `Vec` of `ModuleData` instances.
+/// Each element in `other_modules` provides information regarding a single module that needs
+/// re-resolving because it was part of a namespace package and might now resolve differently.
+///
 /// Note: This won't work with salsa because `Path` is not an ingredient.
 pub fn add_module(db: &mut dyn SemanticDb, path: &Path) -> Option<(Module, Vec<Arc<ModuleData>>)> {
     // No locking is required because we're holding a mutable reference to `modules`.
 
     // TODO This needs tests
 
-    // Note: Intentionally by-pass caching here. Module should not be in the cache yet.
+    // Note: Intentionally bypass caching here. Module should not be in the cache yet.
     let module = path_to_module(db, path).ok()??;
 
     // The code below is to handle the addition of `__init__.py` files.
@@ -405,15 +514,15 @@ pub fn add_module(db: &mut dyn SemanticDb, path: &Path) -> Option<(Module, Vec<A
     let jar: &mut SemanticJar = db.jar_mut();
     let modules = &mut jar.module_resolver;
 
-    modules.by_file.retain(|_, id| {
+    modules.by_file.retain(|_, module| {
         if modules
             .modules
-            .get(id)
+            .get(module)
             .unwrap()
             .name
             .starts_with(&parent_name)
         {
-            to_remove.push(*id);
+            to_remove.push(*module);
             false
         } else {
             true
@@ -422,8 +531,8 @@ pub fn add_module(db: &mut dyn SemanticDb, path: &Path) -> Option<(Module, Vec<A
 
     // TODO remove need for this vec
     let mut removed = Vec::with_capacity(to_remove.len());
-    for id in &to_remove {
-        removed.push(modules.remove_module_by_id(*id));
+    for module in &to_remove {
+        removed.push(modules.remove_module(*module));
     }
 
     Some((module, removed))
@@ -432,14 +541,14 @@ pub fn add_module(db: &mut dyn SemanticDb, path: &Path) -> Option<(Module, Vec<A
 #[derive(Default)]
 pub struct ModuleResolver {
     /// The search paths where modules are located (and searched). Corresponds to `sys.path` at runtime.
-    search_paths: Vec<ModuleSearchPath>,
+    search_paths: OrderedSearchPaths,
 
     // Locking: Locking is done by acquiring a (write) lock on `by_name`. This is because `by_name` is the primary
     // lookup method. Acquiring locks in any other ordering can result in deadlocks.
-    /// Resolves a module name to it's module id.
+    /// Looks up a module by name
     by_name: FxDashMap<ModuleName, Module>,
 
-    /// All known modules, indexed by the module id.
+    /// A map of all known modules to data about those modules
     modules: FxDashMap<Module, Arc<ModuleData>>,
 
     /// Lookup from absolute path to module.
@@ -449,7 +558,7 @@ pub struct ModuleResolver {
 }
 
 impl ModuleResolver {
-    pub fn new(search_paths: Vec<ModuleSearchPath>) -> Self {
+    fn new(search_paths: OrderedSearchPaths) -> Self {
         Self {
             search_paths,
             modules: FxDashMap::default(),
@@ -459,24 +568,27 @@ impl ModuleResolver {
         }
     }
 
-    pub(crate) fn remove_module(&mut self, file_id: FileId) {
+    /// Remove a module from the inner cache
+    pub(crate) fn remove_module_by_file(&mut self, file_id: FileId) {
         // No locking is required because we're holding a mutable reference to `self`.
-        let Some((_, id)) = self.by_file.remove(&file_id) else {
+        let Some((_, module)) = self.by_file.remove(&file_id) else {
             return;
         };
 
-        self.remove_module_by_id(id);
+        self.remove_module(module);
     }
 
-    fn remove_module_by_id(&mut self, id: Module) -> Arc<ModuleData> {
-        let (_, module) = self.modules.remove(&id).unwrap();
+    fn remove_module(&mut self, module: Module) -> Arc<ModuleData> {
+        let (_, module_data) = self.modules.remove(&module).unwrap();
 
-        self.by_name.remove(&module.name).unwrap();
+        self.by_name.remove(&module_data.name).unwrap();
 
-        // It's possible that multiple paths map to the same id. Search all other paths referencing the same module id.
-        self.by_file.retain(|_, current_id| *current_id != id);
+        // It's possible that multiple paths map to the same module.
+        // Search all other paths referencing the same module.
+        self.by_file
+            .retain(|_, current_module| *current_module != module);
 
-        module
+        module_data
     }
 }
 
@@ -505,15 +617,19 @@ impl ModulePath {
         Self { root, file_id }
     }
 
+    /// The search path that was used to locate the module
     pub fn root(&self) -> &ModuleSearchPath {
         &self.root
     }
 
+    /// The file containing the source code for the module
     pub fn file(&self) -> FileId {
         self.file_id
     }
 }
 
+/// Given a module name and a list of search paths in which to lookup modules,
+/// attempt to resolve the module name
 fn resolve_name(
     name: &ModuleName,
     search_paths: &[ModuleSearchPath],
@@ -635,7 +751,9 @@ enum PackageKind {
     /// A root package or module. E.g. `foo` in `foo.bar.baz` or just `foo`.
     Root,
 
-    /// A regular sub-package where the parent contains an `__init__.py`. For example `bar` in `foo.bar` when the `foo` directory contains an `__init__.py`.
+    /// A regular sub-package where the parent contains an `__init__.py`.
+    ///
+    /// For example, `bar` in `foo.bar` when the `foo` directory contains an `__init__.py`.
     Regular,
 
     /// A sub-package in a namespace package. A namespace package is a package without an `__init__.py`.
@@ -652,22 +770,27 @@ impl PackageKind {
 
 #[cfg(test)]
 mod tests {
+    use std::io::{Cursor, Read};
     use std::num::NonZeroU32;
+    use std::path::{Path, PathBuf};
+
+    use zip::ZipArchive;
 
     use crate::db::tests::TestDb;
     use crate::db::SourceDb;
     use crate::module::{
         path_to_module, resolve_module, set_module_search_paths, ModuleKind, ModuleName,
-        ModuleSearchPath, ModuleSearchPathKind,
+        ModuleResolutionInputs, TYPESHED_STDLIB_DIRECTORY,
     };
-    use crate::symbols::Dependency;
+    use crate::semantic::Dependency;
 
     struct TestCase {
         temp_dir: tempfile::TempDir,
         db: TestDb,
 
-        src: ModuleSearchPath,
-        site_packages: ModuleSearchPath,
+        src: PathBuf,
+        custom_typeshed: PathBuf,
+        site_packages: PathBuf,
     }
 
     fn create_resolver() -> std::io::Result<TestCase> {
@@ -675,25 +798,31 @@ mod tests {
 
         let src = temp_dir.path().join("src");
         let site_packages = temp_dir.path().join("site_packages");
+        let custom_typeshed = temp_dir.path().join("typeshed");
 
         std::fs::create_dir(&src)?;
         std::fs::create_dir(&site_packages)?;
+        std::fs::create_dir(&custom_typeshed)?;
 
-        let src = ModuleSearchPath::new(src.canonicalize()?, ModuleSearchPathKind::FirstParty);
-        let site_packages = ModuleSearchPath::new(
-            site_packages.canonicalize()?,
-            ModuleSearchPathKind::ThirdParty,
-        );
+        let src = src.canonicalize()?;
+        let site_packages = site_packages.canonicalize()?;
+        let custom_typeshed = custom_typeshed.canonicalize()?;
 
-        let roots = vec![src.clone(), site_packages.clone()];
+        let search_paths = ModuleResolutionInputs {
+            extra_paths: vec![],
+            workspace_root: src.clone(),
+            site_packages: Some(site_packages.clone()),
+            custom_typeshed: Some(custom_typeshed.clone()),
+        };
 
         let mut db = TestDb::default();
-        set_module_search_paths(&mut db, roots);
+        set_module_search_paths(&mut db, search_paths);
 
         Ok(TestCase {
             temp_dir,
             db,
             src,
+            custom_typeshed,
             site_packages,
         })
     }
@@ -707,7 +836,7 @@ mod tests {
             ..
         } = create_resolver()?;
 
-        let foo_path = src.path().join("foo.py");
+        let foo_path = src.join("foo.py");
         std::fs::write(&foo_path, "print('Hello, world!')")?;
 
         let foo_module = resolve_module(&db, ModuleName::new("foo"))?.unwrap();
@@ -718,7 +847,7 @@ mod tests {
         );
 
         assert_eq!(ModuleName::new("foo"), foo_module.name(&db)?);
-        assert_eq!(&src, foo_module.path(&db)?.root());
+        assert_eq!(&src, foo_module.path(&db)?.root().path());
         assert_eq!(ModuleKind::Module, foo_module.kind(&db)?);
         assert_eq!(&foo_path, &*db.file_path(foo_module.path(&db)?.file()));
 
@@ -727,6 +856,98 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn stdlib() -> anyhow::Result<()> {
+        let TestCase {
+            db,
+            custom_typeshed,
+            ..
+        } = create_resolver()?;
+        let stdlib_dir = custom_typeshed.join(TYPESHED_STDLIB_DIRECTORY);
+        std::fs::create_dir_all(&stdlib_dir).unwrap();
+        let functools_path = stdlib_dir.join("functools.py");
+        std::fs::write(&functools_path, "def update_wrapper(): ...").unwrap();
+        let functools_module = resolve_module(&db, ModuleName::new("functools"))?.unwrap();
+
+        assert_eq!(
+            Some(functools_module),
+            resolve_module(&db, ModuleName::new("functools"))?
+        );
+        assert_eq!(&stdlib_dir, functools_module.path(&db)?.root().path());
+        assert_eq!(ModuleKind::Module, functools_module.kind(&db)?);
+        assert_eq!(
+            &functools_path,
+            &*db.file_path(functools_module.path(&db)?.file())
+        );
+
+        assert_eq!(
+            Some(functools_module),
+            path_to_module(&db, &functools_path)?
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn first_party_precedence_over_stdlib() -> anyhow::Result<()> {
+        let TestCase {
+            db,
+            src,
+            custom_typeshed,
+            ..
+        } = create_resolver()?;
+
+        let stdlib_dir = custom_typeshed.join(TYPESHED_STDLIB_DIRECTORY);
+        std::fs::create_dir_all(&stdlib_dir).unwrap();
+        std::fs::create_dir_all(&src).unwrap();
+
+        let stdlib_functools_path = stdlib_dir.join("functools.py");
+        let first_party_functools_path = src.join("functools.py");
+        std::fs::write(stdlib_functools_path, "def update_wrapper(): ...").unwrap();
+        std::fs::write(&first_party_functools_path, "def update_wrapper(): ...").unwrap();
+        let functools_module = resolve_module(&db, ModuleName::new("functools"))?.unwrap();
+
+        assert_eq!(
+            Some(functools_module),
+            resolve_module(&db, ModuleName::new("functools"))?
+        );
+        assert_eq!(&src, functools_module.path(&db).unwrap().root().path());
+        assert_eq!(ModuleKind::Module, functools_module.kind(&db)?);
+        assert_eq!(
+            &first_party_functools_path,
+            &*db.file_path(functools_module.path(&db)?.file())
+        );
+
+        assert_eq!(
+            Some(functools_module),
+            path_to_module(&db, &first_party_functools_path)?
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn typeshed_zip_created_at_build_time() -> anyhow::Result<()> {
+        // The file path here is hardcoded in this crate's `build.rs` script.
+        // Luckily this crate will fail to build if this file isn't available at build time.
+        const TYPESHED_ZIP_BYTES: &[u8] =
+            include_bytes!(concat!(env!("OUT_DIR"), "/zipped_typeshed.zip"));
+        assert!(!TYPESHED_ZIP_BYTES.is_empty());
+        let mut typeshed_zip_archive = ZipArchive::new(Cursor::new(TYPESHED_ZIP_BYTES))?;
+
+        let path_to_functools = Path::new("stdlib").join("functools.pyi");
+        let mut functools_module_stub = typeshed_zip_archive
+            .by_name(path_to_functools.to_str().unwrap())
+            .unwrap();
+        assert!(functools_module_stub.is_file());
+
+        let mut functools_module_stub_source = String::new();
+        functools_module_stub.read_to_string(&mut functools_module_stub_source)?;
+
+        assert!(functools_module_stub_source.contains("def update_wrapper("));
+        Ok(())
+    }
+
     #[test]
     fn resolve_package() -> anyhow::Result<()> {
         let TestCase {
@@ -736,7 +957,7 @@ mod tests {
             ..
         } = create_resolver()?;
 
-        let foo_dir = src.path().join("foo");
+        let foo_dir = src.join("foo");
         let foo_path = foo_dir.join("__init__.py");
         std::fs::create_dir(&foo_dir)?;
         std::fs::write(&foo_path, "print('Hello, world!')")?;
@@ -744,7 +965,7 @@ mod tests {
         let foo_module = resolve_module(&db, ModuleName::new("foo"))?.unwrap();
 
         assert_eq!(ModuleName::new("foo"), foo_module.name(&db)?);
-        assert_eq!(&src, foo_module.path(&db)?.root());
+        assert_eq!(&src, foo_module.path(&db)?.root().path());
         assert_eq!(&foo_path, &*db.file_path(foo_module.path(&db)?.file()));
 
         assert_eq!(Some(foo_module), path_to_module(&db, &foo_path)?);
@@ -764,17 +985,17 @@ mod tests {
             ..
         } = create_resolver()?;
 
-        let foo_dir = src.path().join("foo");
+        let foo_dir = src.join("foo");
         let foo_init = foo_dir.join("__init__.py");
         std::fs::create_dir(&foo_dir)?;
         std::fs::write(&foo_init, "print('Hello, world!')")?;
 
-        let foo_py = src.path().join("foo.py");
+        let foo_py = src.join("foo.py");
         std::fs::write(&foo_py, "print('Hello, world!')")?;
 
         let foo_module = resolve_module(&db, ModuleName::new("foo"))?.unwrap();
 
-        assert_eq!(&src, foo_module.path(&db)?.root());
+        assert_eq!(&src, foo_module.path(&db)?.root().path());
         assert_eq!(&foo_init, &*db.file_path(foo_module.path(&db)?.file()));
         assert_eq!(ModuleKind::Package, foo_module.kind(&db)?);
 
@@ -793,14 +1014,14 @@ mod tests {
             ..
         } = create_resolver()?;
 
-        let foo_stub = src.path().join("foo.pyi");
-        let foo_py = src.path().join("foo.py");
+        let foo_stub = src.join("foo.pyi");
+        let foo_py = src.join("foo.py");
         std::fs::write(&foo_stub, "x: int")?;
         std::fs::write(&foo_py, "print('Hello, world!')")?;
 
         let foo = resolve_module(&db, ModuleName::new("foo"))?.unwrap();
 
-        assert_eq!(&src, foo.path(&db)?.root());
+        assert_eq!(&src, foo.path(&db)?.root().path());
         assert_eq!(&foo_stub, &*db.file_path(foo.path(&db)?.file()));
 
         assert_eq!(Some(foo), path_to_module(&db, &foo_stub)?);
@@ -818,7 +1039,7 @@ mod tests {
             ..
         } = create_resolver()?;
 
-        let foo = src.path().join("foo");
+        let foo = src.join("foo");
         let bar = foo.join("bar");
         let baz = bar.join("baz.py");
 
@@ -829,7 +1050,7 @@ mod tests {
 
         let baz_module = resolve_module(&db, ModuleName::new("foo.bar.baz"))?.unwrap();
 
-        assert_eq!(&src, baz_module.path(&db)?.root());
+        assert_eq!(&src, baz_module.path(&db)?.root().path());
         assert_eq!(&baz, &*db.file_path(baz_module.path(&db)?.file()));
 
         assert_eq!(Some(baz_module), path_to_module(&db, &baz)?);
@@ -844,6 +1065,7 @@ mod tests {
             temp_dir: _,
             src,
             site_packages,
+            ..
         } = create_resolver()?;
 
         // From [PEP420](https://peps.python.org/pep-0420/#nested-namespace-packages).
@@ -859,14 +1081,14 @@ mod tests {
         //       two.py
         // ```
 
-        let parent1 = src.path().join("parent");
+        let parent1 = src.join("parent");
         let child1 = parent1.join("child");
         let one = child1.join("one.py");
 
         std::fs::create_dir_all(child1)?;
         std::fs::write(&one, "print('Hello, world!')")?;
 
-        let parent2 = site_packages.path().join("parent");
+        let parent2 = site_packages.join("parent");
         let child2 = parent2.join("child");
         let two = child2.join("two.py");
 
@@ -890,6 +1112,7 @@ mod tests {
             temp_dir: _,
             src,
             site_packages,
+            ..
         } = create_resolver()?;
 
         // Adopted test case from the [PEP420 examples](https://peps.python.org/pep-0420/#nested-namespace-packages).
@@ -905,7 +1128,7 @@ mod tests {
         //       two.py
         // ```
 
-        let parent1 = src.path().join("parent");
+        let parent1 = src.join("parent");
         let child1 = parent1.join("child");
         let one = child1.join("one.py");
 
@@ -913,7 +1136,7 @@ mod tests {
         std::fs::write(child1.join("__init__.py"), "print('Hello, world!')")?;
         std::fs::write(&one, "print('Hello, world!')")?;
 
-        let parent2 = site_packages.path().join("parent");
+        let parent2 = site_packages.join("parent");
         let child2 = parent2.join("child");
         let two = child2.join("two.py");
 
@@ -938,17 +1161,18 @@ mod tests {
             src,
             site_packages,
             temp_dir: _temp_dir,
+            ..
         } = create_resolver()?;
 
-        let foo_src = src.path().join("foo.py");
-        let foo_site_packages = site_packages.path().join("foo.py");
+        let foo_src = src.join("foo.py");
+        let foo_site_packages = site_packages.join("foo.py");
 
         std::fs::write(&foo_src, "")?;
         std::fs::write(&foo_site_packages, "")?;
 
         let foo_module = resolve_module(&db, ModuleName::new("foo"))?.unwrap();
 
-        assert_eq!(&src, foo_module.path(&db)?.root());
+        assert_eq!(&src, foo_module.path(&db)?.root().path());
         assert_eq!(&foo_src, &*db.file_path(foo_module.path(&db)?.file()));
 
         assert_eq!(Some(foo_module), path_to_module(&db, &foo_src)?);
@@ -967,8 +1191,8 @@ mod tests {
             ..
         } = create_resolver()?;
 
-        let foo = src.path().join("foo.py");
-        let bar = src.path().join("bar.py");
+        let foo = src.join("foo.py");
+        let bar = src.join("bar.py");
 
         std::fs::write(&foo, "")?;
         std::os::unix::fs::symlink(&foo, &bar)?;
@@ -978,12 +1202,12 @@ mod tests {
 
         assert_ne!(foo_module, bar_module);
 
-        assert_eq!(&src, foo_module.path(&db)?.root());
+        assert_eq!(&src, foo_module.path(&db)?.root().path());
         assert_eq!(&foo, &*db.file_path(foo_module.path(&db)?.file()));
 
         // Bar has a different name but it should point to the same file.
 
-        assert_eq!(&src, bar_module.path(&db)?.root());
+        assert_eq!(&src, bar_module.path(&db)?.root().path());
         assert_eq!(foo_module.path(&db)?.file(), bar_module.path(&db)?.file());
         assert_eq!(&foo, &*db.file_path(bar_module.path(&db)?.file()));
 
@@ -1002,7 +1226,7 @@ mod tests {
             ..
         } = create_resolver()?;
 
-        let foo_dir = src.path().join("foo");
+        let foo_dir = src.join("foo");
         let foo_path = foo_dir.join("__init__.py");
         let bar_path = foo_dir.join("bar.py");
 

crates/red_knot/src/parse.rs

@@ -1,85 +1,33 @@
 use std::ops::{Deref, DerefMut};
 use std::sync::Arc;
 
-use ruff_python_ast as ast;
-use ruff_python_parser::{Mode, ParseError};
-use ruff_text_size::{Ranged, TextRange};
+use ruff_python_ast::ModModule;
+use ruff_python_parser::Parsed;
 
 use crate::cache::KeyValueCache;
 use crate::db::{QueryResult, SourceDb};
 use crate::files::FileId;
 use crate::source::source_text;
 
-#[derive(Debug, Clone, PartialEq)]
-pub struct Parsed {
-    inner: Arc<ParsedInner>,
-}
-
-#[derive(Debug, PartialEq)]
-struct ParsedInner {
-    ast: ast::ModModule,
-    errors: Vec<ParseError>,
-}
-
-impl Parsed {
-    fn new(ast: ast::ModModule, errors: Vec<ParseError>) -> Self {
-        Self {
-            inner: Arc::new(ParsedInner { ast, errors }),
-        }
-    }
-
-    pub(crate) fn from_text(text: &str) -> Self {
-        let result = ruff_python_parser::parse(text, Mode::Module);
-
-        let (module, errors) = match result {
-            Ok(ast::Mod::Module(module)) => (module, vec![]),
-            Ok(ast::Mod::Expression(expression)) => (
-                ast::ModModule {
-                    range: expression.range(),
-                    body: vec![ast::Stmt::Expr(ast::StmtExpr {
-                        range: expression.range(),
-                        value: expression.body,
-                    })],
-                },
-                vec![],
-            ),
-            Err(errors) => (
-                ast::ModModule {
-                    range: TextRange::default(),
-                    body: Vec::new(),
-                },
-                vec![errors],
-            ),
-        };
-
-        Parsed::new(module, errors)
-    }
-
-    pub fn ast(&self) -> &ast::ModModule {
-        &self.inner.ast
-    }
-
-    pub fn errors(&self) -> &[ParseError] {
-        &self.inner.errors
-    }
-}
-
 #[tracing::instrument(level = "debug", skip(db))]
-pub(crate) fn parse(db: &dyn SourceDb, file_id: FileId) -> QueryResult<Parsed> {
+pub(crate) fn parse(db: &dyn SourceDb, file_id: FileId) -> QueryResult<Arc<Parsed<ModModule>>> {
     let jar = db.jar()?;
 
     jar.parsed.get(&file_id, |file_id| {
         let source = source_text(db, *file_id)?;
 
-        Ok(Parsed::from_text(source.text()))
+        Ok(Arc::new(ruff_python_parser::parse_unchecked_source(
+            source.text(),
+            source.kind().into(),
+        )))
     })
 }
 
 #[derive(Debug, Default)]
-pub struct ParsedStorage(KeyValueCache<FileId, Parsed>);
+pub struct ParsedStorage(KeyValueCache<FileId, Arc<Parsed<ModModule>>>);
 
 impl Deref for ParsedStorage {
-    type Target = KeyValueCache<FileId, Parsed>;
+    type Target = KeyValueCache<FileId, Arc<Parsed<ModModule>>>;
 
     fn deref(&self) -> &Self::Target {
         &self.0

crates/red_knot/src/program/check.rs

@@ -6,7 +6,7 @@ use crate::files::FileId;
 use crate::lint::{lint_semantic, lint_syntax, Diagnostics};
 use crate::module::{file_to_module, resolve_module};
 use crate::program::Program;
-use crate::symbols::{symbol_table, Dependency};
+use crate::semantic::{semantic_index, Dependency};
 
 impl Program {
     /// Checks all open files in the workspace and its dependencies.
@@ -28,8 +28,8 @@ impl Program {
     fn check_file(&self, file: FileId, context: &CheckFileContext) -> QueryResult<Diagnostics> {
         self.cancelled()?;
 
-        let symbol_table = symbol_table(self, file)?;
-        let dependencies = symbol_table.dependencies();
+        let index = semantic_index(self, file)?;
+        let dependencies = index.symbol_table().dependencies();
 
         if !dependencies.is_empty() {
             let module = file_to_module(self, file)?;

crates/red_knot/src/program/mod.rs

@@ -42,8 +42,8 @@ impl Program {
 
         let (source, semantic, lint) = self.jars_mut();
         for change in aggregated_changes.iter() {
-            semantic.module_resolver.remove_module(change.id);
-            semantic.symbol_tables.remove(&change.id);
+            semantic.module_resolver.remove_module_by_file(change.id);
+            semantic.semantic_indices.remove(&change.id);
             source.sources.remove(&change.id);
             source.parsed.remove(&change.id);
             // TODO: remove all dependent modules as well

crates/red_knot/src/semantic.rs

@@ -0,0 +1,883 @@
+use std::num::NonZeroU32;
+
+use ruff_python_ast as ast;
+use ruff_python_ast::visitor::source_order::SourceOrderVisitor;
+use ruff_python_ast::AstNode;
+
+use crate::ast_ids::{NodeKey, TypedNodeKey};
+use crate::cache::KeyValueCache;
+use crate::db::{QueryResult, SemanticDb, SemanticJar};
+use crate::files::FileId;
+use crate::module::Module;
+use crate::module::ModuleName;
+use crate::parse::parse;
+use crate::Name;
+pub(crate) use definitions::Definition;
+use definitions::{ImportDefinition, ImportFromDefinition};
+pub(crate) use flow_graph::ConstrainedDefinition;
+use flow_graph::{FlowGraph, FlowGraphBuilder, FlowNodeId, ReachableDefinitionsIterator};
+use ruff_index::{newtype_index, IndexVec};
+use rustc_hash::FxHashMap;
+use std::ops::{Deref, DerefMut};
+use std::sync::Arc;
+pub(crate) use symbol_table::{Dependency, SymbolId};
+use symbol_table::{ScopeId, ScopeKind, SymbolFlags, SymbolTable, SymbolTableBuilder};
+pub(crate) use types::{infer_definition_type, infer_symbol_public_type, Type, TypeStore};
+
+mod definitions;
+mod flow_graph;
+mod symbol_table;
+mod types;
+
+#[tracing::instrument(level = "debug", skip(db))]
+pub fn semantic_index(db: &dyn SemanticDb, file_id: FileId) -> QueryResult<Arc<SemanticIndex>> {
+    let jar: &SemanticJar = db.jar()?;
+
+    jar.semantic_indices.get(&file_id, |_| {
+        let parsed = parse(db.upcast(), file_id)?;
+        Ok(Arc::from(SemanticIndex::from_ast(parsed.syntax())))
+    })
+}
+
+#[tracing::instrument(level = "debug", skip(db))]
+pub fn resolve_global_symbol(
+    db: &dyn SemanticDb,
+    module: Module,
+    name: &str,
+) -> QueryResult<Option<GlobalSymbolId>> {
+    let file_id = module.path(db)?.file();
+    let symbol_table = &semantic_index(db, file_id)?.symbol_table;
+    let Some(symbol_id) = symbol_table.root_symbol_id_by_name(name) else {
+        return Ok(None);
+    };
+    Ok(Some(GlobalSymbolId { file_id, symbol_id }))
+}
+
+#[newtype_index]
+pub struct ExpressionId;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct GlobalSymbolId {
+    pub(crate) file_id: FileId,
+    pub(crate) symbol_id: SymbolId,
+}
+
+#[derive(Debug)]
+pub struct SemanticIndex {
+    symbol_table: SymbolTable,
+    flow_graph: FlowGraph,
+    expressions: FxHashMap<NodeKey, ExpressionId>,
+    expressions_by_id: IndexVec<ExpressionId, NodeKey>,
+}
+
+impl SemanticIndex {
+    pub fn from_ast(module: &ast::ModModule) -> Self {
+        let root_scope_id = SymbolTable::root_scope_id();
+        let mut indexer = SemanticIndexer {
+            symbol_table_builder: SymbolTableBuilder::new(),
+            flow_graph_builder: FlowGraphBuilder::new(),
+            scopes: vec![ScopeState {
+                scope_id: root_scope_id,
+                current_flow_node_id: FlowGraph::start(),
+            }],
+            expressions: FxHashMap::default(),
+            expressions_by_id: IndexVec::default(),
+            current_definition: None,
+        };
+        indexer.visit_body(&module.body);
+        indexer.finish()
+    }
+
+    fn resolve_expression_id<'a>(
+        &self,
+        ast: &'a ast::ModModule,
+        expression_id: ExpressionId,
+    ) -> ast::AnyNodeRef<'a> {
+        let node_key = self.expressions_by_id[expression_id];
+        node_key
+            .resolve(ast.as_any_node_ref())
+            .expect("node to resolve")
+    }
+
+    /// Return an iterator over all definitions of `symbol_id` reachable from `use_expr`. The value
+    /// of `symbol_id` in `use_expr` must originate from one of the iterated definitions (or from
+    /// an external reassignment of the name outside of this scope).
+    pub fn reachable_definitions(
+        &self,
+        symbol_id: SymbolId,
+        use_expr: &ast::Expr,
+    ) -> ReachableDefinitionsIterator {
+        let expression_id = self.expression_id(use_expr);
+        ReachableDefinitionsIterator::new(
+            &self.flow_graph,
+            symbol_id,
+            self.flow_graph.for_expr(expression_id),
+        )
+    }
+
+    pub fn expression_id(&self, expression: &ast::Expr) -> ExpressionId {
+        self.expressions[&NodeKey::from_node(expression.into())]
+    }
+
+    pub fn symbol_table(&self) -> &SymbolTable {
+        &self.symbol_table
+    }
+}
+
+#[derive(Debug)]
+struct ScopeState {
+    scope_id: ScopeId,
+    current_flow_node_id: FlowNodeId,
+}
+
+#[derive(Debug)]
+struct SemanticIndexer {
+    symbol_table_builder: SymbolTableBuilder,
+    flow_graph_builder: FlowGraphBuilder,
+    scopes: Vec<ScopeState>,
+    /// the definition whose target(s) we are currently walking
+    current_definition: Option<Definition>,
+    expressions: FxHashMap<NodeKey, ExpressionId>,
+    expressions_by_id: IndexVec<ExpressionId, NodeKey>,
+}
+
+impl SemanticIndexer {
+    pub(crate) fn finish(mut self) -> SemanticIndex {
+        let SemanticIndexer {
+            flow_graph_builder,
+            symbol_table_builder,
+            ..
+        } = self;
+        self.expressions.shrink_to_fit();
+        self.expressions_by_id.shrink_to_fit();
+        SemanticIndex {
+            flow_graph: flow_graph_builder.finish(),
+            symbol_table: symbol_table_builder.finish(),
+            expressions: self.expressions,
+            expressions_by_id: self.expressions_by_id,
+        }
+    }
+
+    fn set_current_flow_node(&mut self, new_flow_node_id: FlowNodeId) {
+        let scope_state = self.scopes.last_mut().expect("scope stack is never empty");
+        scope_state.current_flow_node_id = new_flow_node_id;
+    }
+
+    fn current_flow_node(&self) -> FlowNodeId {
+        self.scopes
+            .last()
+            .expect("scope stack is never empty")
+            .current_flow_node_id
+    }
+
+    fn add_or_update_symbol(&mut self, identifier: &str, flags: SymbolFlags) -> SymbolId {
+        self.symbol_table_builder
+            .add_or_update_symbol(self.cur_scope(), identifier, flags)
+    }
+
+    fn add_or_update_symbol_with_def(
+        &mut self,
+        identifier: &str,
+        definition: Definition,
+    ) -> SymbolId {
+        let symbol_id = self.add_or_update_symbol(identifier, SymbolFlags::IS_DEFINED);
+        self.symbol_table_builder
+            .add_definition(symbol_id, definition.clone());
+        let new_flow_node_id =
+            self.flow_graph_builder
+                .add_definition(symbol_id, definition, self.current_flow_node());
+        self.set_current_flow_node(new_flow_node_id);
+        symbol_id
+    }
+
+    fn push_scope(
+        &mut self,
+        name: &str,
+        kind: ScopeKind,
+        definition: Option<Definition>,
+        defining_symbol: Option<SymbolId>,
+    ) -> ScopeId {
+        let scope_id = self.symbol_table_builder.add_child_scope(
+            self.cur_scope(),
+            name,
+            kind,
+            definition,
+            defining_symbol,
+        );
+        self.scopes.push(ScopeState {
+            scope_id,
+            current_flow_node_id: FlowGraph::start(),
+        });
+        scope_id
+    }
+
+    fn pop_scope(&mut self) -> ScopeId {
+        self.scopes
+            .pop()
+            .expect("Scope stack should never be empty")
+            .scope_id
+    }
+
+    fn cur_scope(&self) -> ScopeId {
+        self.scopes
+            .last()
+            .expect("Scope stack should never be empty")
+            .scope_id
+    }
+
+    fn record_scope_for_node(&mut self, node_key: NodeKey, scope_id: ScopeId) {
+        self.symbol_table_builder
+            .record_scope_for_node(node_key, scope_id);
+    }
+
+    fn insert_constraint(&mut self, expr: &ast::Expr) {
+        let node_key = NodeKey::from_node(expr.into());
+        let expression_id = self.expressions[&node_key];
+        let constraint = self
+            .flow_graph_builder
+            .add_constraint(self.current_flow_node(), expression_id);
+        self.set_current_flow_node(constraint);
+    }
+
+    fn with_type_params(
+        &mut self,
+        name: &str,
+        params: &Option<Box<ast::TypeParams>>,
+        definition: Option<Definition>,
+        defining_symbol: Option<SymbolId>,
+        nested: impl FnOnce(&mut Self) -> ScopeId,
+    ) -> ScopeId {
+        if let Some(type_params) = params {
+            self.push_scope(name, ScopeKind::Annotation, definition, defining_symbol);
+            for type_param in &type_params.type_params {
+                let name = match type_param {
+                    ast::TypeParam::TypeVar(ast::TypeParamTypeVar { name, .. }) => name,
+                    ast::TypeParam::ParamSpec(ast::TypeParamParamSpec { name, .. }) => name,
+                    ast::TypeParam::TypeVarTuple(ast::TypeParamTypeVarTuple { name, .. }) => name,
+                };
+                self.add_or_update_symbol(name, SymbolFlags::IS_DEFINED);
+            }
+        }
+        let scope_id = nested(self);
+        if params.is_some() {
+            self.pop_scope();
+        }
+        scope_id
+    }
+}
+
+impl SourceOrderVisitor<'_> for SemanticIndexer {
+    fn visit_expr(&mut self, expr: &ast::Expr) {
+        let node_key = NodeKey::from_node(expr.into());
+        let expression_id = self.expressions_by_id.push(node_key);
+
+        debug_assert_eq!(
+            expression_id,
+            self.flow_graph_builder
+                .record_expr(self.current_flow_node())
+        );
+
+        debug_assert_eq!(
+            expression_id,
+            self.symbol_table_builder
+                .record_expression(self.cur_scope())
+        );
+
+        self.expressions.insert(node_key, expression_id);
+
+        match expr {
+            ast::Expr::Name(ast::ExprName { id, ctx, .. }) => {
+                let 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(),
+                };
+                self.add_or_update_symbol(id, flags);
+                if flags.contains(SymbolFlags::IS_DEFINED) {
+                    if let Some(curdef) = self.current_definition.clone() {
+                        self.add_or_update_symbol_with_def(id, curdef);
+                    }
+                }
+                ast::visitor::source_order::walk_expr(self, expr);
+            }
+            ast::Expr::Named(node) => {
+                debug_assert!(self.current_definition.is_none());
+                self.current_definition =
+                    Some(Definition::NamedExpr(TypedNodeKey::from_node(node)));
+                // TODO walrus in comprehensions is implicitly nonlocal
+                self.visit_expr(&node.target);
+                self.current_definition = None;
+                self.visit_expr(&node.value);
+            }
+            ast::Expr::If(ast::ExprIf {
+                body, test, orelse, ..
+            }) => {
+                // TODO detect statically known truthy or falsy test (via type inference, not naive
+                // AST inspection, so we can't simplify here, need to record test expression in CFG
+                // for later checking)
+
+                self.visit_expr(test);
+
+                let if_branch = self.flow_graph_builder.add_branch(self.current_flow_node());
+
+                self.set_current_flow_node(if_branch);
+                self.insert_constraint(test);
+                self.visit_expr(body);
+
+                let post_body = self.current_flow_node();
+
+                self.set_current_flow_node(if_branch);
+                self.visit_expr(orelse);
+
+                let post_else = self
+                    .flow_graph_builder
+                    .add_phi(self.current_flow_node(), post_body);
+
+                self.set_current_flow_node(post_else);
+            }
+            _ => {
+                ast::visitor::source_order::walk_expr(self, expr);
+            }
+        }
+    }
+
+    fn visit_stmt(&mut self, stmt: &ast::Stmt) {
+        // TODO need to capture more definition statements here
+        match stmt {
+            ast::Stmt::ClassDef(node) => {
+                let node_key = TypedNodeKey::from_node(node);
+                let def = Definition::ClassDef(node_key.clone());
+                let symbol_id = self.add_or_update_symbol_with_def(&node.name, def.clone());
+                for decorator in &node.decorator_list {
+                    self.visit_decorator(decorator);
+                }
+                let scope_id = self.with_type_params(
+                    &node.name,
+                    &node.type_params,
+                    Some(def.clone()),
+                    Some(symbol_id),
+                    |indexer| {
+                        if let Some(arguments) = &node.arguments {
+                            indexer.visit_arguments(arguments);
+                        }
+                        let scope_id = indexer.push_scope(
+                            &node.name,
+                            ScopeKind::Class,
+                            Some(def.clone()),
+                            Some(symbol_id),
+                        );
+                        indexer.visit_body(&node.body);
+                        indexer.pop_scope();
+                        scope_id
+                    },
+                );
+                self.record_scope_for_node(*node_key.erased(), scope_id);
+            }
+            ast::Stmt::FunctionDef(node) => {
+                let node_key = TypedNodeKey::from_node(node);
+                let def = Definition::FunctionDef(node_key.clone());
+                let symbol_id = self.add_or_update_symbol_with_def(&node.name, def.clone());
+                for decorator in &node.decorator_list {
+                    self.visit_decorator(decorator);
+                }
+                let scope_id = self.with_type_params(
+                    &node.name,
+                    &node.type_params,
+                    Some(def.clone()),
+                    Some(symbol_id),
+                    |indexer| {
+                        indexer.visit_parameters(&node.parameters);
+                        for expr in &node.returns {
+                            indexer.visit_annotation(expr);
+                        }
+                        let scope_id = indexer.push_scope(
+                            &node.name,
+                            ScopeKind::Function,
+                            Some(def.clone()),
+                            Some(symbol_id),
+                        );
+                        indexer.visit_body(&node.body);
+                        indexer.pop_scope();
+                        scope_id
+                    },
+                );
+                self.record_scope_for_node(*node_key.erased(), scope_id);
+            }
+            ast::Stmt::Import(ast::StmtImport { names, .. }) => {
+                for alias in names {
+                    let symbol_name = if let Some(asname) = &alias.asname {
+                        asname.id.as_str()
+                    } else {
+                        alias.name.id.split('.').next().unwrap()
+                    };
+
+                    let module = ModuleName::new(&alias.name.id);
+
+                    let def = Definition::Import(ImportDefinition {
+                        module: module.clone(),
+                    });
+                    self.add_or_update_symbol_with_def(symbol_name, def);
+                    self.symbol_table_builder
+                        .add_dependency(Dependency::Module(module));
+                }
+            }
+            ast::Stmt::ImportFrom(ast::StmtImportFrom {
+                module,
+                names,
+                level,
+                ..
+            }) => {
+                let module = module.as_ref().map(|m| ModuleName::new(&m.id));
+
+                for alias in names {
+                    let symbol_name = if let Some(asname) = &alias.asname {
+                        asname.id.as_str()
+                    } else {
+                        alias.name.id.as_str()
+                    };
+                    let def = Definition::ImportFrom(ImportFromDefinition {
+                        module: module.clone(),
+                        name: Name::new(&alias.name.id),
+                        level: *level,
+                    });
+                    self.add_or_update_symbol_with_def(symbol_name, def);
+                }
+
+                let dependency = if let Some(module) = module {
+                    match NonZeroU32::new(*level) {
+                        Some(level) => Dependency::Relative {
+                            level,
+                            module: Some(module),
+                        },
+                        None => Dependency::Module(module),
+                    }
+                } else {
+                    Dependency::Relative {
+                        level: NonZeroU32::new(*level)
+                            .expect("Import without a module to have a level > 0"),
+                        module,
+                    }
+                };
+
+                self.symbol_table_builder.add_dependency(dependency);
+            }
+            ast::Stmt::Assign(node) => {
+                debug_assert!(self.current_definition.is_none());
+                self.visit_expr(&node.value);
+                self.current_definition =
+                    Some(Definition::Assignment(TypedNodeKey::from_node(node)));
+                for expr in &node.targets {
+                    self.visit_expr(expr);
+                }
+
+                self.current_definition = None;
+            }
+            ast::Stmt::If(node) => {
+                // TODO detect statically known truthy or falsy test (via type inference, not naive
+                // AST inspection, so we can't simplify here, need to record test expression in CFG
+                // for later checking)
+
+                // we visit the if "test" condition first regardless
+                self.visit_expr(&node.test);
+
+                // create branch node: does the if test pass or not?
+                let if_branch = self.flow_graph_builder.add_branch(self.current_flow_node());
+
+                // visit the body of the `if` clause
+                self.set_current_flow_node(if_branch);
+                self.insert_constraint(&node.test);
+                self.visit_body(&node.body);
+
+                // Flow node for the last if/elif condition branch; represents the "no branch
+                // taken yet" possibility (where "taking a branch" means that the condition in an
+                // if or elif evaluated to true and control flow went into that clause).
+                let mut prior_branch = if_branch;
+
+                // Flow node for the state after the prior if/elif/else clause; represents "we have
+                // taken one of the branches up to this point." Initially set to the post-if-clause
+                // state, later will be set to the phi node joining that possible path with the
+                // possibility that we took a later if/elif/else clause instead.
+                let mut post_prior_clause = self.current_flow_node();
+
+                // Flag to mark if the final clause is an "else" -- if so, that means the "match no
+                // clauses" path is not possible, we have to go through one of the clauses.
+                let mut last_branch_is_else = false;
+
+                for clause in &node.elif_else_clauses {
+                    if let Some(test) = &clause.test {
+                        self.visit_expr(test);
+                        // This is an elif clause. Create a new branch node. Its predecessor is the
+                        // previous branch node, because we can only take one branch in an entire
+                        // if/elif/else chain, so if we take this branch, it can only be because we
+                        // didn't take the previous one.
+                        prior_branch = self.flow_graph_builder.add_branch(prior_branch);
+                        self.set_current_flow_node(prior_branch);
+                        self.insert_constraint(test);
+                    } else {
+                        // This is an else clause. No need to create a branch node; there's no
+                        // branch here, if we haven't taken any previous branch, we definitely go
+                        // into the "else" clause.
+                        self.set_current_flow_node(prior_branch);
+                        last_branch_is_else = true;
+                    }
+                    self.visit_elif_else_clause(clause);
+                    // Update `post_prior_clause` to a new phi node joining the possibility that we
+                    // took any of the previous branches with the possibility that we took the one
+                    // just visited.
+                    post_prior_clause = self
+                        .flow_graph_builder
+                        .add_phi(self.current_flow_node(), post_prior_clause);
+                }
+
+                if !last_branch_is_else {
+                    // Final branch was not an "else", which means it's possible we took zero
+                    // branches in the entire if/elif chain, so we need one more phi node to join
+                    // the "no branches taken" possibility.
+                    post_prior_clause = self
+                        .flow_graph_builder
+                        .add_phi(post_prior_clause, prior_branch);
+                }
+
+                // Onward, with current flow node set to our final Phi node.
+                self.set_current_flow_node(post_prior_clause);
+            }
+            _ => {
+                ast::visitor::source_order::walk_stmt(self, stmt);
+            }
+        }
+    }
+}
+
+#[derive(Debug, Default)]
+pub struct SemanticIndexStorage(KeyValueCache<FileId, Arc<SemanticIndex>>);
+
+impl Deref for SemanticIndexStorage {
+    type Target = KeyValueCache<FileId, Arc<SemanticIndex>>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for SemanticIndexStorage {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::semantic::symbol_table::{Symbol, SymbolIterator};
+    use ruff_python_ast as ast;
+    use ruff_python_ast::ModModule;
+    use ruff_python_parser::{Mode, Parsed};
+
+    use super::{Definition, ScopeKind, SemanticIndex, SymbolId};
+
+    fn parse(code: &str) -> Parsed<ModModule> {
+        ruff_python_parser::parse_unchecked(code, Mode::Module)
+            .try_into_module()
+            .unwrap()
+    }
+
+    fn names<I>(it: SymbolIterator<I>) -> Vec<&str>
+    where
+        I: Iterator<Item = SymbolId>,
+    {
+        let mut symbols: Vec<_> = it.map(Symbol::name).collect();
+        symbols.sort_unstable();
+        symbols
+    }
+
+    #[test]
+    fn empty() {
+        let parsed = parse("");
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()).len(), 0);
+    }
+
+    #[test]
+    fn simple() {
+        let parsed = parse("x");
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["x"]);
+        assert_eq!(
+            table
+                .definitions(table.root_symbol_id_by_name("x").unwrap())
+                .len(),
+            0
+        );
+    }
+
+    #[test]
+    fn annotation_only() {
+        let parsed = parse("x: int");
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["int", "x"]);
+        // TODO record definition
+    }
+
+    #[test]
+    fn import() {
+        let parsed = parse("import foo");
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["foo"]);
+        assert_eq!(
+            table
+                .definitions(table.root_symbol_id_by_name("foo").unwrap())
+                .len(),
+            1
+        );
+    }
+
+    #[test]
+    fn import_sub() {
+        let parsed = parse("import foo.bar");
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["foo"]);
+    }
+
+    #[test]
+    fn import_as() {
+        let parsed = parse("import foo.bar as baz");
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["baz"]);
+    }
+
+    #[test]
+    fn import_from() {
+        let parsed = parse("from bar import foo");
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["foo"]);
+        assert_eq!(
+            table
+                .definitions(table.root_symbol_id_by_name("foo").unwrap())
+                .len(),
+            1
+        );
+        assert!(
+            table.root_symbol_id_by_name("foo").is_some_and(|sid| {
+                let s = sid.symbol(&table);
+                s.is_defined() || !s.is_used()
+            }),
+            "symbols that are defined get the defined flag"
+        );
+    }
+
+    #[test]
+    fn assign() {
+        let parsed = parse("x = foo");
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["foo", "x"]);
+        assert_eq!(
+            table
+                .definitions(table.root_symbol_id_by_name("x").unwrap())
+                .len(),
+            1
+        );
+        assert!(
+            table.root_symbol_id_by_name("foo").is_some_and(|sid| {
+                let s = sid.symbol(&table);
+                !s.is_defined() && s.is_used()
+            }),
+            "a symbol used but not defined in a scope should have only the used flag"
+        );
+    }
+
+    #[test]
+    fn class_scope() {
+        let parsed = parse(
+            "
+                class C:
+                    x = 1
+                y = 2
+                ",
+        );
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["C", "y"]);
+        let scopes = table.root_child_scope_ids();
+        assert_eq!(scopes.len(), 1);
+        let c_scope = scopes[0].scope(&table);
+        assert_eq!(c_scope.kind(), ScopeKind::Class);
+        assert_eq!(c_scope.name(), "C");
+        assert_eq!(names(table.symbols_for_scope(scopes[0])), vec!["x"]);
+        assert_eq!(
+            table
+                .definitions(table.root_symbol_id_by_name("C").unwrap())
+                .len(),
+            1
+        );
+    }
+
+    #[test]
+    fn func_scope() {
+        let parsed = parse(
+            "
+                def func():
+                    x = 1
+                y = 2
+                ",
+        );
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["func", "y"]);
+        let scopes = table.root_child_scope_ids();
+        assert_eq!(scopes.len(), 1);
+        let func_scope = scopes[0].scope(&table);
+        assert_eq!(func_scope.kind(), ScopeKind::Function);
+        assert_eq!(func_scope.name(), "func");
+        assert_eq!(names(table.symbols_for_scope(scopes[0])), vec!["x"]);
+        assert_eq!(
+            table
+                .definitions(table.root_symbol_id_by_name("func").unwrap())
+                .len(),
+            1
+        );
+    }
+
+    #[test]
+    fn dupes() {
+        let parsed = parse(
+            "
+                def func():
+                    x = 1
+                def func():
+                    y = 2
+                ",
+        );
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["func"]);
+        let scopes = table.root_child_scope_ids();
+        assert_eq!(scopes.len(), 2);
+        let func_scope_1 = scopes[0].scope(&table);
+        let func_scope_2 = scopes[1].scope(&table);
+        assert_eq!(func_scope_1.kind(), ScopeKind::Function);
+        assert_eq!(func_scope_1.name(), "func");
+        assert_eq!(func_scope_2.kind(), ScopeKind::Function);
+        assert_eq!(func_scope_2.name(), "func");
+        assert_eq!(names(table.symbols_for_scope(scopes[0])), vec!["x"]);
+        assert_eq!(names(table.symbols_for_scope(scopes[1])), vec!["y"]);
+        assert_eq!(
+            table
+                .definitions(table.root_symbol_id_by_name("func").unwrap())
+                .len(),
+            2
+        );
+    }
+
+    #[test]
+    fn generic_func() {
+        let parsed = parse(
+            "
+                def func[T]():
+                    x = 1
+                ",
+        );
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["func"]);
+        let scopes = table.root_child_scope_ids();
+        assert_eq!(scopes.len(), 1);
+        let ann_scope_id = scopes[0];
+        let ann_scope = ann_scope_id.scope(&table);
+        assert_eq!(ann_scope.kind(), ScopeKind::Annotation);
+        assert_eq!(ann_scope.name(), "func");
+        assert_eq!(names(table.symbols_for_scope(ann_scope_id)), vec!["T"]);
+        let scopes = table.child_scope_ids_of(ann_scope_id);
+        assert_eq!(scopes.len(), 1);
+        let func_scope_id = scopes[0];
+        let func_scope = func_scope_id.scope(&table);
+        assert_eq!(func_scope.kind(), ScopeKind::Function);
+        assert_eq!(func_scope.name(), "func");
+        assert_eq!(names(table.symbols_for_scope(func_scope_id)), vec!["x"]);
+    }
+
+    #[test]
+    fn generic_class() {
+        let parsed = parse(
+            "
+                class C[T]:
+                    x = 1
+                ",
+        );
+        let table = SemanticIndex::from_ast(parsed.syntax()).symbol_table;
+        assert_eq!(names(table.root_symbols()), vec!["C"]);
+        let scopes = table.root_child_scope_ids();
+        assert_eq!(scopes.len(), 1);
+        let ann_scope_id = scopes[0];
+        let ann_scope = ann_scope_id.scope(&table);
+        assert_eq!(ann_scope.kind(), ScopeKind::Annotation);
+        assert_eq!(ann_scope.name(), "C");
+        assert_eq!(names(table.symbols_for_scope(ann_scope_id)), vec!["T"]);
+        assert!(
+            table
+                .symbol_by_name(ann_scope_id, "T")
+                .is_some_and(|s| s.is_defined() && !s.is_used()),
+            "type parameters are defined by the scope that introduces them"
+        );
+        let scopes = table.child_scope_ids_of(ann_scope_id);
+        assert_eq!(scopes.len(), 1);
+        let func_scope_id = scopes[0];
+        let func_scope = func_scope_id.scope(&table);
+        assert_eq!(func_scope.kind(), ScopeKind::Class);
+        assert_eq!(func_scope.name(), "C");
+        assert_eq!(names(table.symbols_for_scope(func_scope_id)), vec!["x"]);
+    }
+
+    #[test]
+    fn reachability_trivial() {
+        let parsed = parse("x = 1; x");
+        let ast = parsed.syntax();
+        let index = SemanticIndex::from_ast(ast);
+        let table = &index.symbol_table;
+        let x_sym = table
+            .root_symbol_id_by_name("x")
+            .expect("x symbol should exist");
+        let ast::Stmt::Expr(ast::StmtExpr { value: x_use, .. }) = &ast.body[1] else {
+            panic!("should be an expr")
+        };
+        let x_defs: Vec<_> = index
+            .reachable_definitions(x_sym, x_use)
+            .map(|constrained_definition| constrained_definition.definition)
+            .collect();
+        assert_eq!(x_defs.len(), 1);
+        let Definition::Assignment(node_key) = &x_defs[0] else {
+            panic!("def should be an assignment")
+        };
+        let Some(def_node) = node_key.resolve(ast.into()) else {
+            panic!("node key should resolve")
+        };
+        let ast::Expr::NumberLiteral(ast::ExprNumberLiteral {
+            value: ast::Number::Int(num),
+            ..
+        }) = &*def_node.value
+        else {
+            panic!("should be a number literal")
+        };
+        assert_eq!(*num, 1);
+    }
+
+    #[test]
+    fn expression_scope() {
+        let parsed = parse("x = 1;\ndef test():\n  y = 4");
+        let ast = parsed.syntax();
+        let index = SemanticIndex::from_ast(ast);
+        let table = &index.symbol_table;
+
+        let x_sym = table
+            .root_symbol_by_name("x")
+            .expect("x symbol should exist");
+
+        let x_stmt = ast.body[0].as_assign_stmt().unwrap();
+
+        let x_id = index.expression_id(&x_stmt.targets[0]);
+
+        assert_eq!(table.scope_of_expression(x_id).kind(), ScopeKind::Module);
+        assert_eq!(table.scope_id_of_expression(x_id), x_sym.scope_id());
+
+        let def = ast.body[1].as_function_def_stmt().unwrap();
+        let y_stmt = def.body[0].as_assign_stmt().unwrap();
+        let y_id = index.expression_id(&y_stmt.targets[0]);
+
+        assert_eq!(table.scope_of_expression(y_id).kind(), ScopeKind::Function);
+    }
+}

crates/red_knot/src/semantic/definitions.rs

@@ -0,0 +1,52 @@
+use crate::ast_ids::TypedNodeKey;
+use crate::semantic::ModuleName;
+use crate::Name;
+use ruff_python_ast as ast;
+
+// TODO storing TypedNodeKey for definitions means we have to search to find them again in the AST;
+// this is at best O(log n). If looking up definitions is a bottleneck we should look for
+// alternatives here.
+// TODO intern Definitions in SymbolTable and reference using IDs?
+#[derive(Clone, Debug)]
+pub enum Definition {
+    // For the import cases, we don't need reference to any arbitrary AST subtrees (annotations,
+    // RHS), and referencing just the import statement node is imprecise (a single import statement
+    // can assign many symbols, we'd have to re-search for the one we care about), so we just copy
+    // the small amount of information we need from the AST.
+    Import(ImportDefinition),
+    ImportFrom(ImportFromDefinition),
+    ClassDef(TypedNodeKey<ast::StmtClassDef>),
+    FunctionDef(TypedNodeKey<ast::StmtFunctionDef>),
+    Assignment(TypedNodeKey<ast::StmtAssign>),
+    AnnotatedAssignment(TypedNodeKey<ast::StmtAnnAssign>),
+    NamedExpr(TypedNodeKey<ast::ExprNamed>),
+    /// represents the implicit initial definition of every name as "unbound"
+    Unbound,
+    // TODO with statements, except handlers, function args...
+}
+
+#[derive(Clone, Debug)]
+pub struct ImportDefinition {
+    pub module: ModuleName,
+}
+
+#[derive(Clone, Debug)]
+pub struct ImportFromDefinition {
+    pub module: Option<ModuleName>,
+    pub name: Name,
+    pub level: u32,
+}
+
+impl ImportFromDefinition {
+    pub fn module(&self) -> Option<&ModuleName> {
+        self.module.as_ref()
+    }
+
+    pub fn name(&self) -> &Name {
+        &self.name
+    }
+
+    pub fn level(&self) -> u32 {
+        self.level
+    }
+}

crates/red_knot/src/semantic/flow_graph.rs

@@ -0,0 +1,270 @@
+use super::symbol_table::SymbolId;
+use crate::semantic::{Definition, ExpressionId};
+use ruff_index::{newtype_index, IndexVec};
+use std::iter::FusedIterator;
+use std::ops::Range;
+
+#[newtype_index]
+pub struct FlowNodeId;
+
+#[derive(Debug)]
+pub(crate) enum FlowNode {
+    Start,
+    Definition(DefinitionFlowNode),
+    Branch(BranchFlowNode),
+    Phi(PhiFlowNode),
+    Constraint(ConstraintFlowNode),
+}
+
+/// A point in control flow where a symbol is defined
+#[derive(Debug)]
+pub(crate) struct DefinitionFlowNode {
+    symbol_id: SymbolId,
+    definition: Definition,
+    predecessor: FlowNodeId,
+}
+
+/// A branch in control flow
+#[derive(Debug)]
+pub(crate) struct BranchFlowNode {
+    predecessor: FlowNodeId,
+}
+
+/// A join point where control flow paths come together
+#[derive(Debug)]
+pub(crate) struct PhiFlowNode {
+    first_predecessor: FlowNodeId,
+    second_predecessor: FlowNodeId,
+}
+
+/// A branch test which may apply constraints to a symbol's type
+#[derive(Debug)]
+pub(crate) struct ConstraintFlowNode {
+    predecessor: FlowNodeId,
+    test_expression: ExpressionId,
+}
+
+#[derive(Debug)]
+pub struct FlowGraph {
+    flow_nodes_by_id: IndexVec<FlowNodeId, FlowNode>,
+    expression_map: IndexVec<ExpressionId, FlowNodeId>,
+}
+
+impl FlowGraph {
+    pub fn start() -> FlowNodeId {
+        FlowNodeId::from_usize(0)
+    }
+
+    pub fn for_expr(&self, expr: ExpressionId) -> FlowNodeId {
+        self.expression_map[expr]
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct FlowGraphBuilder {
+    flow_graph: FlowGraph,
+}
+
+impl FlowGraphBuilder {
+    pub(crate) fn new() -> Self {
+        let mut graph = FlowGraph {
+            flow_nodes_by_id: IndexVec::default(),
+            expression_map: IndexVec::default(),
+        };
+        graph.flow_nodes_by_id.push(FlowNode::Start);
+        Self { flow_graph: graph }
+    }
+
+    pub(crate) fn add(&mut self, node: FlowNode) -> FlowNodeId {
+        self.flow_graph.flow_nodes_by_id.push(node)
+    }
+
+    pub(crate) fn add_definition(
+        &mut self,
+        symbol_id: SymbolId,
+        definition: Definition,
+        predecessor: FlowNodeId,
+    ) -> FlowNodeId {
+        self.add(FlowNode::Definition(DefinitionFlowNode {
+            symbol_id,
+            definition,
+            predecessor,
+        }))
+    }
+
+    pub(crate) fn add_branch(&mut self, predecessor: FlowNodeId) -> FlowNodeId {
+        self.add(FlowNode::Branch(BranchFlowNode { predecessor }))
+    }
+
+    pub(crate) fn add_phi(
+        &mut self,
+        first_predecessor: FlowNodeId,
+        second_predecessor: FlowNodeId,
+    ) -> FlowNodeId {
+        self.add(FlowNode::Phi(PhiFlowNode {
+            first_predecessor,
+            second_predecessor,
+        }))
+    }
+
+    pub(crate) fn add_constraint(
+        &mut self,
+        predecessor: FlowNodeId,
+        test_expression: ExpressionId,
+    ) -> FlowNodeId {
+        self.add(FlowNode::Constraint(ConstraintFlowNode {
+            predecessor,
+            test_expression,
+        }))
+    }
+
+    pub(super) fn record_expr(&mut self, node_id: FlowNodeId) -> ExpressionId {
+        self.flow_graph.expression_map.push(node_id)
+    }
+
+    pub(super) fn finish(mut self) -> FlowGraph {
+        self.flow_graph.flow_nodes_by_id.shrink_to_fit();
+        self.flow_graph.expression_map.shrink_to_fit();
+        self.flow_graph
+    }
+}
+
+/// A definition, and the set of constraints between a use and the definition
+#[derive(Debug, Clone)]
+pub struct ConstrainedDefinition {
+    pub definition: Definition,
+    pub constraints: Vec<ExpressionId>,
+}
+
+/// A flow node and the constraints we passed through to reach it
+#[derive(Debug)]
+struct FlowState {
+    node_id: FlowNodeId,
+    constraints_range: Range<usize>,
+}
+
+#[derive(Debug)]
+pub struct ReachableDefinitionsIterator<'a> {
+    flow_graph: &'a FlowGraph,
+    symbol_id: SymbolId,
+    pending: Vec<FlowState>,
+    constraints: Vec<ExpressionId>,
+}
+
+impl<'a> ReachableDefinitionsIterator<'a> {
+    pub fn new(flow_graph: &'a FlowGraph, symbol_id: SymbolId, start_node_id: FlowNodeId) -> Self {
+        Self {
+            flow_graph,
+            symbol_id,
+            pending: vec![FlowState {
+                node_id: start_node_id,
+                constraints_range: 0..0,
+            }],
+            constraints: vec![],
+        }
+    }
+}
+
+impl<'a> Iterator for ReachableDefinitionsIterator<'a> {
+    type Item = ConstrainedDefinition;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let FlowState {
+            mut node_id,
+            mut constraints_range,
+        } = self.pending.pop()?;
+        self.constraints.truncate(constraints_range.end + 1);
+        loop {
+            match &self.flow_graph.flow_nodes_by_id[node_id] {
+                FlowNode::Start => {
+                    // constraints on unbound are irrelevant
+                    return Some(ConstrainedDefinition {
+                        definition: Definition::Unbound,
+                        constraints: vec![],
+                    });
+                }
+                FlowNode::Definition(def_node) => {
+                    if def_node.symbol_id == self.symbol_id {
+                        return Some(ConstrainedDefinition {
+                            definition: def_node.definition.clone(),
+                            constraints: self.constraints[constraints_range].to_vec(),
+                        });
+                    }
+                    node_id = def_node.predecessor;
+                }
+                FlowNode::Branch(branch_node) => {
+                    node_id = branch_node.predecessor;
+                }
+                FlowNode::Phi(phi_node) => {
+                    self.pending.push(FlowState {
+                        node_id: phi_node.first_predecessor,
+                        constraints_range: constraints_range.clone(),
+                    });
+                    node_id = phi_node.second_predecessor;
+                }
+                FlowNode::Constraint(constraint_node) => {
+                    node_id = constraint_node.predecessor;
+                    self.constraints.push(constraint_node.test_expression);
+                    constraints_range.end += 1;
+                }
+            }
+        }
+    }
+}
+
+impl<'a> FusedIterator for ReachableDefinitionsIterator<'a> {}
+
+impl std::fmt::Display for FlowGraph {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        writeln!(f, "flowchart TD")?;
+        for (id, node) in self.flow_nodes_by_id.iter_enumerated() {
+            write!(f, "  id{}", id.as_u32())?;
+            match node {
+                FlowNode::Start => writeln!(f, r"[\Start/]")?,
+                FlowNode::Definition(def_node) => {
+                    writeln!(f, r"(Define symbol {})", def_node.symbol_id.as_u32())?;
+                    writeln!(
+                        f,
+                        r"  id{}-->id{}",
+                        def_node.predecessor.as_u32(),
+                        id.as_u32()
+                    )?;
+                }
+                FlowNode::Branch(branch_node) => {
+                    writeln!(f, r"{{Branch}}")?;
+                    writeln!(
+                        f,
+                        r"  id{}-->id{}",
+                        branch_node.predecessor.as_u32(),
+                        id.as_u32()
+                    )?;
+                }
+                FlowNode::Phi(phi_node) => {
+                    writeln!(f, r"((Phi))")?;
+                    writeln!(
+                        f,
+                        r"  id{}-->id{}",
+                        phi_node.second_predecessor.as_u32(),
+                        id.as_u32()
+                    )?;
+                    writeln!(
+                        f,
+                        r"  id{}-->id{}",
+                        phi_node.first_predecessor.as_u32(),
+                        id.as_u32()
+                    )?;
+                }
+                FlowNode::Constraint(constraint_node) => {
+                    writeln!(f, r"((Constraint))")?;
+                    writeln!(
+                        f,
+                        r"  id{}-->id{}",
+                        constraint_node.predecessor.as_u32(),
+                        id.as_u32()
+                    )?;
+                }
+            }
+        }
+        Ok(())
+    }
+}

crates/red_knot/src/semantic/symbol_table.rs

@@ -0,0 +1,560 @@
+#![allow(dead_code)]
+
+use std::hash::{Hash, Hasher};
+use std::iter::{Copied, DoubleEndedIterator, FusedIterator};
+use std::num::NonZeroU32;
+
+use bitflags::bitflags;
+use hashbrown::hash_map::{Keys, RawEntryMut};
+use rustc_hash::{FxHashMap, FxHasher};
+
+use ruff_index::{newtype_index, IndexVec};
+
+use crate::ast_ids::NodeKey;
+use crate::module::ModuleName;
+use crate::semantic::{Definition, ExpressionId};
+use crate::Name;
+
+type Map<K, V> = hashbrown::HashMap<K, V, ()>;
+
+#[newtype_index]
+pub struct ScopeId;
+
+impl ScopeId {
+    pub fn scope(self, table: &SymbolTable) -> &Scope {
+        &table.scopes_by_id[self]
+    }
+}
+
+#[newtype_index]
+pub struct SymbolId;
+
+impl SymbolId {
+    pub fn symbol(self, table: &SymbolTable) -> &Symbol {
+        &table.symbols_by_id[self]
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub enum ScopeKind {
+    Module,
+    Annotation,
+    Class,
+    Function,
+}
+
+#[derive(Debug)]
+pub struct Scope {
+    name: Name,
+    kind: ScopeKind,
+    parent: Option<ScopeId>,
+    children: Vec<ScopeId>,
+    /// the definition (e.g. class or function) that created this scope
+    definition: Option<Definition>,
+    /// the symbol (e.g. class or function) that owns this scope
+    defining_symbol: Option<SymbolId>,
+    /// symbol IDs, hashed by symbol name
+    symbols_by_name: Map<SymbolId, ()>,
+}
+
+impl Scope {
+    pub fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    pub fn kind(&self) -> ScopeKind {
+        self.kind
+    }
+
+    pub fn definition(&self) -> Option<Definition> {
+        self.definition.clone()
+    }
+
+    pub fn defining_symbol(&self) -> Option<SymbolId> {
+        self.defining_symbol
+    }
+}
+
+#[derive(Debug)]
+pub(crate) enum Kind {
+    FreeVar,
+    CellVar,
+    CellVarAssigned,
+    ExplicitGlobal,
+    ImplicitGlobal,
+}
+
+bitflags! {
+    #[derive(Copy,Clone,Debug)]
+    pub struct SymbolFlags: u8 {
+        const IS_USED         = 1 << 0;
+        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
+        const MARKED_NONLOCAL = 1 << 3;
+    }
+}
+
+#[derive(Debug)]
+pub struct Symbol {
+    name: Name,
+    flags: SymbolFlags,
+    scope_id: ScopeId,
+    // kind: Kind,
+}
+
+impl Symbol {
+    pub fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    pub fn scope_id(&self) -> ScopeId {
+        self.scope_id
+    }
+
+    /// Is the symbol used in its containing scope?
+    pub fn is_used(&self) -> bool {
+        self.flags.contains(SymbolFlags::IS_USED)
+    }
+
+    /// Is the symbol defined in its containing scope?
+    pub fn is_defined(&self) -> bool {
+        self.flags.contains(SymbolFlags::IS_DEFINED)
+    }
+
+    // TODO: implement Symbol.kind 2-pass analysis to categorize as: free-var, cell-var,
+    // explicit-global, implicit-global and implement Symbol.kind by modifying the preorder
+    // traversal code
+}
+
+#[derive(Debug, Clone)]
+pub enum Dependency {
+    Module(ModuleName),
+    Relative {
+        level: NonZeroU32,
+        module: Option<ModuleName>,
+    },
+}
+
+/// Table of all symbols in all scopes for a module.
+#[derive(Debug)]
+pub struct SymbolTable {
+    scopes_by_id: IndexVec<ScopeId, Scope>,
+    symbols_by_id: IndexVec<SymbolId, Symbol>,
+    /// the definitions for each symbol
+    defs: FxHashMap<SymbolId, Vec<Definition>>,
+    /// map of AST node (e.g. class/function def) to sub-scope it creates
+    scopes_by_node: FxHashMap<NodeKey, ScopeId>,
+    /// Maps expressions to their enclosing scope.
+    expression_scopes: IndexVec<ExpressionId, ScopeId>,
+    /// dependencies of this module
+    dependencies: Vec<Dependency>,
+}
+
+impl SymbolTable {
+    pub fn dependencies(&self) -> &[Dependency] {
+        &self.dependencies
+    }
+
+    pub const fn root_scope_id() -> ScopeId {
+        ScopeId::from_usize(0)
+    }
+
+    pub fn root_scope(&self) -> &Scope {
+        &self.scopes_by_id[SymbolTable::root_scope_id()]
+    }
+
+    pub fn symbol_ids_for_scope(&self, scope_id: ScopeId) -> Copied<Keys<SymbolId, ()>> {
+        self.scopes_by_id[scope_id].symbols_by_name.keys().copied()
+    }
+
+    pub fn symbols_for_scope(
+        &self,
+        scope_id: ScopeId,
+    ) -> SymbolIterator<Copied<Keys<SymbolId, ()>>> {
+        SymbolIterator {
+            table: self,
+            ids: self.symbol_ids_for_scope(scope_id),
+        }
+    }
+
+    pub fn root_symbol_ids(&self) -> Copied<Keys<SymbolId, ()>> {
+        self.symbol_ids_for_scope(SymbolTable::root_scope_id())
+    }
+
+    pub fn root_symbols(&self) -> SymbolIterator<Copied<Keys<SymbolId, ()>>> {
+        self.symbols_for_scope(SymbolTable::root_scope_id())
+    }
+
+    pub fn child_scope_ids_of(&self, scope_id: ScopeId) -> &[ScopeId] {
+        &self.scopes_by_id[scope_id].children
+    }
+
+    pub fn child_scopes_of(&self, scope_id: ScopeId) -> ScopeIterator<&[ScopeId]> {
+        ScopeIterator {
+            table: self,
+            ids: self.child_scope_ids_of(scope_id),
+        }
+    }
+
+    pub fn root_child_scope_ids(&self) -> &[ScopeId] {
+        self.child_scope_ids_of(SymbolTable::root_scope_id())
+    }
+
+    pub fn root_child_scopes(&self) -> ScopeIterator<&[ScopeId]> {
+        self.child_scopes_of(SymbolTable::root_scope_id())
+    }
+
+    pub fn symbol_id_by_name(&self, scope_id: ScopeId, name: &str) -> Option<SymbolId> {
+        let scope = &self.scopes_by_id[scope_id];
+        let hash = SymbolTable::hash_name(name);
+        let name = Name::new(name);
+        Some(
+            *scope
+                .symbols_by_name
+                .raw_entry()
+                .from_hash(hash, |symid| self.symbols_by_id[*symid].name == name)?
+                .0,
+        )
+    }
+
+    pub fn symbol_by_name(&self, scope_id: ScopeId, name: &str) -> Option<&Symbol> {
+        Some(&self.symbols_by_id[self.symbol_id_by_name(scope_id, name)?])
+    }
+
+    pub fn root_symbol_id_by_name(&self, name: &str) -> Option<SymbolId> {
+        self.symbol_id_by_name(SymbolTable::root_scope_id(), name)
+    }
+
+    pub fn root_symbol_by_name(&self, name: &str) -> Option<&Symbol> {
+        self.symbol_by_name(SymbolTable::root_scope_id(), name)
+    }
+
+    pub fn scope_id_of_symbol(&self, symbol_id: SymbolId) -> ScopeId {
+        self.symbols_by_id[symbol_id].scope_id
+    }
+
+    pub fn scope_of_symbol(&self, symbol_id: SymbolId) -> &Scope {
+        &self.scopes_by_id[self.scope_id_of_symbol(symbol_id)]
+    }
+
+    pub fn scope_id_of_expression(&self, expression: ExpressionId) -> ScopeId {
+        self.expression_scopes[expression]
+    }
+
+    pub fn scope_of_expression(&self, expr_id: ExpressionId) -> &Scope {
+        &self.scopes_by_id[self.scope_id_of_expression(expr_id)]
+    }
+
+    pub fn parent_scopes(
+        &self,
+        scope_id: ScopeId,
+    ) -> ScopeIterator<impl Iterator<Item = ScopeId> + '_> {
+        ScopeIterator {
+            table: self,
+            ids: std::iter::successors(Some(scope_id), |scope| self.scopes_by_id[*scope].parent),
+        }
+    }
+
+    pub fn parent_scope(&self, scope_id: ScopeId) -> Option<ScopeId> {
+        self.scopes_by_id[scope_id].parent
+    }
+
+    pub fn scope_id_for_node(&self, node_key: &NodeKey) -> ScopeId {
+        self.scopes_by_node[node_key]
+    }
+
+    pub fn definitions(&self, symbol_id: SymbolId) -> &[Definition] {
+        self.defs
+            .get(&symbol_id)
+            .map(std::vec::Vec::as_slice)
+            .unwrap_or_default()
+    }
+
+    pub fn all_definitions(&self) -> impl Iterator<Item = (SymbolId, &Definition)> + '_ {
+        self.defs
+            .iter()
+            .flat_map(|(sym_id, defs)| defs.iter().map(move |def| (*sym_id, def)))
+    }
+
+    fn hash_name(name: &str) -> u64 {
+        let mut hasher = FxHasher::default();
+        name.hash(&mut hasher);
+        hasher.finish()
+    }
+}
+
+pub struct SymbolIterator<'a, I> {
+    table: &'a SymbolTable,
+    ids: I,
+}
+
+impl<'a, I> Iterator for SymbolIterator<'a, I>
+where
+    I: Iterator<Item = SymbolId>,
+{
+    type Item = &'a Symbol;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let id = self.ids.next()?;
+        Some(&self.table.symbols_by_id[id])
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.ids.size_hint()
+    }
+}
+
+impl<'a, I> FusedIterator for SymbolIterator<'a, I> where
+    I: Iterator<Item = SymbolId> + FusedIterator
+{
+}
+
+impl<'a, I> DoubleEndedIterator for SymbolIterator<'a, I>
+where
+    I: Iterator<Item = SymbolId> + DoubleEndedIterator,
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        let id = self.ids.next_back()?;
+        Some(&self.table.symbols_by_id[id])
+    }
+}
+
+// TODO maybe get rid of this and just do all data access via methods on ScopeId?
+pub struct ScopeIterator<'a, I> {
+    table: &'a SymbolTable,
+    ids: I,
+}
+
+/// iterate (`ScopeId`, `Scope`) pairs for given `ScopeId` iterator
+impl<'a, I> Iterator for ScopeIterator<'a, I>
+where
+    I: Iterator<Item = ScopeId>,
+{
+    type Item = (ScopeId, &'a Scope);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let id = self.ids.next()?;
+        Some((id, &self.table.scopes_by_id[id]))
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.ids.size_hint()
+    }
+}
+
+impl<'a, I> FusedIterator for ScopeIterator<'a, I> where I: Iterator<Item = ScopeId> + FusedIterator {}
+
+impl<'a, I> DoubleEndedIterator for ScopeIterator<'a, I>
+where
+    I: Iterator<Item = ScopeId> + DoubleEndedIterator,
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        let id = self.ids.next_back()?;
+        Some((id, &self.table.scopes_by_id[id]))
+    }
+}
+
+#[derive(Debug)]
+pub(super) struct SymbolTableBuilder {
+    symbol_table: SymbolTable,
+}
+
+impl SymbolTableBuilder {
+    pub(super) fn new() -> Self {
+        let mut table = SymbolTable {
+            scopes_by_id: IndexVec::new(),
+            symbols_by_id: IndexVec::new(),
+            defs: FxHashMap::default(),
+            scopes_by_node: FxHashMap::default(),
+            expression_scopes: IndexVec::new(),
+            dependencies: Vec::new(),
+        };
+        table.scopes_by_id.push(Scope {
+            name: Name::new("<module>"),
+            kind: ScopeKind::Module,
+            parent: None,
+            children: Vec::new(),
+            definition: None,
+            defining_symbol: None,
+            symbols_by_name: Map::default(),
+        });
+        Self {
+            symbol_table: table,
+        }
+    }
+
+    pub(super) fn finish(self) -> SymbolTable {
+        let mut symbol_table = self.symbol_table;
+        symbol_table.scopes_by_id.shrink_to_fit();
+        symbol_table.symbols_by_id.shrink_to_fit();
+        symbol_table.defs.shrink_to_fit();
+        symbol_table.scopes_by_node.shrink_to_fit();
+        symbol_table.expression_scopes.shrink_to_fit();
+        symbol_table.dependencies.shrink_to_fit();
+        symbol_table
+    }
+
+    pub(super) fn add_or_update_symbol(
+        &mut self,
+        scope_id: ScopeId,
+        name: &str,
+        flags: SymbolFlags,
+    ) -> SymbolId {
+        let hash = SymbolTable::hash_name(name);
+        let scope = &mut self.symbol_table.scopes_by_id[scope_id];
+        let name = Name::new(name);
+
+        let entry = scope
+            .symbols_by_name
+            .raw_entry_mut()
+            .from_hash(hash, |existing| {
+                self.symbol_table.symbols_by_id[*existing].name == name
+            });
+
+        match entry {
+            RawEntryMut::Occupied(entry) => {
+                if let Some(symbol) = self.symbol_table.symbols_by_id.get_mut(*entry.key()) {
+                    symbol.flags.insert(flags);
+                };
+                *entry.key()
+            }
+            RawEntryMut::Vacant(entry) => {
+                let id = self.symbol_table.symbols_by_id.push(Symbol {
+                    name,
+                    flags,
+                    scope_id,
+                });
+                entry.insert_with_hasher(hash, id, (), |symid| {
+                    SymbolTable::hash_name(&self.symbol_table.symbols_by_id[*symid].name)
+                });
+                id
+            }
+        }
+    }
+
+    pub(super) fn add_definition(&mut self, symbol_id: SymbolId, definition: Definition) {
+        self.symbol_table
+            .defs
+            .entry(symbol_id)
+            .or_default()
+            .push(definition);
+    }
+
+    pub(super) fn add_child_scope(
+        &mut self,
+        parent_scope_id: ScopeId,
+        name: &str,
+        kind: ScopeKind,
+        definition: Option<Definition>,
+        defining_symbol: Option<SymbolId>,
+    ) -> ScopeId {
+        let new_scope_id = self.symbol_table.scopes_by_id.push(Scope {
+            name: Name::new(name),
+            kind,
+            parent: Some(parent_scope_id),
+            children: Vec::new(),
+            definition,
+            defining_symbol,
+            symbols_by_name: Map::default(),
+        });
+        let parent_scope = &mut self.symbol_table.scopes_by_id[parent_scope_id];
+        parent_scope.children.push(new_scope_id);
+        new_scope_id
+    }
+
+    pub(super) fn record_scope_for_node(&mut self, node_key: NodeKey, scope_id: ScopeId) {
+        self.symbol_table.scopes_by_node.insert(node_key, scope_id);
+    }
+
+    pub(super) fn add_dependency(&mut self, dependency: Dependency) {
+        self.symbol_table.dependencies.push(dependency);
+    }
+
+    /// Records the scope for the current expression
+    pub(super) fn record_expression(&mut self, scope: ScopeId) -> ExpressionId {
+        self.symbol_table.expression_scopes.push(scope)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{ScopeKind, SymbolFlags, SymbolTable, SymbolTableBuilder};
+
+    #[test]
+    fn insert_same_name_symbol_twice() {
+        let mut builder = SymbolTableBuilder::new();
+        let root_scope_id = SymbolTable::root_scope_id();
+        let symbol_id_1 =
+            builder.add_or_update_symbol(root_scope_id, "foo", SymbolFlags::IS_DEFINED);
+        let symbol_id_2 = builder.add_or_update_symbol(root_scope_id, "foo", SymbolFlags::IS_USED);
+        let table = builder.finish();
+
+        assert_eq!(symbol_id_1, symbol_id_2);
+        assert!(symbol_id_1.symbol(&table).is_used(), "flags must merge");
+        assert!(symbol_id_1.symbol(&table).is_defined(), "flags must merge");
+    }
+
+    #[test]
+    fn insert_different_named_symbols() {
+        let mut builder = SymbolTableBuilder::new();
+        let root_scope_id = SymbolTable::root_scope_id();
+        let symbol_id_1 = builder.add_or_update_symbol(root_scope_id, "foo", SymbolFlags::empty());
+        let symbol_id_2 = builder.add_or_update_symbol(root_scope_id, "bar", SymbolFlags::empty());
+
+        assert_ne!(symbol_id_1, symbol_id_2);
+    }
+
+    #[test]
+    fn add_child_scope_with_symbol() {
+        let mut builder = SymbolTableBuilder::new();
+        let root_scope_id = SymbolTable::root_scope_id();
+        let foo_symbol_top =
+            builder.add_or_update_symbol(root_scope_id, "foo", SymbolFlags::empty());
+        let c_scope = builder.add_child_scope(root_scope_id, "C", ScopeKind::Class, None, None);
+        let foo_symbol_inner = builder.add_or_update_symbol(c_scope, "foo", SymbolFlags::empty());
+
+        assert_ne!(foo_symbol_top, foo_symbol_inner);
+    }
+
+    #[test]
+    fn scope_from_id() {
+        let table = SymbolTableBuilder::new().finish();
+        let root_scope_id = SymbolTable::root_scope_id();
+        let scope = root_scope_id.scope(&table);
+
+        assert_eq!(scope.name.as_str(), "<module>");
+        assert_eq!(scope.kind, ScopeKind::Module);
+    }
+
+    #[test]
+    fn symbol_from_id() {
+        let mut builder = SymbolTableBuilder::new();
+        let root_scope_id = SymbolTable::root_scope_id();
+        let foo_symbol_id =
+            builder.add_or_update_symbol(root_scope_id, "foo", SymbolFlags::empty());
+        let table = builder.finish();
+        let symbol = foo_symbol_id.symbol(&table);
+
+        assert_eq!(symbol.name(), "foo");
+    }
+
+    #[test]
+    fn bigger_symbol_table() {
+        let mut builder = SymbolTableBuilder::new();
+        let root_scope_id = SymbolTable::root_scope_id();
+        let foo_symbol_id =
+            builder.add_or_update_symbol(root_scope_id, "foo", SymbolFlags::empty());
+        builder.add_or_update_symbol(root_scope_id, "bar", SymbolFlags::empty());
+        builder.add_or_update_symbol(root_scope_id, "baz", SymbolFlags::empty());
+        builder.add_or_update_symbol(root_scope_id, "qux", SymbolFlags::empty());
+        let table = builder.finish();
+
+        let foo_symbol_id_2 = table
+            .root_symbol_id_by_name("foo")
+            .expect("foo symbol to be found");
+
+        assert_eq!(foo_symbol_id_2, foo_symbol_id);
+    }
+}

crates/red_knot/src/semantic/types.rs

@@ -2,19 +2,23 @@
 use crate::ast_ids::NodeKey;
 use crate::db::{QueryResult, SemanticDb, SemanticJar};
 use crate::files::FileId;
-use crate::symbols::{symbol_table, GlobalSymbolId, ScopeId, ScopeKind, SymbolId};
+use crate::module::{Module, ModuleName};
+use crate::semantic::{
+    resolve_global_symbol, semantic_index, GlobalSymbolId, ScopeId, ScopeKind, SymbolId,
+};
 use crate::{FxDashMap, FxIndexSet, Name};
 use ruff_index::{newtype_index, IndexVec};
+use ruff_python_ast as ast;
 use rustc_hash::FxHashMap;
 
 pub(crate) mod infer;
 
-pub(crate) use infer::{infer_definition_type, infer_symbol_type};
+pub(crate) use infer::{infer_definition_type, infer_symbol_public_type};
 
 /// unique ID for a type
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 pub enum Type {
-    /// the dynamic or gradual type: a statically-unknown set of values
+    /// the dynamic type: a statically-unknown set of values
     Any,
     /// the empty set of values
     Never,
@@ -23,14 +27,19 @@ pub enum Type {
     Unknown,
     /// name is not bound to any value
     Unbound,
+    /// the None object (TODO remove this in favor of Instance(types.NoneType)
+    None,
     /// a specific function object
     Function(FunctionTypeId),
+    /// a specific module object
+    Module(ModuleTypeId),
     /// a specific class object
     Class(ClassTypeId),
     /// the set of Python objects with the given class in their __class__'s method resolution order
     Instance(ClassTypeId),
     Union(UnionTypeId),
     Intersection(IntersectionTypeId),
+    IntLiteral(i64),
     // TODO protocols, callable types, overloads, generics, type vars
 }
 
@@ -46,6 +55,90 @@ impl Type {
     pub const fn is_unknown(&self) -> bool {
         matches!(self, Type::Unknown)
     }
+
+    pub fn get_member(&self, db: &dyn SemanticDb, name: &Name) -> QueryResult<Option<Type>> {
+        match self {
+            Type::Any => Ok(Some(Type::Any)),
+            Type::Never => todo!("attribute lookup on Never type"),
+            Type::Unknown => Ok(Some(Type::Unknown)),
+            Type::Unbound => todo!("attribute lookup on Unbound type"),
+            Type::None => todo!("attribute lookup on None type"),
+            Type::Function(_) => todo!("attribute lookup on Function type"),
+            Type::Module(module_id) => module_id.get_member(db, name),
+            Type::Class(class_id) => class_id.get_class_member(db, name),
+            Type::Instance(_) => {
+                // TODO MRO? get_own_instance_member, get_instance_member
+                todo!("attribute lookup on Instance type")
+            }
+            Type::Union(union_id) => {
+                let jar: &SemanticJar = db.jar()?;
+                let _todo_union_ref = jar.type_store.get_union(*union_id);
+                // TODO perform the get_member on each type in the union
+                // TODO return the union of those results
+                // TODO if any of those results is `None` then include Unknown in the result union
+                todo!("attribute lookup on Union type")
+            }
+            Type::Intersection(_) => {
+                // TODO perform the get_member on each type in the intersection
+                // TODO return the intersection of those results
+                todo!("attribute lookup on Intersection type")
+            }
+            Type::IntLiteral(_) => {
+                // TODO raise error
+                Ok(Some(Type::Unknown))
+            }
+        }
+    }
+
+    // when this is fully fleshed out, it will use the db arg and may return QueryError
+    #[allow(clippy::unnecessary_wraps)]
+    pub fn resolve_bin_op(
+        &self,
+        _db: &dyn SemanticDb,
+        op: ast::Operator,
+        right_ty: Type,
+    ) -> QueryResult<Type> {
+        match self {
+            Type::Any => Ok(Type::Any),
+            Type::Unknown => Ok(Type::Unknown),
+            Type::IntLiteral(n) => {
+                match right_ty {
+                    Type::IntLiteral(m) => {
+                        match op {
+                            ast::Operator::Add => Ok(n
+                                .checked_add(m)
+                                .map(Type::IntLiteral)
+                                // TODO builtins.int
+                                .unwrap_or(Type::Unknown)),
+                            ast::Operator::Sub => Ok(n
+                                .checked_sub(m)
+                                .map(Type::IntLiteral)
+                                // TODO builtins.int
+                                .unwrap_or(Type::Unknown)),
+                            ast::Operator::Mult => Ok(n
+                                .checked_mul(m)
+                                .map(Type::IntLiteral)
+                                // TODO builtins.int
+                                .unwrap_or(Type::Unknown)),
+                            ast::Operator::Div => Ok(n
+                                .checked_div(m)
+                                .map(Type::IntLiteral)
+                                // TODO builtins.int
+                                .unwrap_or(Type::Unknown)),
+                            ast::Operator::Mod => Ok(n
+                                .checked_rem(m)
+                                .map(Type::IntLiteral)
+                                // TODO division by zero error
+                                .unwrap_or(Type::Unknown)),
+                            _ => todo!("complete binop op support for IntLiteral"),
+                        }
+                    }
+                    _ => todo!("complete binop right_ty support for IntLiteral"),
+                }
+            }
+            _ => todo!("complete binop support"),
+        }
+    }
 }
 
 impl From<FunctionTypeId> for Type {
@@ -80,7 +173,7 @@ impl TypeStore {
         self.modules.remove(&file_id);
     }
 
-    pub fn cache_symbol_type(&self, symbol: GlobalSymbolId, ty: Type) {
+    pub fn cache_symbol_public_type(&self, symbol: GlobalSymbolId, ty: Type) {
         self.add_or_get_module(symbol.file_id)
             .symbol_types
             .insert(symbol.symbol_id, ty);
@@ -92,7 +185,7 @@ impl TypeStore {
             .insert(node_key, ty);
     }
 
-    pub fn get_cached_symbol_type(&self, symbol: GlobalSymbolId) -> Option<Type> {
+    pub fn get_cached_symbol_public_type(&self, symbol: GlobalSymbolId) -> Option<Type> {
         self.try_get_module(symbol.file_id)?
             .symbol_types
             .get(&symbol.symbol_id)
@@ -120,7 +213,7 @@ impl TypeStore {
         self.modules.get(&file_id)
     }
 
-    fn add_function(
+    fn add_function_type(
         &self,
         file_id: FileId,
         name: &str,
@@ -132,7 +225,18 @@ impl TypeStore {
             .add_function(name, symbol_id, scope_id, decorators)
     }
 
-    fn add_class(
+    fn add_function(
+        &self,
+        file_id: FileId,
+        name: &str,
+        symbol_id: SymbolId,
+        scope_id: ScopeId,
+        decorators: Vec<Type>,
+    ) -> Type {
+        Type::Function(self.add_function_type(file_id, name, symbol_id, scope_id, decorators))
+    }
+
+    fn add_class_type(
         &self,
         file_id: FileId,
         name: &str,
@@ -143,12 +247,36 @@ impl TypeStore {
             .add_class(name, scope_id, bases)
     }
 
-    fn add_union(&mut self, file_id: FileId, elems: &[Type]) -> UnionTypeId {
+    fn add_class(&self, file_id: FileId, name: &str, scope_id: ScopeId, bases: Vec<Type>) -> Type {
+        Type::Class(self.add_class_type(file_id, name, scope_id, bases))
+    }
+
+    /// add "raw" union type with exactly given elements
+    fn add_union_type(&self, file_id: FileId, elems: &[Type]) -> UnionTypeId {
         self.add_or_get_module(file_id).add_union(elems)
     }
 
-    fn add_intersection(
-        &mut self,
+    /// add union with normalization; may not return a `UnionType`
+    fn add_union(&self, file_id: FileId, elems: &[Type]) -> Type {
+        let mut flattened = Vec::with_capacity(elems.len());
+        for ty in elems {
+            match ty {
+                Type::Union(union_id) => flattened.extend(union_id.elements(self)),
+                _ => flattened.push(*ty),
+            }
+        }
+        // TODO don't add identical unions
+        // TODO de-duplicate union elements
+        match flattened[..] {
+            [] => Type::Never,
+            [ty] => ty,
+            _ => Type::Union(self.add_union_type(file_id, &flattened)),
+        }
+    }
+
+    /// add "raw" intersection type with exactly given elements
+    fn add_intersection_type(
+        &self,
         file_id: FileId,
         positive: &[Type],
         negative: &[Type],
@@ -157,6 +285,38 @@ impl TypeStore {
             .add_intersection(positive, negative)
     }
 
+    /// add intersection with normalization; may not return an `IntersectionType`
+    fn add_intersection(&self, file_id: FileId, positive: &[Type], negative: &[Type]) -> Type {
+        let mut pos_flattened = Vec::with_capacity(positive.len());
+        let mut neg_flattened = Vec::with_capacity(negative.len());
+        for ty in positive {
+            match ty {
+                Type::Intersection(intersection_id) => {
+                    pos_flattened.extend(intersection_id.positive(self));
+                    neg_flattened.extend(intersection_id.negative(self));
+                }
+                _ => pos_flattened.push(*ty),
+            }
+        }
+        for ty in negative {
+            match ty {
+                Type::Intersection(intersection_id) => {
+                    pos_flattened.extend(intersection_id.negative(self));
+                    neg_flattened.extend(intersection_id.positive(self));
+                }
+                _ => neg_flattened.push(*ty),
+            }
+        }
+        // TODO don't add identical intersections
+        // TODO deduplicate intersection elements
+        // TODO maintain DNF form (union of intersections)
+        match (&pos_flattened[..], &neg_flattened[..]) {
+            ([], []) => Type::Any, // TODO should be object
+            ([ty], []) => *ty,
+            (pos, neg) => Type::Intersection(self.add_intersection_type(file_id, pos, neg)),
+        }
+    }
+
     fn get_function(&self, id: FunctionTypeId) -> FunctionTypeRef {
         FunctionTypeRef {
             module_store: self.get_module(id.file_id),
@@ -292,10 +452,11 @@ impl FunctionTypeId {
         self,
         db: &dyn SemanticDb,
     ) -> QueryResult<Option<ClassTypeId>> {
-        let table = symbol_table(db, self.file_id)?;
+        let index = semantic_index(db, self.file_id)?;
+        let table = index.symbol_table();
         let FunctionType { symbol_id, .. } = *self.function(db)?;
-        let scope_id = symbol_id.symbol(&table).scope_id();
-        let scope = scope_id.scope(&table);
+        let scope_id = symbol_id.symbol(table).scope_id();
+        let scope = scope_id.scope(table);
         if !matches!(scope.kind(), ScopeKind::Class) {
             return Ok(None);
         };
@@ -336,6 +497,31 @@ impl FunctionTypeId {
     }
 }
 
+#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
+pub struct ModuleTypeId {
+    module: Module,
+    file_id: FileId,
+}
+
+impl ModuleTypeId {
+    fn module(self, db: &dyn SemanticDb) -> QueryResult<ModuleStoreRef> {
+        let jar: &SemanticJar = db.jar()?;
+        Ok(jar.type_store.add_or_get_module(self.file_id).downgrade())
+    }
+
+    pub(crate) fn name(self, db: &dyn SemanticDb) -> QueryResult<ModuleName> {
+        self.module.name(db)
+    }
+
+    fn get_member(self, db: &dyn SemanticDb, name: &Name) -> QueryResult<Option<Type>> {
+        if let Some(symbol_id) = resolve_global_symbol(db, self.module, name)? {
+            Ok(Some(infer_symbol_public_type(db, symbol_id)?))
+        } else {
+            Ok(None)
+        }
+    }
+}
+
 #[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
 pub struct ClassTypeId {
     file_id: FileId,
@@ -375,9 +561,9 @@ impl ClassTypeId {
     fn get_own_class_member(self, db: &dyn SemanticDb, name: &Name) -> QueryResult<Option<Type>> {
         // TODO: this should distinguish instance-only members (e.g. `x: int`) and not return them
         let ClassType { scope_id, .. } = *self.class(db)?;
-        let table = symbol_table(db, self.file_id)?;
-        if let Some(symbol_id) = table.symbol_id_by_name(scope_id, name) {
-            Ok(Some(infer_symbol_type(
+        let index = semantic_index(db, self.file_id)?;
+        if let Some(symbol_id) = index.symbol_table().symbol_id_by_name(scope_id, name) {
+            Ok(Some(infer_symbol_public_type(
                 db,
                 GlobalSymbolId {
                     file_id: self.file_id,
@@ -389,7 +575,13 @@ impl ClassTypeId {
         }
     }
 
-    // TODO: get_own_instance_member, get_class_member, get_instance_member
+    /// Get own class member or fall back to super-class member.
+    fn get_class_member(self, db: &dyn SemanticDb, name: &Name) -> QueryResult<Option<Type>> {
+        self.get_own_class_member(db, name)
+            .or_else(|_| self.get_super_class_member(db, name))
+    }
+
+    // TODO: get_own_instance_member, get_instance_member
 }
 
 #[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
@@ -398,12 +590,31 @@ pub struct UnionTypeId {
     union_id: ModuleUnionTypeId,
 }
 
+impl UnionTypeId {
+    pub fn elements(self, type_store: &TypeStore) -> Vec<Type> {
+        let union = type_store.get_union(self);
+        union.elements.iter().copied().collect()
+    }
+}
+
 #[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
 pub struct IntersectionTypeId {
     file_id: FileId,
     intersection_id: ModuleIntersectionTypeId,
 }
 
+impl IntersectionTypeId {
+    pub fn positive(self, type_store: &TypeStore) -> Vec<Type> {
+        let intersection = type_store.get_intersection(self);
+        intersection.positive.iter().copied().collect()
+    }
+
+    pub fn negative(self, type_store: &TypeStore) -> Vec<Type> {
+        let intersection = type_store.get_intersection(self);
+        intersection.negative.iter().copied().collect()
+    }
+}
+
 #[newtype_index]
 struct ModuleFunctionTypeId;
 
@@ -427,7 +638,7 @@ struct ModuleTypeStore {
     unions: IndexVec<ModuleUnionTypeId, UnionType>,
     /// arena of all intersection types created in this module
     intersections: IndexVec<ModuleIntersectionTypeId, IntersectionType>,
-    /// cached types of symbols in this module
+    /// cached public types of symbols in this module
     symbol_types: FxHashMap<SymbolId, Type>,
     /// cached types of AST nodes in this module
     node_types: FxHashMap<NodeKey, Type>,
@@ -529,6 +740,11 @@ impl std::fmt::Display for DisplayType<'_> {
             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::Module(module_id) => {
+                // NOTE: something like this?: "<module 'module-name' from 'path-from-fileid'>"
+                todo!("{module_id:?}")
+            }
             // TODO functions and classes should display using a fully qualified name
             Type::Class(class_id) => {
                 f.write_str("Literal[")?;
@@ -547,6 +763,7 @@ impl std::fmt::Display for DisplayType<'_> {
                 .get_module(int_id.file_id)
                 .get_intersection(int_id.intersection_id)
                 .display(f, self.store),
+            Type::IntLiteral(n) => write!(f, "Literal[{n}]"),
         }
     }
 }
@@ -605,16 +822,42 @@ pub(crate) struct UnionType {
 
 impl UnionType {
     fn display(&self, f: &mut std::fmt::Formatter<'_>, store: &TypeStore) -> std::fmt::Result {
-        f.write_str("(")?;
+        let (int_literals, other_types): (Vec<Type>, Vec<Type>) = self
+            .elements
+            .iter()
+            .copied()
+            .partition(|ty| matches!(ty, Type::IntLiteral(_)));
         let mut first = true;
-        for ty in &self.elements {
+        if !int_literals.is_empty() {
+            f.write_str("Literal[")?;
+            let mut nums: Vec<i64> = int_literals
+                .into_iter()
+                .filter_map(|ty| {
+                    if let Type::IntLiteral(n) = ty {
+                        Some(n)
+                    } else {
+                        None
+                    }
+                })
+                .collect();
+            nums.sort_unstable();
+            for num in nums {
+                if !first {
+                    f.write_str(", ")?;
+                }
+                write!(f, "{num}")?;
+                first = false;
+            }
+            f.write_str("]")?;
+        }
+        for ty in other_types {
             if !first {
                 f.write_str(" | ")?;
             };
             first = false;
             write!(f, "{}", ty.display(store))?;
         }
-        f.write_str(")")
+        Ok(())
     }
 }
 
@@ -634,7 +877,6 @@ pub(crate) struct IntersectionType {
 
 impl IntersectionType {
     fn display(&self, f: &mut std::fmt::Formatter<'_>, store: &TypeStore) -> std::fmt::Result {
-        f.write_str("(")?;
         let mut first = true;
         for (neg, ty) in self
             .positive
@@ -651,25 +893,79 @@ impl IntersectionType {
             };
             write!(f, "{}", ty.display(store))?;
         }
-        f.write_str(")")
+        Ok(())
     }
 }
 
 #[cfg(test)]
 mod tests {
+    use super::Type;
     use std::path::Path;
 
     use crate::files::Files;
-    use crate::symbols::{SymbolFlags, SymbolTable};
-    use crate::types::{Type, TypeStore};
+    use crate::semantic::symbol_table::SymbolTableBuilder;
+    use crate::semantic::{FileId, ScopeId, SymbolFlags, SymbolTable, TypeStore};
     use crate::FxIndexSet;
 
+    struct TestCase {
+        store: TypeStore,
+        files: Files,
+        file_id: FileId,
+        root_scope: ScopeId,
+    }
+
+    fn create_test() -> TestCase {
+        let files = Files::default();
+        let file_id = files.intern(Path::new("/foo"));
+        TestCase {
+            store: TypeStore::default(),
+            files,
+            file_id,
+            root_scope: SymbolTable::root_scope_id(),
+        }
+    }
+
+    fn assert_union_elements(store: &TypeStore, union: Type, elements: &[Type]) {
+        let Type::Union(union_id) = union else {
+            panic!("should be a union")
+        };
+
+        assert_eq!(
+            store.get_union(union_id).elements,
+            elements.iter().copied().collect::<FxIndexSet<_>>()
+        );
+    }
+
+    fn assert_intersection_elements(
+        store: &TypeStore,
+        intersection: Type,
+        positive: &[Type],
+        negative: &[Type],
+    ) {
+        let Type::Intersection(intersection_id) = intersection else {
+            panic!("should be a intersection")
+        };
+
+        assert_eq!(
+            store.get_intersection(intersection_id).positive,
+            positive.iter().copied().collect::<FxIndexSet<_>>()
+        );
+        assert_eq!(
+            store.get_intersection(intersection_id).negative,
+            negative.iter().copied().collect::<FxIndexSet<_>>()
+        );
+    }
+
     #[test]
     fn add_class() {
-        let store = TypeStore::default();
-        let files = Files::default();
-        let file_id = files.intern(Path::new("/foo"));
-        let id = store.add_class(file_id, "C", SymbolTable::root_scope_id(), Vec::new());
+        let TestCase {
+            store,
+            file_id,
+            root_scope,
+            ..
+        } = create_test();
+
+        let id = store.add_class_type(file_id, "C", root_scope, Vec::new());
         assert_eq!(store.get_class(id).name(), "C");
         let inst = Type::Instance(id);
         assert_eq!(format!("{}", inst.display(&store)), "C");
@@ -677,21 +973,26 @@ mod tests {
 
     #[test]
     fn add_function() {
-        let store = TypeStore::default();
-        let files = Files::default();
-        let file_id = files.intern(Path::new("/foo"));
-        let mut table = SymbolTable::new();
-        let func_symbol = table.add_or_update_symbol(
+        let TestCase {
+            store,
+            file_id,
+            root_scope,
+            ..
+        } = create_test();
+
+        let mut builder = SymbolTableBuilder::new();
+        let func_symbol = builder.add_or_update_symbol(
             SymbolTable::root_scope_id(),
             "func",
             SymbolFlags::IS_DEFINED,
         );
+        builder.finish();
 
-        let id = store.add_function(
+        let id = store.add_function_type(
             file_id,
             "func",
             func_symbol,
-            SymbolTable::root_scope_id(),
+            root_scope,
             vec![Type::Unknown],
         );
         assert_eq!(store.get_function(id).name(), "func");
@@ -702,44 +1003,117 @@ mod tests {
 
     #[test]
     fn add_union() {
-        let mut store = TypeStore::default();
-        let files = Files::default();
-        let file_id = files.intern(Path::new("/foo"));
-        let c1 = store.add_class(file_id, "C1", SymbolTable::root_scope_id(), Vec::new());
-        let c2 = store.add_class(file_id, "C2", SymbolTable::root_scope_id(), Vec::new());
+        let TestCase {
+            store,
+            file_id,
+            root_scope,
+            ..
+        } = create_test();
+
+        let c1 = store.add_class_type(file_id, "C1", root_scope, Vec::new());
+        let c2 = store.add_class_type(file_id, "C2", root_scope, Vec::new());
         let elems = vec![Type::Instance(c1), Type::Instance(c2)];
-        let id = store.add_union(file_id, &elems);
-        assert_eq!(
-            store.get_union(id).elements,
-            elems.into_iter().collect::<FxIndexSet<_>>()
-        );
+        let id = store.add_union_type(file_id, &elems);
         let union = Type::Union(id);
-        assert_eq!(format!("{}", union.display(&store)), "(C1 | C2)");
+
+        assert_union_elements(&store, union, &elems);
+        assert_eq!(format!("{}", union.display(&store)), "C1 | C2");
     }
 
     #[test]
     fn add_intersection() {
-        let mut store = TypeStore::default();
-        let files = Files::default();
-        let file_id = files.intern(Path::new("/foo"));
-        let c1 = store.add_class(file_id, "C1", SymbolTable::root_scope_id(), Vec::new());
-        let c2 = store.add_class(file_id, "C2", SymbolTable::root_scope_id(), Vec::new());
-        let c3 = store.add_class(file_id, "C3", SymbolTable::root_scope_id(), Vec::new());
+        let TestCase {
+            store,
+            file_id,
+            root_scope,
+            ..
+        } = create_test();
+
+        let c1 = store.add_class_type(file_id, "C1", root_scope, Vec::new());
+        let c2 = store.add_class_type(file_id, "C2", root_scope, Vec::new());
+        let c3 = store.add_class_type(file_id, "C3", root_scope, Vec::new());
         let pos = vec![Type::Instance(c1), Type::Instance(c2)];
         let neg = vec![Type::Instance(c3)];
-        let id = store.add_intersection(file_id, &pos, &neg);
-        assert_eq!(
-            store.get_intersection(id).positive,
-            pos.into_iter().collect::<FxIndexSet<_>>()
-        );
-        assert_eq!(
-            store.get_intersection(id).negative,
-            neg.into_iter().collect::<FxIndexSet<_>>()
-        );
+        let id = store.add_intersection_type(file_id, &pos, &neg);
         let intersection = Type::Intersection(id);
-        assert_eq!(
-            format!("{}", intersection.display(&store)),
-            "(C1 & C2 & ~C3)"
-        );
+
+        assert_intersection_elements(&store, intersection, &pos, &neg);
+        assert_eq!(format!("{}", intersection.display(&store)), "C1 & C2 & ~C3");
+    }
+
+    #[test]
+    fn flatten_union_zero_elements() {
+        let TestCase { store, file_id, .. } = create_test();
+
+        let ty = store.add_union(file_id, &[]);
+
+        assert!(matches!(ty, Type::Never), "{ty:?} should be Never");
+    }
+
+    #[test]
+    fn flatten_union_one_element() {
+        let TestCase { store, file_id, .. } = create_test();
+
+        let ty = store.add_union(file_id, &[Type::None]);
+
+        assert!(matches!(ty, Type::None), "{ty:?} should be None");
+    }
+
+    #[test]
+    fn flatten_nested_union() {
+        let TestCase { store, file_id, .. } = create_test();
+
+        let l1 = Type::IntLiteral(1);
+        let l2 = Type::IntLiteral(2);
+        let u1 = store.add_union(file_id, &[l1, l2]);
+        let u2 = store.add_union(file_id, &[u1, Type::None]);
+
+        assert_union_elements(&store, u2, &[l1, l2, Type::None]);
+    }
+
+    #[test]
+    fn flatten_intersection_zero_elements() {
+        let TestCase { store, file_id, .. } = create_test();
+
+        let ty = store.add_intersection(file_id, &[], &[]);
+
+        // TODO should be object, not Any
+        assert!(matches!(ty, Type::Any), "{ty:?} should be object");
+    }
+
+    #[test]
+    fn flatten_intersection_one_positive_element() {
+        let TestCase { store, file_id, .. } = create_test();
+
+        let ty = store.add_intersection(file_id, &[Type::None], &[]);
+
+        assert!(matches!(ty, Type::None), "{ty:?} should be None");
+    }
+
+    #[test]
+    fn flatten_intersection_one_negative_element() {
+        let TestCase { store, file_id, .. } = create_test();
+
+        let ty = store.add_intersection(file_id, &[], &[Type::None]);
+
+        assert_intersection_elements(&store, ty, &[], &[Type::None]);
+    }
+
+    #[test]
+    fn flatten_nested_intersection() {
+        let TestCase {
+            store,
+            file_id,
+            root_scope,
+            ..
+        } = create_test();
+
+        let c1 = Type::Instance(store.add_class_type(file_id, "C1", root_scope, vec![]));
+        let c2 = Type::Instance(store.add_class_type(file_id, "C2", root_scope, vec![]));
+        let c1sub = Type::Instance(store.add_class_type(file_id, "C1sub", root_scope, vec![c1]));
+        let i1 = store.add_intersection(file_id, &[c1, c2], &[c1sub]);
+        let i2 = store.add_intersection(file_id, &[i1, Type::None], &[]);
+
+        assert_intersection_elements(&store, i2, &[c1, c2, Type::None], &[c1sub]);
     }
 }

crates/red_knot/src/semantic/types/infer.rs

@@ -0,0 +1,762 @@
+#![allow(dead_code)]
+
+use ruff_python_ast as ast;
+use ruff_python_ast::AstNode;
+use std::fmt::Debug;
+
+use crate::db::{QueryResult, SemanticDb, SemanticJar};
+
+use crate::module::{resolve_module, ModuleName};
+use crate::parse::parse;
+use crate::semantic::types::{ModuleTypeId, Type};
+use crate::semantic::{
+    resolve_global_symbol, semantic_index, ConstrainedDefinition, Definition, GlobalSymbolId,
+    ImportDefinition, ImportFromDefinition,
+};
+use crate::{FileId, Name};
+
+// FIXME: Figure out proper dead-lock free synchronisation now that this takes `&db` instead of `&mut db`.
+/// Resolve the public-facing type for a symbol (the type seen by other scopes: other modules, or
+/// nested functions). Because calls to nested functions and imports can occur anywhere in control
+/// flow, this type must be conservative and consider all definitions of the symbol that could
+/// possibly be seen by another scope. Currently we take the most conservative approach, which is
+/// the union of all definitions. We may be able to narrow this in future to eliminate definitions
+/// which can't possibly (or at least likely) be seen by any other scope, so that e.g. we could
+/// infer `Literal["1"]` instead of `Literal[1] | Literal["1"]` for `x` in `x = x; x = str(x);`.
+#[tracing::instrument(level = "trace", skip(db))]
+pub fn infer_symbol_public_type(db: &dyn SemanticDb, symbol: GlobalSymbolId) -> QueryResult<Type> {
+    let index = semantic_index(db, symbol.file_id)?;
+    let defs = index.symbol_table().definitions(symbol.symbol_id).to_vec();
+    let jar: &SemanticJar = db.jar()?;
+
+    if let Some(ty) = jar.type_store.get_cached_symbol_public_type(symbol) {
+        return Ok(ty);
+    }
+
+    let ty = infer_type_from_definitions(db, symbol, defs.iter().cloned())?;
+
+    jar.type_store.cache_symbol_public_type(symbol, ty);
+
+    // TODO record dependencies
+    Ok(ty)
+}
+
+/// Infer type of a symbol as union of the given `Definitions`.
+fn infer_type_from_definitions<T>(
+    db: &dyn SemanticDb,
+    symbol: GlobalSymbolId,
+    definitions: T,
+) -> QueryResult<Type>
+where
+    T: Debug + IntoIterator<Item = Definition>,
+{
+    infer_type_from_constrained_definitions(
+        db,
+        symbol,
+        definitions
+            .into_iter()
+            .map(|definition| ConstrainedDefinition {
+                definition,
+                constraints: vec![],
+            }),
+    )
+}
+
+/// Infer type of a symbol as union of the given `ConstrainedDefinitions`.
+fn infer_type_from_constrained_definitions<T>(
+    db: &dyn SemanticDb,
+    symbol: GlobalSymbolId,
+    constrained_definitions: T,
+) -> QueryResult<Type>
+where
+    T: IntoIterator<Item = ConstrainedDefinition>,
+{
+    let jar: &SemanticJar = db.jar()?;
+    let mut tys = constrained_definitions
+        .into_iter()
+        .map(|def| infer_constrained_definition_type(db, symbol, def.clone()))
+        .peekable();
+    if let Some(first) = tys.next() {
+        if tys.peek().is_some() {
+            Ok(jar.type_store.add_union(
+                symbol.file_id,
+                &Iterator::chain(std::iter::once(first), tys).collect::<QueryResult<Vec<_>>>()?,
+            ))
+        } else {
+            first
+        }
+    } else {
+        Ok(Type::Unknown)
+    }
+}
+
+/// Infer type for a ConstrainedDefinition (intersection of the definition type and the
+/// constraints)
+#[tracing::instrument(level = "trace", skip(db))]
+pub fn infer_constrained_definition_type(
+    db: &dyn SemanticDb,
+    symbol: GlobalSymbolId,
+    constrained_definition: ConstrainedDefinition,
+) -> QueryResult<Type> {
+    let ConstrainedDefinition {
+        definition,
+        constraints,
+    } = constrained_definition;
+    let index = semantic_index(db, symbol.file_id)?;
+    let parsed = parse(db.upcast(), symbol.file_id)?;
+    let mut intersected_types = vec![infer_definition_type(db, symbol, definition)?];
+    for constraint in constraints {
+        if let Some(constraint_type) = infer_constraint_type(
+            db,
+            symbol,
+            index.resolve_expression_id(parsed.syntax(), constraint),
+        )? {
+            intersected_types.push(constraint_type);
+        }
+    }
+    let jar: &SemanticJar = db.jar()?;
+    Ok(jar
+        .type_store
+        .add_intersection(symbol.file_id, &intersected_types, &[]))
+}
+
+/// Infer a type for a Definition
+#[tracing::instrument(level = "trace", skip(db))]
+pub fn infer_definition_type(
+    db: &dyn SemanticDb,
+    symbol: GlobalSymbolId,
+    definition: Definition,
+) -> QueryResult<Type> {
+    let jar: &SemanticJar = db.jar()?;
+    let type_store = &jar.type_store;
+    let file_id = symbol.file_id;
+
+    match definition {
+        Definition::Unbound => Ok(Type::Unbound),
+        Definition::Import(ImportDefinition {
+            module: module_name,
+        }) => {
+            if let Some(module) = resolve_module(db, module_name.clone())? {
+                Ok(Type::Module(ModuleTypeId { module, file_id }))
+            } else {
+                Ok(Type::Unknown)
+            }
+        }
+        Definition::ImportFrom(ImportFromDefinition {
+            module,
+            name,
+            level,
+        }) => {
+            // TODO relative imports
+            assert!(matches!(level, 0));
+            let module_name = ModuleName::new(module.as_ref().expect("TODO relative imports"));
+            let Some(module) = resolve_module(db, module_name.clone())? else {
+                return Ok(Type::Unknown);
+            };
+
+            if let Some(remote_symbol) = resolve_global_symbol(db, module, &name)? {
+                infer_symbol_public_type(db, remote_symbol)
+            } else {
+                Ok(Type::Unknown)
+            }
+        }
+        Definition::ClassDef(node_key) => {
+            if let Some(ty) = type_store.get_cached_node_type(file_id, node_key.erased()) {
+                Ok(ty)
+            } else {
+                let parsed = parse(db.upcast(), file_id)?;
+                let ast = parsed.syntax();
+                let index = semantic_index(db, file_id)?;
+                let node = node_key.resolve_unwrap(ast.as_any_node_ref());
+
+                let mut bases = Vec::with_capacity(node.bases().len());
+
+                for base in node.bases() {
+                    bases.push(infer_expr_type(db, file_id, base)?);
+                }
+                let scope_id = index.symbol_table().scope_id_for_node(node_key.erased());
+                let ty = type_store.add_class(file_id, &node.name.id, scope_id, bases);
+                type_store.cache_node_type(file_id, *node_key.erased(), ty);
+                Ok(ty)
+            }
+        }
+        Definition::FunctionDef(node_key) => {
+            if let Some(ty) = type_store.get_cached_node_type(file_id, node_key.erased()) {
+                Ok(ty)
+            } else {
+                let parsed = parse(db.upcast(), file_id)?;
+                let ast = parsed.syntax();
+                let index = semantic_index(db, file_id)?;
+                let node = node_key
+                    .resolve(ast.as_any_node_ref())
+                    .expect("node key should resolve");
+
+                let decorator_tys = node
+                    .decorator_list
+                    .iter()
+                    .map(|decorator| infer_expr_type(db, file_id, &decorator.expression))
+                    .collect::<QueryResult<_>>()?;
+                let scope_id = index.symbol_table().scope_id_for_node(node_key.erased());
+                let ty = type_store.add_function(
+                    file_id,
+                    &node.name.id,
+                    symbol.symbol_id,
+                    scope_id,
+                    decorator_tys,
+                );
+                type_store.cache_node_type(file_id, *node_key.erased(), ty);
+                Ok(ty)
+            }
+        }
+        Definition::Assignment(node_key) => {
+            let parsed = parse(db.upcast(), file_id)?;
+            let ast = parsed.syntax();
+            let node = node_key.resolve_unwrap(ast.as_any_node_ref());
+            // TODO handle unpacking assignment
+            infer_expr_type(db, file_id, &node.value)
+        }
+        Definition::AnnotatedAssignment(node_key) => {
+            let parsed = parse(db.upcast(), file_id)?;
+            let ast = parsed.syntax();
+            let node = node_key.resolve_unwrap(ast.as_any_node_ref());
+            // TODO actually look at the annotation
+            let Some(value) = &node.value else {
+                return Ok(Type::Unknown);
+            };
+            // TODO handle unpacking assignment
+            infer_expr_type(db, file_id, value)
+        }
+        Definition::NamedExpr(node_key) => {
+            let parsed = parse(db.upcast(), file_id)?;
+            let ast = parsed.syntax();
+            let node = node_key.resolve_unwrap(ast.as_any_node_ref());
+            infer_expr_type(db, file_id, &node.value)
+        }
+    }
+}
+
+/// Return the type that the given constraint (an expression from a control-flow test) requires the
+/// given symbol to have. For example, returns the Type "~None" as the constraint type if given the
+/// symbol ID for x and the expression ID for `x is not None`. Returns (Rust) None if the given
+/// expression applies no constraints on the given symbol.
+#[tracing::instrument(level = "trace", skip(db))]
+fn infer_constraint_type(
+    db: &dyn SemanticDb,
+    symbol_id: GlobalSymbolId,
+    // TODO this should preferably take an &ast::Expr instead of AnyNodeRef
+    expression: ast::AnyNodeRef,
+) -> QueryResult<Option<Type>> {
+    let file_id = symbol_id.file_id;
+    let index = semantic_index(db, file_id)?;
+    let jar: &SemanticJar = db.jar()?;
+    let symbol_name = symbol_id.symbol_id.symbol(&index.symbol_table).name();
+    // TODO narrowing attributes
+    // TODO narrowing dict keys
+    // TODO isinstance, ==/!=, type(...), literals, bools...
+    match expression {
+        ast::AnyNodeRef::ExprCompare(ast::ExprCompare {
+            left,
+            ops,
+            comparators,
+            ..
+        }) => {
+            // TODO chained comparisons
+            match left.as_ref() {
+                ast::Expr::Name(ast::ExprName { id, .. }) if id == symbol_name => match ops[0] {
+                    ast::CmpOp::Is | ast::CmpOp::IsNot => {
+                        Ok(match infer_expr_type(db, file_id, &comparators[0])? {
+                            Type::None => Some(Type::None),
+                            _ => None,
+                        }
+                        .map(|ty| {
+                            if matches!(ops[0], ast::CmpOp::IsNot) {
+                                jar.type_store.add_intersection(file_id, &[], &[ty])
+                            } else {
+                                ty
+                            }
+                        }))
+                    }
+                    _ => Ok(None),
+                },
+                _ => Ok(None),
+            }
+        }
+        _ => Ok(None),
+    }
+}
+
+/// Infer type of the given expression.
+fn infer_expr_type(db: &dyn SemanticDb, file_id: FileId, expr: &ast::Expr) -> QueryResult<Type> {
+    // TODO cache the resolution of the type on the node
+    let index = semantic_index(db, file_id)?;
+    match expr {
+        ast::Expr::NoneLiteral(_) => Ok(Type::None),
+        ast::Expr::NumberLiteral(ast::ExprNumberLiteral { value, .. }) => {
+            match value {
+                ast::Number::Int(n) => {
+                    // TODO support big int literals
+                    Ok(n.as_i64().map(Type::IntLiteral).unwrap_or(Type::Unknown))
+                }
+                // TODO builtins.float or builtins.complex
+                _ => Ok(Type::Unknown),
+            }
+        }
+        ast::Expr::Name(name) => {
+            // TODO look up in the correct scope, don't assume global
+            if let Some(symbol_id) = index.symbol_table().root_symbol_id_by_name(&name.id) {
+                infer_type_from_constrained_definitions(
+                    db,
+                    GlobalSymbolId { file_id, symbol_id },
+                    index.reachable_definitions(symbol_id, expr),
+                )
+            } else {
+                Ok(Type::Unknown)
+            }
+        }
+        ast::Expr::Attribute(ast::ExprAttribute { value, attr, .. }) => {
+            let value_type = infer_expr_type(db, file_id, value)?;
+            let attr_name = &Name::new(&attr.id);
+            value_type
+                .get_member(db, attr_name)
+                .map(|ty| ty.unwrap_or(Type::Unknown))
+        }
+        ast::Expr::BinOp(ast::ExprBinOp {
+            left, op, right, ..
+        }) => {
+            let left_ty = infer_expr_type(db, file_id, left)?;
+            let right_ty = infer_expr_type(db, file_id, right)?;
+            // TODO add reverse bin op support if right <: left
+            left_ty.resolve_bin_op(db, *op, right_ty)
+        }
+        ast::Expr::Named(ast::ExprNamed { value, .. }) => infer_expr_type(db, file_id, value),
+        ast::Expr::If(ast::ExprIf { body, orelse, .. }) => {
+            // TODO detect statically known truthy or falsy test
+            let body_ty = infer_expr_type(db, file_id, body)?;
+            let else_ty = infer_expr_type(db, file_id, orelse)?;
+            let jar: &SemanticJar = db.jar()?;
+            Ok(jar.type_store.add_union(file_id, &[body_ty, else_ty]))
+        }
+        _ => todo!("expression type resolution for {:?}", expr),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use std::path::PathBuf;
+
+    use crate::db::tests::TestDb;
+    use crate::db::{HasJar, SemanticJar};
+    use crate::module::{
+        resolve_module, set_module_search_paths, ModuleName, ModuleResolutionInputs,
+    };
+    use crate::semantic::{infer_symbol_public_type, resolve_global_symbol, Type};
+    use crate::Name;
+
+    // TODO with virtual filesystem we shouldn't have to write files to disk for these
+    // tests
+
+    struct TestCase {
+        temp_dir: tempfile::TempDir,
+        db: TestDb,
+
+        src: PathBuf,
+    }
+
+    fn create_test() -> std::io::Result<TestCase> {
+        let temp_dir = tempfile::tempdir()?;
+
+        let src = temp_dir.path().join("src");
+        std::fs::create_dir(&src)?;
+        let src = src.canonicalize()?;
+
+        let search_paths = ModuleResolutionInputs {
+            extra_paths: vec![],
+            workspace_root: src.clone(),
+            site_packages: None,
+            custom_typeshed: None,
+        };
+
+        let mut db = TestDb::default();
+        set_module_search_paths(&mut db, search_paths);
+
+        Ok(TestCase { temp_dir, db, src })
+    }
+
+    fn write_to_path(case: &TestCase, relative_path: &str, contents: &str) -> anyhow::Result<()> {
+        let path = case.src.join(relative_path);
+        std::fs::write(path, contents)?;
+        Ok(())
+    }
+
+    fn get_public_type(
+        case: &TestCase,
+        module_name: &str,
+        variable_name: &str,
+    ) -> anyhow::Result<Type> {
+        let db = &case.db;
+        let module = resolve_module(db, ModuleName::new(module_name))?.expect("Module to exist");
+        let symbol = resolve_global_symbol(db, module, variable_name)?.expect("symbol to exist");
+
+        Ok(infer_symbol_public_type(db, symbol)?)
+    }
+
+    fn assert_public_type(
+        case: &TestCase,
+        module_name: &str,
+        variable_name: &str,
+        type_name: &str,
+    ) -> anyhow::Result<()> {
+        let ty = get_public_type(case, module_name, variable_name)?;
+
+        let jar = HasJar::<SemanticJar>::jar(&case.db)?;
+        assert_eq!(format!("{}", ty.display(&jar.type_store)), type_name);
+        Ok(())
+    }
+
+    #[test]
+    fn follow_import_to_class() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(&case, "a.py", "from b import C as D; E = D")?;
+        write_to_path(&case, "b.py", "class C: pass")?;
+
+        assert_public_type(&case, "a", "E", "Literal[C]")
+    }
+
+    #[test]
+    fn resolve_base_class_by_name() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "mod.py",
+            "
+                class Base: pass
+                class Sub(Base): pass
+            ",
+        )?;
+
+        let ty = get_public_type(&case, "mod", "Sub")?;
+
+        let Type::Class(class_id) = ty else {
+            panic!("Sub is not a Class")
+        };
+        let jar = HasJar::<SemanticJar>::jar(&case.db)?;
+        let base_names: Vec<_> = jar
+            .type_store
+            .get_class(class_id)
+            .bases()
+            .iter()
+            .map(|base_ty| format!("{}", base_ty.display(&jar.type_store)))
+            .collect();
+
+        assert_eq!(base_names, vec!["Literal[Base]"]);
+
+        Ok(())
+    }
+
+    #[test]
+    fn resolve_method() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "mod.py",
+            "
+                class C:
+                    def f(self): pass
+            ",
+        )?;
+
+        let ty = get_public_type(&case, "mod", "C")?;
+
+        let Type::Class(class_id) = ty else {
+            panic!("C is not a Class");
+        };
+
+        let member_ty = class_id
+            .get_own_class_member(&case.db, &Name::new("f"))
+            .expect("C.f to resolve");
+
+        let Some(Type::Function(func_id)) = member_ty else {
+            panic!("C.f is not a Function");
+        };
+
+        let jar = HasJar::<SemanticJar>::jar(&case.db)?;
+        let function = jar.type_store.get_function(func_id);
+        assert_eq!(function.name(), "f");
+
+        Ok(())
+    }
+
+    #[test]
+    fn resolve_module_member() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(&case, "a.py", "import b; D = b.C")?;
+        write_to_path(&case, "b.py", "class C: pass")?;
+
+        assert_public_type(&case, "a", "D", "Literal[C]")
+    }
+
+    #[test]
+    fn resolve_literal() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(&case, "a.py", "x = 1")?;
+
+        assert_public_type(&case, "a", "x", "Literal[1]")
+    }
+
+    #[test]
+    fn resolve_union() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                if flag:
+                    x = 1
+                else:
+                    x = 2
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[1, 2]")
+    }
+
+    #[test]
+    fn resolve_visible_def() -> anyhow::Result<()> {
+        let case = create_test()?;
+        write_to_path(&case, "a.py", "y = 1; y = 2; x = y")?;
+        assert_public_type(&case, "a", "x", "Literal[2]")
+    }
+
+    #[test]
+    fn join_paths() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                y = 1
+                y = 2
+                if flag:
+                    y = 3
+                x = y
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[2, 3]")
+    }
+
+    #[test]
+    fn maybe_unbound() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                if flag:
+                    y = 1
+                x = y
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[1] | Unbound")
+    }
+
+    #[test]
+    fn if_elif_else() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                y = 1
+                y = 2
+                if flag:
+                    y = 3
+                elif flag2:
+                    y = 4
+                else:
+                    r = y
+                    y = 5
+                    s = y
+                x = y
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[3, 4, 5]")?;
+        assert_public_type(&case, "a", "r", "Literal[2]")?;
+        assert_public_type(&case, "a", "s", "Literal[5]")
+    }
+
+    #[test]
+    fn if_elif() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                y = 1
+                y = 2
+                if flag:
+                    y = 3
+                elif flag2:
+                    y = 4
+                x = y
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[2, 3, 4]")
+    }
+
+    #[test]
+    fn literal_int_arithmetic() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                a = 2 + 1
+                b = a - 4
+                c = a * b
+                d = c / 3
+                e = 5 % 3
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "a", "Literal[3]")?;
+        assert_public_type(&case, "a", "b", "Literal[-1]")?;
+        assert_public_type(&case, "a", "c", "Literal[-3]")?;
+        assert_public_type(&case, "a", "d", "Literal[-1]")?;
+        assert_public_type(&case, "a", "e", "Literal[2]")
+    }
+
+    #[test]
+    fn walrus() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                x = (y := 1) + 1
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[2]")?;
+        assert_public_type(&case, "a", "y", "Literal[1]")
+    }
+
+    #[test]
+    fn ifexpr() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                x = 1 if flag else 2
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[1, 2]")
+    }
+
+    #[test]
+    fn ifexpr_walrus() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                y = z = 0
+                x = (y := 1) if flag else (z := 2)
+                a = y
+                b = z
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[1, 2]")?;
+        assert_public_type(&case, "a", "a", "Literal[0, 1]")?;
+        assert_public_type(&case, "a", "b", "Literal[0, 2]")
+    }
+
+    #[test]
+    fn ifexpr_walrus_2() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                y = 0
+                (y := 1) if flag else (y := 2)
+                a = y
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "a", "Literal[1, 2]")
+    }
+
+    #[test]
+    fn ifexpr_nested() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                x = 1 if flag else 2 if flag2 else 3
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[1, 2, 3]")
+    }
+
+    #[test]
+    fn none() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                x = 1 if flag else None
+            ",
+        )?;
+
+        assert_public_type(&case, "a", "x", "Literal[1] | None")
+    }
+
+    #[test]
+    fn narrow_none() -> anyhow::Result<()> {
+        let case = create_test()?;
+
+        write_to_path(
+            &case,
+            "a.py",
+            "
+                x = 1 if flag else None
+                y = 0
+                if x is not None:
+                    y = x
+                z = y
+            ",
+        )?;
+
+        // TODO normalization of unions and intersections: this type is technically correct but
+        // begging for normalization
+        assert_public_type(&case, "a", "z", "Literal[0] | Literal[1] | None & ~None")
+    }
+}

crates/red_knot/src/source.rs

@@ -53,6 +53,16 @@ pub enum SourceKind {
     IpyNotebook(Arc<Notebook>),
 }
 
+impl<'a> From<&'a SourceKind> for PySourceType {
+    fn from(value: &'a SourceKind) -> Self {
+        match value {
+            SourceKind::Python(_) => PySourceType::Python,
+            SourceKind::Stub(_) => PySourceType::Stub,
+            SourceKind::IpyNotebook(_) => PySourceType::Ipynb,
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub struct Source {
     kind: SourceKind,

crates/red_knot/src/types/infer.rs

@@ -1,292 +0,0 @@
-#![allow(dead_code)]
-
-use ruff_python_ast as ast;
-use ruff_python_ast::AstNode;
-
-use crate::db::{QueryResult, SemanticDb, SemanticJar};
-
-use crate::module::ModuleName;
-use crate::parse::parse;
-use crate::symbols::{
-    resolve_global_symbol, symbol_table, Definition, GlobalSymbolId, ImportFromDefinition,
-};
-use crate::types::Type;
-use crate::FileId;
-
-// FIXME: Figure out proper dead-lock free synchronisation now that this takes `&db` instead of `&mut db`.
-#[tracing::instrument(level = "trace", skip(db))]
-pub fn infer_symbol_type(db: &dyn SemanticDb, symbol: GlobalSymbolId) -> QueryResult<Type> {
-    let symbols = symbol_table(db, symbol.file_id)?;
-    let defs = symbols.definitions(symbol.symbol_id);
-    let jar: &SemanticJar = db.jar()?;
-
-    if let Some(ty) = jar.type_store.get_cached_symbol_type(symbol) {
-        return Ok(ty);
-    }
-
-    // TODO handle multiple defs, conditional defs...
-    assert_eq!(defs.len(), 1);
-
-    let ty = infer_definition_type(db, symbol, defs[0].clone())?;
-
-    jar.type_store.cache_symbol_type(symbol, ty);
-
-    // TODO record dependencies
-    Ok(ty)
-}
-
-#[tracing::instrument(level = "trace", skip(db))]
-pub fn infer_definition_type(
-    db: &dyn SemanticDb,
-    symbol: GlobalSymbolId,
-    definition: Definition,
-) -> QueryResult<Type> {
-    let jar: &SemanticJar = db.jar()?;
-    let type_store = &jar.type_store;
-    let file_id = symbol.file_id;
-
-    match definition {
-        Definition::ImportFrom(ImportFromDefinition {
-            module,
-            name,
-            level,
-        }) => {
-            // TODO relative imports
-            assert!(matches!(level, 0));
-            let module_name = ModuleName::new(module.as_ref().expect("TODO relative imports"));
-            if let Some(remote_symbol) = resolve_global_symbol(db, module_name, &name)? {
-                infer_symbol_type(db, remote_symbol)
-            } else {
-                Ok(Type::Unknown)
-            }
-        }
-        Definition::ClassDef(node_key) => {
-            if let Some(ty) = type_store.get_cached_node_type(file_id, node_key.erased()) {
-                Ok(ty)
-            } else {
-                let parsed = parse(db.upcast(), file_id)?;
-                let ast = parsed.ast();
-                let table = symbol_table(db, file_id)?;
-                let node = node_key.resolve_unwrap(ast.as_any_node_ref());
-
-                let mut bases = Vec::with_capacity(node.bases().len());
-
-                for base in node.bases() {
-                    bases.push(infer_expr_type(db, file_id, base)?);
-                }
-                let scope_id = table.scope_id_for_node(node_key.erased());
-                let ty = Type::Class(type_store.add_class(file_id, &node.name.id, scope_id, bases));
-                type_store.cache_node_type(file_id, *node_key.erased(), ty);
-                Ok(ty)
-            }
-        }
-        Definition::FunctionDef(node_key) => {
-            if let Some(ty) = type_store.get_cached_node_type(file_id, node_key.erased()) {
-                Ok(ty)
-            } else {
-                let parsed = parse(db.upcast(), file_id)?;
-                let ast = parsed.ast();
-                let table = symbol_table(db, file_id)?;
-                let node = node_key
-                    .resolve(ast.as_any_node_ref())
-                    .expect("node key should resolve");
-
-                let decorator_tys = node
-                    .decorator_list
-                    .iter()
-                    .map(|decorator| infer_expr_type(db, file_id, &decorator.expression))
-                    .collect::<QueryResult<_>>()?;
-                let scope_id = table.scope_id_for_node(node_key.erased());
-                let ty = type_store
-                    .add_function(
-                        file_id,
-                        &node.name.id,
-                        symbol.symbol_id,
-                        scope_id,
-                        decorator_tys,
-                    )
-                    .into();
-                type_store.cache_node_type(file_id, *node_key.erased(), ty);
-                Ok(ty)
-            }
-        }
-        Definition::Assignment(node_key) => {
-            let parsed = parse(db.upcast(), file_id)?;
-            let ast = parsed.ast();
-            let node = node_key.resolve_unwrap(ast.as_any_node_ref());
-            // TODO handle unpacking assignment correctly
-            infer_expr_type(db, file_id, &node.value)
-        }
-        _ => todo!("other kinds of definitions"),
-    }
-}
-
-fn infer_expr_type(db: &dyn SemanticDb, file_id: FileId, expr: &ast::Expr) -> QueryResult<Type> {
-    // TODO cache the resolution of the type on the node
-    let symbols = symbol_table(db, file_id)?;
-    match expr {
-        ast::Expr::Name(name) => {
-            // TODO look up in the correct scope, don't assume global
-            if let Some(symbol_id) = symbols.root_symbol_id_by_name(&name.id) {
-                infer_symbol_type(db, GlobalSymbolId { file_id, symbol_id })
-            } else {
-                Ok(Type::Unknown)
-            }
-        }
-        _ => todo!("full expression type resolution"),
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::db::tests::TestDb;
-    use crate::db::{HasJar, SemanticJar};
-    use crate::module::{
-        resolve_module, set_module_search_paths, ModuleName, ModuleSearchPath, ModuleSearchPathKind,
-    };
-    use crate::symbols::{symbol_table, GlobalSymbolId};
-    use crate::types::{infer_symbol_type, Type};
-    use crate::Name;
-
-    // TODO with virtual filesystem we shouldn't have to write files to disk for these
-    // tests
-
-    struct TestCase {
-        temp_dir: tempfile::TempDir,
-        db: TestDb,
-
-        src: ModuleSearchPath,
-    }
-
-    fn create_test() -> std::io::Result<TestCase> {
-        let temp_dir = tempfile::tempdir()?;
-
-        let src = temp_dir.path().join("src");
-        std::fs::create_dir(&src)?;
-        let src = ModuleSearchPath::new(src.canonicalize()?, ModuleSearchPathKind::FirstParty);
-
-        let roots = vec![src.clone()];
-
-        let mut db = TestDb::default();
-        set_module_search_paths(&mut db, roots);
-
-        Ok(TestCase { temp_dir, db, src })
-    }
-
-    #[test]
-    fn follow_import_to_class() -> anyhow::Result<()> {
-        let case = create_test()?;
-        let db = &case.db;
-
-        let a_path = case.src.path().join("a.py");
-        let b_path = case.src.path().join("b.py");
-        std::fs::write(a_path, "from b import C as D; E = D")?;
-        std::fs::write(b_path, "class C: pass")?;
-        let a_file = resolve_module(db, ModuleName::new("a"))?
-            .expect("module should be found")
-            .path(db)?
-            .file();
-        let a_syms = symbol_table(db, a_file)?;
-        let e_sym = a_syms
-            .root_symbol_id_by_name("E")
-            .expect("E symbol should be found");
-
-        let ty = infer_symbol_type(
-            db,
-            GlobalSymbolId {
-                file_id: a_file,
-                symbol_id: e_sym,
-            },
-        )?;
-
-        let jar = HasJar::<SemanticJar>::jar(db)?;
-        assert!(matches!(ty, Type::Class(_)));
-        assert_eq!(format!("{}", ty.display(&jar.type_store)), "Literal[C]");
-
-        Ok(())
-    }
-
-    #[test]
-    fn resolve_base_class_by_name() -> anyhow::Result<()> {
-        let case = create_test()?;
-        let db = &case.db;
-
-        let path = case.src.path().join("mod.py");
-        std::fs::write(path, "class Base: pass\nclass Sub(Base): pass")?;
-        let file = resolve_module(db, ModuleName::new("mod"))?
-            .expect("module should be found")
-            .path(db)?
-            .file();
-        let syms = symbol_table(db, file)?;
-        let sym = syms
-            .root_symbol_id_by_name("Sub")
-            .expect("Sub symbol should be found");
-
-        let ty = infer_symbol_type(
-            db,
-            GlobalSymbolId {
-                file_id: file,
-                symbol_id: sym,
-            },
-        )?;
-
-        let Type::Class(class_id) = ty else {
-            panic!("Sub is not a Class")
-        };
-        let jar = HasJar::<SemanticJar>::jar(db)?;
-        let base_names: Vec<_> = jar
-            .type_store
-            .get_class(class_id)
-            .bases()
-            .iter()
-            .map(|base_ty| format!("{}", base_ty.display(&jar.type_store)))
-            .collect();
-
-        assert_eq!(base_names, vec!["Literal[Base]"]);
-
-        Ok(())
-    }
-
-    #[test]
-    fn resolve_method() -> anyhow::Result<()> {
-        let case = create_test()?;
-        let db = &case.db;
-
-        let path = case.src.path().join("mod.py");
-        std::fs::write(path, "class C:\n  def f(self): pass")?;
-        let file = resolve_module(db, ModuleName::new("mod"))?
-            .expect("module should be found")
-            .path(db)?
-            .file();
-        let syms = symbol_table(db, file)?;
-        let sym = syms
-            .root_symbol_id_by_name("C")
-            .expect("C symbol should be found");
-
-        let ty = infer_symbol_type(
-            db,
-            GlobalSymbolId {
-                file_id: file,
-                symbol_id: sym,
-            },
-        )?;
-
-        let Type::Class(class_id) = ty else {
-            panic!("C is not a Class");
-        };
-
-        let member_ty = class_id
-            .get_own_class_member(db, &Name::new("f"))
-            .expect("C.f to resolve");
-
-        let Some(Type::Function(func_id)) = member_ty else {
-            panic!("C.f is not a Function");
-        };
-
-        let jar = HasJar::<SemanticJar>::jar(db)?;
-        let function = jar.type_store.get_function(func_id);
-        assert_eq!(function.name(), "f");
-
-        Ok(())
-    }
-}

crates/red_knot/src/typeshed_versions.rs

@@ -0,0 +1,526 @@
+use std::collections::BTreeMap;
+use std::fmt;
+use std::num::{NonZeroU16, NonZeroUsize};
+use std::ops::{RangeFrom, RangeInclusive};
+use std::str::FromStr;
+
+use rustc_hash::FxHashMap;
+use smol_str::SmolStr;
+
+use ruff_python_stdlib::identifiers::is_identifier;
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct TypeshedVersionsParseError {
+    line_number: NonZeroU16,
+    reason: TypeshedVersionsParseErrorKind,
+}
+
+impl fmt::Display for TypeshedVersionsParseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let TypeshedVersionsParseError {
+            line_number,
+            reason,
+        } = self;
+        write!(
+            f,
+            "Error while parsing line {line_number} of typeshed's VERSIONS file: {reason}"
+        )
+    }
+}
+
+impl std::error::Error for TypeshedVersionsParseError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        if let TypeshedVersionsParseErrorKind::IntegerParsingFailure { err, .. } = &self.reason {
+            Some(err)
+        } else {
+            None
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum TypeshedVersionsParseErrorKind {
+    TooManyLines(NonZeroUsize),
+    UnexpectedNumberOfColons,
+    InvalidModuleName(String),
+    UnexpectedNumberOfHyphens,
+    UnexpectedNumberOfPeriods(String),
+    IntegerParsingFailure {
+        version: String,
+        err: std::num::ParseIntError,
+    },
+}
+
+impl fmt::Display for TypeshedVersionsParseErrorKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::TooManyLines(num_lines) => write!(
+                f,
+                "File has too many lines ({num_lines}); maximum allowed is {}",
+                NonZeroU16::MAX
+            ),
+            Self::UnexpectedNumberOfColons => {
+                f.write_str("Expected every non-comment line to have exactly one colon")
+            }
+            Self::InvalidModuleName(name) => write!(
+                f,
+                "Expected all components of '{name}' to be valid Python identifiers"
+            ),
+            Self::UnexpectedNumberOfHyphens => {
+                f.write_str("Expected every non-comment line to have exactly one '-' character")
+            }
+            Self::UnexpectedNumberOfPeriods(format) => write!(
+                f,
+                "Expected all versions to be in the form {{MAJOR}}.{{MINOR}}; got '{format}'"
+            ),
+            Self::IntegerParsingFailure { version, err } => write!(
+                f,
+                "Failed to convert '{version}' to a pair of integers due to {err}",
+            ),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct TypeshedVersions(FxHashMap<SmolStr, PyVersionRange>);
+
+impl TypeshedVersions {
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+
+    pub fn contains_module(&self, module_name: impl Into<SmolStr>) -> bool {
+        self.0.contains_key(&module_name.into())
+    }
+
+    pub fn module_exists_on_version(
+        &self,
+        module: impl Into<SmolStr>,
+        version: impl Into<PyVersion>,
+    ) -> bool {
+        let version = version.into();
+        let mut module: Option<SmolStr> = Some(module.into());
+        while let Some(module_to_try) = module {
+            if let Some(range) = self.0.get(&module_to_try) {
+                return range.contains(version);
+            }
+            module = module_to_try
+                .rsplit_once('.')
+                .map(|(parent, _)| SmolStr::new(parent));
+        }
+        false
+    }
+}
+
+impl FromStr for TypeshedVersions {
+    type Err = TypeshedVersionsParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut map = FxHashMap::default();
+
+        for (line_index, line) in s.lines().enumerate() {
+            // humans expect line numbers to be 1-indexed
+            let line_number = NonZeroUsize::new(line_index.saturating_add(1)).unwrap();
+
+            let Ok(line_number) = NonZeroU16::try_from(line_number) else {
+                return Err(TypeshedVersionsParseError {
+                    line_number: NonZeroU16::MAX,
+                    reason: TypeshedVersionsParseErrorKind::TooManyLines(line_number),
+                });
+            };
+
+            let Some(content) = line.split('#').map(str::trim).next() else {
+                continue;
+            };
+            if content.is_empty() {
+                continue;
+            }
+
+            let mut parts = content.split(':').map(str::trim);
+            let (Some(module_name), Some(rest), None) = (parts.next(), parts.next(), parts.next())
+            else {
+                return Err(TypeshedVersionsParseError {
+                    line_number,
+                    reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfColons,
+                });
+            };
+
+            let module_name = SmolStr::new(module_name);
+            if !module_name.split('.').all(is_identifier) {
+                return Err(TypeshedVersionsParseError {
+                    line_number,
+                    reason: TypeshedVersionsParseErrorKind::InvalidModuleName(
+                        module_name.to_string(),
+                    ),
+                });
+            }
+
+            match PyVersionRange::from_str(rest) {
+                Ok(version) => map.insert(module_name, version),
+                Err(reason) => {
+                    return Err(TypeshedVersionsParseError {
+                        line_number,
+                        reason,
+                    })
+                }
+            };
+        }
+
+        Ok(Self(map))
+    }
+}
+
+impl fmt::Display for TypeshedVersions {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let sorted_items: BTreeMap<&SmolStr, &PyVersionRange> = self.0.iter().collect();
+        for (module_name, range) in sorted_items {
+            writeln!(f, "{module_name}: {range}")?;
+        }
+        Ok(())
+    }
+}
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+enum PyVersionRange {
+    AvailableFrom(RangeFrom<PyVersion>),
+    AvailableWithin(RangeInclusive<PyVersion>),
+}
+
+impl PyVersionRange {
+    fn contains(&self, version: PyVersion) -> bool {
+        match self {
+            Self::AvailableFrom(inner) => inner.contains(&version),
+            Self::AvailableWithin(inner) => inner.contains(&version),
+        }
+    }
+}
+
+impl FromStr for PyVersionRange {
+    type Err = TypeshedVersionsParseErrorKind;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut parts = s.split('-').map(str::trim);
+        match (parts.next(), parts.next(), parts.next()) {
+            (Some(lower), Some(""), None) => Ok(Self::AvailableFrom((lower.parse()?)..)),
+            (Some(lower), Some(upper), None) => {
+                Ok(Self::AvailableWithin((lower.parse()?)..=(upper.parse()?)))
+            }
+            _ => Err(TypeshedVersionsParseErrorKind::UnexpectedNumberOfHyphens),
+        }
+    }
+}
+
+impl fmt::Display for PyVersionRange {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::AvailableFrom(range_from) => write!(f, "{}-", range_from.start),
+            Self::AvailableWithin(range_inclusive) => {
+                write!(f, "{}-{}", range_inclusive.start(), range_inclusive.end())
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct PyVersion {
+    major: u8,
+    minor: u8,
+}
+
+impl FromStr for PyVersion {
+    type Err = TypeshedVersionsParseErrorKind;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut parts = s.split('.').map(str::trim);
+        let (Some(major), Some(minor), None) = (parts.next(), parts.next(), parts.next()) else {
+            return Err(TypeshedVersionsParseErrorKind::UnexpectedNumberOfPeriods(
+                s.to_string(),
+            ));
+        };
+        let major = match u8::from_str(major) {
+            Ok(major) => major,
+            Err(err) => {
+                return Err(TypeshedVersionsParseErrorKind::IntegerParsingFailure {
+                    version: s.to_string(),
+                    err,
+                })
+            }
+        };
+        let minor = match u8::from_str(minor) {
+            Ok(minor) => minor,
+            Err(err) => {
+                return Err(TypeshedVersionsParseErrorKind::IntegerParsingFailure {
+                    version: s.to_string(),
+                    err,
+                })
+            }
+        };
+        Ok(Self { major, minor })
+    }
+}
+
+impl fmt::Display for PyVersion {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let PyVersion { major, minor } = self;
+        write!(f, "{major}.{minor}")
+    }
+}
+
+// TODO: unify with the PythonVersion enum in the linter/formatter crates?
+#[derive(Copy, Clone, Hash, Debug, PartialEq, Eq, PartialOrd, Ord, Default)]
+pub enum SupportedPyVersion {
+    Py37,
+    #[default]
+    Py38,
+    Py39,
+    Py310,
+    Py311,
+    Py312,
+    Py313,
+}
+
+impl From<SupportedPyVersion> for PyVersion {
+    fn from(value: SupportedPyVersion) -> Self {
+        match value {
+            SupportedPyVersion::Py37 => PyVersion { major: 3, minor: 7 },
+            SupportedPyVersion::Py38 => PyVersion { major: 3, minor: 8 },
+            SupportedPyVersion::Py39 => PyVersion { major: 3, minor: 9 },
+            SupportedPyVersion::Py310 => PyVersion {
+                major: 3,
+                minor: 10,
+            },
+            SupportedPyVersion::Py311 => PyVersion {
+                major: 3,
+                minor: 11,
+            },
+            SupportedPyVersion::Py312 => PyVersion {
+                major: 3,
+                minor: 12,
+            },
+            SupportedPyVersion::Py313 => PyVersion {
+                major: 3,
+                minor: 13,
+            },
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::num::{IntErrorKind, NonZeroU16};
+
+    use super::*;
+
+    use insta::assert_snapshot;
+
+    #[allow(unsafe_code)]
+    const ONE: NonZeroU16 = unsafe { NonZeroU16::new_unchecked(1) };
+
+    #[test]
+    fn can_parse_vendored_versions_file() {
+        let versions_data = include_str!(concat!(
+            env!("CARGO_MANIFEST_DIR"),
+            "/vendor/typeshed/stdlib/VERSIONS"
+        ));
+
+        let versions = TypeshedVersions::from_str(versions_data).unwrap();
+        assert!(versions.len() > 100);
+        assert!(versions.len() < 1000);
+
+        assert!(versions.contains_module("asyncio"));
+        assert!(versions.module_exists_on_version("asyncio", SupportedPyVersion::Py310));
+
+        assert!(versions.contains_module("asyncio.staggered"));
+        assert!(versions.module_exists_on_version("asyncio.staggered", SupportedPyVersion::Py38));
+        assert!(!versions.module_exists_on_version("asyncio.staggered", SupportedPyVersion::Py37));
+
+        assert!(versions.contains_module("audioop"));
+        assert!(versions.module_exists_on_version("audioop", SupportedPyVersion::Py312));
+        assert!(!versions.module_exists_on_version("audioop", SupportedPyVersion::Py313));
+    }
+
+    #[test]
+    fn can_parse_mock_versions_file() {
+        const VERSIONS: &str = "\
+# a comment
+    # some more comment
+# yet more comment
+
+
+# and some more comment
+
+bar: 2.7-3.10
+
+# more comment
+bar.baz: 3.1-3.9
+foo: 3.8-   # trailing comment
+";
+        let parsed_versions = TypeshedVersions::from_str(VERSIONS).unwrap();
+        assert_eq!(parsed_versions.len(), 3);
+        assert_snapshot!(parsed_versions.to_string(), @r###"
+        bar: 2.7-3.10
+        bar.baz: 3.1-3.9
+        foo: 3.8-
+        "###
+        );
+
+        assert!(parsed_versions.contains_module("foo"));
+        assert!(!parsed_versions.module_exists_on_version("foo", SupportedPyVersion::Py37));
+        assert!(parsed_versions.module_exists_on_version("foo", SupportedPyVersion::Py38));
+        assert!(parsed_versions.module_exists_on_version("foo", SupportedPyVersion::Py311));
+
+        assert!(parsed_versions.contains_module("bar"));
+        assert!(parsed_versions.module_exists_on_version("bar", SupportedPyVersion::Py37));
+        assert!(parsed_versions.module_exists_on_version("bar", SupportedPyVersion::Py310));
+        assert!(!parsed_versions.module_exists_on_version("bar", SupportedPyVersion::Py311));
+
+        assert!(parsed_versions.contains_module("bar.baz"));
+        assert!(parsed_versions.module_exists_on_version("bar.baz", SupportedPyVersion::Py37));
+        assert!(parsed_versions.module_exists_on_version("bar.baz", SupportedPyVersion::Py39));
+        assert!(!parsed_versions.module_exists_on_version("bar.baz", SupportedPyVersion::Py310));
+
+        assert!(!parsed_versions.contains_module("spam"));
+        assert!(!parsed_versions.module_exists_on_version("spam", SupportedPyVersion::Py37));
+        assert!(!parsed_versions.module_exists_on_version("spam", SupportedPyVersion::Py313));
+    }
+
+    #[test]
+    fn invalid_huge_versions_file() {
+        let offset = 100;
+        let too_many = u16::MAX as usize + offset;
+
+        let mut massive_versions_file = String::new();
+        for i in 0..too_many {
+            massive_versions_file.push_str(&format!("x{i}: 3.8-\n"));
+        }
+
+        assert_eq!(
+            TypeshedVersions::from_str(&massive_versions_file),
+            Err(TypeshedVersionsParseError {
+                line_number: NonZeroU16::MAX,
+                reason: TypeshedVersionsParseErrorKind::TooManyLines(
+                    NonZeroUsize::new(too_many + 1 - offset).unwrap()
+                )
+            })
+        );
+    }
+
+    #[test]
+    fn invalid_typeshed_versions_bad_colon_number() {
+        assert_eq!(
+            TypeshedVersions::from_str("foo 3.7"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfColons
+            })
+        );
+        assert_eq!(
+            TypeshedVersions::from_str("foo:: 3.7"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfColons
+            })
+        );
+    }
+
+    #[test]
+    fn invalid_typeshed_versions_non_identifier_modules() {
+        assert_eq!(
+            TypeshedVersions::from_str("not!an!identifier!: 3.7"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::InvalidModuleName(
+                    "not!an!identifier!".to_string()
+                )
+            })
+        );
+        assert_eq!(
+            TypeshedVersions::from_str("(also_not).(an_identifier): 3.7"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::InvalidModuleName(
+                    "(also_not).(an_identifier)".to_string()
+                )
+            })
+        );
+    }
+
+    #[test]
+    fn invalid_typeshed_versions_bad_hyphen_number() {
+        assert_eq!(
+            TypeshedVersions::from_str("foo: 3.8"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfHyphens
+            })
+        );
+        assert_eq!(
+            TypeshedVersions::from_str("foo: 3.8--"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfHyphens
+            })
+        );
+        assert_eq!(
+            TypeshedVersions::from_str("foo: 3.8--3.9"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfHyphens
+            })
+        );
+    }
+
+    #[test]
+    fn invalid_typeshed_versions_bad_period_number() {
+        assert_eq!(
+            TypeshedVersions::from_str("foo: 38-"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfPeriods("38".to_string())
+            })
+        );
+        assert_eq!(
+            TypeshedVersions::from_str("foo: 3..8-"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfPeriods(
+                    "3..8".to_string()
+                )
+            })
+        );
+        assert_eq!(
+            TypeshedVersions::from_str("foo: 3.8-3..11"),
+            Err(TypeshedVersionsParseError {
+                line_number: ONE,
+                reason: TypeshedVersionsParseErrorKind::UnexpectedNumberOfPeriods(
+                    "3..11".to_string()
+                )
+            })
+        );
+    }
+
+    #[test]
+    fn invalid_typeshed_versions_non_digits() {
+        let err = TypeshedVersions::from_str("foo: 1.two-").unwrap_err();
+        assert_eq!(err.line_number, ONE);
+        let TypeshedVersionsParseErrorKind::IntegerParsingFailure { version, err } = err.reason
+        else {
+            panic!()
+        };
+        assert_eq!(version, "1.two".to_string());
+        assert_eq!(*err.kind(), IntErrorKind::InvalidDigit);
+
+        let err = TypeshedVersions::from_str("foo: 3.8-four.9").unwrap_err();
+        assert_eq!(err.line_number, ONE);
+        let TypeshedVersionsParseErrorKind::IntegerParsingFailure { version, err } = err.reason
+        else {
+            panic!()
+        };
+        assert_eq!(version, "four.9".to_string());
+        assert_eq!(*err.kind(), IntErrorKind::InvalidDigit);
+    }
+}

crates/red_knot/vendor/typeshed/source_commit.txt

@@ -1 +1 @@
-a9d7e861f7a46ae7acd56569326adef302e10f29
+4b6558c12ac43cd40716cd6452fe98a632ae65d7

crates/red_knot/vendor/typeshed/stdlib/VERSIONS

@@ -166,7 +166,7 @@ ipaddress: 3.3-
 itertools: 3.0-
 json: 3.0-
 keyword: 3.0-
-lib2to3: 3.0-
+lib2to3: 3.0-3.12
 linecache: 3.0-
 locale: 3.0-
 logging: 3.0-

crates/red_knot/vendor/typeshed/stdlib/_ctypes.pyi

@@ -201,7 +201,7 @@ class Array(_CData, Generic[_CT]):
     # Sized and _CData prevents using _CDataMeta.
     def __len__(self) -> int: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 def addressof(obj: _CData) -> int: ...
 def alignment(obj_or_type: _CData | type[_CData]) -> int: ...

crates/red_knot/vendor/typeshed/stdlib/_socket.pyi

@@ -783,7 +783,7 @@ def ntohl(x: int, /) -> int: ...  # param & ret val are 32-bit ints
 def ntohs(x: int, /) -> int: ...  # param & ret val are 16-bit ints
 def htonl(x: int, /) -> int: ...  # param & ret val are 32-bit ints
 def htons(x: int, /) -> int: ...  # param & ret val are 16-bit ints
-def inet_aton(ip_string: str, /) -> bytes: ...  # ret val 4 bytes in length
+def inet_aton(ip_addr: str, /) -> bytes: ...  # ret val 4 bytes in length
 def inet_ntoa(packed_ip: ReadableBuffer, /) -> str: ...
 def inet_pton(address_family: int, ip_string: str, /) -> bytes: ...
 def inet_ntop(address_family: int, packed_ip: ReadableBuffer, /) -> str: ...
@@ -797,7 +797,7 @@ if sys.platform != "win32":
     def socketpair(family: int = ..., type: int = ..., proto: int = ..., /) -> tuple[socket, socket]: ...
 
 def if_nameindex() -> list[tuple[int, str]]: ...
-def if_nametoindex(name: str, /) -> int: ...
+def if_nametoindex(oname: str, /) -> int: ...
 def if_indextoname(index: int, /) -> str: ...
 
 CAPI: object

crates/red_knot/vendor/typeshed/stdlib/_stat.pyi

@@ -64,19 +64,19 @@ UF_NODUMP: Literal[0x00000001]
 UF_NOUNLINK: Literal[0x00000010]
 UF_OPAQUE: Literal[0x00000008]
 
-def S_IMODE(mode: int) -> int: ...
-def S_IFMT(mode: int) -> int: ...
-def S_ISBLK(mode: int) -> bool: ...
-def S_ISCHR(mode: int) -> bool: ...
-def S_ISDIR(mode: int) -> bool: ...
-def S_ISDOOR(mode: int) -> bool: ...
-def S_ISFIFO(mode: int) -> bool: ...
-def S_ISLNK(mode: int) -> bool: ...
-def S_ISPORT(mode: int) -> bool: ...
-def S_ISREG(mode: int) -> bool: ...
-def S_ISSOCK(mode: int) -> bool: ...
-def S_ISWHT(mode: int) -> bool: ...
-def filemode(mode: int) -> str: ...
+def S_IMODE(mode: int, /) -> int: ...
+def S_IFMT(mode: int, /) -> int: ...
+def S_ISBLK(mode: int, /) -> bool: ...
+def S_ISCHR(mode: int, /) -> bool: ...
+def S_ISDIR(mode: int, /) -> bool: ...
+def S_ISDOOR(mode: int, /) -> bool: ...
+def S_ISFIFO(mode: int, /) -> bool: ...
+def S_ISLNK(mode: int, /) -> bool: ...
+def S_ISPORT(mode: int, /) -> bool: ...
+def S_ISREG(mode: int, /) -> bool: ...
+def S_ISSOCK(mode: int, /) -> bool: ...
+def S_ISWHT(mode: int, /) -> bool: ...
+def filemode(mode: int, /) -> str: ...
 
 if sys.platform == "win32":
     IO_REPARSE_TAG_SYMLINK: int
@@ -101,3 +101,17 @@ if sys.platform == "win32":
     FILE_ATTRIBUTE_SYSTEM: Literal[4]
     FILE_ATTRIBUTE_TEMPORARY: Literal[256]
     FILE_ATTRIBUTE_VIRTUAL: Literal[65536]
+
+if sys.version_info >= (3, 13):
+    SF_SETTABLE: Literal[0x3FFF0000]
+    # https://github.com/python/cpython/issues/114081#issuecomment-2119017790
+    # SF_RESTRICTED: Literal[0x00080000]
+    SF_FIRMLINK: Literal[0x00800000]
+    SF_DATALESS: Literal[0x40000000]
+
+    SF_SUPPORTED: Literal[0x9F0000]
+    SF_SYNTHETIC: Literal[0xC0000000]
+
+    UF_TRACKED: Literal[0x00000040]
+    UF_DATAVAULT: Literal[0x00000080]
+    UF_SETTABLE: Literal[0x0000FFFF]

crates/red_knot/vendor/typeshed/stdlib/_typeshed/__init__.pyi

@@ -326,6 +326,8 @@ class structseq(Generic[_T_co]):
     # but only has any meaning if you supply it a dict where the keys are strings.
     # https://github.com/python/typeshed/pull/6560#discussion_r767149830
     def __new__(cls: type[Self], sequence: Iterable[_T_co], dict: dict[str, Any] = ...) -> Self: ...
+    if sys.version_info >= (3, 13):
+        def __replace__(self: Self, **kwargs: Any) -> Self: ...
 
 # Superset of typing.AnyStr that also includes LiteralString
 AnyOrLiteralStr = TypeVar("AnyOrLiteralStr", str, bytes, LiteralString)  # noqa: Y001

crates/red_knot/vendor/typeshed/stdlib/_weakref.pyi

@@ -27,7 +27,7 @@ class ReferenceType(Generic[_T]):
     def __eq__(self, value: object, /) -> bool: ...
     def __hash__(self) -> int: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 ref = ReferenceType
 

crates/red_knot/vendor/typeshed/stdlib/_weakrefset.pyi

@@ -48,4 +48,4 @@ class WeakSet(MutableSet[_T]):
     def __or__(self, other: Iterable[_S]) -> WeakSet[_S | _T]: ...
     def isdisjoint(self, other: Iterable[_T]) -> bool: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...

crates/red_knot/vendor/typeshed/stdlib/argparse.pyi

@@ -318,19 +318,36 @@ class Action(_AttributeHolder):
     required: bool
     help: str | None
     metavar: str | tuple[str, ...] | None
-    def __init__(
-        self,
-        option_strings: Sequence[str],
-        dest: str,
-        nargs: int | str | None = None,
-        const: _T | None = None,
-        default: _T | str | None = None,
-        type: Callable[[str], _T] | FileType | None = None,
-        choices: Iterable[_T] | None = None,
-        required: bool = False,
-        help: str | None = None,
-        metavar: str | tuple[str, ...] | None = None,
-    ) -> None: ...
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str,
+            nargs: int | str | None = None,
+            const: _T | None = None,
+            default: _T | str | None = None,
+            type: Callable[[str], _T] | FileType | None = None,
+            choices: Iterable[_T] | None = None,
+            required: bool = False,
+            help: str | None = None,
+            metavar: str | tuple[str, ...] | None = None,
+            deprecated: bool = False,
+        ) -> None: ...
+    else:
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str,
+            nargs: int | str | None = None,
+            const: _T | None = None,
+            default: _T | str | None = None,
+            type: Callable[[str], _T] | FileType | None = None,
+            choices: Iterable[_T] | None = None,
+            required: bool = False,
+            help: str | None = None,
+            metavar: str | tuple[str, ...] | None = None,
+        ) -> None: ...
+
     def __call__(
         self, parser: ArgumentParser, namespace: Namespace, values: str | Sequence[Any] | None, option_string: str | None = None
     ) -> None: ...
@@ -339,29 +356,56 @@ class Action(_AttributeHolder):
 
 if sys.version_info >= (3, 12):
     class BooleanOptionalAction(Action):
-        @overload
-        def __init__(
-            self,
-            option_strings: Sequence[str],
-            dest: str,
-            default: bool | None = None,
-            *,
-            required: bool = False,
-            help: str | None = None,
-        ) -> None: ...
-        @overload
-        @deprecated("The `type`, `choices`, and `metavar` parameters are ignored and will be removed in Python 3.14.")
-        def __init__(
-            self,
-            option_strings: Sequence[str],
-            dest: str,
-            default: _T | bool | None = None,
-            type: Callable[[str], _T] | FileType | None = sentinel,
-            choices: Iterable[_T] | None = sentinel,
-            required: bool = False,
-            help: str | None = None,
-            metavar: str | tuple[str, ...] | None = sentinel,
-        ) -> None: ...
+        if sys.version_info >= (3, 13):
+            @overload
+            def __init__(
+                self,
+                option_strings: Sequence[str],
+                dest: str,
+                default: bool | None = None,
+                *,
+                required: bool = False,
+                help: str | None = None,
+                deprecated: bool = False,
+            ) -> None: ...
+            @overload
+            @deprecated("The `type`, `choices`, and `metavar` parameters are ignored and will be removed in Python 3.14.")
+            def __init__(
+                self,
+                option_strings: Sequence[str],
+                dest: str,
+                default: _T | bool | None = None,
+                type: Callable[[str], _T] | FileType | None = sentinel,
+                choices: Iterable[_T] | None = sentinel,
+                required: bool = False,
+                help: str | None = None,
+                metavar: str | tuple[str, ...] | None = sentinel,
+                deprecated: bool = False,
+            ) -> None: ...
+        else:
+            @overload
+            def __init__(
+                self,
+                option_strings: Sequence[str],
+                dest: str,
+                default: bool | None = None,
+                *,
+                required: bool = False,
+                help: str | None = None,
+            ) -> None: ...
+            @overload
+            @deprecated("The `type`, `choices`, and `metavar` parameters are ignored and will be removed in Python 3.14.")
+            def __init__(
+                self,
+                option_strings: Sequence[str],
+                dest: str,
+                default: _T | bool | None = None,
+                type: Callable[[str], _T] | FileType | None = sentinel,
+                choices: Iterable[_T] | None = sentinel,
+                required: bool = False,
+                help: str | None = None,
+                metavar: str | tuple[str, ...] | None = sentinel,
+            ) -> None: ...
 
 elif sys.version_info >= (3, 9):
     class BooleanOptionalAction(Action):
@@ -431,7 +475,19 @@ class _StoreAction(Action): ...
 
 # undocumented
 class _StoreConstAction(Action):
-    if sys.version_info >= (3, 11):
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str,
+            const: Any | None = None,
+            default: Any = None,
+            required: bool = False,
+            help: str | None = None,
+            metavar: str | tuple[str, ...] | None = None,
+            deprecated: bool = False,
+        ) -> None: ...
+    elif sys.version_info >= (3, 11):
         def __init__(
             self,
             option_strings: Sequence[str],
@@ -456,15 +512,37 @@ class _StoreConstAction(Action):
 
 # undocumented
 class _StoreTrueAction(_StoreConstAction):
-    def __init__(
-        self, option_strings: Sequence[str], dest: str, default: bool = False, required: bool = False, help: str | None = None
-    ) -> None: ...
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str,
+            default: bool = False,
+            required: bool = False,
+            help: str | None = None,
+            deprecated: bool = False,
+        ) -> None: ...
+    else:
+        def __init__(
+            self, option_strings: Sequence[str], dest: str, default: bool = False, required: bool = False, help: str | None = None
+        ) -> None: ...
 
 # undocumented
 class _StoreFalseAction(_StoreConstAction):
-    def __init__(
-        self, option_strings: Sequence[str], dest: str, default: bool = True, required: bool = False, help: str | None = None
-    ) -> None: ...
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str,
+            default: bool = True,
+            required: bool = False,
+            help: str | None = None,
+            deprecated: bool = False,
+        ) -> None: ...
+    else:
+        def __init__(
+            self, option_strings: Sequence[str], dest: str, default: bool = True, required: bool = False, help: str | None = None
+        ) -> None: ...
 
 # undocumented
 class _AppendAction(Action): ...
@@ -474,7 +552,19 @@ class _ExtendAction(_AppendAction): ...
 
 # undocumented
 class _AppendConstAction(Action):
-    if sys.version_info >= (3, 11):
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str,
+            const: Any | None = None,
+            default: Any = None,
+            required: bool = False,
+            help: str | None = None,
+            metavar: str | tuple[str, ...] | None = None,
+            deprecated: bool = False,
+        ) -> None: ...
+    elif sys.version_info >= (3, 11):
         def __init__(
             self,
             option_strings: Sequence[str],
@@ -499,27 +589,72 @@ class _AppendConstAction(Action):
 
 # undocumented
 class _CountAction(Action):
-    def __init__(
-        self, option_strings: Sequence[str], dest: str, default: Any = None, required: bool = False, help: str | None = None
-    ) -> None: ...
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str,
+            default: Any = None,
+            required: bool = False,
+            help: str | None = None,
+            deprecated: bool = False,
+        ) -> None: ...
+    else:
+        def __init__(
+            self, option_strings: Sequence[str], dest: str, default: Any = None, required: bool = False, help: str | None = None
+        ) -> None: ...
 
 # undocumented
 class _HelpAction(Action):
-    def __init__(
-        self, option_strings: Sequence[str], dest: str = "==SUPPRESS==", default: str = "==SUPPRESS==", help: str | None = None
-    ) -> None: ...
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str = "==SUPPRESS==",
+            default: str = "==SUPPRESS==",
+            help: str | None = None,
+            deprecated: bool = False,
+        ) -> None: ...
+    else:
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            dest: str = "==SUPPRESS==",
+            default: str = "==SUPPRESS==",
+            help: str | None = None,
+        ) -> None: ...
 
 # undocumented
 class _VersionAction(Action):
     version: str | None
-    def __init__(
-        self,
-        option_strings: Sequence[str],
-        version: str | None = None,
-        dest: str = "==SUPPRESS==",
-        default: str = "==SUPPRESS==",
-        help: str = "show program's version number and exit",
-    ) -> None: ...
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            version: str | None = None,
+            dest: str = "==SUPPRESS==",
+            default: str = "==SUPPRESS==",
+            help: str | None = None,
+            deprecated: bool = False,
+        ) -> None: ...
+    elif sys.version_info >= (3, 11):
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            version: str | None = None,
+            dest: str = "==SUPPRESS==",
+            default: str = "==SUPPRESS==",
+            help: str | None = None,
+        ) -> None: ...
+    else:
+        def __init__(
+            self,
+            option_strings: Sequence[str],
+            version: str | None = None,
+            dest: str = "==SUPPRESS==",
+            default: str = "==SUPPRESS==",
+            help: str = "show program's version number and exit",
+        ) -> None: ...
 
 # undocumented
 class _SubParsersAction(Action, Generic[_ArgumentParserT]):
@@ -542,7 +677,30 @@ class _SubParsersAction(Action, Generic[_ArgumentParserT]):
 
     # Note: `add_parser` accepts all kwargs of `ArgumentParser.__init__`. It also
     # accepts its own `help` and `aliases` kwargs.
-    if sys.version_info >= (3, 9):
+    if sys.version_info >= (3, 13):
+        def add_parser(
+            self,
+            name: str,
+            *,
+            deprecated: bool = False,
+            help: str | None = ...,
+            aliases: Sequence[str] = ...,
+            # Kwargs from ArgumentParser constructor
+            prog: str | None = ...,
+            usage: str | None = ...,
+            description: str | None = ...,
+            epilog: str | None = ...,
+            parents: Sequence[_ArgumentParserT] = ...,
+            formatter_class: _FormatterClass = ...,
+            prefix_chars: str = ...,
+            fromfile_prefix_chars: str | None = ...,
+            argument_default: Any = ...,
+            conflict_handler: str = ...,
+            add_help: bool = ...,
+            allow_abbrev: bool = ...,
+            exit_on_error: bool = ...,
+        ) -> _ArgumentParserT: ...
+    elif sys.version_info >= (3, 9):
         def add_parser(
             self,
             name: str,

crates/red_knot/vendor/typeshed/stdlib/array.pyi

@@ -87,6 +87,6 @@ class array(MutableSequence[_T]):
     def __buffer__(self, flags: int, /) -> memoryview: ...
     def __release_buffer__(self, buffer: memoryview, /) -> None: ...
     if sys.version_info >= (3, 12):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 ArrayType = array

crates/red_knot/vendor/typeshed/stdlib/asyncio/__init__.pyi

@@ -30,12 +30,12 @@ if sys.platform == "win32":
 else:
     from .unix_events import *
 
-_T = TypeVar("_T")
+_T_co = TypeVar("_T_co", covariant=True)
 
 # Aliases imported by multiple submodules in typeshed
 if sys.version_info >= (3, 12):
-    _AwaitableLike: TypeAlias = Awaitable[_T]  # noqa: Y047
-    _CoroutineLike: TypeAlias = Coroutine[Any, Any, _T]  # noqa: Y047
+    _AwaitableLike: TypeAlias = Awaitable[_T_co]  # noqa: Y047
+    _CoroutineLike: TypeAlias = Coroutine[Any, Any, _T_co]  # noqa: Y047
 else:
-    _AwaitableLike: TypeAlias = Generator[Any, None, _T] | Awaitable[_T]
-    _CoroutineLike: TypeAlias = Generator[Any, None, _T] | Coroutine[Any, Any, _T]
+    _AwaitableLike: TypeAlias = Generator[Any, None, _T_co] | Awaitable[_T_co]
+    _CoroutineLike: TypeAlias = Generator[Any, None, _T_co] | Coroutine[Any, Any, _T_co]

crates/red_knot/vendor/typeshed/stdlib/asyncio/events.pyi

@@ -2,7 +2,7 @@ import ssl
 import sys
 from _typeshed import FileDescriptorLike, ReadableBuffer, StrPath, Unused, WriteableBuffer
 from abc import ABCMeta, abstractmethod
-from collections.abc import Callable, Coroutine, Generator, Sequence
+from collections.abc import Callable, Sequence
 from contextvars import Context
 from socket import AddressFamily, SocketKind, _Address, _RetAddress, socket
 from typing import IO, Any, Literal, Protocol, TypeVar, overload
@@ -43,7 +43,7 @@ _ProtocolFactory: TypeAlias = Callable[[], BaseProtocol]
 _SSLContext: TypeAlias = bool | None | ssl.SSLContext
 
 class _TaskFactory(Protocol):
-    def __call__(self, loop: AbstractEventLoop, factory: Coroutine[Any, Any, _T] | Generator[Any, None, _T], /) -> Future[_T]: ...
+    def __call__(self, loop: AbstractEventLoop, factory: _CoroutineLike[_T], /) -> Future[_T]: ...
 
 class Handle:
     _cancelled: bool

crates/red_knot/vendor/typeshed/stdlib/asyncio/futures.pyi

@@ -52,6 +52,6 @@ class Future(Awaitable[_T], Iterable[_T]):
     @property
     def _loop(self) -> AbstractEventLoop: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 def wrap_future(future: _ConcurrentFuture[_T] | Future[_T], *, loop: AbstractEventLoop | None = None) -> Future[_T]: ...

crates/red_knot/vendor/typeshed/stdlib/asyncio/queues.pyi

@@ -41,7 +41,7 @@ class Queue(Generic[_T], _LoopBoundMixin):  # noqa: Y059
     async def join(self) -> None: ...
     def task_done(self) -> None: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, type: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, type: Any, /) -> GenericAlias: ...
 
 class PriorityQueue(Queue[_T]): ...
 class LifoQueue(Queue[_T]): ...

crates/red_knot/vendor/typeshed/stdlib/asyncio/tasks.pyi

@@ -443,7 +443,7 @@ class Task(Future[_T_co]):  # type: ignore[type-var]  # pyright: ignore[reportIn
         @classmethod
         def all_tasks(cls, loop: AbstractEventLoop | None = None) -> set[Task[Any]]: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 def all_tasks(loop: AbstractEventLoop | None = None) -> set[Task[Any]]: ...
 

crates/red_knot/vendor/typeshed/stdlib/atexit.pyi

@@ -8,5 +8,5 @@ _P = ParamSpec("_P")
 def _clear() -> None: ...
 def _ncallbacks() -> int: ...
 def _run_exitfuncs() -> None: ...
-def register(func: Callable[_P, _T], *args: _P.args, **kwargs: _P.kwargs) -> Callable[_P, _T]: ...
-def unregister(func: Callable[..., object]) -> None: ...
+def register(func: Callable[_P, _T], /, *args: _P.args, **kwargs: _P.kwargs) -> Callable[_P, _T]: ...
+def unregister(func: Callable[..., object], /) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/base64.pyi

@@ -25,6 +25,8 @@ __all__ = [
 
 if sys.version_info >= (3, 10):
     __all__ += ["b32hexencode", "b32hexdecode"]
+if sys.version_info >= (3, 13):
+    __all__ += ["z85decode", "z85encode"]
 
 def b64encode(s: ReadableBuffer, altchars: ReadableBuffer | None = None) -> bytes: ...
 def b64decode(s: str | ReadableBuffer, altchars: str | ReadableBuffer | None = None, validate: bool = False) -> bytes: ...
@@ -57,3 +59,7 @@ def decodebytes(s: ReadableBuffer) -> bytes: ...
 if sys.version_info < (3, 9):
     def encodestring(s: ReadableBuffer) -> bytes: ...
     def decodestring(s: ReadableBuffer) -> bytes: ...
+
+if sys.version_info >= (3, 13):
+    def z85encode(s: ReadableBuffer) -> bytes: ...
+    def z85decode(s: str | ReadableBuffer) -> bytes: ...

crates/red_knot/vendor/typeshed/stdlib/builtins.pyi

@@ -461,7 +461,7 @@ class str(Sequence[str]):
     def format(self: LiteralString, *args: LiteralString, **kwargs: LiteralString) -> LiteralString: ...
     @overload
     def format(self, *args: object, **kwargs: object) -> str: ...
-    def format_map(self, map: _FormatMapMapping) -> str: ...
+    def format_map(self, mapping: _FormatMapMapping, /) -> str: ...
     def index(self, sub: str, start: SupportsIndex | None = ..., end: SupportsIndex | None = ..., /) -> int: ...
     def isalnum(self) -> bool: ...
     def isalpha(self) -> bool: ...
@@ -495,10 +495,20 @@ class str(Sequence[str]):
     def partition(self: LiteralString, sep: LiteralString, /) -> tuple[LiteralString, LiteralString, LiteralString]: ...
     @overload
     def partition(self, sep: str, /) -> tuple[str, str, str]: ...  # type: ignore[misc]
-    @overload
-    def replace(self: LiteralString, old: LiteralString, new: LiteralString, count: SupportsIndex = -1, /) -> LiteralString: ...
-    @overload
-    def replace(self, old: str, new: str, count: SupportsIndex = -1, /) -> str: ...  # type: ignore[misc]
+    if sys.version_info >= (3, 13):
+        @overload
+        def replace(
+            self: LiteralString, old: LiteralString, new: LiteralString, /, count: SupportsIndex = -1
+        ) -> LiteralString: ...
+        @overload
+        def replace(self, old: str, new: str, /, count: SupportsIndex = -1) -> str: ...  # type: ignore[misc]
+    else:
+        @overload
+        def replace(
+            self: LiteralString, old: LiteralString, new: LiteralString, count: SupportsIndex = -1, /
+        ) -> LiteralString: ...
+        @overload
+        def replace(self, old: str, new: str, count: SupportsIndex = -1, /) -> str: ...  # type: ignore[misc]
     if sys.version_info >= (3, 9):
         @overload
         def removeprefix(self: LiteralString, prefix: LiteralString, /) -> LiteralString: ...
@@ -1214,6 +1224,9 @@ class property:
     fset: Callable[[Any, Any], None] | None
     fdel: Callable[[Any], None] | None
     __isabstractmethod__: bool
+    if sys.version_info >= (3, 13):
+        __name__: str
+
     def __init__(
         self,
         fget: Callable[[Any], Any] | None = ...,
@@ -1321,12 +1334,34 @@ def divmod(x: _T_contra, y: SupportsRDivMod[_T_contra, _T_co], /) -> _T_co: ...
 
 # The `globals` argument to `eval` has to be `dict[str, Any]` rather than `dict[str, object]` due to invariance.
 # (The `globals` argument has to be a "real dict", rather than any old mapping, unlike the `locals` argument.)
-def eval(
-    source: str | ReadableBuffer | CodeType, globals: dict[str, Any] | None = None, locals: Mapping[str, object] | None = None, /
-) -> Any: ...
+if sys.version_info >= (3, 13):
+    def eval(
+        source: str | ReadableBuffer | CodeType,
+        /,
+        globals: dict[str, Any] | None = None,
+        locals: Mapping[str, object] | None = None,
+    ) -> Any: ...
+
+else:
+    def eval(
+        source: str | ReadableBuffer | CodeType,
+        globals: dict[str, Any] | None = None,
+        locals: Mapping[str, object] | None = None,
+        /,
+    ) -> Any: ...
 
 # Comment above regarding `eval` applies to `exec` as well
-if sys.version_info >= (3, 11):
+if sys.version_info >= (3, 13):
+    def exec(
+        source: str | ReadableBuffer | CodeType,
+        /,
+        globals: dict[str, Any] | None = None,
+        locals: Mapping[str, object] | None = None,
+        *,
+        closure: tuple[CellType, ...] | None = None,
+    ) -> None: ...
+
+elif sys.version_info >= (3, 11):
     def exec(
         source: str | ReadableBuffer | CodeType,
         globals: dict[str, Any] | None = None,
@@ -2035,3 +2070,7 @@ if sys.version_info >= (3, 11):
         def split(
             self, condition: Callable[[_ExceptionT_co | Self], bool], /
         ) -> tuple[ExceptionGroup[_ExceptionT_co] | None, ExceptionGroup[_ExceptionT_co] | None]: ...
+
+if sys.version_info >= (3, 13):
+    class IncompleteInputError(SyntaxError): ...
+    class PythonFinalizationError(RuntimeError): ...

crates/red_knot/vendor/typeshed/stdlib/calendar.pyi

@@ -4,7 +4,7 @@ import sys
 from _typeshed import Unused
 from collections.abc import Iterable, Sequence
 from time import struct_time
-from typing import ClassVar, Literal
+from typing import ClassVar, Final
 from typing_extensions import TypeAlias
 
 __all__ = [
@@ -154,18 +154,18 @@ month_abbr: Sequence[str]
 
 if sys.version_info >= (3, 12):
     class Month(enum.IntEnum):
-        JANUARY: Literal[1]
-        FEBRUARY: Literal[2]
-        MARCH: Literal[3]
-        APRIL: Literal[4]
-        MAY: Literal[5]
-        JUNE: Literal[6]
-        JULY: Literal[7]
-        AUGUST: Literal[8]
-        SEPTEMBER: Literal[9]
-        OCTOBER: Literal[10]
-        NOVEMBER: Literal[11]
-        DECEMBER: Literal[12]
+        JANUARY = 1
+        FEBRUARY = 2
+        MARCH = 3
+        APRIL = 4
+        MAY = 5
+        JUNE = 6
+        JULY = 7
+        AUGUST = 8
+        SEPTEMBER = 9
+        OCTOBER = 10
+        NOVEMBER = 11
+        DECEMBER = 12
 
     JANUARY = Month.JANUARY
     FEBRUARY = Month.FEBRUARY
@@ -181,13 +181,13 @@ if sys.version_info >= (3, 12):
     DECEMBER = Month.DECEMBER
 
     class Day(enum.IntEnum):
-        MONDAY: Literal[0]
-        TUESDAY: Literal[1]
-        WEDNESDAY: Literal[2]
-        THURSDAY: Literal[3]
-        FRIDAY: Literal[4]
-        SATURDAY: Literal[5]
-        SUNDAY: Literal[6]
+        MONDAY = 0
+        TUESDAY = 1
+        WEDNESDAY = 2
+        THURSDAY = 3
+        FRIDAY = 4
+        SATURDAY = 5
+        SUNDAY = 6
 
     MONDAY = Day.MONDAY
     TUESDAY = Day.TUESDAY
@@ -197,12 +197,12 @@ if sys.version_info >= (3, 12):
     SATURDAY = Day.SATURDAY
     SUNDAY = Day.SUNDAY
 else:
-    MONDAY: Literal[0]
-    TUESDAY: Literal[1]
-    WEDNESDAY: Literal[2]
-    THURSDAY: Literal[3]
-    FRIDAY: Literal[4]
-    SATURDAY: Literal[5]
-    SUNDAY: Literal[6]
+    MONDAY: Final = 0
+    TUESDAY: Final = 1
+    WEDNESDAY: Final = 2
+    THURSDAY: Final = 3
+    FRIDAY: Final = 4
+    SATURDAY: Final = 5
+    SUNDAY: Final = 6
 
-EPOCH: Literal[1970]
+EPOCH: Final = 1970

crates/red_knot/vendor/typeshed/stdlib/code.pyi

@@ -1,3 +1,4 @@
+import sys
 from codeop import CommandCompiler
 from collections.abc import Callable, Mapping
 from types import CodeType
@@ -18,16 +19,34 @@ class InteractiveInterpreter:
 class InteractiveConsole(InteractiveInterpreter):
     buffer: list[str]  # undocumented
     filename: str  # undocumented
-    def __init__(self, locals: Mapping[str, Any] | None = None, filename: str = "<console>") -> None: ...
+    if sys.version_info >= (3, 13):
+        def __init__(
+            self, locals: Mapping[str, Any] | None = None, filename: str = "<console>", *, local_exit: bool = False
+        ) -> None: ...
+        def push(self, line: str, filename: str | None = None) -> bool: ...
+    else:
+        def __init__(self, locals: Mapping[str, Any] | None = None, filename: str = "<console>") -> None: ...
+        def push(self, line: str) -> bool: ...
+
     def interact(self, banner: str | None = None, exitmsg: str | None = None) -> None: ...
-    def push(self, line: str) -> bool: ...
     def resetbuffer(self) -> None: ...
     def raw_input(self, prompt: str = "") -> str: ...
 
-def interact(
-    banner: str | None = None,
-    readfunc: Callable[[str], str] | None = None,
-    local: Mapping[str, Any] | None = None,
-    exitmsg: str | None = None,
-) -> None: ...
+if sys.version_info >= (3, 13):
+    def interact(
+        banner: str | None = None,
+        readfunc: Callable[[str], str] | None = None,
+        local: Mapping[str, Any] | None = None,
+        exitmsg: str | None = None,
+        local_exit: bool = False,
+    ) -> None: ...
+
+else:
+    def interact(
+        banner: str | None = None,
+        readfunc: Callable[[str], str] | None = None,
+        local: Mapping[str, Any] | None = None,
+        exitmsg: str | None = None,
+    ) -> None: ...
+
 def compile_command(source: str, filename: str = "<input>", symbol: str = "single") -> CodeType | None: ...

crates/red_knot/vendor/typeshed/stdlib/concurrent/futures/_base.pyi

@@ -54,7 +54,7 @@ class Future(Generic[_T]):
     def exception(self, timeout: float | None = None) -> BaseException | None: ...
     def set_exception(self, exception: BaseException | None) -> None: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class Executor:
     if sys.version_info >= (3, 9):

crates/red_knot/vendor/typeshed/stdlib/concurrent/futures/thread.pyi

@@ -29,7 +29,7 @@ class _WorkItem(Generic[_S]):
     def __init__(self, future: Future[_S], fn: Callable[..., _S], args: Iterable[Any], kwargs: Mapping[str, Any]) -> None: ...
     def run(self) -> None: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 def _worker(
     executor_reference: ref[Any],

crates/red_knot/vendor/typeshed/stdlib/contextvars.pyi

@@ -30,7 +30,7 @@ class ContextVar(Generic[_T]):
     def set(self, value: _T, /) -> Token[_T]: ...
     def reset(self, token: Token[_T], /) -> None: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 @final
 class Token(Generic[_T]):
@@ -40,7 +40,7 @@ class Token(Generic[_T]):
     def old_value(self) -> Any: ...  # returns either _T or MISSING, but that's hard to express
     MISSING: ClassVar[object]
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 def copy_context() -> Context: ...
 

crates/red_knot/vendor/typeshed/stdlib/csv.pyi

@@ -40,7 +40,6 @@ __all__ = [
     "QUOTE_NONE",
     "Error",
     "Dialect",
-    "__doc__",
     "excel",
     "excel_tab",
     "field_size_limit",
@@ -51,13 +50,14 @@ __all__ = [
     "list_dialects",
     "Sniffer",
     "unregister_dialect",
-    "__version__",
     "DictReader",
     "DictWriter",
     "unix_dialect",
 ]
 if sys.version_info >= (3, 12):
     __all__ += ["QUOTE_STRINGS", "QUOTE_NOTNULL"]
+if sys.version_info < (3, 13):
+    __all__ += ["__doc__", "__version__"]
 
 _T = TypeVar("_T")
 
@@ -111,7 +111,7 @@ class DictReader(Iterator[dict[_T | Any, str | Any]], Generic[_T]):
     def __iter__(self) -> Self: ...
     def __next__(self) -> dict[_T | Any, str | Any]: ...
     if sys.version_info >= (3, 12):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class DictWriter(Generic[_T]):
     fieldnames: Collection[_T]
@@ -139,7 +139,7 @@ class DictWriter(Generic[_T]):
     def writerow(self, rowdict: Mapping[_T, Any]) -> Any: ...
     def writerows(self, rowdicts: Iterable[Mapping[_T, Any]]) -> None: ...
     if sys.version_info >= (3, 12):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class Sniffer:
     preferred: list[str]

crates/red_knot/vendor/typeshed/stdlib/ctypes/__init__.pyi

@@ -76,7 +76,7 @@ class LibraryLoader(Generic[_DLLT]):
     def __getitem__(self, name: str) -> _DLLT: ...
     def LoadLibrary(self, name: str) -> _DLLT: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 cdll: LibraryLoader[CDLL]
 if sys.platform == "win32":

crates/red_knot/vendor/typeshed/stdlib/dataclasses.pyi

@@ -5,7 +5,7 @@ from _typeshed import DataclassInstance
 from builtins import type as Type  # alias to avoid name clashes with fields named "type"
 from collections.abc import Callable, Iterable, Mapping
 from typing import Any, Generic, Literal, Protocol, TypeVar, overload
-from typing_extensions import TypeAlias, TypeGuard
+from typing_extensions import TypeAlias, TypeIs
 
 if sys.version_info >= (3, 9):
     from types import GenericAlias
@@ -143,7 +143,7 @@ class Field(Generic[_T]):
 
     def __set_name__(self, owner: Type[Any], name: str) -> None: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 # NOTE: Actual return type is 'Field[_T]', but we want to help type checkers
 # to understand the magic that happens at runtime.
@@ -214,11 +214,9 @@ else:
 
 def fields(class_or_instance: DataclassInstance | type[DataclassInstance]) -> tuple[Field[Any], ...]: ...
 @overload
-def is_dataclass(obj: DataclassInstance) -> Literal[True]: ...
+def is_dataclass(obj: type) -> TypeIs[type[DataclassInstance]]: ...
 @overload
-def is_dataclass(obj: type) -> TypeGuard[type[DataclassInstance]]: ...
-@overload
-def is_dataclass(obj: object) -> TypeGuard[DataclassInstance | type[DataclassInstance]]: ...
+def is_dataclass(obj: object) -> TypeIs[DataclassInstance | type[DataclassInstance]]: ...
 
 class FrozenInstanceError(AttributeError): ...
 

crates/red_knot/vendor/typeshed/stdlib/datetime.pyi

@@ -79,6 +79,9 @@ class date:
     def isoformat(self) -> str: ...
     def timetuple(self) -> struct_time: ...
     def toordinal(self) -> int: ...
+    if sys.version_info >= (3, 13):
+        def __replace__(self, /, *, year: SupportsIndex = ..., month: SupportsIndex = ..., day: SupportsIndex = ...) -> Self: ...
+
     def replace(self, year: SupportsIndex = ..., month: SupportsIndex = ..., day: SupportsIndex = ...) -> Self: ...
     def __le__(self, value: date, /) -> bool: ...
     def __lt__(self, value: date, /) -> bool: ...
@@ -148,6 +151,19 @@ class time:
     def utcoffset(self) -> timedelta | None: ...
     def tzname(self) -> str | None: ...
     def dst(self) -> timedelta | None: ...
+    if sys.version_info >= (3, 13):
+        def __replace__(
+            self,
+            /,
+            *,
+            hour: SupportsIndex = ...,
+            minute: SupportsIndex = ...,
+            second: SupportsIndex = ...,
+            microsecond: SupportsIndex = ...,
+            tzinfo: _TzInfo | None = ...,
+            fold: int = ...,
+        ) -> Self: ...
+
     def replace(
         self,
         hour: SupportsIndex = ...,
@@ -263,6 +279,22 @@ class datetime(date):
     def date(self) -> _Date: ...
     def time(self) -> _Time: ...
     def timetz(self) -> _Time: ...
+    if sys.version_info >= (3, 13):
+        def __replace__(
+            self,
+            /,
+            *,
+            year: SupportsIndex = ...,
+            month: SupportsIndex = ...,
+            day: SupportsIndex = ...,
+            hour: SupportsIndex = ...,
+            minute: SupportsIndex = ...,
+            second: SupportsIndex = ...,
+            microsecond: SupportsIndex = ...,
+            tzinfo: _TzInfo | None = ...,
+            fold: int = ...,
+        ) -> Self: ...
+
     def replace(
         self,
         year: SupportsIndex = ...,

crates/red_knot/vendor/typeshed/stdlib/difflib.pyi

@@ -55,7 +55,7 @@ class SequenceMatcher(Generic[_T]):
     def quick_ratio(self) -> float: ...
     def real_quick_ratio(self) -> float: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 @overload
 def get_close_matches(word: AnyStr, possibilities: Iterable[AnyStr], n: int = 3, cutoff: float = 0.6) -> list[AnyStr]: ...

crates/red_knot/vendor/typeshed/stdlib/dis.pyi

@@ -47,7 +47,22 @@ if sys.version_info >= (3, 11):
         col_offset: int | None = None
         end_col_offset: int | None = None
 
-if sys.version_info >= (3, 11):
+if sys.version_info >= (3, 13):
+    class _Instruction(NamedTuple):
+        opname: str
+        opcode: int
+        arg: int | None
+        argval: Any
+        argrepr: str
+        offset: int
+        start_offset: int
+        starts_line: bool
+        line_number: int | None
+        label: int | None = None
+        positions: Positions | None = None
+        cache_info: list[tuple[str, int, Any]] | None = None
+
+elif sys.version_info >= (3, 11):
     class _Instruction(NamedTuple):
         opname: str
         opcode: int

crates/red_knot/vendor/typeshed/stdlib/distutils/archive_util.pyi

@@ -1,20 +1,35 @@
+from _typeshed import StrOrBytesPath, StrPath
+from typing import Literal, overload
+
+@overload
 def make_archive(
     base_name: str,
     format: str,
-    root_dir: str | None = None,
+    root_dir: StrOrBytesPath | None = None,
     base_dir: str | None = None,
-    verbose: int = 0,
-    dry_run: int = 0,
+    verbose: bool | Literal[0, 1] = 0,
+    dry_run: bool | Literal[0, 1] = 0,
+    owner: str | None = None,
+    group: str | None = None,
+) -> str: ...
+@overload
+def make_archive(
+    base_name: StrPath,
+    format: str,
+    root_dir: StrOrBytesPath,
+    base_dir: str | None = None,
+    verbose: bool | Literal[0, 1] = 0,
+    dry_run: bool | Literal[0, 1] = 0,
     owner: str | None = None,
     group: str | None = None,
 ) -> str: ...
 def make_tarball(
     base_name: str,
-    base_dir: str,
+    base_dir: StrPath,
     compress: str | None = "gzip",
-    verbose: int = 0,
-    dry_run: int = 0,
+    verbose: bool | Literal[0, 1] = 0,
+    dry_run: bool | Literal[0, 1] = 0,
     owner: str | None = None,
     group: str | None = None,
 ) -> str: ...
-def make_zipfile(base_name: str, base_dir: str, verbose: int = 0, dry_run: int = 0) -> str: ...
+def make_zipfile(base_name: str, base_dir: str, verbose: bool | Literal[0, 1] = 0, dry_run: bool | Literal[0, 1] = 0) -> str: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/ccompiler.pyi

@@ -1,5 +1,7 @@
-from collections.abc import Callable
-from typing import Any
+from _typeshed import BytesPath, StrPath
+from collections.abc import Callable, Iterable
+from distutils.file_util import _BytesPathT, _StrPathT
+from typing import Any, Literal, overload
 from typing_extensions import TypeAlias
 
 _Macro: TypeAlias = tuple[str] | tuple[str, str | None]
@@ -10,7 +12,11 @@ def gen_lib_options(
 def gen_preprocess_options(macros: list[_Macro], include_dirs: list[str]) -> list[str]: ...
 def get_default_compiler(osname: str | None = None, platform: str | None = None) -> str: ...
 def new_compiler(
-    plat: str | None = None, compiler: str | None = None, verbose: int = 0, dry_run: int = 0, force: int = 0
+    plat: str | None = None,
+    compiler: str | None = None,
+    verbose: bool | Literal[0, 1] = 0,
+    dry_run: bool | Literal[0, 1] = 0,
+    force: bool | Literal[0, 1] = 0,
 ) -> CCompiler: ...
 def show_compilers() -> None: ...
 
@@ -25,7 +31,9 @@ class CCompiler:
     library_dirs: list[str]
     runtime_library_dirs: list[str]
     objects: list[str]
-    def __init__(self, verbose: int = 0, dry_run: int = 0, force: int = 0) -> None: ...
+    def __init__(
+        self, verbose: bool | Literal[0, 1] = 0, dry_run: bool | Literal[0, 1] = 0, force: bool | Literal[0, 1] = 0
+    ) -> None: ...
     def add_include_dir(self, dir: str) -> None: ...
     def set_include_dirs(self, dirs: list[str]) -> None: ...
     def add_library(self, libname: str) -> None: ...
@@ -39,7 +47,7 @@ class CCompiler:
     def add_link_object(self, object: str) -> None: ...
     def set_link_objects(self, objects: list[str]) -> None: ...
     def detect_language(self, sources: str | list[str]) -> str | None: ...
-    def find_library_file(self, dirs: list[str], lib: str, debug: bool = ...) -> str | None: ...
+    def find_library_file(self, dirs: list[str], lib: str, debug: bool | Literal[0, 1] = 0) -> str | None: ...
     def has_function(
         self,
         funcname: str,
@@ -58,7 +66,7 @@ class CCompiler:
         output_dir: str | None = None,
         macros: list[_Macro] | None = None,
         include_dirs: list[str] | None = None,
-        debug: bool = ...,
+        debug: bool | Literal[0, 1] = 0,
         extra_preargs: list[str] | None = None,
         extra_postargs: list[str] | None = None,
         depends: list[str] | None = None,
@@ -68,7 +76,7 @@ class CCompiler:
         objects: list[str],
         output_libname: str,
         output_dir: str | None = None,
-        debug: bool = ...,
+        debug: bool | Literal[0, 1] = 0,
         target_lang: str | None = None,
     ) -> None: ...
     def link(
@@ -81,7 +89,7 @@ class CCompiler:
         library_dirs: list[str] | None = None,
         runtime_library_dirs: list[str] | None = None,
         export_symbols: list[str] | None = None,
-        debug: bool = ...,
+        debug: bool | Literal[0, 1] = 0,
         extra_preargs: list[str] | None = None,
         extra_postargs: list[str] | None = None,
         build_temp: str | None = None,
@@ -95,7 +103,7 @@ class CCompiler:
         libraries: list[str] | None = None,
         library_dirs: list[str] | None = None,
         runtime_library_dirs: list[str] | None = None,
-        debug: bool = ...,
+        debug: bool | Literal[0, 1] = 0,
         extra_preargs: list[str] | None = None,
         extra_postargs: list[str] | None = None,
         target_lang: str | None = None,
@@ -109,7 +117,7 @@ class CCompiler:
         library_dirs: list[str] | None = None,
         runtime_library_dirs: list[str] | None = None,
         export_symbols: list[str] | None = None,
-        debug: bool = ...,
+        debug: bool | Literal[0, 1] = 0,
         extra_preargs: list[str] | None = None,
         extra_postargs: list[str] | None = None,
         build_temp: str | None = None,
@@ -124,7 +132,7 @@ class CCompiler:
         library_dirs: list[str] | None = None,
         runtime_library_dirs: list[str] | None = None,
         export_symbols: list[str] | None = None,
-        debug: bool = ...,
+        debug: bool | Literal[0, 1] = 0,
         extra_preargs: list[str] | None = None,
         extra_postargs: list[str] | None = None,
         build_temp: str | None = None,
@@ -139,14 +147,27 @@ class CCompiler:
         extra_preargs: list[str] | None = None,
         extra_postargs: list[str] | None = None,
     ) -> None: ...
-    def executable_filename(self, basename: str, strip_dir: int = 0, output_dir: str = "") -> str: ...
-    def library_filename(self, libname: str, lib_type: str = "static", strip_dir: int = 0, output_dir: str = "") -> str: ...
-    def object_filenames(self, source_filenames: list[str], strip_dir: int = 0, output_dir: str = "") -> list[str]: ...
-    def shared_object_filename(self, basename: str, strip_dir: int = 0, output_dir: str = "") -> str: ...
+    @overload
+    def executable_filename(self, basename: str, strip_dir: Literal[0, False] = 0, output_dir: StrPath = "") -> str: ...
+    @overload
+    def executable_filename(self, basename: StrPath, strip_dir: Literal[1, True], output_dir: StrPath = "") -> str: ...
+    def library_filename(
+        self, libname: str, lib_type: str = "static", strip_dir: bool | Literal[0, 1] = 0, output_dir: StrPath = ""
+    ) -> str: ...
+    def object_filenames(
+        self, source_filenames: Iterable[StrPath], strip_dir: bool | Literal[0, 1] = 0, output_dir: StrPath | None = ""
+    ) -> list[str]: ...
+    @overload
+    def shared_object_filename(self, basename: str, strip_dir: Literal[0, False] = 0, output_dir: StrPath = "") -> str: ...
+    @overload
+    def shared_object_filename(self, basename: StrPath, strip_dir: Literal[1, True], output_dir: StrPath = "") -> str: ...
     def execute(self, func: Callable[..., object], args: tuple[Any, ...], msg: str | None = None, level: int = 1) -> None: ...
     def spawn(self, cmd: list[str]) -> None: ...
     def mkpath(self, name: str, mode: int = 0o777) -> None: ...
-    def move_file(self, src: str, dst: str) -> str: ...
+    @overload
+    def move_file(self, src: StrPath, dst: _StrPathT) -> _StrPathT | str: ...
+    @overload
+    def move_file(self, src: BytesPath, dst: _BytesPathT) -> _BytesPathT | bytes: ...
     def announce(self, msg: str, level: int = 1) -> None: ...
     def warn(self, msg: str) -> None: ...
     def debug_print(self, msg: str) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/cmd.pyi

@@ -1,12 +1,14 @@
-from _typeshed import Incomplete
+from _typeshed import BytesPath, Incomplete, StrOrBytesPath, StrPath, Unused
 from abc import abstractmethod
 from collections.abc import Callable, Iterable
 from distutils.dist import Distribution
-from typing import Any
+from distutils.file_util import _BytesPathT, _StrPathT
+from typing import Any, ClassVar, Literal, overload
 
 class Command:
     distribution: Distribution
-    sub_commands: list[tuple[str, Callable[[Command], bool] | None]]
+    # Any to work around variance issues
+    sub_commands: ClassVar[list[tuple[str, Callable[[Any], bool] | None]]]
     def __init__(self, dist: Distribution) -> None: ...
     @abstractmethod
     def initialize_options(self) -> None: ...
@@ -22,32 +24,63 @@ class Command:
     def ensure_dirname(self, option: str) -> None: ...
     def get_command_name(self) -> str: ...
     def set_undefined_options(self, src_cmd: str, *option_pairs: tuple[str, str]) -> None: ...
-    def get_finalized_command(self, command: str, create: int = 1) -> Command: ...
-    def reinitialize_command(self, command: Command | str, reinit_subcommands: int = 0) -> Command: ...
+    def get_finalized_command(self, command: str, create: bool | Literal[0, 1] = 1) -> Command: ...
+    def reinitialize_command(self, command: Command | str, reinit_subcommands: bool | Literal[0, 1] = 0) -> Command: ...
     def run_command(self, command: str) -> None: ...
     def get_sub_commands(self) -> list[str]: ...
     def warn(self, msg: str) -> None: ...
     def execute(self, func: Callable[..., object], args: Iterable[Any], msg: str | None = None, level: int = 1) -> None: ...
     def mkpath(self, name: str, mode: int = 0o777) -> None: ...
+    @overload
     def copy_file(
-        self, infile: str, outfile: str, preserve_mode: int = 1, preserve_times: int = 1, link: str | None = None, level: Any = 1
-    ) -> tuple[str, bool]: ...  # level is not used
+        self,
+        infile: StrPath,
+        outfile: _StrPathT,
+        preserve_mode: bool | Literal[0, 1] = 1,
+        preserve_times: bool | Literal[0, 1] = 1,
+        link: str | None = None,
+        level: Unused = 1,
+    ) -> tuple[_StrPathT | str, bool]: ...
+    @overload
+    def copy_file(
+        self,
+        infile: BytesPath,
+        outfile: _BytesPathT,
+        preserve_mode: bool | Literal[0, 1] = 1,
+        preserve_times: bool | Literal[0, 1] = 1,
+        link: str | None = None,
+        level: Unused = 1,
+    ) -> tuple[_BytesPathT | bytes, bool]: ...
     def copy_tree(
         self,
-        infile: str,
+        infile: StrPath,
         outfile: str,
-        preserve_mode: int = 1,
-        preserve_times: int = 1,
-        preserve_symlinks: int = 0,
-        level: Any = 1,
-    ) -> list[str]: ...  # level is not used
-    def move_file(self, src: str, dst: str, level: Any = 1) -> str: ...  # level is not used
-    def spawn(self, cmd: Iterable[str], search_path: int = 1, level: Any = 1) -> None: ...  # level is not used
+        preserve_mode: bool | Literal[0, 1] = 1,
+        preserve_times: bool | Literal[0, 1] = 1,
+        preserve_symlinks: bool | Literal[0, 1] = 0,
+        level: Unused = 1,
+    ) -> list[str]: ...
+    @overload
+    def move_file(self, src: StrPath, dst: _StrPathT, level: Unused = 1) -> _StrPathT | str: ...
+    @overload
+    def move_file(self, src: BytesPath, dst: _BytesPathT, level: Unused = 1) -> _BytesPathT | bytes: ...
+    def spawn(self, cmd: Iterable[str], search_path: bool | Literal[0, 1] = 1, level: Unused = 1) -> None: ...
+    @overload
     def make_archive(
         self,
         base_name: str,
         format: str,
-        root_dir: str | None = None,
+        root_dir: StrOrBytesPath | None = None,
+        base_dir: str | None = None,
+        owner: str | None = None,
+        group: str | None = None,
+    ) -> str: ...
+    @overload
+    def make_archive(
+        self,
+        base_name: StrPath,
+        format: str,
+        root_dir: StrOrBytesPath,
         base_dir: str | None = None,
         owner: str | None = None,
         group: str | None = None,
@@ -55,12 +88,12 @@ class Command:
     def make_file(
         self,
         infiles: str | list[str] | tuple[str, ...],
-        outfile: str,
+        outfile: StrOrBytesPath,
         func: Callable[..., object],
         args: list[Any],
         exec_msg: str | None = None,
         skip_msg: str | None = None,
-        level: Any = 1,
-    ) -> None: ...  # level is not used
+        level: Unused = 1,
+    ) -> None: ...
     def ensure_finalized(self) -> None: ...
     def dump_options(self, header: Incomplete | None = None, indent: str = "") -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/command/bdist_msi.pyi

@@ -1,5 +1,5 @@
 import sys
-from typing import Any
+from typing import Any, Literal
 
 from ..cmd import Command
 
@@ -9,9 +9,9 @@ if sys.platform == "win32":
     class PyDialog(Dialog):
         def __init__(self, *args, **kw) -> None: ...
         def title(self, title) -> None: ...
-        def back(self, title, next, name: str = "Back", active: int = 1): ...
-        def cancel(self, title, next, name: str = "Cancel", active: int = 1): ...
-        def next(self, title, next, name: str = "Next", active: int = 1): ...
+        def back(self, title, next, name: str = "Back", active: bool | Literal[0, 1] = 1): ...
+        def cancel(self, title, next, name: str = "Cancel", active: bool | Literal[0, 1] = 1): ...
+        def next(self, title, next, name: str = "Next", active: bool | Literal[0, 1] = 1): ...
         def xbutton(self, name, title, next, xpos): ...
 
     class bdist_msi(Command):

crates/red_knot/vendor/typeshed/stdlib/distutils/command/build.pyi

@@ -1,4 +1,5 @@
-from typing import Any
+from collections.abc import Callable
+from typing import Any, ClassVar
 
 from ..cmd import Command
 
@@ -28,4 +29,5 @@ class build(Command):
     def has_c_libraries(self): ...
     def has_ext_modules(self): ...
     def has_scripts(self): ...
-    sub_commands: Any
+    # Any to work around variance issues
+    sub_commands: ClassVar[list[tuple[str, Callable[[Any], bool] | None]]]

crates/red_knot/vendor/typeshed/stdlib/distutils/command/build_py.pyi

@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Literal
 
 from ..cmd import Command
 from ..util import Mixin2to3 as Mixin2to3
@@ -32,7 +32,7 @@ class build_py(Command):
     def find_all_modules(self): ...
     def get_source_files(self): ...
     def get_module_outfile(self, build_dir, package, module): ...
-    def get_outputs(self, include_bytecode: int = 1): ...
+    def get_outputs(self, include_bytecode: bool | Literal[0, 1] = 1): ...
     def build_module(self, module, module_file, package): ...
     def build_modules(self) -> None: ...
     def build_packages(self) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/command/check.pyi

@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Literal
 from typing_extensions import TypeAlias
 
 from ..cmd import Command
@@ -16,7 +16,7 @@ class SilentReporter(_Reporter):
         report_level,
         halt_level,
         stream: Any | None = ...,
-        debug: int = ...,
+        debug: bool | Literal[0, 1] = 0,
         encoding: str = ...,
         error_handler: str = ...,
     ) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/command/config.pyi

@@ -1,6 +1,7 @@
+from _typeshed import StrOrBytesPath
 from collections.abc import Sequence
 from re import Pattern
-from typing import Any
+from typing import Any, Literal
 
 from ..ccompiler import CCompiler
 from ..cmd import Command
@@ -65,8 +66,8 @@ class config(Command):
         include_dirs: Sequence[str] | None = None,
         libraries: Sequence[str] | None = None,
         library_dirs: Sequence[str] | None = None,
-        decl: int = 0,
-        call: int = 0,
+        decl: bool | Literal[0, 1] = 0,
+        call: bool | Literal[0, 1] = 0,
     ) -> bool: ...
     def check_lib(
         self,
@@ -80,4 +81,4 @@ class config(Command):
         self, header: str, include_dirs: Sequence[str] | None = None, library_dirs: Sequence[str] | None = None, lang: str = "c"
     ) -> bool: ...
 
-def dump_file(filename: str, head: Any | None = None) -> None: ...
+def dump_file(filename: StrOrBytesPath, head: Any | None = None) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/command/install.pyi

@@ -1,4 +1,5 @@
-from typing import Any
+from collections.abc import Callable
+from typing import Any, ClassVar
 
 from ..cmd import Command
 
@@ -60,4 +61,5 @@ class install(Command):
     def has_headers(self): ...
     def has_scripts(self): ...
     def has_data(self): ...
-    sub_commands: Any
+    # Any to work around variance issues
+    sub_commands: ClassVar[list[tuple[str, Callable[[Any], bool] | None]]]

crates/red_knot/vendor/typeshed/stdlib/distutils/command/register.pyi

@@ -1,10 +1,12 @@
-from typing import Any
+from collections.abc import Callable
+from typing import Any, ClassVar
 
 from ..config import PyPIRCCommand
 
 class register(PyPIRCCommand):
     description: str
-    sub_commands: Any
+    # Any to work around variance issues
+    sub_commands: ClassVar[list[tuple[str, Callable[[Any], bool] | None]]]
     list_classifiers: int
     strict: int
     def initialize_options(self) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/command/sdist.pyi

@@ -1,4 +1,5 @@
-from typing import Any
+from collections.abc import Callable
+from typing import Any, ClassVar
 
 from ..cmd import Command
 
@@ -11,7 +12,8 @@ class sdist(Command):
     boolean_options: Any
     help_options: Any
     negative_opt: Any
-    sub_commands: Any
+    # Any to work around variance issues
+    sub_commands: ClassVar[list[tuple[str, Callable[[Any], bool] | None]]]
     READMES: Any
     template: Any
     manifest: Any

crates/red_knot/vendor/typeshed/stdlib/distutils/core.pyi

@@ -3,7 +3,7 @@ from collections.abc import Mapping
 from distutils.cmd import Command as Command
 from distutils.dist import Distribution as Distribution
 from distutils.extension import Extension as Extension
-from typing import Any
+from typing import Any, Literal
 
 USAGE: str
 
@@ -45,7 +45,7 @@ def setup(
     command_packages: list[str] = ...,
     command_options: Mapping[str, Mapping[str, tuple[Any, Any]]] = ...,
     package_data: Mapping[str, list[str]] = ...,
-    include_package_data: bool = ...,
+    include_package_data: bool | Literal[0, 1] = ...,
     libraries: list[str] = ...,
     headers: list[str] = ...,
     ext_package: str = ...,

crates/red_knot/vendor/typeshed/stdlib/distutils/dep_util.pyi

@@ -1,3 +1,14 @@
-def newer(source: str, target: str) -> bool: ...
-def newer_pairwise(sources: list[str], targets: list[str]) -> list[tuple[str, str]]: ...
-def newer_group(sources: list[str], target: str, missing: str = "error") -> bool: ...
+from _typeshed import StrOrBytesPath, SupportsLenAndGetItem
+from collections.abc import Iterable
+from typing import Literal, TypeVar
+
+_SourcesT = TypeVar("_SourcesT", bound=StrOrBytesPath)
+_TargetsT = TypeVar("_TargetsT", bound=StrOrBytesPath)
+
+def newer(source: StrOrBytesPath, target: StrOrBytesPath) -> bool | Literal[1]: ...
+def newer_pairwise(
+    sources: SupportsLenAndGetItem[_SourcesT], targets: SupportsLenAndGetItem[_TargetsT]
+) -> tuple[list[_SourcesT], list[_TargetsT]]: ...
+def newer_group(
+    sources: Iterable[StrOrBytesPath], target: StrOrBytesPath, missing: Literal["error", "ignore", "newer"] = "error"
+) -> Literal[0, 1]: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/dir_util.pyi

@@ -1,13 +1,23 @@
-def mkpath(name: str, mode: int = 0o777, verbose: int = 1, dry_run: int = 0) -> list[str]: ...
-def create_tree(base_dir: str, files: list[str], mode: int = 0o777, verbose: int = 1, dry_run: int = 0) -> None: ...
+from _typeshed import StrOrBytesPath, StrPath
+from collections.abc import Iterable
+from typing import Literal
+
+def mkpath(name: str, mode: int = 0o777, verbose: bool | Literal[0, 1] = 1, dry_run: bool | Literal[0, 1] = 0) -> list[str]: ...
+def create_tree(
+    base_dir: StrPath,
+    files: Iterable[StrPath],
+    mode: int = 0o777,
+    verbose: bool | Literal[0, 1] = 1,
+    dry_run: bool | Literal[0, 1] = 0,
+) -> None: ...
 def copy_tree(
-    src: str,
+    src: StrPath,
     dst: str,
-    preserve_mode: int = 1,
-    preserve_times: int = 1,
-    preserve_symlinks: int = 0,
-    update: int = 0,
-    verbose: int = 1,
-    dry_run: int = 0,
+    preserve_mode: bool | Literal[0, 1] = 1,
+    preserve_times: bool | Literal[0, 1] = 1,
+    preserve_symlinks: bool | Literal[0, 1] = 0,
+    update: bool | Literal[0, 1] = 0,
+    verbose: bool | Literal[0, 1] = 1,
+    dry_run: bool | Literal[0, 1] = 0,
 ) -> list[str]: ...
-def remove_tree(directory: str, verbose: int = 1, dry_run: int = 0) -> None: ...
+def remove_tree(directory: StrOrBytesPath, verbose: bool | Literal[0, 1] = 1, dry_run: bool | Literal[0, 1] = 0) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/dist.pyi

@@ -1,8 +1,8 @@
-from _typeshed import FileDescriptorOrPath, Incomplete, SupportsWrite
+from _typeshed import Incomplete, StrOrBytesPath, StrPath, SupportsWrite
 from collections.abc import Iterable, Mapping
 from distutils.cmd import Command
 from re import Pattern
-from typing import IO, Any, ClassVar, TypeVar, overload
+from typing import IO, Any, ClassVar, Literal, TypeVar, overload
 from typing_extensions import TypeAlias
 
 command_re: Pattern[str]
@@ -11,7 +11,7 @@ _OptionsList: TypeAlias = list[tuple[str, str | None, str, int] | tuple[str, str
 _CommandT = TypeVar("_CommandT", bound=Command)
 
 class DistributionMetadata:
-    def __init__(self, path: FileDescriptorOrPath | None = None) -> None: ...
+    def __init__(self, path: StrOrBytesPath | None = None) -> None: ...
     name: str | None
     version: str | None
     author: str | None
@@ -30,7 +30,7 @@ class DistributionMetadata:
     requires: list[str] | None
     obsoletes: list[str] | None
     def read_pkg_file(self, file: IO[str]) -> None: ...
-    def write_pkg_info(self, base_dir: str) -> None: ...
+    def write_pkg_info(self, base_dir: StrPath) -> None: ...
     def write_pkg_file(self, file: SupportsWrite[str]) -> None: ...
     def get_name(self) -> str: ...
     def get_version(self) -> str: ...
@@ -63,7 +63,10 @@ class Distribution:
     def __init__(self, attrs: Mapping[str, Any] | None = None) -> None: ...
     def get_option_dict(self, command: str) -> dict[str, tuple[str, str]]: ...
     def parse_config_files(self, filenames: Iterable[str] | None = None) -> None: ...
-    def get_command_obj(self, command: str, create: bool = True) -> Command | None: ...
+    @overload
+    def get_command_obj(self, command: str, create: Literal[1, True] = 1) -> Command: ...
+    @overload
+    def get_command_obj(self, command: str, create: Literal[0, False]) -> Command | None: ...
     global_options: ClassVar[_OptionsList]
     common_usage: ClassVar[str]
     display_options: ClassVar[_OptionsList]

crates/red_knot/vendor/typeshed/stdlib/distutils/file_util.pyi

@@ -1,14 +1,38 @@
-from collections.abc import Sequence
+from _typeshed import BytesPath, StrOrBytesPath, StrPath
+from collections.abc import Iterable
+from typing import Literal, TypeVar, overload
 
+_StrPathT = TypeVar("_StrPathT", bound=StrPath)
+_BytesPathT = TypeVar("_BytesPathT", bound=BytesPath)
+
+@overload
 def copy_file(
-    src: str,
-    dst: str,
-    preserve_mode: bool = ...,
-    preserve_times: bool = ...,
-    update: bool = ...,
+    src: StrPath,
+    dst: _StrPathT,
+    preserve_mode: bool | Literal[0, 1] = 1,
+    preserve_times: bool | Literal[0, 1] = 1,
+    update: bool | Literal[0, 1] = 0,
     link: str | None = None,
-    verbose: bool = ...,
-    dry_run: bool = ...,
-) -> tuple[str, str]: ...
-def move_file(src: str, dst: str, verbose: bool = ..., dry_run: bool = ...) -> str: ...
-def write_file(filename: str, contents: Sequence[str]) -> None: ...
+    verbose: bool | Literal[0, 1] = 1,
+    dry_run: bool | Literal[0, 1] = 0,
+) -> tuple[_StrPathT | str, bool]: ...
+@overload
+def copy_file(
+    src: BytesPath,
+    dst: _BytesPathT,
+    preserve_mode: bool | Literal[0, 1] = 1,
+    preserve_times: bool | Literal[0, 1] = 1,
+    update: bool | Literal[0, 1] = 0,
+    link: str | None = None,
+    verbose: bool | Literal[0, 1] = 1,
+    dry_run: bool | Literal[0, 1] = 0,
+) -> tuple[_BytesPathT | bytes, bool]: ...
+@overload
+def move_file(
+    src: StrPath, dst: _StrPathT, verbose: bool | Literal[0, 1] = 0, dry_run: bool | Literal[0, 1] = 0
+) -> _StrPathT | str: ...
+@overload
+def move_file(
+    src: BytesPath, dst: _BytesPathT, verbose: bool | Literal[0, 1] = 0, dry_run: bool | Literal[0, 1] = 0
+) -> _BytesPathT | bytes: ...
+def write_file(filename: StrOrBytesPath, contents: Iterable[str]) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/filelist.pyi

@@ -23,7 +23,11 @@ class FileList:
     def include_pattern(self, pattern: str | Pattern[str], *, is_regex: Literal[True, 1]) -> bool: ...
     @overload
     def include_pattern(
-        self, pattern: str | Pattern[str], anchor: bool | Literal[0, 1] = 1, prefix: str | None = None, is_regex: int = 0
+        self,
+        pattern: str | Pattern[str],
+        anchor: bool | Literal[0, 1] = 1,
+        prefix: str | None = None,
+        is_regex: bool | Literal[0, 1] = 0,
     ) -> bool: ...
     @overload
     def exclude_pattern(
@@ -33,7 +37,11 @@ class FileList:
     def exclude_pattern(self, pattern: str | Pattern[str], *, is_regex: Literal[True, 1]) -> bool: ...
     @overload
     def exclude_pattern(
-        self, pattern: str | Pattern[str], anchor: bool | Literal[0, 1] = 1, prefix: str | None = None, is_regex: int = 0
+        self,
+        pattern: str | Pattern[str],
+        anchor: bool | Literal[0, 1] = 1,
+        prefix: str | None = None,
+        is_regex: bool | Literal[0, 1] = 0,
     ) -> bool: ...
 
 def findall(dir: str = ".") -> list[str]: ...
@@ -46,5 +54,5 @@ def translate_pattern(
 def translate_pattern(pattern: str | Pattern[str], *, is_regex: Literal[True, 1]) -> Pattern[str]: ...
 @overload
 def translate_pattern(
-    pattern: str | Pattern[str], anchor: bool | Literal[0, 1] = 1, prefix: str | None = None, is_regex: int = 0
+    pattern: str | Pattern[str], anchor: bool | Literal[0, 1] = 1, prefix: str | None = None, is_regex: bool | Literal[0, 1] = 0
 ) -> Pattern[str]: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/spawn.pyi

@@ -1,2 +1,6 @@
-def spawn(cmd: list[str], search_path: bool = ..., verbose: bool = ..., dry_run: bool = ...) -> None: ...
+from typing import Literal
+
+def spawn(
+    cmd: list[str], search_path: bool | Literal[0, 1] = 1, verbose: bool | Literal[0, 1] = 0, dry_run: bool | Literal[0, 1] = 0
+) -> None: ...
 def find_executable(executable: str, path: str | None = None) -> str | None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/sysconfig.pyi

@@ -23,8 +23,10 @@ def get_config_vars() -> dict[str, str | int]: ...
 def get_config_vars(arg: str, /, *args: str) -> list[str | int]: ...
 def get_config_h_filename() -> str: ...
 def get_makefile_filename() -> str: ...
-def get_python_inc(plat_specific: bool = ..., prefix: str | None = None) -> str: ...
-def get_python_lib(plat_specific: bool = ..., standard_lib: bool = ..., prefix: str | None = None) -> str: ...
+def get_python_inc(plat_specific: bool | Literal[0, 1] = 0, prefix: str | None = None) -> str: ...
+def get_python_lib(
+    plat_specific: bool | Literal[0, 1] = 0, standard_lib: bool | Literal[0, 1] = 0, prefix: str | None = None
+) -> str: ...
 def customize_compiler(compiler: CCompiler) -> None: ...
 
 if sys.version_info < (3, 10):

crates/red_knot/vendor/typeshed/stdlib/distutils/text_file.pyi

@@ -1,4 +1,4 @@
-from typing import IO
+from typing import IO, Literal
 
 class TextFile:
     def __init__(
@@ -6,12 +6,12 @@ class TextFile:
         filename: str | None = None,
         file: IO[str] | None = None,
         *,
-        strip_comments: bool = ...,
-        lstrip_ws: bool = ...,
-        rstrip_ws: bool = ...,
-        skip_blanks: bool = ...,
-        join_lines: bool = ...,
-        collapse_join: bool = ...,
+        strip_comments: bool | Literal[0, 1] = ...,
+        lstrip_ws: bool | Literal[0, 1] = ...,
+        rstrip_ws: bool | Literal[0, 1] = ...,
+        skip_blanks: bool | Literal[0, 1] = ...,
+        join_lines: bool | Literal[0, 1] = ...,
+        collapse_join: bool | Literal[0, 1] = ...,
     ) -> None: ...
     def open(self, filename: str) -> None: ...
     def close(self) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/distutils/util.pyi

@@ -5,22 +5,26 @@ from typing import Any, Literal
 def get_host_platform() -> str: ...
 def get_platform() -> str: ...
 def convert_path(pathname: str) -> str: ...
-def change_root(new_root: str, pathname: str) -> str: ...
+def change_root(new_root: StrPath, pathname: StrPath) -> str: ...
 def check_environ() -> None: ...
 def subst_vars(s: str, local_vars: Mapping[str, str]) -> None: ...
 def split_quoted(s: str) -> list[str]: ...
 def execute(
-    func: Callable[..., object], args: tuple[Any, ...], msg: str | None = None, verbose: bool = ..., dry_run: bool = ...
+    func: Callable[..., object],
+    args: tuple[Any, ...],
+    msg: str | None = None,
+    verbose: bool | Literal[0, 1] = 0,
+    dry_run: bool | Literal[0, 1] = 0,
 ) -> None: ...
 def strtobool(val: str) -> Literal[0, 1]: ...
 def byte_compile(
     py_files: list[str],
     optimize: int = 0,
-    force: bool = ...,
+    force: bool | Literal[0, 1] = 0,
     prefix: str | None = None,
     base_dir: str | None = None,
-    verbose: bool = ...,
-    dry_run: bool = ...,
+    verbose: bool | Literal[0, 1] = 1,
+    dry_run: bool | Literal[0, 1] = 0,
     direct: bool | None = None,
 ) -> None: ...
 def rfc822_escape(header: str) -> str: ...

crates/red_knot/vendor/typeshed/stdlib/faulthandler.pyi

@@ -10,4 +10,4 @@ def is_enabled() -> bool: ...
 
 if sys.platform != "win32":
     def register(signum: int, file: FileDescriptorLike = ..., all_threads: bool = ..., chain: bool = ...) -> None: ...
-    def unregister(signum: int) -> None: ...
+    def unregister(signum: int, /) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/filecmp.pyi

@@ -52,6 +52,6 @@ class dircmp(Generic[AnyStr]):
     def phase4(self) -> None: ...
     def phase4_closure(self) -> None: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 def clear_cache() -> None: ...

crates/red_knot/vendor/typeshed/stdlib/fileinput.pyi

@@ -200,7 +200,7 @@ class FileInput(Iterator[AnyStr]):
     def isfirstline(self) -> bool: ...
     def isstdin(self) -> bool: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 if sys.version_info >= (3, 10):
     def hook_compressed(

crates/red_knot/vendor/typeshed/stdlib/functools.pyi

@@ -132,7 +132,7 @@ class partial(Generic[_T]):
     def __new__(cls, func: Callable[..., _T], /, *args: Any, **kwargs: Any) -> Self: ...
     def __call__(self, /, *args: Any, **kwargs: Any) -> _T: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 # With protocols, this could change into a generic protocol that defines __get__ and returns _T
 _Descriptor: TypeAlias = Any
@@ -149,7 +149,7 @@ class partialmethod(Generic[_T]):
     @property
     def __isabstractmethod__(self) -> bool: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class _SingleDispatchCallable(Generic[_T]):
     registry: types.MappingProxyType[Any, Callable[..., _T]]
@@ -196,7 +196,7 @@ class cached_property(Generic[_T_co]):
     # __set__ is not defined at runtime, but @cached_property is designed to be settable
     def __set__(self, instance: object, value: _T_co) -> None: ...  # type: ignore[misc]  # pyright: ignore[reportGeneralTypeIssues]
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 if sys.version_info >= (3, 9):
     def cache(user_function: Callable[..., _T], /) -> _lru_cache_wrapper[_T]: ...

crates/red_knot/vendor/typeshed/stdlib/genericpath.pyi

@@ -20,6 +20,8 @@ __all__ = [
 ]
 if sys.version_info >= (3, 12):
     __all__ += ["islink"]
+if sys.version_info >= (3, 13):
+    __all__ += ["isjunction", "isdevdrive", "lexists"]
 
 # All overloads can return empty string. Ideally, Literal[""] would be a valid
 # Iterable[T], so that list[T] | Literal[""] could be used as a return
@@ -50,3 +52,8 @@ def getctime(filename: FileDescriptorOrPath) -> float: ...
 def samefile(f1: FileDescriptorOrPath, f2: FileDescriptorOrPath) -> bool: ...
 def sameopenfile(fp1: int, fp2: int) -> bool: ...
 def samestat(s1: os.stat_result, s2: os.stat_result) -> bool: ...
+
+if sys.version_info >= (3, 13):
+    def isjunction(path: StrOrBytesPath) -> bool: ...
+    def isdevdrive(path: StrOrBytesPath) -> bool: ...
+    def lexists(path: StrOrBytesPath) -> bool: ...

crates/red_knot/vendor/typeshed/stdlib/graphlib.pyi

@@ -23,6 +23,6 @@ class TopologicalSorter(Generic[_T]):
     def get_ready(self) -> tuple[_T, ...]: ...
     def static_order(self) -> Iterable[_T]: ...
     if sys.version_info >= (3, 11):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class CycleError(ValueError): ...

crates/red_knot/vendor/typeshed/stdlib/gzip.pyi

@@ -12,8 +12,8 @@ _ReadBinaryMode: TypeAlias = Literal["r", "rb"]
 _WriteBinaryMode: TypeAlias = Literal["a", "ab", "w", "wb", "x", "xb"]
 _OpenTextMode: TypeAlias = Literal["rt", "at", "wt", "xt"]
 
-READ: Literal[1]  # undocumented
-WRITE: Literal[2]  # undocumented
+READ: object  # undocumented
+WRITE: object  # undocumented
 
 FTEXT: int  # actually Literal[1] # undocumented
 FHCRC: int  # actually Literal[2] # undocumented
@@ -86,7 +86,7 @@ class BadGzipFile(OSError): ...
 
 class GzipFile(_compression.BaseStream):
     myfileobj: FileIO | None
-    mode: Literal[1, 2]
+    mode: object
     name: str
     compress: zlib._Compress
     fileobj: _ReadableFileobj | _WritableFileobj

crates/red_knot/vendor/typeshed/stdlib/http/__init__.pyi

@@ -1,6 +1,5 @@
 import sys
 from enum import IntEnum
-from typing import Literal
 
 if sys.version_info >= (3, 11):
     from enum import StrEnum
@@ -49,11 +48,19 @@ class HTTPStatus(IntEnum):
     GONE = 410
     LENGTH_REQUIRED = 411
     PRECONDITION_FAILED = 412
+    if sys.version_info >= (3, 13):
+        CONTENT_TOO_LARGE = 413
     REQUEST_ENTITY_TOO_LARGE = 413
+    if sys.version_info >= (3, 13):
+        URI_TOO_LONG = 414
     REQUEST_URI_TOO_LONG = 414
     UNSUPPORTED_MEDIA_TYPE = 415
+    if sys.version_info >= (3, 13):
+        RANGE_NOT_SATISFIABLE = 416
     REQUESTED_RANGE_NOT_SATISFIABLE = 416
     EXPECTATION_FAILED = 417
+    if sys.version_info >= (3, 13):
+        UNPROCESSABLE_CONTENT = 422
     UNPROCESSABLE_ENTITY = 422
     LOCKED = 423
     FAILED_DEPENDENCY = 424
@@ -75,9 +82,9 @@ class HTTPStatus(IntEnum):
     MISDIRECTED_REQUEST = 421
     UNAVAILABLE_FOR_LEGAL_REASONS = 451
     if sys.version_info >= (3, 9):
-        EARLY_HINTS: Literal[103]
-        IM_A_TEAPOT: Literal[418]
-        TOO_EARLY: Literal[425]
+        EARLY_HINTS = 103
+        IM_A_TEAPOT = 418
+        TOO_EARLY = 425
     if sys.version_info >= (3, 12):
         @property
         def is_informational(self) -> bool: ...

crates/red_knot/vendor/typeshed/stdlib/http/cookies.pyi

@@ -45,7 +45,7 @@ class Morsel(dict[str, Any], Generic[_T]):
     def __eq__(self, morsel: object) -> bool: ...
     def __setitem__(self, K: str, V: Any) -> None: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any) -> GenericAlias: ...
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class BaseCookie(dict[str, Morsel[_T]], Generic[_T]):
     def __init__(self, input: _DataType | None = None) -> None: ...

crates/red_knot/vendor/typeshed/stdlib/importlib/metadata/__init__.pyi

@@ -240,7 +240,10 @@ class DistributionFinder(MetaPathFinder):
 class MetadataPathFinder(DistributionFinder):
     @classmethod
     def find_distributions(cls, context: DistributionFinder.Context = ...) -> Iterable[PathDistribution]: ...
-    if sys.version_info >= (3, 10):
+    if sys.version_info >= (3, 11):
+        @classmethod
+        def invalidate_caches(cls) -> None: ...
+    elif sys.version_info >= (3, 10):
         # Yes, this is an instance method that has a parameter named "cls"
         def invalidate_caches(cls) -> None: ...
 

crates/red_knot/vendor/typeshed/stdlib/inspect.pyi

@@ -318,6 +318,7 @@ class Signature:
     def bind(self, *args: Any, **kwargs: Any) -> BoundArguments: ...
     def bind_partial(self, *args: Any, **kwargs: Any) -> BoundArguments: ...
     def replace(self, *, parameters: Sequence[Parameter] | type[_void] | None = ..., return_annotation: Any = ...) -> Self: ...
+    __replace__ = replace
     if sys.version_info >= (3, 10):
         @classmethod
         def from_callable(
@@ -332,6 +333,8 @@ class Signature:
     else:
         @classmethod
         def from_callable(cls, obj: _IntrospectableCallable, *, follow_wrapped: bool = True) -> Self: ...
+    if sys.version_info >= (3, 13):
+        def format(self, *, max_width: int | None = None) -> str: ...
 
     def __eq__(self, other: object) -> bool: ...
     def __hash__(self) -> int: ...
@@ -392,6 +395,9 @@ class Parameter:
         default: Any = ...,
         annotation: Any = ...,
     ) -> Self: ...
+    if sys.version_info >= (3, 13):
+        __replace__ = replace
+
     def __eq__(self, other: object) -> bool: ...
     def __hash__(self) -> int: ...
 

crates/red_knot/vendor/typeshed/stdlib/io.pyi

@@ -75,7 +75,7 @@ class IOBase(metaclass=abc.ABCMeta):
     def __del__(self) -> None: ...
     @property
     def closed(self) -> bool: ...
-    def _checkClosed(self, msg: str | None = ...) -> None: ...  # undocumented
+    def _checkClosed(self) -> None: ...  # undocumented
 
 class RawIOBase(IOBase):
     def readall(self) -> bytes: ...