Merge branch 'main' into dcreager/function-enum

* main:
  Update pre-commit dependencies (#17506)
  [red-knot] Simplify visibility constraint handling for `*`-import definitions (#17486)
  [red-knot] Detect (some) invalid protocols (#17488)
  [red-knot] Correctly identify protocol classes (#17487)
  Update dependency ruff to v0.11.6 (#17516)
  Update Rust crate shellexpand to v3.1.1 (#17512)
  Update Rust crate proc-macro2 to v1.0.95 (#17510)
  Update Rust crate rand to v0.9.1 (#17511)
  Update Rust crate libc to v0.2.172 (#17509)
  Update Rust crate jiff to v0.2.9 (#17508)
  Update Rust crate clap to v4.5.37 (#17507)
  Update astral-sh/setup-uv action to v5.4.2 (#17504)
  Update taiki-e/install-action digest to 09dc018 (#17503)
  [red-knot] infer attribute assignments bound in comprehensions (#17396)
  [red-knot] simplify gradually-equivalent types out of unions and intersections (#17467)
  [red-knot] pull primer projects to run from file (#17473)

.github/workflows/build-binaries.yml

@@ -49,7 +49,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build sdist"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           command: sdist
           args: --out dist
@@ -79,7 +79,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels - x86_64"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           target: x86_64
           args: --release --locked --out dist
@@ -121,7 +121,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels - aarch64"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           target: aarch64
           args: --release --locked --out dist
@@ -177,7 +177,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           target: ${{ matrix.platform.target }}
           args: --release --locked --out dist
@@ -230,7 +230,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           target: ${{ matrix.target }}
           manylinux: auto
@@ -304,7 +304,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           target: ${{ matrix.platform.target }}
           manylinux: auto
@@ -370,14 +370,14 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           target: ${{ matrix.target }}
           manylinux: musllinux_1_2
           args: --release --locked --out dist
       - name: "Test wheel"
         if: matrix.target == 'x86_64-unknown-linux-musl'
-        uses: addnab/docker-run-action@v3
+        uses: addnab/docker-run-action@4f65fabd2431ebc8d299f8e5a018d79a769ae185 # v3
         with:
           image: alpine:latest
           options: -v ${{ github.workspace }}:/io -w /io
@@ -435,7 +435,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           target: ${{ matrix.platform.target }}
           manylinux: musllinux_1_2

.github/workflows/ci.yaml

@@ -237,13 +237,13 @@ jobs:
       - name: "Install Rust toolchain"
         run: rustup show
       - name: "Install mold"
-        uses: rui314/setup-mold@v1
+        uses: rui314/setup-mold@e16410e7f8d9e167b74ad5697a9089a35126eb50 # v1
       - name: "Install cargo nextest"
-        uses: taiki-e/install-action@d4635f2de61c8b8104d59cd4aede2060638378cc # v2
+        uses: taiki-e/install-action@09dc018eee06ae1c9e0409786563f534210ceb83 # v2
         with:
           tool: cargo-nextest
       - name: "Install cargo insta"
-        uses: taiki-e/install-action@d4635f2de61c8b8104d59cd4aede2060638378cc # v2
+        uses: taiki-e/install-action@09dc018eee06ae1c9e0409786563f534210ceb83 # v2
         with:
           tool: cargo-insta
       - name: Red-knot mdtests (GitHub annotations)
@@ -291,13 +291,13 @@ jobs:
       - name: "Install Rust toolchain"
         run: rustup show
       - name: "Install mold"
-        uses: rui314/setup-mold@v1
+        uses: rui314/setup-mold@e16410e7f8d9e167b74ad5697a9089a35126eb50 # v1
       - name: "Install cargo nextest"
-        uses: taiki-e/install-action@d4635f2de61c8b8104d59cd4aede2060638378cc # v2
+        uses: taiki-e/install-action@09dc018eee06ae1c9e0409786563f534210ceb83 # v2
         with:
           tool: cargo-nextest
       - name: "Install cargo insta"
-        uses: taiki-e/install-action@d4635f2de61c8b8104d59cd4aede2060638378cc # v2
+        uses: taiki-e/install-action@09dc018eee06ae1c9e0409786563f534210ceb83 # v2
         with:
           tool: cargo-insta
       - name: "Run tests"
@@ -320,7 +320,7 @@ jobs:
       - name: "Install Rust toolchain"
         run: rustup show
       - name: "Install cargo nextest"
-        uses: taiki-e/install-action@d4635f2de61c8b8104d59cd4aede2060638378cc # v2
+        uses: taiki-e/install-action@09dc018eee06ae1c9e0409786563f534210ceb83 # v2
         with:
           tool: cargo-nextest
       - name: "Run tests"
@@ -376,7 +376,7 @@ jobs:
       - name: "Install Rust toolchain"
         run: rustup show
       - name: "Install mold"
-        uses: rui314/setup-mold@v1
+        uses: rui314/setup-mold@e16410e7f8d9e167b74ad5697a9089a35126eb50 # v1
       - name: "Build"
         run: cargo build --release --locked
 
@@ -401,13 +401,13 @@ jobs:
           MSRV: ${{ steps.msrv.outputs.value }}
         run: rustup default "${MSRV}"
       - name: "Install mold"
-        uses: rui314/setup-mold@v1
+        uses: rui314/setup-mold@e16410e7f8d9e167b74ad5697a9089a35126eb50 # v1
       - name: "Install cargo nextest"
-        uses: taiki-e/install-action@d4635f2de61c8b8104d59cd4aede2060638378cc # v2
+        uses: taiki-e/install-action@09dc018eee06ae1c9e0409786563f534210ceb83 # v2
         with:
           tool: cargo-nextest
       - name: "Install cargo insta"
-        uses: taiki-e/install-action@d4635f2de61c8b8104d59cd4aede2060638378cc # v2
+        uses: taiki-e/install-action@09dc018eee06ae1c9e0409786563f534210ceb83 # v2
         with:
           tool: cargo-insta
       - name: "Run tests"
@@ -433,7 +433,7 @@ jobs:
       - name: "Install Rust toolchain"
         run: rustup show
       - name: "Install cargo-binstall"
-        uses: cargo-bins/cargo-binstall@main
+        uses: cargo-bins/cargo-binstall@63aaa5c1932cebabc34eceda9d92a70215dcead6 # v1.12.3
         with:
           tool: cargo-fuzz@0.11.2
       - name: "Install cargo-fuzz"
@@ -455,7 +455,7 @@ jobs:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           persist-credentials: false
-      - uses: astral-sh/setup-uv@0c5e2b8115b80b4c7c5ddf6ffdd634974642d182 # v5.4.1
+      - uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5.4.2
       - uses: actions/download-artifact@95815c38cf2ff2164869cbab79da8d1f422bc89e # v4.2.1
         name: Download Ruff binary to test
         id: download-cached-binary
@@ -641,7 +641,7 @@ jobs:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           persist-credentials: false
-      - uses: cargo-bins/cargo-binstall@main
+      - uses: cargo-bins/cargo-binstall@63aaa5c1932cebabc34eceda9d92a70215dcead6 # v1.12.3
       - run: cargo binstall --no-confirm cargo-shear
       - run: cargo shear
 
@@ -662,7 +662,7 @@ jobs:
       - name: "Prep README.md"
         run: python scripts/transform_readme.py --target pypi
       - name: "Build wheels"
-        uses: PyO3/maturin-action@44479ae1b6b1a57f561e03add8832e62c185eb17 # v1.48.1
+        uses: PyO3/maturin-action@aef21716ff3dcae8a1c301d23ec3e4446972a6e3 # v1.49.1
         with:
           args: --out dist
       - name: "Test wheel"
@@ -681,7 +681,7 @@ jobs:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           persist-credentials: false
-      - uses: astral-sh/setup-uv@0c5e2b8115b80b4c7c5ddf6ffdd634974642d182 # v5.4.1
+      - uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5.4.2
       - name: "Cache pre-commit"
         uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4.2.3
         with:
@@ -720,7 +720,7 @@ jobs:
       - name: "Install Rust toolchain"
         run: rustup show
       - name: Install uv
-        uses: astral-sh/setup-uv@0c5e2b8115b80b4c7c5ddf6ffdd634974642d182 # v5.4.1
+        uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5.4.2
       - name: "Install Insiders dependencies"
         if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
         run: uv pip install -r docs/requirements-insiders.txt --system
@@ -857,7 +857,7 @@ jobs:
         run: rustup show
 
       - name: "Install codspeed"
-        uses: taiki-e/install-action@d4635f2de61c8b8104d59cd4aede2060638378cc # v2
+        uses: taiki-e/install-action@09dc018eee06ae1c9e0409786563f534210ceb83 # v2
         with:
           tool: cargo-codspeed
 

.github/workflows/daily_fuzz.yaml

@@ -34,11 +34,11 @@ jobs:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           persist-credentials: false
-      - uses: astral-sh/setup-uv@0c5e2b8115b80b4c7c5ddf6ffdd634974642d182 # v5.4.1
+      - uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5.4.2
       - name: "Install Rust toolchain"
         run: rustup show
       - name: "Install mold"
-        uses: rui314/setup-mold@v1
+        uses: rui314/setup-mold@e16410e7f8d9e167b74ad5697a9089a35126eb50 # v1
       - uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
       - name: Build ruff
         # A debug build means the script runs slower once it gets started,

.github/workflows/daily_property_tests.yaml

@@ -36,7 +36,7 @@ jobs:
       - name: "Install Rust toolchain"
         run: rustup show
       - name: "Install mold"
-        uses: rui314/setup-mold@v1
+        uses: rui314/setup-mold@e16410e7f8d9e167b74ad5697a9089a35126eb50 # v1
       - uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
       - name: Build Red Knot
         # A release build takes longer (2 min vs 1 min), but the property tests run much faster in release

.github/workflows/mypy_primer.yaml

@@ -35,7 +35,7 @@ jobs:
           persist-credentials: false
 
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@0c5e2b8115b80b4c7c5ddf6ffdd634974642d182 # v5.4.1
+        uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5.4.2
 
       - uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
         with:
@@ -52,6 +52,8 @@ jobs:
         run: |
           cd ruff
 
+          PRIMER_SELECTOR="$(paste -s -d'|' crates/red_knot_python_semantic/resources/primer/good.txt)"
+
           echo "new commit"
           git rev-list --format=%s --max-count=1 "$GITHUB_SHA"
 
@@ -62,13 +64,14 @@ jobs:
 
           cd ..
 
+          echo "Project selector: $PRIMER_SELECTOR"
           # Allow the exit code to be 0 or 1, only fail for actual mypy_primer crashes/bugs
           uvx mypy_primer \
             --repo ruff \
             --type-checker knot \
             --old base_commit \
             --new "$GITHUB_SHA" \
-            --project-selector '/(mypy_primer|black|pyp|git-revise|zipp|arrow|isort|itsdangerous|rich|packaging|pybind11|pyinstrument|typeshed-stats|scrapy|werkzeug|bidict|async-utils)$' \
+            --project-selector "/($PRIMER_SELECTOR)\$" \
             --output concise \
             --debug > mypy_primer.diff || [ $? -eq 1 ]
 

.github/workflows/publish-pypi.yml

@@ -22,7 +22,7 @@ jobs:
       id-token: write
     steps:
       - name: "Install uv"
-        uses: astral-sh/setup-uv@0c5e2b8115b80b4c7c5ddf6ffdd634974642d182 # v5.4.1
+        uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5.4.2
       - uses: actions/download-artifact@95815c38cf2ff2164869cbab79da8d1f422bc89e # v4.2.1
         with:
           pattern: wheels-*

.pre-commit-config.yaml

@@ -79,7 +79,7 @@ repos:
         pass_filenames: false # This makes it a lot faster
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.11.5
+    rev: v0.11.6
     hooks:
       - id: ruff-format
       - id: ruff
@@ -97,7 +97,7 @@ repos:
   # zizmor detects security vulnerabilities in GitHub Actions workflows.
   # Additional configuration for the tool is found in `.github/zizmor.yml`
   - repo: https://github.com/woodruffw/zizmor-pre-commit
-    rev: v1.5.2
+    rev: v1.6.0
     hooks:
       - id: zizmor
 

CHANGELOG.md

@@ -1,5 +1,16 @@
 # Changelog
 
+## 0.11.6
+
+### Preview features
+
+- Avoid adding whitespace to the end of a docstring after an escaped quote ([#17216](https://github.com/astral-sh/ruff/pull/17216))
+- \[`airflow`\] Extract `AIR311` from `AIR301` rules (`AIR301`, `AIR311`) ([#17310](https://github.com/astral-sh/ruff/pull/17310), [#17422](https://github.com/astral-sh/ruff/pull/17422))
+
+### Bug fixes
+
+- Raise syntax error when `\` is at end of file ([#17409](https://github.com/astral-sh/ruff/pull/17409))
+
 ## 0.11.5
 
 ### Preview features

Cargo.lock

@@ -128,9 +128,9 @@ dependencies = [
 
 [[package]]
 name = "anyhow"
-version = "1.0.97"
+version = "1.0.98"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcfed56ad506cb2c684a14971b8861fdc3baaaae314b9e5f9bb532cbe3ba7a4f"
+checksum = "e16d2d3311acee920a9eb8d33b8cbc1787ce4a264e85f964c2404b969bdcd487"
 
 [[package]]
 name = "argfile"
@@ -216,9 +216,9 @@ dependencies = [
 
 [[package]]
 name = "bstr"
-version = "1.11.3"
+version = "1.12.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "531a9155a481e2ee699d4f98f43c0ca4ff8ee1bfd55c31e9e98fb29d2b176fe0"
+checksum = "234113d19d0d7d613b40e86fb654acf958910802bcceab913a4f9e7cda03b1a4"
 dependencies = [
  "memchr",
  "regex-automata 0.4.9",
@@ -334,9 +334,9 @@ dependencies = [
 
 [[package]]
 name = "clap"
-version = "4.5.35"
+version = "4.5.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d8aa86934b44c19c50f87cc2790e19f54f7a67aedb64101c2e1a2e5ecfb73944"
+checksum = "eccb054f56cbd38340b380d4a8e69ef1f02f1af43db2f0cc817a4774d80ae071"
 dependencies = [
  "clap_builder",
  "clap_derive",
@@ -344,9 +344,9 @@ dependencies = [
 
 [[package]]
 name = "clap_builder"
-version = "4.5.35"
+version = "4.5.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2414dbb2dd0695280da6ea9261e327479e9d37b0630f6b53ba2a11c60c679fd9"
+checksum = "efd9466fac8543255d3b1fcad4762c5e116ffe808c8a3043d4263cd4fd4862a2"
 dependencies = [
  "anstream",
  "anstyle",
@@ -478,7 +478,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "117725a109d387c937a1533ce01b450cbde6b88abceea8473c4d7a85853cda3c"
 dependencies = [
  "lazy_static",
- "windows-sys 0.48.0",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -487,7 +487,7 @@ version = "3.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fde0e0ec90c9dfb3b4b1a0891a7dcd0e2bffde2f7efed5fe7c9bb00e5bfb915e"
 dependencies = [
- "windows-sys 0.48.0",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -1553,28 +1553,45 @@ checksum = "4a5f13b858c8d314ee3e8f639011f7ccefe71f97f96e50151fb991f267928e2c"
 
 [[package]]
 name = "jiff"
-version = "0.2.4"
+version = "0.2.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d699bc6dfc879fb1bf9bdff0d4c56f0884fc6f0d0eb0fba397a6d00cd9a6b85e"
+checksum = "59ec30f7142be6fe14e1b021f50b85db8df2d4324ea6e91ec3e5dcde092021d0"
 dependencies = [
  "jiff-static",
+ "jiff-tzdb-platform",
  "log",
  "portable-atomic",
  "portable-atomic-util",
  "serde",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
 name = "jiff-static"
-version = "0.2.4"
+version = "0.2.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8d16e75759ee0aa64c57a56acbf43916987b20c77373cb7e808979e02b93c9f9"
+checksum = "526b834d727fd59d37b076b0c3236d9adde1b1729a4361e20b2026f738cc1dbe"
 dependencies = [
  "proc-macro2",
  "quote",
  "syn 2.0.100",
 ]
 
+[[package]]
+name = "jiff-tzdb"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c1283705eb0a21404d2bfd6eef2a7593d240bc42a0bdb39db0ad6fa2ec026524"
+
+[[package]]
+name = "jiff-tzdb-platform"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "875a5a69ac2bab1a891711cf5eccbec1ce0341ea805560dcd90b7a2e925132e8"
+dependencies = [
+ "jiff-tzdb",
+]
+
 [[package]]
 name = "jobserver"
 version = "0.1.32"
@@ -1628,9 +1645,9 @@ checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 
 [[package]]
 name = "libc"
-version = "0.2.171"
+version = "0.2.172"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c19937216e9d3aa9956d9bb8dfc0b0c8beb6058fc4f7a4dc4d850edf86a237d6"
+checksum = "d750af042f7ef4f724306de029d18836c26c1765a54a6a3f094cbd23a7267ffa"
 
 [[package]]
 name = "libcst"
@@ -1659,9 +1676,9 @@ dependencies = [
 
 [[package]]
 name = "libmimalloc-sys"
-version = "0.1.41"
+version = "0.1.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6b20daca3a4ac14dbdc753c5e90fc7b490a48a9131daed3c9a9ced7b2defd37b"
+checksum = "ec9d6fac27761dabcd4ee73571cdb06b7022dc99089acbe5435691edffaac0f4"
 dependencies = [
  "cc",
  "libc",
@@ -1797,9 +1814,9 @@ checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
 
 [[package]]
 name = "mimalloc"
-version = "0.1.45"
+version = "0.1.46"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "03cb1f88093fe50061ca1195d336ffec131347c7b833db31f9ab62a2d1b7925f"
+checksum = "995942f432bbb4822a7e9c3faa87a695185b0d09273ba85f097b54f4e458f2af"
 dependencies = [
  "libmimalloc-sys",
 ]
@@ -2310,9 +2327,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.94"
+version = "1.0.95"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a31971752e70b8b2686d7e46ec17fb38dad4051d94024c88df49b667caea9c84"
+checksum = "02b3e5e68a3a1a02aad3ec490a98007cbc13c37cbe84a3cd7b8e406d76e7f778"
 dependencies = [
  "unicode-ident",
 ]
@@ -2403,13 +2420,12 @@ dependencies = [
 
 [[package]]
 name = "rand"
-version = "0.9.0"
+version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3779b94aeb87e8bd4e834cee3650289ee9e0d5677f976ecdb6d219e5f4f6cd94"
+checksum = "9fbfd9d094a40bf3ae768db9361049ace4c0e04a4fd6b359518bd7b73a73dd97"
 dependencies = [
  "rand_chacha 0.9.0",
  "rand_core 0.9.3",
- "zerocopy",
 ]
 
 [[package]]
@@ -2476,7 +2492,6 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "argfile",
- "chrono",
  "clap",
  "colored 3.0.0",
  "countme",
@@ -2485,6 +2500,7 @@ dependencies = [
  "filetime",
  "insta",
  "insta-cmd",
+ "jiff",
  "rayon",
  "red_knot_project",
  "red_knot_python_semantic",
@@ -2756,7 +2772,7 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.11.5"
+version = "0.11.6"
 dependencies = [
  "anyhow",
  "argfile",
@@ -2764,7 +2780,6 @@ dependencies = [
  "bincode",
  "bitflags 2.9.0",
  "cachedir",
- "chrono",
  "clap",
  "clap_complete_command",
  "clearscreen",
@@ -2777,6 +2792,7 @@ dependencies = [
  "insta-cmd",
  "is-macro",
  "itertools 0.14.0",
+ "jiff",
  "log",
  "mimalloc",
  "notify",
@@ -2991,12 +3007,11 @@ dependencies = [
 
 [[package]]
 name = "ruff_linter"
-version = "0.11.5"
+version = "0.11.6"
 dependencies = [
  "aho-corasick",
  "anyhow",
  "bitflags 2.9.0",
- "chrono",
  "clap",
  "colored 3.0.0",
  "fern",
@@ -3007,6 +3022,7 @@ dependencies = [
  "is-macro",
  "is-wsl",
  "itertools 0.14.0",
+ "jiff",
  "libcst",
  "log",
  "memchr",
@@ -3067,7 +3083,7 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "itertools 0.14.0",
- "rand 0.9.0",
+ "rand 0.9.1",
  "ruff_diagnostics",
  "ruff_source_file",
  "ruff_text_size",
@@ -3317,7 +3333,7 @@ dependencies = [
 
 [[package]]
 name = "ruff_wasm"
-version = "0.11.5"
+version = "0.11.6"
 dependencies = [
  "console_error_panic_hook",
  "console_log",
@@ -3658,9 +3674,9 @@ dependencies = [
 
 [[package]]
 name = "shellexpand"
-version = "3.1.0"
+version = "3.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da03fa3b94cc19e3ebfc88c4229c49d8f08cdbd1228870a45f0ffdf84988e14b"
+checksum = "8b1fdf65dd6331831494dd616b30351c38e96e45921a27745cf98490458b90bb"
 dependencies = [
  "dirs",
 ]
@@ -4311,7 +4327,7 @@ checksum = "458f7a779bf54acc9f347480ac654f68407d3aab21269a6e3c9f922acd9e2da9"
 dependencies = [
  "getrandom 0.3.2",
  "js-sys",
- "rand 0.9.0",
+ "rand 0.9.1",
  "uuid-macro-internal",
  "wasm-bindgen",
 ]
@@ -4582,7 +4598,7 @@ version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf221c93e13a30d793f7645a0e7762c55d169dbb0a49671918a2319d289b10bb"
 dependencies = [
- "windows-sys 0.48.0",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]

Cargo.toml

@@ -55,7 +55,6 @@ 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 = "0.6.0" }
 clearscreen = { version = "4.0.0" }
@@ -95,6 +94,7 @@ insta-cmd = { version = "0.6.0" }
 is-macro = { version = "0.3.5" }
 is-wsl = { version = "0.4.0" }
 itertools = { version = "0.14.0" }
+jiff = { version = "0.2.0" }
 js-sys = { version = "0.3.69" }
 jod-thread = { version = "0.1.2" }
 libc = { version = "0.2.153" }

README.md

@@ -149,8 +149,8 @@ curl -LsSf https://astral.sh/ruff/install.sh | sh
 powershell -c "irm https://astral.sh/ruff/install.ps1 | iex"
 
 # For a specific version.
-curl -LsSf https://astral.sh/ruff/0.11.5/install.sh | sh
-powershell -c "irm https://astral.sh/ruff/0.11.5/install.ps1 | iex"
+curl -LsSf https://astral.sh/ruff/0.11.6/install.sh | sh
+powershell -c "irm https://astral.sh/ruff/0.11.6/install.ps1 | iex"
 ```
 
 You can also install Ruff via [Homebrew](https://formulae.brew.sh/formula/ruff), [Conda](https://anaconda.org/conda-forge/ruff),
@@ -183,7 +183,7 @@ 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: v0.11.5
+  rev: v0.11.6
   hooks:
     # Run the linter.
     - id: ruff

crates/red_knot/Cargo.toml

@@ -20,12 +20,12 @@ ruff_python_ast = { workspace = true }
 
 anyhow = { workspace = true }
 argfile = { workspace = true }
-chrono = { workspace = true }
 clap = { workspace = true, features = ["wrap_help"] }
 colored = { workspace = true }
 countme = { workspace = true, features = ["enable"] }
 crossbeam = { workspace = true }
 ctrlc = { version = "3.4.4" }
+jiff = { workspace = true }
 rayon = { workspace = true }
 salsa = { workspace = true }
 tracing = { workspace = true, features = ["release_max_level_debug"] }

crates/red_knot/docs/mypy_primer.md

@@ -31,7 +31,7 @@ mypy_primer \
 ```
 
 This will show the diagnostics diff for the `black` project between the `main` branch and your `my/feature` branch. To run the
-diff for all projects, you currently need to copy the project-selector regex from the CI pipeline in `.github/workflows/mypy_primer.yaml`.
+diff for all projects we currently enable in CI, use `--project-selector "/($(paste -s -d'|' crates/red_knot_python_semantic/resources/primer/good.txt))\$"`.
 
 You can also take a look at the [full list of ecosystem projects]. Note that some of them might still need a `knot_paths` configuration
 option to work correctly.

crates/red_knot/src/logging.rs

@@ -190,8 +190,8 @@ where
         let ansi = writer.has_ansi_escapes();
 
         if self.display_timestamp {
-            let timestamp = chrono::Local::now()
-                .format("%Y-%m-%d %H:%M:%S.%f")
+            let timestamp = jiff::Zoned::now()
+                .strftime("%Y-%m-%d %H:%M:%S.%f")
                 .to_string();
             if ansi {
                 write!(writer, "{} ", timestamp.dimmed())?;
@@ -199,7 +199,7 @@ where
                 write!(
                     writer,
                     "{} ",
-                    chrono::Local::now().format("%Y-%m-%d %H:%M:%S.%f")
+                    jiff::Zoned::now().strftime("%Y-%m-%d %H:%M:%S.%f")
                 )?;
             }
         }

crates/red_knot/tests/cli.rs

@@ -252,7 +252,7 @@ fn configuration_rule_severity() -> anyhow::Result<()> {
         r#"
             y = 4 / 0
 
-            for a in range(0, y):
+            for a in range(0, int(y)):
                 x = a
 
             print(x)  # possibly-unresolved-reference
@@ -271,7 +271,7 @@ fn configuration_rule_severity() -> anyhow::Result<()> {
     2 | y = 4 / 0
       |     ^^^^^ Cannot divide object of type `Literal[4]` by zero
     3 |
-    4 | for a in range(0, y):
+    4 | for a in range(0, int(y)):
       |
 
     warning: lint:possibly-unresolved-reference
@@ -307,7 +307,7 @@ fn configuration_rule_severity() -> anyhow::Result<()> {
     2 | y = 4 / 0
       |     ^^^^^ Cannot divide object of type `Literal[4]` by zero
     3 |
-    4 | for a in range(0, y):
+    4 | for a in range(0, int(y)):
       |
 
     Found 1 diagnostic
@@ -328,7 +328,7 @@ fn cli_rule_severity() -> anyhow::Result<()> {
 
         y = 4 / 0
 
-        for a in range(0, y):
+        for a in range(0, int(y)):
             x = a
 
         print(x)  # possibly-unresolved-reference
@@ -358,7 +358,7 @@ fn cli_rule_severity() -> anyhow::Result<()> {
     4 | y = 4 / 0
       |     ^^^^^ Cannot divide object of type `Literal[4]` by zero
     5 |
-    6 | for a in range(0, y):
+    6 | for a in range(0, int(y)):
       |
 
     warning: lint:possibly-unresolved-reference
@@ -405,7 +405,7 @@ fn cli_rule_severity() -> anyhow::Result<()> {
     4 | y = 4 / 0
       |     ^^^^^ Cannot divide object of type `Literal[4]` by zero
     5 |
-    6 | for a in range(0, y):
+    6 | for a in range(0, int(y)):
       |
 
     Found 2 diagnostics
@@ -426,7 +426,7 @@ fn cli_rule_severity_precedence() -> anyhow::Result<()> {
         r#"
         y = 4 / 0
 
-        for a in range(0, y):
+        for a in range(0, int(y)):
             x = a
 
         print(x)  # possibly-unresolved-reference
@@ -445,7 +445,7 @@ fn cli_rule_severity_precedence() -> anyhow::Result<()> {
     2 | y = 4 / 0
       |     ^^^^^ Cannot divide object of type `Literal[4]` by zero
     3 |
-    4 | for a in range(0, y):
+    4 | for a in range(0, int(y)):
       |
 
     warning: lint:possibly-unresolved-reference
@@ -482,7 +482,7 @@ fn cli_rule_severity_precedence() -> anyhow::Result<()> {
     2 | y = 4 / 0
       |     ^^^^^ Cannot divide object of type `Literal[4]` by zero
     3 |
-    4 | for a in range(0, y):
+    4 | for a in range(0, int(y)):
       |
 
     Found 1 diagnostic
@@ -814,7 +814,7 @@ fn user_configuration() -> anyhow::Result<()> {
             r#"
             y = 4 / 0
 
-            for a in range(0, y):
+            for a in range(0, int(y)):
                 x = a
 
             print(x)
@@ -841,7 +841,7 @@ fn user_configuration() -> anyhow::Result<()> {
     2 | y = 4 / 0
       |     ^^^^^ Cannot divide object of type `Literal[4]` by zero
     3 |
-    4 | for a in range(0, y):
+    4 | for a in range(0, int(y)):
       |
 
     warning: lint:possibly-unresolved-reference
@@ -883,7 +883,7 @@ fn user_configuration() -> anyhow::Result<()> {
     2 | y = 4 / 0
       |     ^^^^^ Cannot divide object of type `Literal[4]` by zero
     3 |
-    4 | for a in range(0, y):
+    4 | for a in range(0, int(y)):
       |
 
     error: lint:possibly-unresolved-reference

crates/red_knot_ide/src/db.rs

@@ -10,7 +10,7 @@ pub(crate) mod tests {
 
     use super::Db;
     use red_knot_python_semantic::lint::{LintRegistry, RuleSelection};
-    use red_knot_python_semantic::{default_lint_registry, Db as SemanticDb};
+    use red_knot_python_semantic::{default_lint_registry, Db as SemanticDb, Program};
     use ruff_db::files::{File, Files};
     use ruff_db::system::{DbWithTestSystem, System, TestSystem};
     use ruff_db::vendored::VendoredFileSystem;
@@ -83,6 +83,10 @@ pub(crate) mod tests {
         fn files(&self) -> &Files {
             &self.files
         }
+
+        fn python_version(&self) -> ruff_python_ast::PythonVersion {
+            Program::get(self).python_version(self)
+        }
     }
 
     impl Upcast<dyn SourceDb> for TestDb {

crates/red_knot_project/resources/test/corpus/cycle_narrowing_constraints.py

@@ -0,0 +1,15 @@
+# Regression test for https://github.com/astral-sh/ruff/issues/17215
+# panicked in commit 1a6a10b30
+# error message:
+# dependency graph cycle querying all_narrowing_constraints_for_expression(Id(8591))
+
+def f(a: A, b: B, c: C):
+    unknown_a: UA = make_unknown()
+    unknown_b: UB = make_unknown()
+    unknown_c: UC = make_unknown()
+    unknown_d: UD = make_unknown()
+
+    if unknown_a and unknown_b:
+        if unknown_c:
+            if unknown_d:
+                return a, b, c

crates/red_knot_project/resources/test/corpus/cycle_negative_narrowing_constraints.py

@@ -0,0 +1,22 @@
+# Regression test for https://github.com/astral-sh/ruff/issues/17215
+# panicked in commit 1a6a10b30
+# error message:
+# dependency graph cycle querying all_negative_narrowing_constraints_for_expression(Id(859f))
+
+def f(f1: bool, f2: bool, f3: bool, f4: bool):
+    o1: UnknownClass = make_o()
+    o2: UnknownClass = make_o()
+    o3: UnknownClass = make_o()
+    o4: UnknownClass = make_o()
+
+    if f1 and f2 and f3 and f4:
+        if o1 == o2:
+            return None
+        if o2 == o3:
+            return None
+        if o3 == o4:
+            return None
+        if o4 == o1:
+            return None
+
+    return o1, o2, o3, o4

crates/red_knot_project/src/db.rs

@@ -149,6 +149,10 @@ impl SourceDb for ProjectDatabase {
     fn files(&self) -> &Files {
         &self.files
     }
+
+    fn python_version(&self) -> ruff_python_ast::PythonVersion {
+        Program::get(self).python_version(self)
+    }
 }
 
 #[salsa::db]
@@ -207,7 +211,7 @@ pub(crate) mod tests {
     use salsa::Event;
 
     use red_knot_python_semantic::lint::{LintRegistry, RuleSelection};
-    use red_knot_python_semantic::Db as SemanticDb;
+    use red_knot_python_semantic::{Db as SemanticDb, Program};
     use ruff_db::files::Files;
     use ruff_db::system::{DbWithTestSystem, System, TestSystem};
     use ruff_db::vendored::VendoredFileSystem;
@@ -281,6 +285,10 @@ pub(crate) mod tests {
         fn files(&self) -> &Files {
             &self.files
         }
+
+        fn python_version(&self) -> ruff_python_ast::PythonVersion {
+            Program::get(self).python_version(self)
+        }
     }
 
     impl Upcast<dyn SemanticDb> for TestDb {

crates/red_knot_project/src/lib.rs

@@ -10,7 +10,8 @@ use red_knot_python_semantic::lint::{LintRegistry, LintRegistryBuilder, RuleSele
 use red_knot_python_semantic::register_lints;
 use red_knot_python_semantic::types::check_types;
 use ruff_db::diagnostic::{
-    create_parse_diagnostic, Annotation, Diagnostic, DiagnosticId, Severity, Span,
+    create_parse_diagnostic, create_unsupported_syntax_diagnostic, Annotation, Diagnostic,
+    DiagnosticId, Severity, Span,
 };
 use ruff_db::files::File;
 use ruff_db::parsed::parsed_module;
@@ -424,6 +425,13 @@ fn check_file_impl(db: &dyn Db, file: File) -> Vec<Diagnostic> {
             .map(|error| create_parse_diagnostic(file, error)),
     );
 
+    diagnostics.extend(
+        parsed
+            .unsupported_syntax_errors()
+            .iter()
+            .map(|error| create_unsupported_syntax_diagnostic(file, error)),
+    );
+
     diagnostics.extend(check_types(db.upcast(), file).into_iter().cloned());
 
     diagnostics.sort_unstable_by_key(|diagnostic| {
@@ -520,11 +528,13 @@ mod tests {
     use crate::db::tests::TestDb;
     use crate::{check_file_impl, ProjectMetadata};
     use red_knot_python_semantic::types::check_types;
+    use red_knot_python_semantic::{Program, ProgramSettings, PythonPlatform, SearchPathSettings};
     use ruff_db::files::system_path_to_file;
     use ruff_db::source::source_text;
     use ruff_db::system::{DbWithTestSystem, DbWithWritableSystem as _, SystemPath, SystemPathBuf};
     use ruff_db::testing::assert_function_query_was_not_run;
     use ruff_python_ast::name::Name;
+    use ruff_python_ast::PythonVersion;
 
     #[test]
     fn check_file_skips_type_checking_when_file_cant_be_read() -> ruff_db::system::Result<()> {
@@ -532,6 +542,16 @@ mod tests {
         let mut db = TestDb::new(project);
         let path = SystemPath::new("test.py");
 
+        Program::from_settings(
+            &db,
+            ProgramSettings {
+                python_version: PythonVersion::default(),
+                python_platform: PythonPlatform::default(),
+                search_paths: SearchPathSettings::new(vec![SystemPathBuf::from(".")]),
+            },
+        )
+        .expect("Failed to configure program settings");
+
         db.write_file(path, "x = 10")?;
         let file = system_path_to_file(&db, path).unwrap();
 

crates/red_knot_project/tests/check.rs

@@ -6,7 +6,9 @@ use ruff_db::parsed::parsed_module;
 use ruff_db::system::{SystemPath, SystemPathBuf, TestSystem};
 use ruff_python_ast::visitor::source_order;
 use ruff_python_ast::visitor::source_order::SourceOrderVisitor;
-use ruff_python_ast::{self as ast, Alias, Expr, Parameter, ParameterWithDefault, Stmt};
+use ruff_python_ast::{
+    self as ast, Alias, Comprehension, Expr, Parameter, ParameterWithDefault, Stmt,
+};
 
 fn setup_db(project_root: &SystemPath, system: TestSystem) -> anyhow::Result<ProjectDatabase> {
     let project = ProjectMetadata::discover(project_root, &system)?;
@@ -258,6 +260,14 @@ impl SourceOrderVisitor<'_> for PullTypesVisitor<'_> {
         source_order::walk_expr(self, expr);
     }
 
+    fn visit_comprehension(&mut self, comprehension: &Comprehension) {
+        self.visit_expr(&comprehension.iter);
+        self.visit_target(&comprehension.target);
+        for if_expr in &comprehension.ifs {
+            self.visit_expr(if_expr);
+        }
+    }
+
     fn visit_parameter(&mut self, parameter: &Parameter) {
         let _ty = parameter.inferred_type(&self.model);
 

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

@@ -237,6 +237,11 @@ def _(c: Callable[[Concatenate[int, str, ...], int], int]):
 
 ## Using `typing.ParamSpec`
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 Using a `ParamSpec` in a `Callable` annotation:
 
 ```py

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

@@ -48,6 +48,11 @@ reveal_type(get_foo())  # revealed: Foo
 
 ## Deferred self-reference annotations in a class definition
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from __future__ import annotations
 
@@ -94,6 +99,11 @@ class Foo:
 
 ## Non-deferred self-reference annotations in a class definition
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 class Foo:
     # error: [unresolved-reference]
@@ -146,3 +156,24 @@ def _():
         def f(self) -> C:
             return self
 ```
+
+## Base class references
+
+### Not deferred by __future__.annotations
+
+```py
+from __future__ import annotations
+
+class A(B):  # error: [unresolved-reference]
+    pass
+
+class B:
+    pass
+```
+
+### Deferred in stub files
+
+```pyi
+class A(B): ...
+class B: ...
+```

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

@@ -89,7 +89,7 @@ def _(
     reveal_type(k)  # revealed: Unknown
     reveal_type(p)  # revealed: Unknown
     reveal_type(q)  # revealed: int | Unknown
-    reveal_type(r)  # revealed: @Todo(generics)
+    reveal_type(r)  # revealed: @Todo(unknown type subscript)
 ```
 
 ## Invalid Collection based AST nodes

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

@@ -68,7 +68,7 @@ def x(
     a3: Literal[Literal["w"], Literal["r"], Literal[Literal["w+"]]],
     a4: Literal[True] | Literal[1, 2] | Literal["foo"],
 ):
-    reveal_type(a1)  # revealed: Literal[1, 2, 3, "foo", 5] | None
+    reveal_type(a1)  # revealed: Literal[1, 2, 3, 5, "foo"] | None
     reveal_type(a2)  # revealed: Literal["w", "r"]
     reveal_type(a3)  # revealed: Literal["w", "r", "w+"]
     reveal_type(a4)  # revealed: Literal[True, 1, 2, "foo"]
@@ -108,7 +108,7 @@ def union_example(
         None,
     ],
 ):
-    reveal_type(x)  # revealed: Unknown | Literal[-1, "A", b"A", b"\x00", b"\x07", 0, 1, "B", "foo", "bar", True] | None
+    reveal_type(x)  # revealed: Unknown | Literal[-1, 0, 1, "A", "B", "foo", "bar", b"A", b"\x00", b"\x07", True] | None
 ```
 
 ## Detecting Literal outside typing and typing_extensions
@@ -137,7 +137,7 @@ from other import Literal
 a1: Literal[26]
 
 def f():
-    reveal_type(a1)  # revealed: @Todo(generics)
+    reveal_type(a1)  # revealed: @Todo(unknown type subscript)
 ```
 
 ## Detecting typing_extensions.Literal

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

@@ -72,13 +72,11 @@ reveal_type(baz)  # revealed: Literal["bazfoo"]
 qux = (foo, bar)
 reveal_type(qux)  # revealed: tuple[Literal["foo"], Literal["bar"]]
 
-# TODO: Infer "LiteralString"
-reveal_type(foo.join(qux))  # revealed: @Todo(return type of overloaded function)
+reveal_type(foo.join(qux))  # revealed: LiteralString
 
 template: LiteralString = "{}, {}"
 reveal_type(template)  # revealed: Literal["{}, {}"]
-# TODO: Infer `LiteralString`
-reveal_type(template.format(foo, bar))  # revealed: @Todo(return type of overloaded function)
+reveal_type(template.format(foo, bar))  # revealed: LiteralString
 ```
 
 ### Assignability

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

@@ -1,5 +1,10 @@
 # Starred expression annotations
 
+```toml
+[environment]
+python-version = "3.11"
+```
+
 Type annotations for `*args` can be starred expressions themselves:
 
 ```py

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

@@ -67,21 +67,24 @@ import typing
 
 ####################
 ### Built-ins
+####################
 
 class ListSubclass(typing.List): ...
 
-# revealed: tuple[Literal[ListSubclass], Literal[list], Literal[MutableSequence], Literal[Sequence], Literal[Reversible], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(protocol), Literal[object]]
+# TODO: generic protocols
+# revealed: tuple[Literal[ListSubclass], Literal[list], Literal[MutableSequence], Literal[Sequence], Literal[Reversible], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(`Protocol[]` subscript), @Todo(`Generic[]` subscript), Literal[object]]
 reveal_type(ListSubclass.__mro__)
 
 class DictSubclass(typing.Dict): ...
 
-# TODO: should have `Generic`, should not have `Unknown`
-# revealed: tuple[Literal[DictSubclass], Literal[dict], Unknown, Literal[object]]
+# TODO: generic protocols
+# revealed: tuple[Literal[DictSubclass], Literal[dict], Literal[MutableMapping], Literal[Mapping], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(`Protocol[]` subscript), @Todo(`Generic[]` subscript), Literal[object]]
 reveal_type(DictSubclass.__mro__)
 
 class SetSubclass(typing.Set): ...
 
-# revealed: tuple[Literal[SetSubclass], Literal[set], Literal[MutableSet], Literal[AbstractSet], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(protocol), Literal[object]]
+# TODO: generic protocols
+# revealed: tuple[Literal[SetSubclass], Literal[set], Literal[MutableSet], Literal[AbstractSet], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(`Protocol[]` subscript), @Todo(`Generic[]` subscript), Literal[object]]
 reveal_type(SetSubclass.__mro__)
 
 class FrozenSetSubclass(typing.FrozenSet): ...
@@ -92,11 +95,12 @@ reveal_type(FrozenSetSubclass.__mro__)
 
 ####################
 ### `collections`
+####################
 
 class ChainMapSubclass(typing.ChainMap): ...
 
-# TODO: Should be (ChainMapSubclass, ChainMap, MutableMapping, Mapping, Collection, Sized, Iterable, Container, Generic, object)
-# revealed: tuple[Literal[ChainMapSubclass], Literal[ChainMap], Unknown, Literal[object]]
+# TODO: generic protocols
+# revealed: tuple[Literal[ChainMapSubclass], Literal[ChainMap], Literal[MutableMapping], Literal[Mapping], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(`Protocol[]` subscript), @Todo(`Generic[]` subscript), Literal[object]]
 reveal_type(ChainMapSubclass.__mro__)
 
 class CounterSubclass(typing.Counter): ...
@@ -113,7 +117,8 @@ reveal_type(DefaultDictSubclass.__mro__)
 
 class DequeSubclass(typing.Deque): ...
 
-# revealed: tuple[Literal[DequeSubclass], Literal[deque], Literal[MutableSequence], Literal[Sequence], Literal[Reversible], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(protocol), Literal[object]]
+# TODO: generic protocols
+# revealed: tuple[Literal[DequeSubclass], Literal[deque], Literal[MutableSequence], Literal[Sequence], Literal[Reversible], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(`Protocol[]` subscript), @Todo(`Generic[]` subscript), Literal[object]]
 reveal_type(DequeSubclass.__mro__)
 
 class OrderedDictSubclass(typing.OrderedDict): ...

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

@@ -105,7 +105,7 @@ def f1(
 from typing import Literal
 
 def f(v: Literal["a", r"b", b"c", "d" "e", "\N{LATIN SMALL LETTER F}", "\x67", """h"""]):
-    reveal_type(v)  # revealed: Literal["a", "b", b"c", "de", "f", "g", "h"]
+    reveal_type(v)  # revealed: Literal["a", "b", "de", "f", "g", "h", b"c"]
 ```
 
 ## Class variables

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

@@ -41,7 +41,7 @@ class Foo:
 One thing that is supported is error messages for using special forms in type expressions.
 
 ```py
-from typing_extensions import Unpack, TypeGuard, TypeIs, Concatenate, ParamSpec
+from typing_extensions import Unpack, TypeGuard, TypeIs, Concatenate, ParamSpec, Generic
 
 def _(
     a: Unpack,  # error: [invalid-type-form] "`typing.Unpack` requires exactly one argument when used in a type expression"
@@ -49,6 +49,7 @@ def _(
     c: TypeIs,  # error: [invalid-type-form] "`typing.TypeIs` requires exactly one argument when used in a type expression"
     d: Concatenate,  # error: [invalid-type-form] "`typing.Concatenate` requires at least two arguments when used in a type expression"
     e: ParamSpec,
+    f: Generic,  # error: [invalid-type-form] "`typing.Generic` is not allowed in type expressions"
 ) -> None:
     reveal_type(a)  # revealed: Unknown
     reveal_type(b)  # revealed: Unknown
@@ -65,7 +66,7 @@ You can't inherit from most of these. `typing.Callable` is an exception.
 
 ```py
 from typing import Callable
-from typing_extensions import Self, Unpack, TypeGuard, TypeIs, Concatenate
+from typing_extensions import Self, Unpack, TypeGuard, TypeIs, Concatenate, Generic
 
 class A(Self): ...  # error: [invalid-base]
 class B(Unpack): ...  # error: [invalid-base]
@@ -73,12 +74,18 @@ class C(TypeGuard): ...  # error: [invalid-base]
 class D(TypeIs): ...  # error: [invalid-base]
 class E(Concatenate): ...  # error: [invalid-base]
 class F(Callable): ...
+class G(Generic): ...  # error: [invalid-base] "Cannot inherit from plain `Generic`"
 
 reveal_type(F.__mro__)  # revealed: tuple[Literal[F], @Todo(Support for Callable as a base class), Literal[object]]
 ```
 
 ## Subscriptability
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 Some of these are not subscriptable:
 
 ```py

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

@@ -25,6 +25,11 @@ x = "foo"  # error: [invalid-assignment] "Object of type `Literal["foo"]` is not
 
 ## Tuple annotations are understood
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 `module.py`:
 
 ```py
@@ -56,7 +61,7 @@ reveal_type(d)  # revealed: tuple[tuple[str, str], tuple[int, int]]
 reveal_type(e)  # revealed: @Todo(full tuple[...] support)
 reveal_type(f)  # revealed: @Todo(full tuple[...] support)
 reveal_type(g)  # revealed: @Todo(full tuple[...] support)
-reveal_type(h)  # revealed: tuple[@Todo(generics), @Todo(generics)]
+reveal_type(h)  # revealed: tuple[@Todo(specialized non-generic class), @Todo(specialized non-generic class)]
 
 reveal_type(i)  # revealed: tuple[str | int, str | int]
 reveal_type(j)  # revealed: tuple[str | int]

crates/red_knot_python_semantic/resources/mdtest/attributes.md

@@ -302,7 +302,7 @@ class C:
 
 c_instance = C()
 reveal_type(c_instance.a)  # revealed: Unknown | Literal[1]
-reveal_type(c_instance.b)  # revealed: Unknown | @Todo(starred unpacking)
+reveal_type(c_instance.b)  # revealed: Unknown
 ```
 
 #### Attributes defined in for-loop (unpacking)
@@ -397,15 +397,27 @@ class IntIterable:
     def __iter__(self) -> IntIterator:
         return IntIterator()
 
+class TupleIterator:
+    def __next__(self) -> tuple[int, str]:
+        return (1, "a")
+
+class TupleIterable:
+    def __iter__(self) -> TupleIterator:
+        return TupleIterator()
+
 class C:
     def __init__(self) -> None:
         [... for self.a in IntIterable()]
+        [... for (self.b, self.c) in TupleIterable()]
+        [... for self.d in IntIterable() for self.e in IntIterable()]
 
 c_instance = C()
 
-# TODO: Should be `Unknown | int`
-# error: [unresolved-attribute]
-reveal_type(c_instance.a)  # revealed: Unknown
+reveal_type(c_instance.a)  # revealed: Unknown | int
+reveal_type(c_instance.b)  # revealed: Unknown | int
+reveal_type(c_instance.c)  # revealed: Unknown | str
+reveal_type(c_instance.d)  # revealed: Unknown | int
+reveal_type(c_instance.e)  # revealed: Unknown | int
 ```
 
 #### Conditionally declared / bound attributes
@@ -1665,7 +1677,7 @@ functions are instances of that class:
 def f(): ...
 
 reveal_type(f.__defaults__)  # revealed: @Todo(full tuple[...] support) | None
-reveal_type(f.__kwdefaults__)  # revealed: @Todo(generics) | None
+reveal_type(f.__kwdefaults__)  # revealed: @Todo(specialized non-generic class) | None
 ```
 
 Some attributes are special-cased, however:
@@ -1698,9 +1710,9 @@ Most attribute accesses on bool-literal types are delegated to `builtins.bool`,
 bools are instances of that class:
 
 ```py
-# revealed: bound method Literal[True].__and__(**kwargs: @Todo(todo signature **kwargs)) -> @Todo(return type of overloaded function)
+# revealed: Overload[(value: bool, /) -> bool, (value: int, /) -> int]
 reveal_type(True.__and__)
-# revealed: bound method Literal[False].__or__(**kwargs: @Todo(todo signature **kwargs)) -> @Todo(return type of overloaded function)
+# revealed: Overload[(value: bool, /) -> bool, (value: int, /) -> int]
 reveal_type(False.__or__)
 ```
 
@@ -1716,7 +1728,8 @@ reveal_type(False.real)  # revealed: Literal[0]
 All attribute access on literal `bytes` types is currently delegated to `builtins.bytes`:
 
 ```py
-reveal_type(b"foo".join)  # revealed: bound method Literal[b"foo"].join(iterable_of_bytes: @Todo(generics), /) -> bytes
+# revealed: bound method Literal[b"foo"].join(iterable_of_bytes: @Todo(specialized non-generic class), /) -> bytes
+reveal_type(b"foo".join)
 # revealed: bound method Literal[b"foo"].endswith(suffix: @Todo(Support for `typing.TypeAlias`), start: SupportsIndex | None = ellipsis, end: SupportsIndex | None = ellipsis, /) -> bool
 reveal_type(b"foo".endswith)
 ```
@@ -1819,6 +1832,89 @@ def f(never: Never):
     never.another_attribute = never
 ```
 
+### Cyclic implicit attributes
+
+Inferring types for undeclared implicit attributes can be cyclic:
+
+```py
+class C:
+    def __init__(self):
+        self.x = 1
+
+    def copy(self, other: "C"):
+        self.x = other.x
+
+reveal_type(C().x)  # revealed: Unknown | Literal[1]
+```
+
+If the only assignment to a name is cyclic, we just infer `Unknown` for that attribute:
+
+```py
+class D:
+    def copy(self, other: "D"):
+        self.x = other.x
+
+reveal_type(D().x)  # revealed: Unknown
+```
+
+If there is an annotation for a name, we don't try to infer any type from the RHS of assignments to
+that name, so these cases don't trigger any cycle:
+
+```py
+class E:
+    def __init__(self):
+        self.x: int = 1
+
+    def copy(self, other: "E"):
+        self.x = other.x
+
+reveal_type(E().x)  # revealed: int
+
+class F:
+    def __init__(self):
+        self.x = 1
+
+    def copy(self, other: "F"):
+        self.x: int = other.x
+
+reveal_type(F().x)  # revealed: int
+
+class G:
+    def copy(self, other: "G"):
+        self.x: int = other.x
+
+reveal_type(G().x)  # revealed: int
+```
+
+We can even handle cycles involving multiple classes:
+
+```py
+class A:
+    def __init__(self):
+        self.x = 1
+
+    def copy(self, other: "B"):
+        self.x = other.x
+
+class B:
+    def copy(self, other: "A"):
+        self.x = other.x
+
+reveal_type(B().x)  # revealed: Unknown | Literal[1]
+reveal_type(A().x)  # revealed: Unknown | Literal[1]
+```
+
+This case additionally tests our union/intersection simplification logic:
+
+```py
+class H:
+    def __init__(self):
+        self.x = 1
+
+    def copy(self, other: "H"):
+        self.x = other.x or self.x
+```
+
 ### Builtin types attributes
 
 This test can probably be removed eventually, but we currently include it because we do not yet
@@ -1870,20 +1966,6 @@ reveal_type(Foo.BAR.value)  # revealed: @Todo(Attribute access on enum classes)
 reveal_type(Foo.__members__)  # revealed: @Todo(Attribute access on enum classes)
 ```
 
-## `super()`
-
-`super()` is not supported yet, but we do not emit false positives on `super()` calls.
-
-```py
-class Foo:
-    def bar(self) -> int:
-        return 42
-
-class Bar(Foo):
-    def bar(self) -> int:
-        return super().bar()
-```
-
 ## References
 
 Some of the tests in the *Class and instance variables* section draw inspiration from

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

@@ -310,9 +310,7 @@ reveal_type(A() + 1)  # revealed: A
 reveal_type(1 + A())  # revealed: A
 
 reveal_type(A() + "foo")  # revealed: A
-# TODO should be `A` since `str.__add__` doesn't support `A` instances
-# TODO overloads
-reveal_type("foo" + A())  # revealed: @Todo(return type of overloaded function)
+reveal_type("foo" + A())  # revealed: A
 
 reveal_type(A() + b"foo")  # revealed: A
 # TODO should be `A` since `bytes.__add__` doesn't support `A` instances
@@ -320,16 +318,14 @@ reveal_type(b"foo" + A())  # revealed: bytes
 
 reveal_type(A() + ())  # revealed: A
 # TODO this should be `A`, since `tuple.__add__` doesn't support `A` instances
-reveal_type(() + A())  # revealed: @Todo(return type of overloaded function)
+reveal_type(() + A())  # revealed: @Todo(full tuple[...] support)
 
 literal_string_instance = "foo" * 1_000_000_000
 # the test is not testing what it's meant to be testing if this isn't a `LiteralString`:
 reveal_type(literal_string_instance)  # revealed: LiteralString
 
 reveal_type(A() + literal_string_instance)  # revealed: A
-# TODO should be `A` since `str.__add__` doesn't support `A` instances
-# TODO overloads
-reveal_type(literal_string_instance + A())  # revealed: @Todo(return type of overloaded function)
+reveal_type(literal_string_instance + A())  # revealed: A
 ```
 
 ## Operations involving instances of classes inheriting from `Any`

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

@@ -50,9 +50,11 @@ reveal_type(1 ** (largest_u32 + 1))  # revealed: int
 reveal_type(2**largest_u32)  # revealed: int
 
 def variable(x: int):
-    reveal_type(x**2)  # revealed: @Todo(return type of overloaded function)
-    reveal_type(2**x)  # revealed: @Todo(return type of overloaded function)
-    reveal_type(x**x)  # revealed: @Todo(return type of overloaded function)
+    reveal_type(x**2)  # revealed: int
+    # TODO: should be `Any` (overload 5 on `__pow__`), requires correct overload matching
+    reveal_type(2**x)  # revealed: int
+    # TODO: should be `Any` (overload 5 on `__pow__`), requires correct overload matching
+    reveal_type(x**x)  # revealed: int
 ```
 
 If the second argument is \<0, a `float` is returned at runtime. If the first argument is \<0 but

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

@@ -43,7 +43,7 @@ if True and (x := 1):
 
 ```py
 def _(flag: bool):
-    flag or (x := 1) or reveal_type(x)  # revealed: Literal[1]
+    flag or (x := 1) or reveal_type(x)  # revealed: Never
 
     # error: [unresolved-reference]
     flag or reveal_type(y) or (y := 1)  # revealed: Unknown

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

@@ -21,6 +21,11 @@ reveal_type(get_int_async())  # revealed: @Todo(generic types.CoroutineType)
 
 ## Generic
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 def get_int[T]() -> int:
     return 42

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

@@ -94,7 +94,7 @@ function object. We model this explicitly, which means that we can access `__kwd
 methods, even though it is not available on `types.MethodType`:
 
 ```py
-reveal_type(bound_method.__kwdefaults__)  # revealed: @Todo(generics) | None
+reveal_type(bound_method.__kwdefaults__)  # revealed: @Todo(specialized non-generic class) | None
 ```
 
 ## Basic method calls on class objects and instances
@@ -399,6 +399,11 @@ reveal_type(getattr_static(C, "f").__get__("dummy", C))  # revealed: bound metho
 
 ### Classmethods mixed with other decorators
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 When a `@classmethod` is additionally decorated with another decorator, it is still treated as a
 class method:
 
@@ -410,29 +415,19 @@ def does_nothing[T](f: T) -> T:
 
 class C:
     @classmethod
-    # TODO: no error should be emitted here (needs support for generics)
-    # error: [invalid-argument-type]
     @does_nothing
     def f1(cls: type[C], x: int) -> str:
         return "a"
-    # TODO: no error should be emitted here (needs support for generics)
-    # error: [invalid-argument-type]
+
     @does_nothing
     @classmethod
     def f2(cls: type[C], x: int) -> str:
         return "a"
 
-# TODO: All of these should be `str` (and not emit an error), once we support generics
-
-# error: [call-non-callable]
-reveal_type(C.f1(1))  # revealed: Unknown
-# error: [call-non-callable]
-reveal_type(C().f1(1))  # revealed: Unknown
-
-# error: [call-non-callable]
-reveal_type(C.f2(1))  # revealed: Unknown
-# error: [call-non-callable]
-reveal_type(C().f2(1))  # revealed: Unknown
+reveal_type(C.f1(1))  # revealed: str
+reveal_type(C().f1(1))  # revealed: str
+reveal_type(C.f2(1))  # revealed: str
+reveal_type(C().f2(1))  # revealed: str
 ```
 
 [functions and methods]: https://docs.python.org/3/howto/descriptor.html#functions-and-methods

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

@@ -175,3 +175,41 @@ def _(flag: bool):
     # error: [conflicting-argument-forms] "Argument is used as both a value and a type form in call"
     reveal_type(f(int))  # revealed: str | Literal[True]
 ```
+
+## Size limit on unions of literals
+
+Beyond a certain size, large unions of literal types collapse to their nearest super-type (`int`,
+`bytes`, `str`).
+
+```py
+from typing import Literal
+
+def _(literals_2: Literal[0, 1], b: bool, flag: bool):
+    literals_4 = 2 * literals_2 + literals_2  # Literal[0, 1, 2, 3]
+    literals_16 = 4 * literals_4 + literals_4  # Literal[0, 1, .., 15]
+    literals_64 = 4 * literals_16 + literals_4  # Literal[0, 1, .., 63]
+    literals_128 = 2 * literals_64 + literals_2  # Literal[0, 1, .., 127]
+
+    # Going beyond the MAX_UNION_LITERALS limit (currently 200):
+    literals_256 = 16 * literals_16 + literals_16
+    reveal_type(literals_256)  # revealed: int
+
+    # Going beyond the limit when another type is already part of the union
+    bool_and_literals_128 = b if flag else literals_128  # bool | Literal[0, 1, ..., 127]
+    literals_128_shifted = literals_128 + 128  # Literal[128, 129, ..., 255]
+
+    # Now union the two:
+    reveal_type(bool_and_literals_128 if flag else literals_128_shifted)  # revealed: int
+```
+
+## Simplifying gradually-equivalent types
+
+If two types are gradually equivalent, we can keep just one of them in a union:
+
+```py
+from typing import Any, Union
+from knot_extensions import Intersection, Not
+
+def _(x: Union[Intersection[Any, Not[int]], Intersection[Any, Not[int]]]):
+    reveal_type(x)  # revealed: Any & ~int
+```

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

@@ -0,0 +1,410 @@
+# Super
+
+Python defines the terms *bound super object* and *unbound super object*.
+
+An **unbound super object** is created when `super` is called with only one argument. (e.g.
+`super(A)`). This object may later be bound using the `super.__get__` method. However, this form is
+rarely used in practice.
+
+A **bound super object** is created either by calling `super(pivot_class, owner)` or by using the
+implicit form `super()`, where both the pivot class and the owner are inferred. This is the most
+common usage.
+
+## Basic Usage
+
+### Explicit Super Object
+
+`super(pivot_class, owner)` performs attribute lookup along the MRO, starting immediately after the
+specified pivot class.
+
+```py
+class A:
+    def a(self): ...
+    aa: int = 1
+
+class B(A):
+    def b(self): ...
+    bb: int = 2
+
+class C(B):
+    def c(self): ...
+    cc: int = 3
+
+reveal_type(C.__mro__)  # revealed: tuple[Literal[C], Literal[B], Literal[A], Literal[object]]
+
+super(C, C()).a
+super(C, C()).b
+# error: [unresolved-attribute] "Type `<super: Literal[C], C>` has no attribute `c`"
+super(C, C()).c
+
+super(B, C()).a
+# error: [unresolved-attribute] "Type `<super: Literal[B], C>` has no attribute `b`"
+super(B, C()).b
+# error: [unresolved-attribute] "Type `<super: Literal[B], C>` has no attribute `c`"
+super(B, C()).c
+
+# error: [unresolved-attribute] "Type `<super: Literal[A], C>` has no attribute `a`"
+super(A, C()).a
+# error: [unresolved-attribute] "Type `<super: Literal[A], C>` has no attribute `b`"
+super(A, C()).b
+# error: [unresolved-attribute] "Type `<super: Literal[A], C>` has no attribute `c`"
+super(A, C()).c
+
+reveal_type(super(C, C()).a)  # revealed: bound method C.a() -> Unknown
+reveal_type(super(C, C()).b)  # revealed: bound method C.b() -> Unknown
+reveal_type(super(C, C()).aa)  # revealed: int
+reveal_type(super(C, C()).bb)  # revealed: int
+```
+
+### Implicit Super Object
+
+The implicit form `super()` is same as `super(__class__, <first argument>)`. The `__class__` refers
+to the class that contains the function where `super()` is used. The first argument refers to the
+current method’s first parameter (typically `self` or `cls`).
+
+```py
+from __future__ import annotations
+
+class A:
+    def __init__(self, a: int): ...
+    @classmethod
+    def f(cls): ...
+
+class B(A):
+    def __init__(self, a: int):
+        # TODO: Once `Self` is supported, this should be `<super: Literal[B], B>`
+        reveal_type(super())  # revealed: <super: Literal[B], Unknown>
+        super().__init__(a)
+
+    @classmethod
+    def f(cls):
+        # TODO: Once `Self` is supported, this should be `<super: Literal[B], Literal[B]>`
+        reveal_type(super())  # revealed: <super: Literal[B], Unknown>
+        super().f()
+
+super(B, B(42)).__init__(42)
+super(B, B).f()
+```
+
+### Unbound Super Object
+
+Calling `super(cls)` without a second argument returns an *unbound super object*. This is treated as
+a plain `super` instance and does not support name lookup via the MRO.
+
+```py
+class A:
+    a: int = 42
+
+class B(A): ...
+
+reveal_type(super(B))  # revealed: super
+
+# error: [unresolved-attribute] "Type `super` has no attribute `a`"
+super(B).a
+```
+
+## Attribute Assignment
+
+`super()` objects do not allow attribute assignment — even if the attribute is resolved
+successfully.
+
+```py
+class A:
+    a: int = 3
+
+class B(A): ...
+
+reveal_type(super(B, B()).a)  # revealed: int
+# error: [invalid-assignment] "Cannot assign to attribute `a` on type `<super: Literal[B], B>`"
+super(B, B()).a = 3
+# error: [invalid-assignment] "Cannot assign to attribute `a` on type `super`"
+super(B).a = 5
+```
+
+## Dynamic Types
+
+If any of the arguments is dynamic, we cannot determine the MRO to traverse. When accessing a
+member, it should effectively behave like a dynamic type.
+
+```py
+class A:
+    a: int = 1
+
+def f(x):
+    reveal_type(x)  # revealed: Unknown
+
+    reveal_type(super(x, x))  # revealed: <super: Unknown, Unknown>
+    reveal_type(super(A, x))  # revealed: <super: Literal[A], Unknown>
+    reveal_type(super(x, A()))  # revealed: <super: Unknown, A>
+
+    reveal_type(super(x, x).a)  # revealed: Unknown
+    reveal_type(super(A, x).a)  # revealed: Unknown
+    reveal_type(super(x, A()).a)  # revealed: Unknown
+```
+
+## Implicit `super()` in Complex Structure
+
+```py
+from __future__ import annotations
+
+class A:
+    def test(self):
+        reveal_type(super())  # revealed: <super: Literal[A], Unknown>
+
+    class B:
+        def test(self):
+            reveal_type(super())  # revealed: <super: Literal[B], Unknown>
+
+            class C(A.B):
+                def test(self):
+                    reveal_type(super())  # revealed: <super: Literal[C], Unknown>
+
+            def inner(t: C):
+                reveal_type(super())  # revealed: <super: Literal[B], C>
+            lambda x: reveal_type(super())  # revealed: <super: Literal[B], Unknown>
+```
+
+## Built-ins and Literals
+
+```py
+reveal_type(super(bool, True))  # revealed: <super: Literal[bool], bool>
+reveal_type(super(bool, bool()))  # revealed: <super: Literal[bool], bool>
+reveal_type(super(int, bool()))  # revealed: <super: Literal[int], bool>
+reveal_type(super(int, 3))  # revealed: <super: Literal[int], int>
+reveal_type(super(str, ""))  # revealed: <super: Literal[str], str>
+```
+
+## Descriptor Behavior with Super
+
+Accessing attributes through `super` still invokes descriptor protocol. However, the behavior can
+differ depending on whether the second argument to `super` is a class or an instance.
+
+```py
+class A:
+    def a1(self): ...
+    @classmethod
+    def a2(cls): ...
+
+class B(A): ...
+
+# A.__dict__["a1"].__get__(B(), B)
+reveal_type(super(B, B()).a1)  # revealed: bound method B.a1() -> Unknown
+# A.__dict__["a2"].__get__(B(), B)
+reveal_type(super(B, B()).a2)  # revealed: bound method type[B].a2() -> Unknown
+
+# A.__dict__["a1"].__get__(None, B)
+reveal_type(super(B, B).a1)  # revealed: def a1(self) -> Unknown
+# A.__dict__["a2"].__get__(None, B)
+reveal_type(super(B, B).a2)  # revealed: bound method Literal[B].a2() -> Unknown
+```
+
+## Union of Supers
+
+When the owner is a union type, `super()` is built separately for each branch, and the resulting
+super objects are combined into a union.
+
+```py
+class A: ...
+
+class B:
+    b: int = 42
+
+class C(A, B): ...
+class D(B, A): ...
+
+def f(x: C | D):
+    reveal_type(C.__mro__)  # revealed: tuple[Literal[C], Literal[A], Literal[B], Literal[object]]
+    reveal_type(D.__mro__)  # revealed: tuple[Literal[D], Literal[B], Literal[A], Literal[object]]
+
+    s = super(A, x)
+    reveal_type(s)  # revealed: <super: Literal[A], C> | <super: Literal[A], D>
+
+    # error: [possibly-unbound-attribute] "Attribute `b` on type `<super: Literal[A], C> | <super: Literal[A], D>` is possibly unbound"
+    s.b
+
+def f(flag: bool):
+    x = str() if flag else str("hello")
+    reveal_type(x)  # revealed: Literal["", "hello"]
+    reveal_type(super(str, x))  # revealed: <super: Literal[str], str>
+
+def f(x: int | str):
+    # error: [invalid-super-argument] "`str` is not an instance or subclass of `Literal[int]` in `super(Literal[int], str)` call"
+    super(int, x)
+```
+
+Even when `super()` is constructed separately for each branch of a union, it should behave correctly
+in all cases.
+
+```py
+def f(flag: bool):
+    if flag:
+        class A:
+            x = 1
+            y: int = 1
+
+            a: str = "hello"
+
+        class B(A): ...
+        s = super(B, B())
+    else:
+        class C:
+            x = 2
+            y: int | str = "test"
+
+        class D(C): ...
+        s = super(D, D())
+
+    reveal_type(s)  # revealed: <super: Literal[B], B> | <super: Literal[D], D>
+
+    reveal_type(s.x)  # revealed: Unknown | Literal[1, 2]
+    reveal_type(s.y)  # revealed: int | str
+
+    # error: [possibly-unbound-attribute] "Attribute `a` on type `<super: Literal[B], B> | <super: Literal[D], D>` is possibly unbound"
+    reveal_type(s.a)  # revealed: str
+```
+
+## Supers with Generic Classes
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+```py
+from knot_extensions import TypeOf, static_assert, is_subtype_of
+
+class A[T]:
+    def f(self, a: T) -> T:
+        return a
+
+class B[T](A[T]):
+    def f(self, b: T) -> T:
+        return super().f(b)
+```
+
+## Invalid Usages
+
+### Unresolvable `super()` Calls
+
+If an appropriate class and argument cannot be found, a runtime error will occur.
+
+```py
+from __future__ import annotations
+
+# error: [unavailable-implicit-super-arguments] "Cannot determine implicit arguments for 'super()' in this context"
+reveal_type(super())  # revealed: Unknown
+
+def f():
+    # error: [unavailable-implicit-super-arguments] "Cannot determine implicit arguments for 'super()' in this context"
+    super()
+
+# No first argument in its scope
+class A:
+    # error: [unavailable-implicit-super-arguments] "Cannot determine implicit arguments for 'super()' in this context"
+    s = super()
+
+    def f(self):
+        def g():
+            # error: [unavailable-implicit-super-arguments] "Cannot determine implicit arguments for 'super()' in this context"
+            super()
+        # error: [unavailable-implicit-super-arguments] "Cannot determine implicit arguments for 'super()' in this context"
+        lambda: super()
+
+        # error: [unavailable-implicit-super-arguments] "Cannot determine implicit arguments for 'super()' in this context"
+        (super() for _ in range(10))
+
+    @staticmethod
+    def h():
+        # error: [unavailable-implicit-super-arguments] "Cannot determine implicit arguments for 'super()' in this context"
+        super()
+```
+
+### Failing Condition Checks
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+`super()` requires its first argument to be a valid class, and its second argument to be either an
+instance or a subclass of the first. If either condition is violated, a `TypeError` is raised at
+runtime.
+
+```py
+def f(x: int):
+    # error: [invalid-super-argument] "`int` is not a valid class"
+    super(x, x)
+
+    type IntAlias = int
+    # error: [invalid-super-argument] "`typing.TypeAliasType` is not a valid class"
+    super(IntAlias, 0)
+
+# error: [invalid-super-argument] "`Literal[""]` is not an instance or subclass of `Literal[int]` in `super(Literal[int], Literal[""])` call"
+# revealed: Unknown
+reveal_type(super(int, str()))
+
+# error: [invalid-super-argument] "`Literal[str]` is not an instance or subclass of `Literal[int]` in `super(Literal[int], Literal[str])` call"
+# revealed: Unknown
+reveal_type(super(int, str))
+
+class A: ...
+class B(A): ...
+
+# error: [invalid-super-argument] "`A` is not an instance or subclass of `Literal[B]` in `super(Literal[B], A)` call"
+# revealed: Unknown
+reveal_type(super(B, A()))
+
+# error: [invalid-super-argument] "`object` is not an instance or subclass of `Literal[B]` in `super(Literal[B], object)` call"
+# revealed: Unknown
+reveal_type(super(B, object()))
+
+# error: [invalid-super-argument] "`Literal[A]` is not an instance or subclass of `Literal[B]` in `super(Literal[B], Literal[A])` call"
+# revealed: Unknown
+reveal_type(super(B, A))
+
+# error: [invalid-super-argument] "`Literal[object]` is not an instance or subclass of `Literal[B]` in `super(Literal[B], Literal[object])` call"
+# revealed: Unknown
+reveal_type(super(B, object))
+
+super(object, object()).__class__
+```
+
+### Instance Member Access via `super`
+
+Accessing instance members through `super()` is not allowed.
+
+```py
+from __future__ import annotations
+
+class A:
+    def __init__(self, a: int):
+        self.a = a
+
+class B(A):
+    def __init__(self, a: int):
+        super().__init__(a)
+        # TODO: Once `Self` is supported, this should raise `unresolved-attribute` error
+        super().a
+
+# error: [unresolved-attribute] "Type `<super: Literal[B], B>` has no attribute `a`"
+super(B, B(42)).a
+```
+
+### Dunder Method Resolution
+
+Dunder methods defined in the `owner` (from `super(pivot_class, owner)`) should not affect the super
+object itself. In other words, `super` should not be treated as if it inherits attributes of the
+`owner`.
+
+```py
+class A:
+    def __getitem__(self, key: int) -> int:
+        return 42
+
+class B(A): ...
+
+reveal_type(A()[0])  # revealed: int
+reveal_type(super(B, B()).__getitem__)  # revealed: bound method B.__getitem__(key: int) -> int
+# error: [non-subscriptable] "Cannot subscript object of type `<super: Literal[B], B>` with no `__getitem__` method"
+super(B, B())[0]
+```

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

@@ -50,13 +50,17 @@ reveal_type(x)  # revealed: LiteralString
 if x != "abc":
     reveal_type(x)  # revealed: LiteralString & ~Literal["abc"]
 
-    reveal_type(x == "abc")  # revealed: Literal[False]
-    reveal_type("abc" == x)  # revealed: Literal[False]
+    # TODO: This should be `Literal[False]`
+    reveal_type(x == "abc")  # revealed: bool
+    # TODO: This should be `Literal[False]`
+    reveal_type("abc" == x)  # revealed: bool
     reveal_type(x == "something else")  # revealed: bool
     reveal_type("something else" == x)  # revealed: bool
 
-    reveal_type(x != "abc")  # revealed: Literal[True]
-    reveal_type("abc" != x)  # revealed: Literal[True]
+    # TODO: This should be `Literal[True]`
+    reveal_type(x != "abc")  # revealed: bool
+    # TODO: This should be `Literal[True]`
+    reveal_type("abc" != x)  # revealed: bool
     reveal_type(x != "something else")  # revealed: bool
     reveal_type("something else" != x)  # revealed: bool
 
@@ -79,10 +83,10 @@ def _(x: int):
     if x != 1:
         reveal_type(x)  # revealed: int & ~Literal[1]
 
-        reveal_type(x != 1)  # revealed: Literal[True]
+        reveal_type(x != 1)  # revealed: bool
         reveal_type(x != 2)  # revealed: bool
 
-        reveal_type(x == 1)  # revealed: Literal[False]
+        reveal_type(x == 1)  # revealed: bool
         reveal_type(x == 2)  # revealed: bool
 ```
 

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

@@ -1,5 +1,10 @@
 # Pattern matching
 
+```toml
+[environment]
+python-version = "3.10"
+```
+
 ## With wildcard
 
 ```py

crates/red_knot_python_semantic/resources/mdtest/dataclasses.md

@@ -0,0 +1,731 @@
+# Dataclasses
+
+## Basic
+
+Decorating a class with `@dataclass` is a convenient way to add special methods such as `__init__`,
+`__repr__`, and `__eq__` to a class. The following example shows the basic usage of the `@dataclass`
+decorator. By default, only the three mentioned methods are generated.
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class Person:
+    name: str
+    age: int | None = None
+
+alice1 = Person("Alice", 30)
+alice2 = Person(name="Alice", age=30)
+alice3 = Person(age=30, name="Alice")
+alice4 = Person("Alice", age=30)
+
+reveal_type(alice1)  # revealed: Person
+reveal_type(type(alice1))  # revealed: type[Person]
+
+reveal_type(alice1.name)  # revealed: str
+reveal_type(alice1.age)  # revealed: int | None
+
+reveal_type(repr(alice1))  # revealed: str
+
+reveal_type(alice1 == alice2)  # revealed: bool
+reveal_type(alice1 == "Alice")  # revealed: bool
+
+bob = Person("Bob")
+bob2 = Person("Bob", None)
+bob3 = Person(name="Bob")
+bob4 = Person(name="Bob", age=None)
+```
+
+The signature of the `__init__` method is generated based on the classes attributes. The following
+calls are not valid:
+
+```py
+# error: [missing-argument]
+Person()
+
+# error: [too-many-positional-arguments]
+Person("Eve", 20, "too many arguments")
+
+# error: [invalid-argument-type]
+Person("Eve", "string instead of int")
+
+# error: [invalid-argument-type]
+# error: [invalid-argument-type]
+Person(20, "Eve")
+```
+
+## Signature of `__init__`
+
+TODO: All of the following tests are missing the `self` argument in the `__init__` signature.
+
+Declarations in the class body are used to generate the signature of the `__init__` method. If the
+attributes are not just declarations, but also bindings, the type inferred from bindings is used as
+the default value.
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class D:
+    x: int
+    y: str = "default"
+    z: int | None = 1 + 2
+
+reveal_type(D.__init__)  # revealed: (x: int, y: str = Literal["default"], z: int | None = Literal[3]) -> None
+```
+
+This also works if the declaration and binding are split:
+
+```py
+@dataclass
+class D:
+    x: int | None
+    x = None
+
+reveal_type(D.__init__)  # revealed: (x: int | None = None) -> None
+```
+
+Non-fully static types are handled correctly:
+
+```py
+from typing import Any
+
+@dataclass
+class C:
+    x: Any
+    y: int | Any
+    z: tuple[int, Any]
+
+reveal_type(C.__init__)  # revealed: (x: Any, y: int | Any, z: tuple[int, Any]) -> None
+```
+
+Variables without annotations are ignored:
+
+```py
+@dataclass
+class D:
+    x: int
+    y = 1
+
+reveal_type(D.__init__)  # revealed: (x: int) -> None
+```
+
+If attributes without default values are declared after attributes with default values, a
+`TypeError` will be raised at runtime. Ideally, we would emit a diagnostic in that case:
+
+```py
+@dataclass
+class D:
+    x: int = 1
+    # TODO: this should be an error: field without default defined after field with default
+    y: str
+```
+
+Pure class attributes (`ClassVar`) are not included in the signature of `__init__`:
+
+```py
+from typing import ClassVar
+
+@dataclass
+class D:
+    x: int
+    y: ClassVar[str] = "default"
+    z: bool
+
+reveal_type(D.__init__)  # revealed: (x: int, z: bool) -> None
+
+d = D(1, True)
+reveal_type(d.x)  # revealed: int
+reveal_type(d.y)  # revealed: str
+reveal_type(d.z)  # revealed: bool
+```
+
+Function declarations do not affect the signature of `__init__`:
+
+```py
+@dataclass
+class D:
+    x: int
+
+    def y(self) -> str:
+        return ""
+
+reveal_type(D.__init__)  # revealed: (x: int) -> None
+```
+
+And neither do nested class declarations:
+
+```py
+@dataclass
+class D:
+    x: int
+
+    class Nested:
+        y: str
+
+reveal_type(D.__init__)  # revealed: (x: int) -> None
+```
+
+But if there is a variable annotation with a function or class literal type, the signature of
+`__init__` will include this field:
+
+```py
+from knot_extensions import TypeOf
+
+class SomeClass: ...
+
+def some_function() -> None: ...
+@dataclass
+class D:
+    function_literal: TypeOf[some_function]
+    class_literal: TypeOf[SomeClass]
+    class_subtype_of: type[SomeClass]
+
+# revealed: (function_literal: def some_function() -> None, class_literal: Literal[SomeClass], class_subtype_of: type[SomeClass]) -> None
+reveal_type(D.__init__)
+```
+
+More realistically, dataclasses can have `Callable` attributes:
+
+```py
+from typing import Callable
+
+@dataclass
+class D:
+    c: Callable[[int], str]
+
+reveal_type(D.__init__)  # revealed: (c: (int, /) -> str) -> None
+```
+
+Implicit instance attributes do not affect the signature of `__init__`:
+
+```py
+@dataclass
+class D:
+    x: int
+
+    def f(self, y: str) -> None:
+        self.y: str = y
+
+reveal_type(D(1).y)  # revealed: str
+
+reveal_type(D.__init__)  # revealed: (x: int) -> None
+```
+
+Annotating expressions does not lead to an entry in `__annotations__` at runtime, and so it wouldn't
+be included in the signature of `__init__`. This is a case that we currently don't detect:
+
+```py
+@dataclass
+class D:
+    # (x) is an expression, not a "simple name"
+    (x): int = 1
+
+# TODO: should ideally not include a `x` parameter
+reveal_type(D.__init__)  # revealed: (x: int = Literal[1]) -> None
+```
+
+## `@dataclass` calls with arguments
+
+The `@dataclass` decorator can take several arguments to customize the existence of the generated
+methods. The following test makes sure that we still treat the class as a dataclass if (the default)
+arguments are passed in:
+
+```py
+from dataclasses import dataclass
+
+@dataclass(init=True, repr=True, eq=True)
+class Person:
+    name: str
+    age: int | None = None
+
+alice = Person("Alice", 30)
+reveal_type(repr(alice))  # revealed: str
+reveal_type(alice == alice)  # revealed: bool
+```
+
+If `init` is set to `False`, no `__init__` method is generated:
+
+```py
+from dataclasses import dataclass
+
+@dataclass(init=False)
+class C:
+    x: int
+
+C()  # Okay
+
+# error: [too-many-positional-arguments]
+C(1)
+
+repr(C())
+
+C() == C()
+```
+
+## Other dataclass parameters
+
+### `repr`
+
+A custom `__repr__` method is generated by default. It can be disabled by passing `repr=False`, but
+in that case `__repr__` is still available via `object.__repr__`:
+
+```py
+from dataclasses import dataclass
+
+@dataclass(repr=False)
+class WithoutRepr:
+    x: int
+
+reveal_type(WithoutRepr(1).__repr__)  # revealed: bound method WithoutRepr.__repr__() -> str
+```
+
+### `eq`
+
+The same is true for `__eq__`. Setting `eq=False` disables the generated `__eq__` method, but
+`__eq__` is still available via `object.__eq__`:
+
+```py
+from dataclasses import dataclass
+
+@dataclass(eq=False)
+class WithoutEq:
+    x: int
+
+reveal_type(WithoutEq(1) == WithoutEq(2))  # revealed: bool
+```
+
+### `order`
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+`order` is set to `False` by default. If `order=True`, `__lt__`, `__le__`, `__gt__`, and `__ge__`
+methods will be generated:
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class WithoutOrder:
+    x: int
+
+WithoutOrder(1) < WithoutOrder(2)  # error: [unsupported-operator]
+WithoutOrder(1) <= WithoutOrder(2)  # error: [unsupported-operator]
+WithoutOrder(1) > WithoutOrder(2)  # error: [unsupported-operator]
+WithoutOrder(1) >= WithoutOrder(2)  # error: [unsupported-operator]
+
+@dataclass(order=True)
+class WithOrder:
+    x: int
+
+WithOrder(1) < WithOrder(2)
+WithOrder(1) <= WithOrder(2)
+WithOrder(1) > WithOrder(2)
+WithOrder(1) >= WithOrder(2)
+```
+
+Comparisons are only allowed for `WithOrder` instances:
+
+```py
+WithOrder(1) < 2  # error: [unsupported-operator]
+WithOrder(1) <= 2  # error: [unsupported-operator]
+WithOrder(1) > 2  # error: [unsupported-operator]
+WithOrder(1) >= 2  # error: [unsupported-operator]
+```
+
+This also works for generic dataclasses:
+
+```py
+from dataclasses import dataclass
+
+@dataclass(order=True)
+class GenericWithOrder[T]:
+    x: T
+
+GenericWithOrder[int](1) < GenericWithOrder[int](1)
+
+GenericWithOrder[int](1) < GenericWithOrder[str]("a")  # error: [unsupported-operator]
+```
+
+If a class already defines one of the comparison methods, a `TypeError` is raised at runtime.
+Ideally, we would emit a diagnostic in that case:
+
+```py
+@dataclass(order=True)
+class AlreadyHasCustomDunderLt:
+    x: int
+
+    # TODO: Ideally, we would emit a diagnostic here
+    def __lt__(self, other: object) -> bool:
+        return False
+```
+
+### `unsafe_hash`
+
+To do
+
+### `frozen`
+
+To do
+
+### `match_args`
+
+To do
+
+### `kw_only`
+
+To do
+
+### `slots`
+
+To do
+
+### `weakref_slot`
+
+To do
+
+## Inheritance
+
+### Normal class inheriting from a dataclass
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class Base:
+    x: int
+
+class Derived(Base): ...
+
+d = Derived(1)  # OK
+reveal_type(d.x)  # revealed: int
+```
+
+### Dataclass inheriting from normal class
+
+```py
+from dataclasses import dataclass
+
+class Base:
+    x: int = 1
+
+@dataclass
+class Derived(Base):
+    y: str
+
+d = Derived("a")
+
+# error: [too-many-positional-arguments]
+# error: [invalid-argument-type]
+Derived(1, "a")
+```
+
+### Dataclass inheriting from another dataclass
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class Base:
+    x: int
+    y: str
+
+@dataclass
+class Derived(Base):
+    z: bool
+
+d = Derived(1, "a", True)  # OK
+
+reveal_type(d.x)  # revealed: int
+reveal_type(d.y)  # revealed: str
+reveal_type(d.z)  # revealed: bool
+
+# error: [missing-argument]
+Derived(1, "a")
+
+# error: [missing-argument]
+Derived(True)
+```
+
+### Overwriting attributes from base class
+
+The following example comes from the
+[Python documentation](https://docs.python.org/3/library/dataclasses.html#inheritance). The `x`
+attribute appears just once in the `__init__` signature, and the default value is taken from the
+derived class
+
+```py
+from dataclasses import dataclass
+from typing import Any
+
+@dataclass
+class Base:
+    x: Any = 15.0
+    y: int = 0
+
+@dataclass
+class C(Base):
+    z: int = 10
+    x: int = 15
+
+reveal_type(C.__init__)  # revealed: (x: int = Literal[15], y: int = Literal[0], z: int = Literal[10]) -> None
+```
+
+## Generic dataclasses
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class DataWithDescription[T]:
+    data: T
+    description: str
+
+reveal_type(DataWithDescription[int])  # revealed: Literal[DataWithDescription[int]]
+
+d_int = DataWithDescription[int](1, "description")  # OK
+reveal_type(d_int.data)  # revealed: int
+reveal_type(d_int.description)  # revealed: str
+
+# error: [invalid-argument-type]
+DataWithDescription[int](None, "description")
+```
+
+## Descriptor-typed fields
+
+### Same type in `__get__` and `__set__`
+
+For the following descriptor, the return type of `__get__` and the type of the `value` parameter in
+`__set__` are the same. The generated `__init__` method takes an argument of this type (instead of
+the type of the descriptor), and the default value is also of this type:
+
+```py
+from typing import overload
+from dataclasses import dataclass
+
+class UppercaseString:
+    _value: str = ""
+
+    def __get__(self, instance: object, owner: None | type) -> str:
+        return self._value
+
+    def __set__(self, instance: object, value: str) -> None:
+        self._value = value.upper()
+
+@dataclass
+class C:
+    upper: UppercaseString = UppercaseString()
+
+reveal_type(C.__init__)  # revealed: (upper: str = str) -> None
+
+c = C("abc")
+reveal_type(c.upper)  # revealed: str
+
+# This is also okay:
+C()
+
+# error: [invalid-argument-type]
+C(1)
+
+# error: [too-many-positional-arguments]
+C("a", "b")
+```
+
+### Different types in `__get__` and `__set__`
+
+In general, the type of the `__init__` parameter is determined by the `value` parameter type of the
+`__set__` method (`str` in the example below). However, the default value is generated by calling
+the descriptor's `__get__` method as if it had been called on the class itself, i.e. passing `None`
+for the `instance` argument.
+
+```py
+from typing import Literal, overload
+from dataclasses import dataclass
+
+class ConvertToLength:
+    _len: int = 0
+
+    @overload
+    def __get__(self, instance: None, owner: type) -> Literal[""]: ...
+    @overload
+    def __get__(self, instance: object, owner: type | None) -> int: ...
+    def __get__(self, instance: object | None, owner: type | None) -> str | int:
+        if instance is None:
+            return ""
+
+        return self._len
+
+    def __set__(self, instance, value: str) -> None:
+        self._len = len(value)
+
+@dataclass
+class C:
+    converter: ConvertToLength = ConvertToLength()
+
+reveal_type(C.__init__)  # revealed: (converter: str = Literal[""]) -> None
+
+c = C("abc")
+reveal_type(c.converter)  # revealed: int
+
+# This is also okay:
+C()
+
+# error: [invalid-argument-type]
+C(1)
+
+# error: [too-many-positional-arguments]
+C("a", "b")
+```
+
+### With overloaded `__set__` method
+
+If the `__set__` method is overloaded, we determine the type for the `__init__` parameter as the
+union of all possible `value` parameter types:
+
+```py
+from typing import overload
+from dataclasses import dataclass
+
+class AcceptsStrAndInt:
+    def __get__(self, instance, owner) -> int:
+        return 0
+
+    @overload
+    def __set__(self, instance: object, value: str) -> None: ...
+    @overload
+    def __set__(self, instance: object, value: int) -> None: ...
+    def __set__(self, instance: object, value) -> None:
+        pass
+
+@dataclass
+class C:
+    field: AcceptsStrAndInt = AcceptsStrAndInt()
+
+reveal_type(C.__init__)  # revealed: (field: str | int = int) -> None
+```
+
+## `dataclasses.field`
+
+To do
+
+## Other special cases
+
+### `dataclasses.dataclass`
+
+We also understand dataclasses if they are decorated with the fully qualified name:
+
+```py
+import dataclasses
+
+@dataclasses.dataclass
+class C:
+    x: str
+
+reveal_type(C.__init__)  # revealed: (x: str) -> None
+```
+
+### Dataclass with custom `__init__` method
+
+If a class already defines `__init__`, it is not replaced by the `dataclass` decorator.
+
+```py
+from dataclasses import dataclass
+
+@dataclass(init=True)
+class C:
+    x: str
+
+    def __init__(self, x: int) -> None:
+        self.x = str(x)
+
+C(1)  # OK
+
+# error: [invalid-argument-type]
+C("a")
+```
+
+Similarly, if we set `init=False`, we still recognize the custom `__init__` method:
+
+```py
+@dataclass(init=False)
+class D:
+    def __init__(self, x: int) -> None:
+        self.x = str(x)
+
+D(1)  # OK
+D()  # error: [missing-argument]
+```
+
+### Accessing instance attributes on the class itself
+
+Just like for normal classes, accessing instance attributes on the class itself is not allowed:
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class C:
+    x: int
+
+# error: [unresolved-attribute] "Attribute `x` can only be accessed on instances, not on the class object `Literal[C]` itself."
+C.x
+```
+
+### Return type of `dataclass(...)`
+
+A call like `dataclass(order=True)` returns a callable itself, which is then used as the decorator.
+We can store the callable in a variable and later use it as a decorator:
+
+```py
+from dataclasses import dataclass
+
+dataclass_with_order = dataclass(order=True)
+
+reveal_type(dataclass_with_order)  # revealed: <decorator produced by dataclasses.dataclass>
+
+@dataclass_with_order
+class C:
+    x: int
+
+C(1) < C(2)  # ok
+```
+
+### Using `dataclass` as a function
+
+To do
+
+## Internals
+
+The `dataclass` decorator returns the class itself. This means that the type of `Person` is `type`,
+and attributes like the MRO are unchanged:
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class Person:
+    name: str
+    age: int | None = None
+
+reveal_type(type(Person))  # revealed: Literal[type]
+reveal_type(Person.__mro__)  # revealed: tuple[Literal[Person], Literal[object]]
+```
+
+The generated methods have the following signatures:
+
+```py
+# TODO: `self` is missing here
+reveal_type(Person.__init__)  # revealed: (name: str, age: int | None = None) -> None
+
+reveal_type(Person.__repr__)  # revealed: def __repr__(self) -> str
+
+reveal_type(Person.__eq__)  # revealed: def __eq__(self, value: object, /) -> bool
+```

crates/red_knot_python_semantic/resources/mdtest/decorators.md

@@ -145,10 +145,10 @@ def f(x: int) -> int:
     return x**2
 
 # TODO: Should be `_lru_cache_wrapper[int]`
-reveal_type(f)  # revealed: @Todo(generics)
+reveal_type(f)  # revealed: @Todo(specialized non-generic class)
 
 # TODO: Should be `int`
-reveal_type(f(1))  # revealed: @Todo(generics)
+reveal_type(f(1))  # revealed: @Todo(specialized non-generic class)
 ```
 
 ## Lambdas as decorators

crates/red_knot_python_semantic/resources/mdtest/descriptor_protocol.md

@@ -459,11 +459,9 @@ class Descriptor:
 class C:
     d: Descriptor = Descriptor()
 
-# TODO: should be `Literal["called on class object"]
-reveal_type(C.d)  # revealed: LiteralString
+reveal_type(C.d)  # revealed: Literal["called on class object"]
 
-# TODO: should be `Literal["called on instance"]
-reveal_type(C().d)  # revealed: LiteralString
+reveal_type(C().d)  # revealed: Literal["called on instance"]
 ```
 
 ## Descriptor protocol for dunder methods

crates/red_knot_python_semantic/resources/mdtest/diagnostics/version_related_syntax_errors.md

@@ -0,0 +1,37 @@
+# Version-related syntax error diagnostics
+
+## `match` statement
+
+The `match` statement was introduced in Python 3.10.
+
+### Before 3.10
+
+<!-- snapshot-diagnostics -->
+
+We should emit a syntax error before 3.10.
+
+```toml
+[environment]
+python-version = "3.9"
+```
+
+```py
+match 2:  # error: 1 [invalid-syntax] "Cannot use `match` statement on Python 3.9 (syntax was added in Python 3.10)"
+    case 1:
+        print("it's one")
+```
+
+### After 3.10
+
+On or after 3.10, no error should be reported.
+
+```toml
+[environment]
+python-version = "3.10"
+```
+
+```py
+match 2:
+    case 1:
+        print("it's one")
+```

crates/red_knot_python_semantic/resources/mdtest/directives/assert_never.md

@@ -26,6 +26,11 @@ def _(never: Never, any_: Any, unknown: Unknown, flag: bool):
 
 ## Use case: Type narrowing and exhaustiveness checking
 
+```toml
+[environment]
+python-version = "3.10"
+```
+
 `assert_never` can be used in combination with type narrowing as a way to make sure that all cases
 are handled in a series of `isinstance` checks or other narrowing patterns that are supported.
 

crates/red_knot_python_semantic/resources/mdtest/directives/cast.md

@@ -61,7 +61,7 @@ from knot_extensions import Unknown
 
 def f(x: Any, y: Unknown, z: Any | str | int):
     a = cast(dict[str, Any], x)
-    reveal_type(a)  # revealed: @Todo(generics)
+    reveal_type(a)  # revealed: @Todo(specialized non-generic class)
 
     b = cast(Any, y)
     reveal_type(b)  # revealed: Any

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

@@ -76,6 +76,11 @@ def g(x: Any = "foo"):
 
 ## Stub functions
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ### In Protocol
 
 ```py

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

@@ -56,6 +56,11 @@ def f() -> int:
 
 ### In Protocol
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from typing import Protocol, TypeVar
 
@@ -69,8 +74,6 @@ class Baz(Bar):
 T = TypeVar("T")
 
 class Qux(Protocol[T]):
-    # TODO: no error
-    # error: [invalid-return-type]
     def f(self) -> int: ...
 
 class Foo(Protocol):
@@ -85,6 +88,11 @@ class Lorem(t[0]):
 
 ### In abstract method
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from abc import ABC, abstractmethod
 

crates/red_knot_python_semantic/resources/mdtest/generics/classes.md

@@ -1,5 +1,10 @@
 # Generic classes
 
+```toml
+[environment]
+python-version = "3.13"
+```
+
 ## PEP 695 syntax
 
 TODO: Add a `red_knot_extension` function that asserts whether a function or class is generic.
@@ -40,8 +45,6 @@ from typing import Generic, TypeVar
 
 T = TypeVar("T")
 
-# TODO: no error
-# error: [invalid-base]
 class C(Generic[T]): ...
 ```
 
@@ -149,23 +152,102 @@ If a typevar does not provide a default, we use `Unknown`:
 reveal_type(C())  # revealed: C[Unknown]
 ```
 
+## Inferring generic class parameters from constructors
+
 If the type of a constructor parameter is a class typevar, we can use that to infer the type
-parameter:
+parameter. The types inferred from a type context and from a constructor parameter must be
+consistent with each other.
+
+## `__new__` only
 
 ```py
-class E[T]:
-    def __init__(self, x: T) -> None: ...
+class C[T]:
+    def __new__(cls, x: T) -> "C[T]":
+        return object.__new__(cls)
 
-# TODO: revealed: E[int] or E[Literal[1]]
-reveal_type(E(1))  # revealed: E[Unknown]
+reveal_type(C(1))  # revealed: C[Literal[1]]
+
+# error: [invalid-assignment] "Object of type `C[Literal["five"]]` is not assignable to `C[int]`"
+wrong_innards: C[int] = C("five")
 ```
 
-The types inferred from a type context and from a constructor parameter must be consistent with each
-other:
+## `__init__` only
 
 ```py
-# TODO: error: [invalid-argument-type]
-wrong_innards: E[int] = E("five")
+class C[T]:
+    def __init__(self, x: T) -> None: ...
+
+reveal_type(C(1))  # revealed: C[Literal[1]]
+
+# error: [invalid-assignment] "Object of type `C[Literal["five"]]` is not assignable to `C[int]`"
+wrong_innards: C[int] = C("five")
+```
+
+## Identical `__new__` and `__init__` signatures
+
+```py
+class C[T]:
+    def __new__(cls, x: T) -> "C[T]":
+        return object.__new__(cls)
+
+    def __init__(self, x: T) -> None: ...
+
+reveal_type(C(1))  # revealed: C[Literal[1]]
+
+# error: [invalid-assignment] "Object of type `C[Literal["five"]]` is not assignable to `C[int]`"
+wrong_innards: C[int] = C("five")
+```
+
+## Compatible `__new__` and `__init__` signatures
+
+```py
+class C[T]:
+    def __new__(cls, *args, **kwargs) -> "C[T]":
+        return object.__new__(cls)
+
+    def __init__(self, x: T) -> None: ...
+
+reveal_type(C(1))  # revealed: C[Literal[1]]
+
+# error: [invalid-assignment] "Object of type `C[Literal["five"]]` is not assignable to `C[int]`"
+wrong_innards: C[int] = C("five")
+
+class D[T]:
+    def __new__(cls, x: T) -> "D[T]":
+        return object.__new__(cls)
+
+    def __init__(self, *args, **kwargs) -> None: ...
+
+reveal_type(D(1))  # revealed: D[Literal[1]]
+
+# error: [invalid-assignment] "Object of type `D[Literal["five"]]` is not assignable to `D[int]`"
+wrong_innards: D[int] = D("five")
+```
+
+## `__init__` is itself generic
+
+TODO: These do not currently work yet, because we don't correctly model the nested generic contexts.
+
+```py
+class C[T]:
+    def __init__[S](self, x: T, y: S) -> None: ...
+
+# TODO: no error
+# TODO: revealed: C[Literal[1]]
+# error: [invalid-argument-type]
+reveal_type(C(1, 1))  # revealed: C[Unknown]
+# TODO: no error
+# TODO: revealed: C[Literal[1]]
+# error: [invalid-argument-type]
+reveal_type(C(1, "string"))  # revealed: C[Unknown]
+# TODO: no error
+# TODO: revealed: C[Literal[1]]
+# error: [invalid-argument-type]
+reveal_type(C(1, True))  # revealed: C[Unknown]
+
+# TODO: [invalid-assignment] "Object of type `C[Literal["five"]]` is not assignable to `C[int]`"
+# error: [invalid-argument-type] "Argument to this function is incorrect: Expected `S`, found `Literal[1]`"
+wrong_innards: C[int] = C("five", 1)
 ```
 
 ## Generic subclass
@@ -200,10 +282,7 @@ class C[T]:
     def cannot_shadow_class_typevar[T](self, t: T): ...
 
 c: C[int] = C[int]()
-# TODO: no error
-# TODO: revealed: str or Literal["string"]
-# error: [invalid-argument-type]
-reveal_type(c.method("string"))  # revealed: U
+reveal_type(c.method("string"))  # revealed: Literal["string"]
 ```
 
 ## Cyclic class definition

crates/red_knot_python_semantic/resources/mdtest/generics/functions.md

@@ -1,5 +1,10 @@
 # Generic functions
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ## Typevar must be used at least twice
 
 If you're only using a typevar for a single parameter, you don't need the typevar — just use
@@ -43,33 +48,14 @@ def absurd[T]() -> T:
 If the type of a generic function parameter is a typevar, then we can infer what type that typevar
 is bound to at each call site.
 
-TODO: Note that some of the TODO revealed types have two options, since we haven't decided yet
-whether we want to infer a more specific `Literal` type where possible, or use heuristics to weaken
-the inferred type to e.g. `int`.
-
 ```py
 def f[T](x: T) -> T:
     return x
 
-# TODO: no error
-# TODO: revealed: int or Literal[1]
-# error: [invalid-argument-type]
-reveal_type(f(1))  # revealed: T
-
-# TODO: no error
-# TODO: revealed: float
-# error: [invalid-argument-type]
-reveal_type(f(1.0))  # revealed: T
-
-# TODO: no error
-# TODO: revealed: bool or Literal[true]
-# error: [invalid-argument-type]
-reveal_type(f(True))  # revealed: T
-
-# TODO: no error
-# TODO: revealed: str or Literal["string"]
-# error: [invalid-argument-type]
-reveal_type(f("string"))  # revealed: T
+reveal_type(f(1))  # revealed: Literal[1]
+reveal_type(f(1.0))  # revealed: float
+reveal_type(f(True))  # revealed: Literal[True]
+reveal_type(f("string"))  # revealed: Literal["string"]
 ```
 
 ## Inferring “deep” generic parameter types
@@ -82,7 +68,7 @@ def f[T](x: list[T]) -> T:
     return x[0]
 
 # TODO: revealed: float
-reveal_type(f([1.0, 2.0]))  # revealed: T
+reveal_type(f([1.0, 2.0]))  # revealed: Unknown
 ```
 
 ## Typevar constraints
@@ -93,7 +79,6 @@ in the function.
 
 ```py
 def good_param[T: int](x: T) -> None:
-    # TODO: revealed: T & int
     reveal_type(x)  # revealed: T
 ```
 
@@ -162,61 +147,41 @@ parameters simultaneously.
 def two_params[T](x: T, y: T) -> T:
     return x
 
-# TODO: no error
-# TODO: revealed: str
-# error: [invalid-argument-type]
-# error: [invalid-argument-type]
-reveal_type(two_params("a", "b"))  # revealed: T
+reveal_type(two_params("a", "b"))  # revealed: Literal["a", "b"]
+reveal_type(two_params("a", 1))  # revealed: Literal["a", 1]
+```
 
-# TODO: no error
-# TODO: revealed: str | int
-# error: [invalid-argument-type]
-# error: [invalid-argument-type]
-reveal_type(two_params("a", 1))  # revealed: T
+When one of the parameters is a union, we attempt to find the smallest specialization that satisfies
+all of the constraints.
+
+```py
+def union_param[T](x: T | None) -> T:
+    if x is None:
+        raise ValueError
+    return x
+
+reveal_type(union_param("a"))  # revealed: Literal["a"]
+reveal_type(union_param(1))  # revealed: Literal[1]
+reveal_type(union_param(None))  # revealed: Unknown
 ```
 
 ```py
-def param_with_union[T](x: T | int, y: T) -> T:
+def union_and_nonunion_params[T](x: T | int, y: T) -> T:
     return y
 
-# TODO: no error
-# TODO: revealed: str
-# error: [invalid-argument-type]
-reveal_type(param_with_union(1, "a"))  # revealed: T
-
-# TODO: no error
-# TODO: revealed: str
-# error: [invalid-argument-type]
-# error: [invalid-argument-type]
-reveal_type(param_with_union("a", "a"))  # revealed: T
-
-# TODO: no error
-# TODO: revealed: int
-# error: [invalid-argument-type]
-reveal_type(param_with_union(1, 1))  # revealed: T
-
-# TODO: no error
-# TODO: revealed: str | int
-# error: [invalid-argument-type]
-# error: [invalid-argument-type]
-reveal_type(param_with_union("a", 1))  # revealed: T
+reveal_type(union_and_nonunion_params(1, "a"))  # revealed: Literal["a"]
+reveal_type(union_and_nonunion_params("a", "a"))  # revealed: Literal["a"]
+reveal_type(union_and_nonunion_params(1, 1))  # revealed: Literal[1]
+reveal_type(union_and_nonunion_params(3, 1))  # revealed: Literal[1]
+reveal_type(union_and_nonunion_params("a", 1))  # revealed: Literal["a", 1]
 ```
 
 ```py
 def tuple_param[T, S](x: T | S, y: tuple[T, S]) -> tuple[T, S]:
     return y
 
-# TODO: no error
-# TODO: revealed: tuple[str, int]
-# error: [invalid-argument-type]
-# error: [invalid-argument-type]
-reveal_type(tuple_param("a", ("a", 1)))  # revealed: tuple[T, S]
-
-# TODO: no error
-# TODO: revealed: tuple[str, int]
-# error: [invalid-argument-type]
-# error: [invalid-argument-type]
-reveal_type(tuple_param(1, ("a", 1)))  # revealed: tuple[T, S]
+reveal_type(tuple_param("a", ("a", 1)))  # revealed: tuple[Literal["a"], Literal[1]]
+reveal_type(tuple_param(1, ("a", 1)))  # revealed: tuple[Literal["a"], Literal[1]]
 ```
 
 ## Inferring nested generic function calls
@@ -231,15 +196,6 @@ def f[T](x: T) -> tuple[T, int]:
 def g[T](x: T) -> T | None:
     return x
 
-# TODO: no error
-# TODO: revealed: tuple[str | None, int]
-# error: [invalid-argument-type]
-# error: [invalid-argument-type]
-reveal_type(f(g("a")))  # revealed: tuple[T, int]
-
-# TODO: no error
-# TODO: revealed: tuple[str, int] | None
-# error: [invalid-argument-type]
-# error: [invalid-argument-type]
-reveal_type(g(f("a")))  # revealed: T | None
+reveal_type(f(g("a")))  # revealed: tuple[Literal["a"] | None, int]
+reveal_type(g(f("a")))  # revealed: tuple[Literal["a"], int] | None
 ```

crates/red_knot_python_semantic/resources/mdtest/generics/pep695.md

@@ -1,5 +1,10 @@
 # PEP 695 Generics
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 [PEP 695] and Python 3.12 introduced new, more ergonomic syntax for type variables.
 
 ## Type variables
@@ -59,19 +64,19 @@ is.)
 from knot_extensions import is_fully_static, static_assert
 from typing import Any
 
-def unbounded_unconstrained[T](t: list[T]) -> None:
+def unbounded_unconstrained[T](t: T) -> None:
     static_assert(is_fully_static(T))
 
-def bounded[T: int](t: list[T]) -> None:
+def bounded[T: int](t: T) -> None:
     static_assert(is_fully_static(T))
 
-def bounded_by_gradual[T: Any](t: list[T]) -> None:
+def bounded_by_gradual[T: Any](t: T) -> None:
     static_assert(not is_fully_static(T))
 
-def constrained[T: (int, str)](t: list[T]) -> None:
+def constrained[T: (int, str)](t: T) -> None:
     static_assert(is_fully_static(T))
 
-def constrained_by_gradual[T: (int, Any)](t: list[T]) -> None:
+def constrained_by_gradual[T: (int, Any)](t: T) -> None:
     static_assert(not is_fully_static(T))
 ```
 
@@ -94,7 +99,7 @@ class Base(Super): ...
 class Sub(Base): ...
 class Unrelated: ...
 
-def unbounded_unconstrained[T, U](t: list[T], u: list[U]) -> None:
+def unbounded_unconstrained[T, U](t: T, u: U) -> None:
     static_assert(is_assignable_to(T, T))
     static_assert(is_assignable_to(T, object))
     static_assert(not is_assignable_to(T, Super))
@@ -124,7 +129,7 @@ is a final class, since the typevar can still be specialized to `Never`.)
 from typing import Any
 from typing_extensions import final
 
-def bounded[T: Super](t: list[T]) -> None:
+def bounded[T: Super](t: T) -> None:
     static_assert(is_assignable_to(T, Super))
     static_assert(not is_assignable_to(T, Sub))
     static_assert(not is_assignable_to(Super, T))
@@ -135,7 +140,7 @@ def bounded[T: Super](t: list[T]) -> None:
     static_assert(not is_subtype_of(Super, T))
     static_assert(not is_subtype_of(Sub, T))
 
-def bounded_by_gradual[T: Any](t: list[T]) -> None:
+def bounded_by_gradual[T: Any](t: T) -> None:
     static_assert(is_assignable_to(T, Any))
     static_assert(is_assignable_to(Any, T))
     static_assert(is_assignable_to(T, Super))
@@ -153,7 +158,7 @@ def bounded_by_gradual[T: Any](t: list[T]) -> None:
 @final
 class FinalClass: ...
 
-def bounded_final[T: FinalClass](t: list[T]) -> None:
+def bounded_final[T: FinalClass](t: T) -> None:
     static_assert(is_assignable_to(T, FinalClass))
     static_assert(not is_assignable_to(FinalClass, T))
 
@@ -167,14 +172,14 @@ true even if both typevars are bounded by the same final class, since you can sp
 typevars to `Never` in addition to that final class.
 
 ```py
-def two_bounded[T: Super, U: Super](t: list[T], u: list[U]) -> None:
+def two_bounded[T: Super, U: Super](t: T, u: U) -> None:
     static_assert(not is_assignable_to(T, U))
     static_assert(not is_assignable_to(U, T))
 
     static_assert(not is_subtype_of(T, U))
     static_assert(not is_subtype_of(U, T))
 
-def two_final_bounded[T: FinalClass, U: FinalClass](t: list[T], u: list[U]) -> None:
+def two_final_bounded[T: FinalClass, U: FinalClass](t: T, u: U) -> None:
     static_assert(not is_assignable_to(T, U))
     static_assert(not is_assignable_to(U, T))
 
@@ -189,7 +194,7 @@ intersection of all of its constraints is a subtype of the typevar.
 ```py
 from knot_extensions import Intersection
 
-def constrained[T: (Base, Unrelated)](t: list[T]) -> None:
+def constrained[T: (Base, Unrelated)](t: T) -> None:
     static_assert(not is_assignable_to(T, Super))
     static_assert(not is_assignable_to(T, Base))
     static_assert(not is_assignable_to(T, Sub))
@@ -214,7 +219,7 @@ def constrained[T: (Base, Unrelated)](t: list[T]) -> None:
     static_assert(not is_subtype_of(Super | Unrelated, T))
     static_assert(is_subtype_of(Intersection[Base, Unrelated], T))
 
-def constrained_by_gradual[T: (Base, Any)](t: list[T]) -> None:
+def constrained_by_gradual[T: (Base, Any)](t: T) -> None:
     static_assert(is_assignable_to(T, Super))
     static_assert(is_assignable_to(T, Base))
     static_assert(not is_assignable_to(T, Sub))
@@ -256,7 +261,7 @@ distinct constraints, meaning that there is (still) no guarantee that they will
 the same type.
 
 ```py
-def two_constrained[T: (int, str), U: (int, str)](t: list[T], u: list[U]) -> None:
+def two_constrained[T: (int, str), U: (int, str)](t: T, u: U) -> None:
     static_assert(not is_assignable_to(T, U))
     static_assert(not is_assignable_to(U, T))
 
@@ -266,7 +271,7 @@ def two_constrained[T: (int, str), U: (int, str)](t: list[T], u: list[U]) -> Non
 @final
 class AnotherFinalClass: ...
 
-def two_final_constrained[T: (FinalClass, AnotherFinalClass), U: (FinalClass, AnotherFinalClass)](t: list[T], u: list[U]) -> None:
+def two_final_constrained[T: (FinalClass, AnotherFinalClass), U: (FinalClass, AnotherFinalClass)](t: T, u: U) -> None:
     static_assert(not is_assignable_to(T, U))
     static_assert(not is_assignable_to(U, T))
 
@@ -285,7 +290,7 @@ non-singleton type.
 ```py
 from knot_extensions import is_singleton, is_single_valued, static_assert
 
-def unbounded_unconstrained[T](t: list[T]) -> None:
+def unbounded_unconstrained[T](t: T) -> None:
     static_assert(not is_singleton(T))
     static_assert(not is_single_valued(T))
 ```
@@ -294,7 +299,7 @@ A bounded typevar is not a singleton, even if its bound is a singleton, since it
 specialized to `Never`.
 
 ```py
-def bounded[T: None](t: list[T]) -> None:
+def bounded[T: None](t: T) -> None:
     static_assert(not is_singleton(T))
     static_assert(not is_single_valued(T))
 ```
@@ -305,14 +310,14 @@ specialize a constrained typevar to a subtype of a constraint.)
 ```py
 from typing_extensions import Literal
 
-def constrained_non_singletons[T: (int, str)](t: list[T]) -> None:
+def constrained_non_singletons[T: (int, str)](t: T) -> None:
     static_assert(not is_singleton(T))
     static_assert(not is_single_valued(T))
 
-def constrained_singletons[T: (Literal[True], Literal[False])](t: list[T]) -> None:
+def constrained_singletons[T: (Literal[True], Literal[False])](t: T) -> None:
     static_assert(is_singleton(T))
 
-def constrained_single_valued[T: (Literal[True], tuple[()])](t: list[T]) -> None:
+def constrained_single_valued[T: (Literal[True], tuple[()])](t: T) -> None:
     static_assert(is_single_valued(T))
 ```
 
@@ -507,6 +512,20 @@ def remove_constraint[T: (int, str, bool)](t: T) -> None:
         reveal_type(x)  # revealed: T & Any
 ```
 
+The intersection of a typevar with any other type is assignable to (and if fully static, a subtype
+of) itself.
+
+```py
+from knot_extensions import is_assignable_to, is_subtype_of, static_assert, Not
+
+def intersection_is_assignable[T](t: T) -> None:
+    static_assert(is_assignable_to(Intersection[T, None], T))
+    static_assert(is_assignable_to(Intersection[T, Not[None]], T))
+
+    static_assert(is_subtype_of(Intersection[T, None], T))
+    static_assert(is_subtype_of(Intersection[T, Not[None]], T))
+```
+
 ## Narrowing
 
 We can use narrowing expressions to eliminate some of the possibilities of a constrained typevar:

crates/red_knot_python_semantic/resources/mdtest/generics/scoping.md

@@ -1,5 +1,10 @@
 # Scoping rules for type variables
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 Most of these tests come from the [Scoping rules for type variables][scoping] section of the typing
 spec.
 
@@ -59,14 +64,8 @@ to a different type each time.
 def f[T](x: T) -> T:
     return x
 
-# TODO: no error
-# TODO: revealed: int or Literal[1]
-# error: [invalid-argument-type]
-reveal_type(f(1))  # revealed: T
-# TODO: no error
-# TODO: revealed: str or Literal["a"]
-# error: [invalid-argument-type]
-reveal_type(f("a"))  # revealed: T
+reveal_type(f(1))  # revealed: Literal[1]
+reveal_type(f("a"))  # revealed: Literal["a"]
 ```
 
 ## Methods can mention class typevars
@@ -138,8 +137,6 @@ from typing import TypeVar, Generic
 T = TypeVar("T")
 S = TypeVar("S")
 
-# TODO: no error
-# error: [invalid-base]
 class Legacy(Generic[T]):
     def m(self, x: T, y: S) -> S:
         return y
@@ -157,10 +154,7 @@ class C[T]:
         return y
 
 c: C[int] = C()
-# TODO: no errors
-# TODO: revealed: str
-# error: [invalid-argument-type]
-reveal_type(c.m(1, "string"))  # revealed: S
+reveal_type(c.m(1, "string"))  # revealed: Literal["string"]
 ```
 
 ## Unbound typevars
@@ -178,13 +172,11 @@ S = TypeVar("S")
 
 def f(x: T) -> None:
     x: list[T] = []
-    # TODO: error
+    # TODO: invalid-assignment error
     y: list[S] = []
 
-# TODO: no error
-# error: [invalid-base]
 class C(Generic[T]):
-    # TODO: error
+    # TODO: error: cannot use S if it's not in the current generic context
     x: list[S] = []
 
     # This is not an error, as shown in the previous test
@@ -204,11 +196,11 @@ S = TypeVar("S")
 
 def f[T](x: T) -> None:
     x: list[T] = []
-    # TODO: error
+    # TODO: invalid assignment error
     y: list[S] = []
 
 class C[T]:
-    # TODO: error
+    # TODO: error: cannot use S if it's not in the current generic context
     x: list[S] = []
 
     def m1(self, x: S) -> S:
@@ -263,8 +255,7 @@ def f[T](x: T, y: T) -> None:
     class Ok[S]: ...
     # TODO: error for reuse of typevar
     class Bad1[T]: ...
-    # TODO: no non-subscriptable error, error for reuse of typevar
-    # error: [non-subscriptable]
+    # TODO: error for reuse of typevar
     class Bad2(Iterable[T]): ...
 ```
 
@@ -277,8 +268,7 @@ class C[T]:
     class Ok1[S]: ...
     # TODO: error for reuse of typevar
     class Bad1[T]: ...
-    # TODO: no non-subscriptable error, error for reuse of typevar
-    # error: [non-subscriptable]
+    # TODO: error for reuse of typevar
     class Bad2(Iterable[T]): ...
 ```
 
@@ -292,7 +282,7 @@ class C[T]:
     ok1: list[T] = []
 
     class Bad:
-        # TODO: error
+        # TODO: error: cannot refer to T in nested scope
         bad: list[T] = []
 
     class Inner[S]: ...

crates/red_knot_python_semantic/resources/mdtest/generics/variance.md

@@ -0,0 +1,277 @@
+# Variance
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+Type variables have a property called _variance_ that affects the subtyping and assignability
+relations. Much more detail can be found in the [spec]. To summarize, each typevar is either
+**covariant**, **contravariant**, **invariant**, or **bivariant**. (Note that bivariance is not
+currently mentioned in the typing spec, but is a fourth case that we must consider.)
+
+For all of the examples below, we will consider a typevar `T`, a generic class using that typevar
+`C[T]`, and two types `A` and `B`.
+
+## Covariance
+
+With a covariant typevar, subtyping is in "alignment": if `A <: B`, then `C[A] <: C[B]`.
+
+Types that "produce" data on demand are covariant in their typevar. If you expect a sequence of
+`int`s, someone can safely provide a sequence of `bool`s, since each `bool` element that you would
+get from the sequence is a valid `int`.
+
+```py
+from knot_extensions import is_assignable_to, is_equivalent_to, is_gradual_equivalent_to, is_subtype_of, static_assert, Unknown
+from typing import Any
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    def receive(self) -> T:
+        raise ValueError
+
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_assignable_to(C[B], C[A]))
+static_assert(not is_assignable_to(C[A], C[B]))
+static_assert(is_assignable_to(C[A], C[Any]))
+static_assert(is_assignable_to(C[B], C[Any]))
+static_assert(is_assignable_to(C[Any], C[A]))
+static_assert(is_assignable_to(C[Any], C[B]))
+
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+static_assert(not is_subtype_of(C[A], C[Any]))
+static_assert(not is_subtype_of(C[B], C[Any]))
+static_assert(not is_subtype_of(C[Any], C[A]))
+static_assert(not is_subtype_of(C[Any], C[B]))
+
+static_assert(is_equivalent_to(C[A], C[A]))
+static_assert(is_equivalent_to(C[B], C[B]))
+static_assert(not is_equivalent_to(C[B], C[A]))
+static_assert(not is_equivalent_to(C[A], C[B]))
+static_assert(not is_equivalent_to(C[A], C[Any]))
+static_assert(not is_equivalent_to(C[B], C[Any]))
+static_assert(not is_equivalent_to(C[Any], C[A]))
+static_assert(not is_equivalent_to(C[Any], C[B]))
+
+static_assert(is_gradual_equivalent_to(C[A], C[A]))
+static_assert(is_gradual_equivalent_to(C[B], C[B]))
+static_assert(is_gradual_equivalent_to(C[Any], C[Any]))
+static_assert(is_gradual_equivalent_to(C[Any], C[Unknown]))
+static_assert(not is_gradual_equivalent_to(C[B], C[A]))
+static_assert(not is_gradual_equivalent_to(C[A], C[B]))
+static_assert(not is_gradual_equivalent_to(C[A], C[Any]))
+static_assert(not is_gradual_equivalent_to(C[B], C[Any]))
+static_assert(not is_gradual_equivalent_to(C[Any], C[A]))
+static_assert(not is_gradual_equivalent_to(C[Any], C[B]))
+```
+
+## Contravariance
+
+With a contravariant typevar, subtyping is in "opposition": if `A <: B`, then `C[B] <: C[A]`.
+
+Types that "consume" data are contravariant in their typevar. If you expect a consumer that receives
+`bool`s, someone can safely provide a consumer that expects to receive `int`s, since each `bool`
+that you pass into the consumer is a valid `int`.
+
+```py
+from knot_extensions import is_assignable_to, is_equivalent_to, is_gradual_equivalent_to, is_subtype_of, static_assert, Unknown
+from typing import Any
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    def send(self, value: T): ...
+
+static_assert(not is_assignable_to(C[B], C[A]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_assignable_to(C[A], C[B]))
+static_assert(is_assignable_to(C[A], C[Any]))
+static_assert(is_assignable_to(C[B], C[Any]))
+static_assert(is_assignable_to(C[Any], C[A]))
+static_assert(is_assignable_to(C[Any], C[B]))
+
+static_assert(not is_subtype_of(C[B], C[A]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_subtype_of(C[A], C[B]))
+static_assert(not is_subtype_of(C[A], C[Any]))
+static_assert(not is_subtype_of(C[B], C[Any]))
+static_assert(not is_subtype_of(C[Any], C[A]))
+static_assert(not is_subtype_of(C[Any], C[B]))
+
+static_assert(is_equivalent_to(C[A], C[A]))
+static_assert(is_equivalent_to(C[B], C[B]))
+static_assert(not is_equivalent_to(C[B], C[A]))
+static_assert(not is_equivalent_to(C[A], C[B]))
+static_assert(not is_equivalent_to(C[A], C[Any]))
+static_assert(not is_equivalent_to(C[B], C[Any]))
+static_assert(not is_equivalent_to(C[Any], C[A]))
+static_assert(not is_equivalent_to(C[Any], C[B]))
+
+static_assert(is_gradual_equivalent_to(C[A], C[A]))
+static_assert(is_gradual_equivalent_to(C[B], C[B]))
+static_assert(is_gradual_equivalent_to(C[Any], C[Any]))
+static_assert(is_gradual_equivalent_to(C[Any], C[Unknown]))
+static_assert(not is_gradual_equivalent_to(C[B], C[A]))
+static_assert(not is_gradual_equivalent_to(C[A], C[B]))
+static_assert(not is_gradual_equivalent_to(C[A], C[Any]))
+static_assert(not is_gradual_equivalent_to(C[B], C[Any]))
+static_assert(not is_gradual_equivalent_to(C[Any], C[A]))
+static_assert(not is_gradual_equivalent_to(C[Any], C[B]))
+```
+
+## Invariance
+
+With an invariant typevar, _no_ specializations of the generic class are subtypes of each other.
+
+This often occurs for types that are both producers _and_ consumers, like a mutable `list`.
+Iterating over the elements in a list would work with a covariant typevar, just like with the
+"producer" type above. Appending elements to a list would work with a contravariant typevar, just
+like with the "consumer" type above. However, a typevar cannot be both covariant and contravariant
+at the same time!
+
+If you expect a mutable list of `int`s, it's not safe for someone to provide you with a mutable list
+of `bool`s, since you might try to add an element to the list: if you try to add an `int`, the list
+would no longer only contain elements that are subtypes of `bool`.
+
+Conversely, if you expect a mutable list of `bool`s, it's not safe for someone to provide you with a
+mutable list of `int`s, since you might try to extract elements from the list: you expect every
+element that you extract to be a subtype of `bool`, but the list can contain any `int`.
+
+In the end, if you expect a mutable list, you must always be given a list of exactly that type,
+since we can't know in advance which of the allowed methods you'll want to use.
+
+```py
+from knot_extensions import is_assignable_to, is_equivalent_to, is_gradual_equivalent_to, is_subtype_of, static_assert, Unknown
+from typing import Any
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    def send(self, value: T): ...
+    def receive(self) -> T:
+        raise ValueError
+
+static_assert(not is_assignable_to(C[B], C[A]))
+static_assert(not is_assignable_to(C[A], C[B]))
+static_assert(is_assignable_to(C[A], C[Any]))
+static_assert(is_assignable_to(C[B], C[Any]))
+static_assert(is_assignable_to(C[Any], C[A]))
+static_assert(is_assignable_to(C[Any], C[B]))
+
+static_assert(not is_subtype_of(C[B], C[A]))
+static_assert(not is_subtype_of(C[A], C[B]))
+static_assert(not is_subtype_of(C[A], C[Any]))
+static_assert(not is_subtype_of(C[B], C[Any]))
+static_assert(not is_subtype_of(C[Any], C[A]))
+static_assert(not is_subtype_of(C[Any], C[B]))
+
+static_assert(is_equivalent_to(C[A], C[A]))
+static_assert(is_equivalent_to(C[B], C[B]))
+static_assert(not is_equivalent_to(C[B], C[A]))
+static_assert(not is_equivalent_to(C[A], C[B]))
+static_assert(not is_equivalent_to(C[A], C[Any]))
+static_assert(not is_equivalent_to(C[B], C[Any]))
+static_assert(not is_equivalent_to(C[Any], C[A]))
+static_assert(not is_equivalent_to(C[Any], C[B]))
+
+static_assert(is_gradual_equivalent_to(C[A], C[A]))
+static_assert(is_gradual_equivalent_to(C[B], C[B]))
+static_assert(is_gradual_equivalent_to(C[Any], C[Any]))
+static_assert(is_gradual_equivalent_to(C[Any], C[Unknown]))
+static_assert(not is_gradual_equivalent_to(C[B], C[A]))
+static_assert(not is_gradual_equivalent_to(C[A], C[B]))
+static_assert(not is_gradual_equivalent_to(C[A], C[Any]))
+static_assert(not is_gradual_equivalent_to(C[B], C[Any]))
+static_assert(not is_gradual_equivalent_to(C[Any], C[A]))
+static_assert(not is_gradual_equivalent_to(C[Any], C[B]))
+```
+
+## Bivariance
+
+With a bivariant typevar, _all_ specializations of the generic class are subtypes of (and in fact,
+equivalent to) each other.
+
+This is a bit of pathological case, which really only happens when the class doesn't use the typevar
+at all. (If it did, it would have to be covariant, contravariant, or invariant, depending on _how_
+the typevar was used.)
+
+```py
+from knot_extensions import is_assignable_to, is_equivalent_to, is_gradual_equivalent_to, is_subtype_of, static_assert, Unknown
+from typing import Any
+
+class A: ...
+class B(A): ...
+
+class C[T]:
+    pass
+
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_assignable_to(C[B], C[A]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_assignable_to(C[A], C[B]))
+static_assert(is_assignable_to(C[A], C[Any]))
+static_assert(is_assignable_to(C[B], C[Any]))
+static_assert(is_assignable_to(C[Any], C[A]))
+static_assert(is_assignable_to(C[Any], C[B]))
+
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_subtype_of(C[B], C[A]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_subtype_of(C[A], C[B]))
+static_assert(not is_subtype_of(C[A], C[Any]))
+static_assert(not is_subtype_of(C[B], C[Any]))
+static_assert(not is_subtype_of(C[Any], C[A]))
+static_assert(not is_subtype_of(C[Any], C[B]))
+
+static_assert(is_equivalent_to(C[A], C[A]))
+static_assert(is_equivalent_to(C[B], C[B]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_equivalent_to(C[B], C[A]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_equivalent_to(C[A], C[B]))
+static_assert(not is_equivalent_to(C[A], C[Any]))
+static_assert(not is_equivalent_to(C[B], C[Any]))
+static_assert(not is_equivalent_to(C[Any], C[A]))
+static_assert(not is_equivalent_to(C[Any], C[B]))
+
+static_assert(is_gradual_equivalent_to(C[A], C[A]))
+static_assert(is_gradual_equivalent_to(C[B], C[B]))
+static_assert(is_gradual_equivalent_to(C[Any], C[Any]))
+static_assert(is_gradual_equivalent_to(C[Any], C[Unknown]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_gradual_equivalent_to(C[B], C[A]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_gradual_equivalent_to(C[A], C[B]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_gradual_equivalent_to(C[A], C[Any]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_gradual_equivalent_to(C[B], C[Any]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_gradual_equivalent_to(C[Any], C[A]))
+# TODO: no error
+# error: [static-assert-error]
+static_assert(is_gradual_equivalent_to(C[Any], C[B]))
+```
+
+[spec]: https://typing.python.org/en/latest/spec/generics.html#variance

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

@@ -122,6 +122,11 @@ from c import Y  # error: [unresolved-import]
 
 ## Esoteric definitions and redefinintions
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 We understand all public symbols defined in an external module as being imported by a `*` import,
 not just those that are defined in `StmtAssign` nodes and `StmtAnnAssign` nodes. This section
 provides tests for definitions, and redefinitions, that use more esoteric AST nodes.
@@ -626,6 +631,30 @@ reveal_type(X)  # revealed: Unknown
 reveal_type(Y)  # revealed: bool
 ```
 
+### An implicit import in a `.pyi` file later overridden by another assignment
+
+`a.pyi`:
+
+```pyi
+X: bool = True
+```
+
+`b.pyi`:
+
+```pyi
+from a import X
+
+X: bool = False
+```
+
+`c.py`:
+
+```py
+from b import *
+
+reveal_type(X)  # revealed: bool
+```
+
 ## Visibility constraints
 
 If an `importer` module contains a `from exporter import *` statement in its global namespace, the
@@ -865,15 +894,10 @@ from exporter import *
 
 reveal_type(X)  # revealed: bool
 
-# TODO none of these should error, should all reveal `bool`
-# error: [unresolved-reference]
-reveal_type(_private)  # revealed: Unknown
-# error: [unresolved-reference]
-reveal_type(__protected)  # revealed: Unknown
-# error: [unresolved-reference]
-reveal_type(__dunder__)  # revealed: Unknown
-# error: [unresolved-reference]
-reveal_type(___thunder___)  # revealed: Unknown
+reveal_type(_private)  # revealed: bool
+reveal_type(__protected)  # revealed: bool
+reveal_type(__dunder__)  # revealed: bool
+reveal_type(___thunder___)  # revealed: bool
 
 # TODO: should emit [unresolved-reference] diagnostic & reveal `Unknown`
 reveal_type(Y)  # revealed: bool
@@ -1072,6 +1096,44 @@ reveal_type(Y)  # revealed: bool
 reveal_type(Z)  # revealed: Unknown
 ```
 
+### `__all__` conditionally defined in a statically known branch (2)
+
+The same example again, but with a different `python-version` set:
+
+```toml
+[environment]
+python-version = "3.10"
+```
+
+`exporter.py`:
+
+```py
+import sys
+
+X: bool = True
+
+if sys.version_info >= (3, 11):
+    __all__ = ["X", "Y"]
+    Y: bool = True
+else:
+    __all__ = ("Z",)
+    Z: bool = True
+```
+
+`importer.py`:
+
+```py
+from exporter import *
+
+# TODO: should reveal `Unknown` and emit `[unresolved-reference]`
+reveal_type(X)  # revealed: bool
+
+# error: [unresolved-reference]
+reveal_type(Y)  # revealed: Unknown
+
+reveal_type(Z)  # revealed: bool
+```
+
 ### `__all__` conditionally mutated in a statically known branch
 
 ```toml
@@ -1084,11 +1146,11 @@ python-version = "3.11"
 ```py
 import sys
 
-__all__ = ["X"]
+__all__ = []
 X: bool = True
 
 if sys.version_info >= (3, 11):
-    __all__.append("Y")
+    __all__.extend(["X", "Y"])
     Y: bool = True
 else:
     __all__.append("Z")
@@ -1107,6 +1169,45 @@ reveal_type(Y)  # revealed: bool
 reveal_type(Z)  # revealed: Unknown
 ```
 
+### `__all__` conditionally mutated in a statically known branch (2)
+
+The same example again, but with a different `python-version` set:
+
+```toml
+[environment]
+python-version = "3.10"
+```
+
+`exporter.py`:
+
+```py
+import sys
+
+__all__ = []
+X: bool = True
+
+if sys.version_info >= (3, 11):
+    __all__.extend(["X", "Y"])
+    Y: bool = True
+else:
+    __all__.append("Z")
+    Z: bool = True
+```
+
+`importer.py`:
+
+```py
+from exporter import *
+
+# TODO: should reveal `Unknown` & emit `[unresolved-reference]
+reveal_type(X)  # revealed: bool
+
+# error: [unresolved-reference]
+reveal_type(Y)  # revealed: Unknown
+
+reveal_type(Z)  # revealed: bool
+```
+
 ### Empty `__all__`
 
 An empty `__all__` is valid, but a `*` import from a module with an empty `__all__` results in 0
@@ -1166,6 +1267,7 @@ from b import *
 
 # TODO: should not error, should reveal `bool`
 # (`X` is re-exported from `b.pyi` due to presence in `__all__`)
+# See https://github.com/astral-sh/ruff/issues/16159
 #
 # error: [unresolved-reference]
 reveal_type(X)  # revealed: Unknown

crates/red_knot_python_semantic/resources/mdtest/intersection_types.md

@@ -842,7 +842,7 @@ def unknown(
 
 ### Mixed dynamic types
 
-We currently do not simplify mixed dynamic types, but might consider doing so in the future:
+Gradually-equivalent types can be simplified out of intersections:
 
 ```py
 from typing import Any
@@ -854,10 +854,10 @@ def mixed(
     i3: Intersection[Not[Any], Unknown],
     i4: Intersection[Not[Any], Not[Unknown]],
 ) -> None:
-    reveal_type(i1)  # revealed: Any & Unknown
-    reveal_type(i2)  # revealed: Any & Unknown
-    reveal_type(i3)  # revealed: Any & Unknown
-    reveal_type(i4)  # revealed: Any & Unknown
+    reveal_type(i1)  # revealed: Any
+    reveal_type(i2)  # revealed: Any
+    reveal_type(i3)  # revealed: Any
+    reveal_type(i4)  # revealed: Any
 ```
 
 ## Invalid

crates/red_knot_python_semantic/resources/mdtest/metaclass.md

@@ -216,6 +216,11 @@ reveal_type(A.__class__)  # revealed: type[Unknown]
 
 ## PEP 695 generic
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 class M(type): ...
 class A[T: str](metaclass=M): ...

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

@@ -0,0 +1,53 @@
+# Narrowing with assert statements
+
+## `assert` a value `is None` or `is not None`
+
+```py
+def _(x: str | None, y: str | None):
+    assert x is not None
+    reveal_type(x)  # revealed: str
+    assert y is None
+    reveal_type(y)  # revealed: None
+```
+
+## `assert` a value is truthy or falsy
+
+```py
+def _(x: bool, y: bool):
+    assert x
+    reveal_type(x)  # revealed: Literal[True]
+    assert not y
+    reveal_type(y)  # revealed: Literal[False]
+```
+
+## `assert` with `is` and `==` for literals
+
+```py
+from typing import Literal
+
+def _(x: Literal[1, 2, 3], y: Literal[1, 2, 3]):
+    assert x is 2
+    reveal_type(x)  # revealed: Literal[2]
+    assert y == 2
+    reveal_type(y)  # revealed: Literal[1, 2, 3]
+```
+
+## `assert` with `isinstance`
+
+```py
+def _(x: int | str):
+    assert isinstance(x, int)
+    reveal_type(x)  # revealed: int
+```
+
+## `assert` a value `in` a tuple
+
+```py
+from typing import Literal
+
+def _(x: Literal[1, 2, 3], y: Literal[1, 2, 3]):
+    assert x in (1, 2)
+    reveal_type(x)  # revealed: Literal[1, 2]
+    assert y not in (1, 2)
+    reveal_type(y)  # revealed: Literal[3]
+```

crates/red_knot_python_semantic/resources/mdtest/narrow/conditionals/boolean.md

@@ -223,3 +223,15 @@ def _(x: str | None, y: str | None):
     if y is not x:
         reveal_type(y)  # revealed: str | None
 ```
+
+## Assignment expressions
+
+```py
+def f() -> bool:
+    return True
+
+if x := f():
+    reveal_type(x)  # revealed: Literal[True]
+else:
+    reveal_type(x)  # revealed: Literal[False]
+```

crates/red_knot_python_semantic/resources/mdtest/narrow/conditionals/elif_else.md

@@ -47,3 +47,16 @@ def _(flag1: bool, flag2: bool):
         # TODO should be Never
         reveal_type(x)  # revealed: Literal[1, 2]
 ```
+
+## Assignment expressions
+
+```py
+def f() -> int | str | None: ...
+
+if isinstance(x := f(), int):
+    reveal_type(x)  # revealed: int
+elif isinstance(x, str):
+    reveal_type(x)  # revealed: str & ~int
+else:
+    reveal_type(x)  # revealed: None
+```

crates/red_knot_python_semantic/resources/mdtest/narrow/conditionals/in.md

@@ -78,3 +78,17 @@ def _(x: Literal[1, "a", "b", "c", "d"]):
     else:
         reveal_type(x)  # revealed: Literal[1, "d"]
 ```
+
+## Assignment expressions
+
+```py
+from typing import Literal
+
+def f() -> Literal[1, 2, 3]:
+    return 1
+
+if (x := f()) in (1,):
+    reveal_type(x)  # revealed: Literal[1]
+else:
+    reveal_type(x)  # revealed: Literal[2, 3]
+```

crates/red_knot_python_semantic/resources/mdtest/narrow/conditionals/is.md

@@ -100,3 +100,16 @@ def _(flag: bool):
     else:
         reveal_type(x)  # revealed: Literal[42]
 ```
+
+## Assignment expressions
+
+```py
+from typing import Literal
+
+def f() -> Literal[1, 2] | None: ...
+
+if (x := f()) is None:
+    reveal_type(x)  # revealed: None
+else:
+    reveal_type(x)  # revealed: Literal[1, 2]
+```

crates/red_knot_python_semantic/resources/mdtest/narrow/conditionals/is_not.md

@@ -82,3 +82,14 @@ def _(x_flag: bool, y_flag: bool):
         reveal_type(x)  # revealed: bool
         reveal_type(y)  # revealed: bool
 ```
+
+## Assignment expressions
+
+```py
+def f() -> int | str | None: ...
+
+if (x := f()) is not None:
+    reveal_type(x)  # revealed: int | str
+else:
+    reveal_type(x)  # revealed: None
+```

crates/red_knot_python_semantic/resources/mdtest/narrow/conditionals/not_eq.md

@@ -89,3 +89,18 @@ def _(flag1: bool, flag2: bool, a: int):
     else:
         reveal_type(x)  # revealed: Literal[1, 2]
 ```
+
+## Assignment expressions
+
+```py
+from typing import Literal
+
+def f() -> Literal[1, 2, 3]:
+    return 1
+
+if (x := f()) != 1:
+    reveal_type(x)  # revealed: Literal[2, 3]
+else:
+    # TODO should be Literal[1]
+    reveal_type(x)  # revealed: Literal[1, 2, 3]
+```

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

@@ -1,5 +1,10 @@
 # Narrowing for `match` statements
 
+```toml
+[environment]
+python-version = "3.10"
+```
+
 ## Single `match` pattern
 
 ```py
@@ -34,8 +39,7 @@ match x:
     case A():
         reveal_type(x)  # revealed: A
     case B():
-        # TODO could be `B & ~A`
-        reveal_type(x)  # revealed: B
+        reveal_type(x)  # revealed: B & ~A
 
 reveal_type(x)  # revealed: object
 ```
@@ -83,7 +87,7 @@ match x:
     case 6.0:
         reveal_type(x)  # revealed: float
     case 1j:
-        reveal_type(x)  # revealed: complex
+        reveal_type(x)  # revealed: complex & ~float
     case b"foo":
         reveal_type(x)  # revealed: Literal[b"foo"]
 
@@ -129,11 +133,11 @@ match x:
     case "foo" | 42 | None:
         reveal_type(x)  # revealed: Literal["foo", 42] | None
     case "foo" | tuple():
-        reveal_type(x)  # revealed: Literal["foo"] | tuple
+        reveal_type(x)  # revealed: tuple
     case True | False:
         reveal_type(x)  # revealed: bool
     case 3.14 | 2.718 | 1.414:
-        reveal_type(x)  # revealed: float
+        reveal_type(x)  # revealed: float & ~tuple
 
 reveal_type(x)  # revealed: object
 ```
@@ -160,3 +164,49 @@ match x:
 
 reveal_type(x)  # revealed: object
 ```
+
+## Narrowing due to guard
+
+```py
+def get_object() -> object:
+    return object()
+
+x = get_object()
+
+reveal_type(x)  # revealed: object
+
+match x:
+    case str() | float() if type(x) is str:
+        reveal_type(x)  #  revealed: str
+    case "foo" | 42 | None if isinstance(x, int):
+        reveal_type(x)  #  revealed: Literal[42]
+    case False if x:
+        reveal_type(x)  #  revealed: Never
+    case "foo" if x := "bar":
+        reveal_type(x)  # revealed: Literal["bar"]
+
+reveal_type(x)  # revealed: object
+```
+
+## Guard and reveal_type in guard
+
+```py
+def get_object() -> object:
+    return object()
+
+x = get_object()
+
+reveal_type(x)  # revealed: object
+
+match x:
+    case str() | float() if type(x) is str and reveal_type(x):  # revealed: str
+        pass
+    case "foo" | 42 | None if isinstance(x, int) and reveal_type(x):  #  revealed: Literal[42]
+        pass
+    case False if x and reveal_type(x):  #  revealed: Never
+        pass
+    case "foo" if (x := "bar") and reveal_type(x):  #  revealed: Literal["bar"]
+        pass
+
+reveal_type(x)  # revealed: object
+```

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

@@ -246,7 +246,7 @@ class MetaTruthy(type):
 
 class MetaDeferred(type):
     def __bool__(self) -> MetaAmbiguous:
-        return MetaAmbiguous()
+        raise NotImplementedError
 
 class AmbiguousClass(metaclass=MetaAmbiguous): ...
 class FalsyClass(metaclass=MetaFalsy): ...

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

@@ -111,6 +111,11 @@ def _(x: A | B):
 
 ## Narrowing for generic classes
 
+```toml
+[environment]
+python-version = "3.13"
+```
+
 Note that `type` returns the runtime class of an object, which does _not_ include specializations in
 the case of a generic class. (The typevars are erased.) That means we cannot narrow the type to the
 specialization that we compare with; we must narrow to an unknown specialization of the generic
@@ -139,3 +144,13 @@ def _(x: Base):
         # express a constraint like `Base & ~ProperSubtypeOf[Base]`.
         reveal_type(x)  # revealed: Base
 ```
+
+## Assignment expressions
+
+```py
+def _(x: object):
+    if (y := type(x)) is bool:
+        reveal_type(y)  # revealed: Literal[bool]
+    if (type(y := x)) is bool:
+        reveal_type(y)  # revealed: bool
+```

crates/red_knot_python_semantic/resources/mdtest/overloads.md

@@ -0,0 +1,638 @@
+# Overloads
+
+Reference: <https://typing.python.org/en/latest/spec/overload.html>
+
+## `typing.overload`
+
+The definition of `typing.overload` in typeshed is an identity function.
+
+```py
+from typing import overload
+
+def foo(x: int) -> int:
+    return x
+
+reveal_type(foo)  # revealed: def foo(x: int) -> int
+bar = overload(foo)
+reveal_type(bar)  # revealed: def foo(x: int) -> int
+```
+
+## Functions
+
+```py
+from typing import overload
+
+@overload
+def add() -> None: ...
+@overload
+def add(x: int) -> int: ...
+@overload
+def add(x: int, y: int) -> int: ...
+def add(x: int | None = None, y: int | None = None) -> int | None:
+    return (x or 0) + (y or 0)
+
+reveal_type(add)  # revealed: Overload[() -> None, (x: int) -> int, (x: int, y: int) -> int]
+reveal_type(add())  # revealed: None
+reveal_type(add(1))  # revealed: int
+reveal_type(add(1, 2))  # revealed: int
+```
+
+## Overriding
+
+These scenarios are to verify that the overloaded and non-overloaded definitions are correctly
+overridden by each other.
+
+An overloaded function is overriding another overloaded function:
+
+```py
+from typing import overload
+
+@overload
+def foo() -> None: ...
+@overload
+def foo(x: int) -> int: ...
+def foo(x: int | None = None) -> int | None:
+    return x
+
+reveal_type(foo)  # revealed: Overload[() -> None, (x: int) -> int]
+reveal_type(foo())  # revealed: None
+reveal_type(foo(1))  # revealed: int
+
+@overload
+def foo() -> None: ...
+@overload
+def foo(x: str) -> str: ...
+def foo(x: str | None = None) -> str | None:
+    return x
+
+reveal_type(foo)  # revealed: Overload[() -> None, (x: str) -> str]
+reveal_type(foo())  # revealed: None
+reveal_type(foo(""))  # revealed: str
+```
+
+A non-overloaded function is overriding an overloaded function:
+
+```py
+def foo(x: int) -> int:
+    return x
+
+reveal_type(foo)  # revealed: def foo(x: int) -> int
+```
+
+An overloaded function is overriding a non-overloaded function:
+
+```py
+reveal_type(foo)  # revealed: def foo(x: int) -> int
+
+@overload
+def foo() -> None: ...
+@overload
+def foo(x: bytes) -> bytes: ...
+def foo(x: bytes | None = None) -> bytes | None:
+    return x
+
+reveal_type(foo)  # revealed: Overload[() -> None, (x: bytes) -> bytes]
+reveal_type(foo())  # revealed: None
+reveal_type(foo(b""))  # revealed: bytes
+```
+
+## Methods
+
+```py
+from typing import overload
+
+class Foo1:
+    @overload
+    def method(self) -> None: ...
+    @overload
+    def method(self, x: int) -> int: ...
+    def method(self, x: int | None = None) -> int | None:
+        return x
+
+foo1 = Foo1()
+reveal_type(foo1.method)  # revealed: Overload[() -> None, (x: int) -> int]
+reveal_type(foo1.method())  # revealed: None
+reveal_type(foo1.method(1))  # revealed: int
+
+class Foo2:
+    @overload
+    def method(self) -> None: ...
+    @overload
+    def method(self, x: str) -> str: ...
+    def method(self, x: str | None = None) -> str | None:
+        return x
+
+foo2 = Foo2()
+reveal_type(foo2.method)  # revealed: Overload[() -> None, (x: str) -> str]
+reveal_type(foo2.method())  # revealed: None
+reveal_type(foo2.method(""))  # revealed: str
+```
+
+## Constructor
+
+```py
+from typing import overload
+
+class Foo:
+    @overload
+    def __init__(self) -> None: ...
+    @overload
+    def __init__(self, x: int) -> None: ...
+    def __init__(self, x: int | None = None) -> None:
+        self.x = x
+
+foo = Foo()
+reveal_type(foo)  # revealed: Foo
+reveal_type(foo.x)  # revealed: Unknown | int | None
+
+foo1 = Foo(1)
+reveal_type(foo1)  # revealed: Foo
+reveal_type(foo1.x)  # revealed: Unknown | int | None
+```
+
+## Version specific
+
+Function definitions can vary between multiple Python versions.
+
+### Overload and non-overload (3.9)
+
+Here, the same function is overloaded in one version and not in another.
+
+```toml
+[environment]
+python-version = "3.9"
+```
+
+```py
+import sys
+from typing import overload
+
+if sys.version_info < (3, 10):
+    def func(x: int) -> int:
+        return x
+
+elif sys.version_info <= (3, 12):
+    @overload
+    def func() -> None: ...
+    @overload
+    def func(x: int) -> int: ...
+    def func(x: int | None = None) -> int | None:
+        return x
+
+reveal_type(func)  # revealed: def func(x: int) -> int
+func()  # error: [missing-argument]
+```
+
+### Overload and non-overload (3.10)
+
+```toml
+[environment]
+python-version = "3.10"
+```
+
+```py
+import sys
+from typing import overload
+
+if sys.version_info < (3, 10):
+    def func(x: int) -> int:
+        return x
+
+elif sys.version_info <= (3, 12):
+    @overload
+    def func() -> None: ...
+    @overload
+    def func(x: int) -> int: ...
+    def func(x: int | None = None) -> int | None:
+        return x
+
+reveal_type(func)  # revealed: Overload[() -> None, (x: int) -> int]
+reveal_type(func())  # revealed: None
+reveal_type(func(1))  # revealed: int
+```
+
+### Some overloads are version specific (3.9)
+
+```toml
+[environment]
+python-version = "3.9"
+```
+
+`overloaded.pyi`:
+
+```pyi
+import sys
+from typing import overload
+
+if sys.version_info >= (3, 10):
+    @overload
+    def func() -> None: ...
+
+@overload
+def func(x: int) -> int: ...
+@overload
+def func(x: str) -> str: ...
+```
+
+`main.py`:
+
+```py
+from overloaded import func
+
+reveal_type(func)  # revealed: Overload[(x: int) -> int, (x: str) -> str]
+func()  # error: [no-matching-overload]
+reveal_type(func(1))  # revealed: int
+reveal_type(func(""))  # revealed: str
+```
+
+### Some overloads are version specific (3.10)
+
+```toml
+[environment]
+python-version = "3.10"
+```
+
+`overloaded.pyi`:
+
+```pyi
+import sys
+from typing import overload
+
+@overload
+def func() -> None: ...
+
+if sys.version_info >= (3, 10):
+    @overload
+    def func(x: int) -> int: ...
+
+@overload
+def func(x: str) -> str: ...
+```
+
+`main.py`:
+
+```py
+from overloaded import func
+
+reveal_type(func)  # revealed: Overload[() -> None, (x: int) -> int, (x: str) -> str]
+reveal_type(func())  # revealed: None
+reveal_type(func(1))  # revealed: int
+reveal_type(func(""))  # revealed: str
+```
+
+## Generic
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+For an overloaded generic function, it's not necessary for all overloads to be generic.
+
+```py
+from typing import overload
+
+@overload
+def func() -> None: ...
+@overload
+def func[T](x: T) -> T: ...
+def func[T](x: T | None = None) -> T | None:
+    return x
+
+reveal_type(func)  # revealed: Overload[() -> None, (x: T) -> T]
+reveal_type(func())  # revealed: None
+reveal_type(func(1))  # revealed: Literal[1]
+reveal_type(func(""))  # revealed: Literal[""]
+```
+
+## Invalid
+
+### At least two overloads
+
+At least two `@overload`-decorated definitions must be present.
+
+```py
+from typing import overload
+
+# TODO: error
+@overload
+def func(x: int) -> int: ...
+def func(x: int | str) -> int | str:
+    return x
+```
+
+### Overload without an implementation
+
+#### Regular modules
+
+In regular modules, a series of `@overload`-decorated definitions must be followed by exactly one
+non-`@overload`-decorated definition (for the same function/method).
+
+```py
+from typing import overload
+
+# TODO: error because implementation does not exists
+@overload
+def func(x: int) -> int: ...
+@overload
+def func(x: str) -> str: ...
+
+class Foo:
+    # TODO: error because implementation does not exists
+    @overload
+    def method(self, x: int) -> int: ...
+    @overload
+    def method(self, x: str) -> str: ...
+```
+
+#### Stub files
+
+Overload definitions within stub files are exempt from this check.
+
+```pyi
+from typing import overload
+
+@overload
+def func(x: int) -> int: ...
+@overload
+def func(x: str) -> str: ...
+```
+
+#### Protocols
+
+Overload definitions within protocols are exempt from this check.
+
+```py
+from typing import Protocol, overload
+
+class Foo(Protocol):
+    @overload
+    def f(self, x: int) -> int: ...
+    @overload
+    def f(self, x: str) -> str: ...
+```
+
+#### Abstract methods
+
+Overload definitions within abstract base classes are exempt from this check.
+
+```py
+from abc import ABC, abstractmethod
+from typing import overload
+
+class AbstractFoo(ABC):
+    @overload
+    @abstractmethod
+    def f(self, x: int) -> int: ...
+    @overload
+    @abstractmethod
+    def f(self, x: str) -> str: ...
+```
+
+Using the `@abstractmethod` decorator requires that the class's metaclass is `ABCMeta` or is derived
+from it.
+
+```py
+class Foo:
+    # TODO: Error because implementation does not exists
+    @overload
+    @abstractmethod
+    def f(self, x: int) -> int: ...
+    @overload
+    @abstractmethod
+    def f(self, x: str) -> str: ...
+```
+
+And, the `@abstractmethod` decorator must be present on all the `@overload`-ed methods.
+
+```py
+class PartialFoo1(ABC):
+    @overload
+    @abstractmethod
+    def f(self, x: int) -> int: ...
+    @overload
+    def f(self, x: str) -> str: ...
+
+class PartialFoo(ABC):
+    @overload
+    def f(self, x: int) -> int: ...
+    @overload
+    @abstractmethod
+    def f(self, x: str) -> str: ...
+```
+
+### Inconsistent decorators
+
+#### `@staticmethod` / `@classmethod`
+
+If one overload signature is decorated with `@staticmethod` or `@classmethod`, all overload
+signatures must be similarly decorated. The implementation, if present, must also have a consistent
+decorator.
+
+```py
+from __future__ import annotations
+
+from typing import overload
+
+class CheckStaticMethod:
+    # TODO: error because `@staticmethod` does not exist on all overloads
+    @overload
+    def method1(x: int) -> int: ...
+    @overload
+    def method1(x: str) -> str: ...
+    @staticmethod
+    def method1(x: int | str) -> int | str:
+        return x
+    # TODO: error because `@staticmethod` does not exist on all overloads
+    @overload
+    def method2(x: int) -> int: ...
+    @overload
+    @staticmethod
+    def method2(x: str) -> str: ...
+    @staticmethod
+    def method2(x: int | str) -> int | str:
+        return x
+    # TODO: error because `@staticmethod` does not exist on the implementation
+    @overload
+    @staticmethod
+    def method3(x: int) -> int: ...
+    @overload
+    @staticmethod
+    def method3(x: str) -> str: ...
+    def method3(x: int | str) -> int | str:
+        return x
+
+    @overload
+    @staticmethod
+    def method4(x: int) -> int: ...
+    @overload
+    @staticmethod
+    def method4(x: str) -> str: ...
+    @staticmethod
+    def method4(x: int | str) -> int | str:
+        return x
+
+class CheckClassMethod:
+    def __init__(self, x: int) -> None:
+        self.x = x
+    # TODO: error because `@classmethod` does not exist on all overloads
+    @overload
+    @classmethod
+    def try_from1(cls, x: int) -> CheckClassMethod: ...
+    @overload
+    def try_from1(cls, x: str) -> None: ...
+    @classmethod
+    def try_from1(cls, x: int | str) -> CheckClassMethod | None:
+        if isinstance(x, int):
+            return cls(x)
+        return None
+    # TODO: error because `@classmethod` does not exist on all overloads
+    @overload
+    def try_from2(cls, x: int) -> CheckClassMethod: ...
+    @overload
+    @classmethod
+    def try_from2(cls, x: str) -> None: ...
+    @classmethod
+    def try_from2(cls, x: int | str) -> CheckClassMethod | None:
+        if isinstance(x, int):
+            return cls(x)
+        return None
+    # TODO: error because `@classmethod` does not exist on the implementation
+    @overload
+    @classmethod
+    def try_from3(cls, x: int) -> CheckClassMethod: ...
+    @overload
+    @classmethod
+    def try_from3(cls, x: str) -> None: ...
+    def try_from3(cls, x: int | str) -> CheckClassMethod | None:
+        if isinstance(x, int):
+            return cls(x)
+        return None
+
+    @overload
+    @classmethod
+    def try_from4(cls, x: int) -> CheckClassMethod: ...
+    @overload
+    @classmethod
+    def try_from4(cls, x: str) -> None: ...
+    @classmethod
+    def try_from4(cls, x: int | str) -> CheckClassMethod | None:
+        if isinstance(x, int):
+            return cls(x)
+        return None
+```
+
+#### `@final` / `@override`
+
+If a `@final` or `@override` decorator is supplied for a function with overloads, the decorator
+should be applied only to the overload implementation if it is present.
+
+```py
+from typing_extensions import final, overload, override
+
+class Foo:
+    @overload
+    def method1(self, x: int) -> int: ...
+    @overload
+    def method1(self, x: str) -> str: ...
+    @final
+    def method1(self, x: int | str) -> int | str:
+        return x
+    # TODO: error because `@final` is not on the implementation
+    @overload
+    @final
+    def method2(self, x: int) -> int: ...
+    @overload
+    def method2(self, x: str) -> str: ...
+    def method2(self, x: int | str) -> int | str:
+        return x
+    # TODO: error because `@final` is not on the implementation
+    @overload
+    def method3(self, x: int) -> int: ...
+    @overload
+    @final
+    def method3(self, x: str) -> str: ...
+    def method3(self, x: int | str) -> int | str:
+        return x
+
+class Base:
+    @overload
+    def method(self, x: int) -> int: ...
+    @overload
+    def method(self, x: str) -> str: ...
+    def method(self, x: int | str) -> int | str:
+        return x
+
+class Sub1(Base):
+    @overload
+    def method(self, x: int) -> int: ...
+    @overload
+    def method(self, x: str) -> str: ...
+    @override
+    def method(self, x: int | str) -> int | str:
+        return x
+
+class Sub2(Base):
+    # TODO: error because `@override` is not on the implementation
+    @overload
+    def method(self, x: int) -> int: ...
+    @overload
+    @override
+    def method(self, x: str) -> str: ...
+    def method(self, x: int | str) -> int | str:
+        return x
+
+class Sub3(Base):
+    # TODO: error because `@override` is not on the implementation
+    @overload
+    @override
+    def method(self, x: int) -> int: ...
+    @overload
+    def method(self, x: str) -> str: ...
+    def method(self, x: int | str) -> int | str:
+        return x
+```
+
+#### `@final` / `@override` in stub files
+
+If an overload implementation isn’t present (for example, in a stub file), the `@final` or
+`@override` decorator should be applied only to the first overload.
+
+```pyi
+from typing_extensions import final, overload, override
+
+class Foo:
+    @overload
+    @final
+    def method1(self, x: int) -> int: ...
+    @overload
+    def method1(self, x: str) -> str: ...
+
+    # TODO: error because `@final` is not on the first overload
+    @overload
+    def method2(self, x: int) -> int: ...
+    @final
+    @overload
+    def method2(self, x: str) -> str: ...
+
+class Base:
+    @overload
+    def method(self, x: int) -> int: ...
+    @overload
+    def method(self, x: str) -> str: ...
+
+class Sub1(Base):
+    @overload
+    @override
+    def method(self, x: int) -> int: ...
+    @overload
+    def method(self, x: str) -> str: ...
+
+class Sub2(Base):
+    # TODO: error because `@override` is not on the first overload
+    @overload
+    def method(self, x: int) -> int: ...
+    @overload
+    @override
+    def method(self, x: str) -> str: ...
+```

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

@@ -14,7 +14,7 @@ reveal_type(__package__)  # revealed: str | None
 reveal_type(__doc__)  # revealed: str | None
 reveal_type(__spec__)  # revealed: ModuleSpec | None
 
-reveal_type(__path__)  # revealed: @Todo(generics)
+reveal_type(__path__)  # revealed: @Todo(specialized non-generic class)
 
 class X:
     reveal_type(__name__)  # revealed: str
@@ -59,7 +59,7 @@ reveal_type(typing.__eq__)  # revealed: bound method ModuleType.__eq__(value: ob
 reveal_type(typing.__class__)  # revealed: Literal[ModuleType]
 
 # TODO: needs support generics; should be `dict[str, Any]`:
-reveal_type(typing.__dict__)  # revealed: @Todo(generics)
+reveal_type(typing.__dict__)  # revealed: @Todo(specialized non-generic class)
 ```
 
 Typeshed includes a fake `__getattr__` method in the stub for `types.ModuleType` to help out with
@@ -92,8 +92,8 @@ import foo
 from foo import __dict__ as foo_dict
 
 # TODO: needs support generics; should be `dict[str, Any]` for both of these:
-reveal_type(foo.__dict__)  # revealed: @Todo(generics)
-reveal_type(foo_dict)  # revealed: @Todo(generics)
+reveal_type(foo.__dict__)  # revealed: @Todo(specialized non-generic class)
+reveal_type(foo_dict)  # revealed: @Todo(specialized non-generic class)
 ```
 
 ## Conditionally global or `ModuleType` attribute

crates/red_knot_python_semantic/resources/mdtest/snapshots/version_related_syntax_errors.md_-_Version-related_syntax_error_diagnostics_-_`match`_statement_-_Before_3.10.snap

@@ -0,0 +1,32 @@
+---
+source: crates/red_knot_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: version_related_syntax_errors.md - Version-related syntax error diagnostics - `match` statement - Before 3.10
+mdtest path: crates/red_knot_python_semantic/resources/mdtest/diagnostics/version_related_syntax_errors.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+1 | match 2:  # error: 1 [invalid-syntax] "Cannot use `match` statement on Python 3.9 (syntax was added in Python 3.10)"
+2 |     case 1:
+3 |         print("it's one")
+```
+
+# Diagnostics
+
+```
+error: invalid-syntax
+ --> /src/mdtest_snippet.py:1:1
+  |
+1 | match 2:  # error: 1 [invalid-syntax] "Cannot use `match` statement on Python 3.9 (syntax was added in Python 3.10)"
+  | ^^^^^ Cannot use `match` statement on Python 3.9 (syntax was added in Python 3.10)
+2 |     case 1:
+3 |         print("it's one")
+  |
+
+```

crates/red_knot_python_semantic/resources/mdtest/statically_known_branches.md

@@ -996,6 +996,11 @@ reveal_type(x)  # revealed: Literal[1]
 
 ## `match` statements
 
+```toml
+[environment]
+python-version = "3.10"
+```
+
 ### Single-valued types, always true
 
 ```py
@@ -1118,6 +1123,7 @@ def _(s: str):
 ```toml
 [environment]
 python-platform = "darwin"
+python-version = "3.10"
 ```
 
 ```py

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

@@ -2,6 +2,11 @@
 
 ## Cyclical class definition
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 In type stubs, classes can reference themselves in their base class definitions. For example, in
 `typeshed`, we have `class str(Sequence[str]): ...`.
 

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

@@ -24,8 +24,7 @@ reveal_type(y)  # revealed: Unknown
 
 def _(n: int):
     a = b"abcde"[n]
-    # TODO: Support overloads... Should be `bytes`
-    reveal_type(a)  # revealed: @Todo(return type of overloaded function)
+    reveal_type(a)  # revealed: int
 ```
 
 ## Slices
@@ -43,11 +42,9 @@ b[::0]  # error: [zero-stepsize-in-slice]
 
 def _(m: int, n: int):
     byte_slice1 = b[m:n]
-    # TODO: Support overloads... Should be `bytes`
-    reveal_type(byte_slice1)  # revealed: @Todo(return type of overloaded function)
+    reveal_type(byte_slice1)  # revealed: bytes
 
 def _(s: bytes) -> bytes:
     byte_slice2 = s[0:5]
-    # TODO: Support overloads... Should be `bytes`
-    return reveal_type(byte_slice2)  # revealed: @Todo(return type of overloaded function)
+    return reveal_type(byte_slice2)  # revealed: bytes
 ```

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

@@ -12,13 +12,13 @@ x = [1, 2, 3]
 reveal_type(x)  # revealed: list
 
 # TODO reveal int
-reveal_type(x[0])  # revealed: @Todo(return type of overloaded function)
+reveal_type(x[0])  # revealed: Unknown
 
 # TODO reveal list
-reveal_type(x[0:1])  # revealed: @Todo(return type of overloaded function)
+reveal_type(x[0:1])  # revealed: @Todo(specialized non-generic class)
 
-# TODO error
-reveal_type(x["a"])  # revealed: @Todo(return type of overloaded function)
+# error: [call-non-callable]
+reveal_type(x["a"])  # revealed: Unknown
 ```
 
 ## Assignments within list assignment
@@ -29,9 +29,11 @@ In assignment, we might also have a named assignment. This should also get type
 x = [1, 2, 3]
 x[0 if (y := 2) else 1] = 5
 
-# TODO error? (indeterminite index type)
+# TODO: better error than "method `__getitem__` not callable on type `list`"
+# error: [call-non-callable]
 x["a" if (y := 2) else 1] = 6
 
-# TODO error (can't index via string)
+# TODO: better error than "method `__getitem__` not callable on type `list`"
+# error: [call-non-callable]
 x["a" if (y := 2) else "b"] = 6
 ```

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

@@ -21,8 +21,7 @@ reveal_type(b)  # revealed: Unknown
 
 def _(n: int):
     a = "abcde"[n]
-    # TODO: Support overloads... Should be `str`
-    reveal_type(a)  # revealed: @Todo(return type of overloaded function)
+    reveal_type(a)  # revealed: LiteralString
 ```
 
 ## Slices
@@ -75,12 +74,10 @@ def _(m: int, n: int, s2: str):
     s[::0]  # error: [zero-stepsize-in-slice]
 
     substring1 = s[m:n]
-    # TODO: Support overloads... Should be `LiteralString`
-    reveal_type(substring1)  # revealed: @Todo(return type of overloaded function)
+    reveal_type(substring1)  # revealed: LiteralString
 
     substring2 = s2[0:5]
-    # TODO: Support overloads... Should be `str`
-    reveal_type(substring2)  # revealed: @Todo(return type of overloaded function)
+    reveal_type(substring2)  # revealed: str
 ```
 
 ## Unsupported slice types

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

@@ -69,8 +69,8 @@ def _(m: int, n: int):
     t[::0]  # error: [zero-stepsize-in-slice]
 
     tuple_slice = t[m:n]
-    # TODO: Support overloads... Should be `tuple[Literal[1, 'a', b"b"] | None, ...]`
-    reveal_type(tuple_slice)  # revealed: @Todo(return type of overloaded function)
+    # TODO: Should be `tuple[Literal[1, 'a', b"b"] | None, ...]`
+    reveal_type(tuple_slice)  # revealed: @Todo(full tuple[...] support)
 ```
 
 ## Inheritance
@@ -117,6 +117,7 @@ from typing import Tuple
 
 class C(Tuple): ...
 
-# revealed: tuple[Literal[C], Literal[tuple], Literal[Sequence], Literal[Reversible], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(protocol), Literal[object]]
+# TODO: generic protocols
+# revealed: tuple[Literal[C], Literal[tuple], Literal[Sequence], Literal[Reversible], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(`Protocol[]` subscript), @Todo(`Generic[]` subscript), Literal[object]]
 reveal_type(C.__mro__)
 ```

crates/red_knot_python_semantic/resources/mdtest/type_api.md

@@ -23,16 +23,30 @@ def negate(n1: Not[int], n2: Not[Not[int]], n3: Not[Not[Not[int]]]) -> None:
     reveal_type(n2)  # revealed: int
     reveal_type(n3)  # revealed: ~int
 
-def static_truthiness(not_one: Not[Literal[1]]) -> None:
-    static_assert(not_one != 1)
-    static_assert(not (not_one == 1))
-
 # error: "Special form `knot_extensions.Not` expected exactly one type parameter"
 n: Not[int, str]
+
+def static_truthiness(not_one: Not[Literal[1]]) -> None:
+    # TODO: `bool` is not incorrect, but these would ideally be `Literal[True]` and `Literal[False]`
+    # respectively, since all possible runtime objects that are created by the literal syntax `1`
+    # are members of the type `Literal[1]`
+    reveal_type(not_one is not 1)  # revealed: bool
+    reveal_type(not_one is 1)  # revealed: bool
+
+    # But these are both `bool`, rather than `Literal[True]` or `Literal[False]`
+    # as there are many runtime objects that inhabit the type `~Literal[1]`
+    # but still compare equal to `1`. Two examples are `1.0` and `True`.
+    reveal_type(not_one != 1)  # revealed: bool
+    reveal_type(not_one == 1)  # revealed: bool
 ```
 
 ### Intersection
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from knot_extensions import Intersection, Not, is_subtype_of, static_assert
 from typing_extensions import Literal, Never
@@ -170,13 +184,11 @@ Static assertions can be used to enforce narrowing constraints:
 ```py
 from knot_extensions import static_assert
 
-def f(x: int) -> None:
-    if x != 0:
-        static_assert(x != 0)
+def f(x: int | None) -> None:
+    if x is not None:
+        static_assert(x is not None)
     else:
-        # `int` can be subclassed, so we cannot assert that `x == 0` here:
-        # error: "Static assertion error: argument of type `bool` has an ambiguous static truthiness"
-        static_assert(x == 0)
+        static_assert(x is None)
 ```
 
 ### Truthy expressions

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_assignable_to.md

@@ -504,4 +504,53 @@ c: Callable[[Any], str] = f
 c: Callable[[Any], str] = g
 ```
 
+### Method types
+
+```py
+from typing import Any, Callable
+
+class A:
+    def f(self, x: Any) -> str:
+        return ""
+
+    def g(self, x: Any) -> int:
+        return 1
+
+c: Callable[[Any], str] = A().f
+
+# error: [invalid-assignment] "Object of type `bound method A.g(x: Any) -> int` is not assignable to `(Any, /) -> str`"
+c: Callable[[Any], str] = A().g
+```
+
+### Overloads
+
+`overloaded.pyi`:
+
+```pyi
+from typing import Any, overload
+
+@overload
+def overloaded() -> None: ...
+@overload
+def overloaded(a: str) -> str: ...
+@overload
+def overloaded(a: str, b: Any) -> str: ...
+```
+
+```py
+from overloaded import overloaded
+from typing import Any, Callable
+
+c: Callable[[], None] = overloaded
+c: Callable[[str], str] = overloaded
+c: Callable[[str, Any], Any] = overloaded
+c: Callable[..., str] = overloaded
+
+# error: [invalid-assignment]
+c: Callable[..., int] = overloaded
+
+# error: [invalid-assignment]
+c: Callable[[int], str] = overloaded
+```
+
 [typing documentation]: https://typing.python.org/en/latest/spec/concepts.html#the-assignable-to-or-consistent-subtyping-relation

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_disjoint_from.md

@@ -246,6 +246,11 @@ static_assert(is_disjoint_from(Intersection[LiteralString, Not[AlwaysFalsy]], No
 
 ### Class, module and function literals
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from types import ModuleType, FunctionType
 from knot_extensions import TypeOf, is_disjoint_from, static_assert

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_equivalent_to.md

@@ -254,4 +254,8 @@ from knot_extensions import is_equivalent_to, static_assert
 static_assert(is_equivalent_to(int | Callable[[int | str], None], Callable[[str | int], None] | int))
 ```
 
+### Overloads
+
+TODO
+
 [the equivalence relation]: https://typing.python.org/en/latest/spec/glossary.html#term-equivalent

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_fully_static.md

@@ -99,3 +99,34 @@ static_assert(not is_fully_static(CallableTypeOf[f13]))
 static_assert(not is_fully_static(CallableTypeOf[f14]))
 static_assert(not is_fully_static(CallableTypeOf[f15]))
 ```
+
+## Overloads
+
+`overloaded.pyi`:
+
+```pyi
+from typing import Any, overload
+
+@overload
+def gradual() -> None: ...
+@overload
+def gradual(a: Any) -> None: ...
+
+@overload
+def static() -> None: ...
+@overload
+def static(x: int) -> None: ...
+@overload
+def static(x: str) -> str: ...
+```
+
+```py
+from knot_extensions import CallableTypeOf, TypeOf, is_fully_static, static_assert
+from overloaded import gradual, static
+
+static_assert(is_fully_static(TypeOf[gradual]))
+static_assert(is_fully_static(TypeOf[static]))
+
+static_assert(not is_fully_static(CallableTypeOf[gradual]))
+static_assert(is_fully_static(CallableTypeOf[static]))
+```

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_gradual_equivalent_to.md

@@ -47,10 +47,7 @@ static_assert(is_gradual_equivalent_to(Intersection[str | int, Not[type[Any]]],
 static_assert(not is_gradual_equivalent_to(str | int, int | str | bytes))
 static_assert(not is_gradual_equivalent_to(str | int | bytes, int | str | dict))
 
-# TODO: No errors
-# error: [static-assert-error]
 static_assert(is_gradual_equivalent_to(Unknown, Unknown | Any))
-# error: [static-assert-error]
 static_assert(is_gradual_equivalent_to(Unknown, Intersection[Unknown, Any]))
 ```
 
@@ -157,4 +154,6 @@ def f6(a, /): ...
 static_assert(not is_gradual_equivalent_to(CallableTypeOf[f1], CallableTypeOf[f6]))
 ```
 
+TODO: Overloads
+
 [materializations]: https://typing.python.org/en/latest/spec/glossary.html#term-materialize

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_subtype_of.md

@@ -1,5 +1,10 @@
 # Subtype relation
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 The `is_subtype_of(S, T)` relation below checks if type `S` is a subtype of type `T`.
 
 A fully static type `S` is a subtype of another fully static type `T` iff the set of values
@@ -1148,5 +1153,187 @@ static_assert(not is_subtype_of(TypeOf[A.g], Callable[[], int]))
 static_assert(is_subtype_of(TypeOf[A.f], Callable[[A, int], int]))
 ```
 
+### Overloads
+
+#### Subtype overloaded
+
+For `B <: A`, if a callable `B` is overloaded with two or more signatures, it is a subtype of
+callable `A` if _at least one_ of the overloaded signatures in `B` is a subtype of `A`.
+
+`overloaded.pyi`:
+
+```pyi
+from typing import overload
+
+class A: ...
+class B: ...
+class C: ...
+
+@overload
+def overloaded(x: A) -> None: ...
+@overload
+def overloaded(x: B) -> None: ...
+```
+
+```py
+from knot_extensions import CallableTypeOf, is_subtype_of, static_assert
+from overloaded import A, B, C, overloaded
+
+def accepts_a(x: A) -> None: ...
+def accepts_b(x: B) -> None: ...
+def accepts_c(x: C) -> None: ...
+
+static_assert(is_subtype_of(CallableTypeOf[overloaded], CallableTypeOf[accepts_a]))
+static_assert(is_subtype_of(CallableTypeOf[overloaded], CallableTypeOf[accepts_b]))
+static_assert(not is_subtype_of(CallableTypeOf[overloaded], CallableTypeOf[accepts_c]))
+```
+
+#### Supertype overloaded
+
+For `B <: A`, if a callable `A` is overloaded with two or more signatures, callable `B` is a subtype
+of `A` if `B` is a subtype of _all_ of the signatures in `A`.
+
+`overloaded.pyi`:
+
+```pyi
+from typing import overload
+
+class Grandparent: ...
+class Parent(Grandparent): ...
+class Child(Parent): ...
+
+@overload
+def overloaded(a: Child) -> None: ...
+@overload
+def overloaded(a: Parent) -> None: ...
+@overload
+def overloaded(a: Grandparent) -> None: ...
+```
+
+```py
+from knot_extensions import CallableTypeOf, is_subtype_of, static_assert
+from overloaded import Grandparent, Parent, Child, overloaded
+
+# This is a subtype of only the first overload
+def child(a: Child) -> None: ...
+
+# This is a subtype of the first and second overload
+def parent(a: Parent) -> None: ...
+
+# This is the only function that's a subtype of all overloads
+def grandparent(a: Grandparent) -> None: ...
+
+static_assert(not is_subtype_of(CallableTypeOf[child], CallableTypeOf[overloaded]))
+static_assert(not is_subtype_of(CallableTypeOf[parent], CallableTypeOf[overloaded]))
+static_assert(is_subtype_of(CallableTypeOf[grandparent], CallableTypeOf[overloaded]))
+```
+
+#### Both overloads
+
+For `B <: A`, if both `A` and `B` is a callable that's overloaded with two or more signatures, then
+`B` is a subtype of `A` if for _every_ signature in `A`, there is _at least one_ signature in `B`
+that is a subtype of it.
+
+`overloaded.pyi`:
+
+```pyi
+from typing import overload
+
+class Grandparent: ...
+class Parent(Grandparent): ...
+class Child(Parent): ...
+class Other: ...
+
+@overload
+def pg(a: Parent) -> None: ...
+@overload
+def pg(a: Grandparent) -> None: ...
+
+@overload
+def po(a: Parent) -> None: ...
+@overload
+def po(a: Other) -> None: ...
+
+@overload
+def go(a: Grandparent) -> None: ...
+@overload
+def go(a: Other) -> None: ...
+
+@overload
+def cpg(a: Child) -> None: ...
+@overload
+def cpg(a: Parent) -> None: ...
+@overload
+def cpg(a: Grandparent) -> None: ...
+
+@overload
+def empty_go() -> Child: ...
+@overload
+def empty_go(a: Grandparent) -> None: ...
+@overload
+def empty_go(a: Other) -> Other: ...
+
+@overload
+def empty_cp() -> Parent: ...
+@overload
+def empty_cp(a: Child) -> None: ...
+@overload
+def empty_cp(a: Parent) -> None: ...
+```
+
+```py
+from knot_extensions import CallableTypeOf, is_subtype_of, static_assert
+from overloaded import pg, po, go, cpg, empty_go, empty_cp
+
+static_assert(is_subtype_of(CallableTypeOf[pg], CallableTypeOf[cpg]))
+static_assert(is_subtype_of(CallableTypeOf[cpg], CallableTypeOf[pg]))
+
+static_assert(not is_subtype_of(CallableTypeOf[po], CallableTypeOf[pg]))
+static_assert(not is_subtype_of(CallableTypeOf[pg], CallableTypeOf[po]))
+
+static_assert(is_subtype_of(CallableTypeOf[go], CallableTypeOf[pg]))
+static_assert(not is_subtype_of(CallableTypeOf[pg], CallableTypeOf[go]))
+
+# Overload 1 in `empty_go` is a subtype of overload 1 in `empty_cp`
+# Overload 2 in `empty_go` is a subtype of overload 2 in `empty_cp`
+# Overload 2 in `empty_go` is a subtype of overload 3 in `empty_cp`
+#
+# All overloads in `empty_cp` has a subtype in `empty_go`
+static_assert(is_subtype_of(CallableTypeOf[empty_go], CallableTypeOf[empty_cp]))
+
+static_assert(not is_subtype_of(CallableTypeOf[empty_cp], CallableTypeOf[empty_go]))
+```
+
+#### Order of overloads
+
+Order of overloads is irrelevant for subtyping.
+
+`overloaded.pyi`:
+
+```pyi
+from typing import overload
+
+class A: ...
+class B: ...
+
+@overload
+def overload_ab(x: A) -> None: ...
+@overload
+def overload_ab(x: B) -> None: ...
+
+@overload
+def overload_ba(x: B) -> None: ...
+@overload
+def overload_ba(x: A) -> None: ...
+```
+
+```py
+from overloaded import overload_ab, overload_ba
+from knot_extensions import CallableTypeOf, is_subtype_of, static_assert
+
+static_assert(is_subtype_of(CallableTypeOf[overload_ab], CallableTypeOf[overload_ba]))
+static_assert(is_subtype_of(CallableTypeOf[overload_ba], CallableTypeOf[overload_ab]))
+```
+
 [special case for float and complex]: https://typing.python.org/en/latest/spec/special-types.html#special-cases-for-float-and-complex
 [typing documentation]: https://typing.python.org/en/latest/spec/concepts.html#subtype-supertype-and-type-equivalence

crates/red_knot_python_semantic/resources/mdtest/union_types.md

@@ -166,3 +166,51 @@ def _(
     reveal_type(i1)  # revealed: P & Q
     reveal_type(i2)  # revealed: P & Q
 ```
+
+## Unions of literals with `AlwaysTruthy` and `AlwaysFalsy`
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+```py
+from typing import Literal
+from knot_extensions import AlwaysTruthy, AlwaysFalsy
+
+type strings = Literal["foo", ""]
+type ints = Literal[0, 1]
+type bytes = Literal[b"foo", b""]
+
+def _(
+    strings_or_truthy: strings | AlwaysTruthy,
+    truthy_or_strings: AlwaysTruthy | strings,
+    strings_or_falsy: strings | AlwaysFalsy,
+    falsy_or_strings: AlwaysFalsy | strings,
+    ints_or_truthy: ints | AlwaysTruthy,
+    truthy_or_ints: AlwaysTruthy | ints,
+    ints_or_falsy: ints | AlwaysFalsy,
+    falsy_or_ints: AlwaysFalsy | ints,
+    bytes_or_truthy: bytes | AlwaysTruthy,
+    truthy_or_bytes: AlwaysTruthy | bytes,
+    bytes_or_falsy: bytes | AlwaysFalsy,
+    falsy_or_bytes: AlwaysFalsy | bytes,
+):
+    reveal_type(strings_or_truthy)  # revealed: Literal[""] | AlwaysTruthy
+    reveal_type(truthy_or_strings)  # revealed: AlwaysTruthy | Literal[""]
+
+    reveal_type(strings_or_falsy)  # revealed: Literal["foo"] | AlwaysFalsy
+    reveal_type(falsy_or_strings)  # revealed: AlwaysFalsy | Literal["foo"]
+
+    reveal_type(ints_or_truthy)  # revealed: Literal[0] | AlwaysTruthy
+    reveal_type(truthy_or_ints)  # revealed: AlwaysTruthy | Literal[0]
+
+    reveal_type(ints_or_falsy)  # revealed: Literal[1] | AlwaysFalsy
+    reveal_type(falsy_or_ints)  # revealed: AlwaysFalsy | Literal[1]
+
+    reveal_type(bytes_or_truthy)  # revealed: Literal[b""] | AlwaysTruthy
+    reveal_type(truthy_or_bytes)  # revealed: AlwaysTruthy | Literal[b""]
+
+    reveal_type(bytes_or_falsy)  # revealed: Literal[b"foo"] | AlwaysFalsy
+    reveal_type(falsy_or_bytes)  # revealed: AlwaysFalsy | Literal[b"foo"]
+```

crates/red_knot_python_semantic/resources/mdtest/unpacking.md

@@ -708,3 +708,95 @@ with ContextManager() as (a, b, c):
     reveal_type(b)  # revealed: Unknown
     reveal_type(c)  # revealed: Unknown
 ```
+
+## Comprehension
+
+Unpacking in a comprehension.
+
+### Same types
+
+```py
+def _(arg: tuple[tuple[int, int], tuple[int, int]]):
+    # revealed: tuple[int, int]
+    [reveal_type((a, b)) for a, b in arg]
+```
+
+### Mixed types (1)
+
+```py
+def _(arg: tuple[tuple[int, int], tuple[int, str]]):
+    # revealed: tuple[int, int | str]
+    [reveal_type((a, b)) for a, b in arg]
+```
+
+### Mixed types (2)
+
+```py
+def _(arg: tuple[tuple[int, str], tuple[str, int]]):
+    # revealed: tuple[int | str, str | int]
+    [reveal_type((a, b)) for a, b in arg]
+```
+
+### Mixed types (3)
+
+```py
+def _(arg: tuple[tuple[int, int, int], tuple[int, str, bytes], tuple[int, int, str]]):
+    # revealed: tuple[int, int | str, int | bytes | str]
+    [reveal_type((a, b, c)) for a, b, c in arg]
+```
+
+### Same literal values
+
+```py
+# revealed: tuple[Literal[1, 3], Literal[2, 4]]
+[reveal_type((a, b)) for a, b in ((1, 2), (3, 4))]
+```
+
+### Mixed literal values (1)
+
+```py
+# revealed: tuple[Literal[1, "a"], Literal[2, "b"]]
+[reveal_type((a, b)) for a, b in ((1, 2), ("a", "b"))]
+```
+
+### Mixed literals values (2)
+
+```py
+# error: "Object of type `Literal[1]` is not iterable"
+# error: "Object of type `Literal[2]` is not iterable"
+# error: "Object of type `Literal[4]` is not iterable"
+# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
+# revealed: tuple[Unknown | Literal[3, 5], Unknown | Literal["a", "b"]]
+[reveal_type((a, b)) for a, b in (1, 2, (3, "a"), 4, (5, "b"), "c")]
+```
+
+### Custom iterator (1)
+
+```py
+class Iterator:
+    def __next__(self) -> tuple[int, int]:
+        return (1, 2)
+
+class Iterable:
+    def __iter__(self) -> Iterator:
+        return Iterator()
+
+# revealed: tuple[int, int]
+[reveal_type((a, b)) for a, b in Iterable()]
+```
+
+### Custom iterator (2)
+
+```py
+class Iterator:
+    def __next__(self) -> bytes:
+        return b""
+
+class Iterable:
+    def __iter__(self) -> Iterator:
+        return Iterator()
+
+def _(arg: tuple[tuple[int, str], Iterable]):
+    # revealed: tuple[int | bytes, str | bytes]
+    [reveal_type((a, b)) for a, b in arg]
+```

crates/red_knot_python_semantic/resources/primer/good.txt

@@ -0,0 +1,23 @@
+arrow
+async-utils
+bidict
+black
+dacite
+git-revise
+isort
+itsdangerous
+mypy_primer
+packaging
+paroxython
+porcupine
+psycopg
+pybind11
+pyinstrument
+pyp
+python-chess
+python-htmlgen
+rich
+scrapy
+typeshed-stats
+werkzeug
+zipp

crates/red_knot_python_semantic/src/db.rs

@@ -98,6 +98,10 @@ pub(crate) mod tests {
         fn files(&self) -> &Files {
             &self.files
         }
+
+        fn python_version(&self) -> PythonVersion {
+            Program::get(self).python_version(self)
+        }
     }
 
     impl Upcast<dyn SourceDb> for TestDb {

crates/red_knot_python_semantic/src/module_resolver/module.rs

@@ -116,6 +116,7 @@ pub enum KnownModule {
     Sys,
     #[allow(dead_code)]
     Abc, // currently only used in tests
+    Dataclasses,
     Collections,
     Inspect,
     KnotExtensions,
@@ -132,6 +133,7 @@ impl KnownModule {
             Self::TypingExtensions => "typing_extensions",
             Self::Sys => "sys",
             Self::Abc => "abc",
+            Self::Dataclasses => "dataclasses",
             Self::Collections => "collections",
             Self::Inspect => "inspect",
             Self::KnotExtensions => "knot_extensions",

crates/red_knot_python_semantic/src/semantic_index.rs

@@ -497,11 +497,10 @@ impl FusedIterator for ChildrenIter<'_> {}
 mod tests {
     use ruff_db::files::{system_path_to_file, File};
     use ruff_db::parsed::parsed_module;
-    use ruff_db::system::DbWithWritableSystem as _;
-    use ruff_python_ast as ast;
+    use ruff_python_ast::{self as ast};
     use ruff_text_size::{Ranged, TextRange};
 
-    use crate::db::tests::TestDb;
+    use crate::db::tests::{TestDb, TestDbBuilder};
     use crate::semantic_index::ast_ids::{HasScopedUseId, ScopedUseId};
     use crate::semantic_index::definition::{Definition, DefinitionKind};
     use crate::semantic_index::symbol::{
@@ -528,11 +527,15 @@ mod tests {
         file: File,
     }
 
-    fn test_case(content: impl AsRef<str>) -> TestCase {
-        let mut db = TestDb::new();
-        db.write_file("test.py", content).unwrap();
+    fn test_case(content: &str) -> TestCase {
+        const FILENAME: &str = "test.py";
 
-        let file = system_path_to_file(&db, "test.py").unwrap();
+        let db = TestDbBuilder::new()
+            .with_file(FILENAME, content)
+            .build()
+            .unwrap();
+
+        let file = system_path_to_file(&db, FILENAME).unwrap();
 
         TestCase { db, file }
     }
@@ -937,7 +940,7 @@ def f(a: str, /, b: str, c: int = 1, *args, d: int = 2, **kwargs):
             panic!("expected generator definition")
         };
         let target = comprehension.target();
-        let name = target.id().as_str();
+        let name = target.as_name_expr().unwrap().id().as_str();
 
         assert_eq!(name, "x");
         assert_eq!(target.range(), TextRange::new(23.into(), 24.into()));

crates/red_knot_python_semantic/src/semantic_index/ast_ids.rs

@@ -58,6 +58,13 @@ pub trait HasScopedUseId {
     fn scoped_use_id(&self, db: &dyn Db, scope: ScopeId) -> ScopedUseId;
 }
 
+impl HasScopedUseId for ast::Identifier {
+    fn scoped_use_id(&self, db: &dyn Db, scope: ScopeId) -> ScopedUseId {
+        let ast_ids = ast_ids(db, scope);
+        ast_ids.use_id(self)
+    }
+}
+
 impl HasScopedUseId for ast::ExprName {
     fn scoped_use_id(&self, db: &dyn Db, scope: ScopeId) -> ScopedUseId {
         let expression_ref = ExprRef::from(self);
@@ -157,7 +164,7 @@ impl AstIdsBuilder {
     }
 
     /// Adds `expr` to the use ids map and returns its id.
-    pub(super) fn record_use(&mut self, expr: &ast::Expr) -> ScopedUseId {
+    pub(super) fn record_use(&mut self, expr: impl Into<ExpressionNodeKey>) -> ScopedUseId {
         let use_id = self.uses_map.len().into();
 
         self.uses_map.insert(expr.into(), use_id);
@@ -196,4 +203,10 @@ pub(crate) mod node_key {
             Self(NodeKey::from_node(value))
         }
     }
+
+    impl From<&ast::Identifier> for ExpressionNodeKey {
+        fn from(value: &ast::Identifier) -> Self {
+            Self(NodeKey::from_node(value))
+        }
+    }
 }

crates/red_knot_python_semantic/src/semantic_index/builder.rs

@@ -18,11 +18,12 @@ use crate::semantic_index::ast_ids::node_key::ExpressionNodeKey;
 use crate::semantic_index::ast_ids::AstIdsBuilder;
 use crate::semantic_index::definition::{
     AnnotatedAssignmentDefinitionKind, AnnotatedAssignmentDefinitionNodeRef,
-    AssignmentDefinitionKind, AssignmentDefinitionNodeRef, ComprehensionDefinitionNodeRef,
-    Definition, DefinitionCategory, DefinitionKind, DefinitionNodeKey, DefinitionNodeRef,
-    Definitions, ExceptHandlerDefinitionNodeRef, ForStmtDefinitionKind, ForStmtDefinitionNodeRef,
-    ImportDefinitionNodeRef, ImportFromDefinitionNodeRef, MatchPatternDefinitionNodeRef,
-    StarImportDefinitionNodeRef, TargetKind, WithItemDefinitionKind, WithItemDefinitionNodeRef,
+    AssignmentDefinitionKind, AssignmentDefinitionNodeRef, ComprehensionDefinitionKind,
+    ComprehensionDefinitionNodeRef, Definition, DefinitionCategory, DefinitionKind,
+    DefinitionNodeKey, DefinitionNodeRef, Definitions, ExceptHandlerDefinitionNodeRef,
+    ForStmtDefinitionKind, ForStmtDefinitionNodeRef, ImportDefinitionNodeRef,
+    ImportFromDefinitionNodeRef, MatchPatternDefinitionNodeRef, StarImportDefinitionNodeRef,
+    TargetKind, WithItemDefinitionKind, WithItemDefinitionNodeRef,
 };
 use crate::semantic_index::expression::{Expression, ExpressionKind};
 use crate::semantic_index::predicate::{
@@ -354,15 +355,14 @@ impl<'db> SemanticIndexBuilder<'db> {
         self.current_use_def_map_mut().merge(state);
     }
 
-    /// Return a 2-element tuple, where the first element is the [`ScopedSymbolId`] of the
-    /// symbol added, and the second element is a boolean indicating whether the symbol was *newly*
-    /// added or not
-    fn add_symbol(&mut self, name: Name) -> (ScopedSymbolId, bool) {
+    /// Add a symbol to the symbol table and the use-def map.
+    /// Return the [`ScopedSymbolId`] that uniquely identifies the symbol in both.
+    fn add_symbol(&mut self, name: Name) -> ScopedSymbolId {
         let (symbol_id, added) = self.current_symbol_table().add_symbol(name);
         if added {
             self.current_use_def_map_mut().add_symbol(symbol_id);
         }
-        (symbol_id, added)
+        symbol_id
     }
 
     fn add_attribute(&mut self, name: Name) -> ScopedSymbolId {
@@ -569,7 +569,6 @@ impl<'db> SemanticIndexBuilder<'db> {
     }
 
     /// Records a visibility constraint by applying it to all live bindings and declarations.
-    #[must_use = "A visibility constraint must always be negated after it is added"]
     fn record_visibility_constraint(
         &mut self,
         predicate: Predicate<'db>,
@@ -797,7 +796,7 @@ impl<'db> SemanticIndexBuilder<'db> {
                         ..
                     }) => (name, &None, default),
                 };
-                let (symbol, _) = self.add_symbol(name.id.clone());
+                let symbol = self.add_symbol(name.id.clone());
                 // TODO create Definition for PEP 695 typevars
                 // note that the "bound" on the typevar is a totally different thing than whether
                 // or not a name is "bound" by a typevar declaration; the latter is always true.
@@ -851,31 +850,35 @@ impl<'db> SemanticIndexBuilder<'db> {
 
         // The `iter` of the first generator is evaluated in the outer scope, while all subsequent
         // nodes are evaluated in the inner scope.
-        self.add_standalone_expression(&generator.iter);
+        let value = self.add_standalone_expression(&generator.iter);
         self.visit_expr(&generator.iter);
         self.push_scope(scope);
 
-        self.push_assignment(CurrentAssignment::Comprehension {
-            node: generator,
-            first: true,
-        });
-        self.visit_expr(&generator.target);
-        self.pop_assignment();
+        self.add_unpackable_assignment(
+            &Unpackable::Comprehension {
+                node: generator,
+                first: true,
+            },
+            &generator.target,
+            value,
+        );
 
         for expr in &generator.ifs {
             self.visit_expr(expr);
         }
 
         for generator in generators_iter {
-            self.add_standalone_expression(&generator.iter);
+            let value = self.add_standalone_expression(&generator.iter);
             self.visit_expr(&generator.iter);
 
-            self.push_assignment(CurrentAssignment::Comprehension {
-                node: generator,
-                first: false,
-            });
-            self.visit_expr(&generator.target);
-            self.pop_assignment();
+            self.add_unpackable_assignment(
+                &Unpackable::Comprehension {
+                    node: generator,
+                    first: false,
+                },
+                &generator.target,
+                value,
+            );
 
             for expr in &generator.ifs {
                 self.visit_expr(expr);
@@ -891,20 +894,20 @@ impl<'db> SemanticIndexBuilder<'db> {
             self.declare_parameter(parameter);
         }
         if let Some(vararg) = parameters.vararg.as_ref() {
-            let (symbol, _) = self.add_symbol(vararg.name.id().clone());
+            let symbol = self.add_symbol(vararg.name.id().clone());
             self.add_definition(
                 symbol,
                 DefinitionNodeRef::VariadicPositionalParameter(vararg),
             );
         }
         if let Some(kwarg) = parameters.kwarg.as_ref() {
-            let (symbol, _) = self.add_symbol(kwarg.name.id().clone());
+            let symbol = self.add_symbol(kwarg.name.id().clone());
             self.add_definition(symbol, DefinitionNodeRef::VariadicKeywordParameter(kwarg));
         }
     }
 
     fn declare_parameter(&mut self, parameter: &'db ast::ParameterWithDefault) {
-        let (symbol, _) = self.add_symbol(parameter.name().id().clone());
+        let symbol = self.add_symbol(parameter.name().id().clone());
 
         let definition = self.add_definition(symbol, parameter);
 
@@ -934,9 +937,30 @@ impl<'db> SemanticIndexBuilder<'db> {
 
         let current_assignment = match target {
             ast::Expr::List(_) | ast::Expr::Tuple(_) => {
+                if matches!(unpackable, Unpackable::Comprehension { .. }) {
+                    debug_assert_eq!(
+                        self.scopes[self.current_scope()].node().scope_kind(),
+                        ScopeKind::Comprehension
+                    );
+                }
+                // The first iterator of the comprehension is evaluated in the outer scope, while all subsequent
+                // nodes are evaluated in the inner scope.
+                // SAFETY: The current scope is the comprehension, and the comprehension scope must have a parent scope.
+                let value_file_scope =
+                    if let Unpackable::Comprehension { first: true, .. } = unpackable {
+                        self.scope_stack
+                            .iter()
+                            .rev()
+                            .nth(1)
+                            .expect("The comprehension scope must have a parent scope")
+                            .file_scope_id
+                    } else {
+                        self.current_scope()
+                    };
                 let unpack = Some(Unpack::new(
                     self.db,
                     self.file,
+                    value_file_scope,
                     self.current_scope(),
                     // SAFETY: `target` belongs to the `self.module` tree
                     #[allow(unsafe_code)]
@@ -1114,7 +1138,18 @@ where
                 // The symbol for the function name itself has to be evaluated
                 // at the end to match the runtime evaluation of parameter defaults
                 // and return-type annotations.
-                let (symbol, _) = self.add_symbol(name.id.clone());
+                let symbol = self.add_symbol(name.id.clone());
+
+                // Record a use of the function name in the scope that it is defined in, so that it
+                // can be used to find previously defined functions with the same name. This is
+                // used to collect all the overloaded definitions of a function. This needs to be
+                // done on the `Identifier` node as opposed to `ExprName` because that's what the
+                // AST uses.
+                self.mark_symbol_used(symbol);
+                let use_id = self.current_ast_ids().record_use(name);
+                self.current_use_def_map_mut()
+                    .record_use(symbol, use_id, NodeKey::from_node(name));
+
                 self.add_definition(symbol, function_def);
             }
             ast::Stmt::ClassDef(class) => {
@@ -1138,11 +1173,11 @@ where
                 );
 
                 // In Python runtime semantics, a class is registered after its scope is evaluated.
-                let (symbol, _) = self.add_symbol(class.name.id.clone());
+                let symbol = self.add_symbol(class.name.id.clone());
                 self.add_definition(symbol, class);
             }
             ast::Stmt::TypeAlias(type_alias) => {
-                let (symbol, _) = self.add_symbol(
+                let symbol = self.add_symbol(
                     type_alias
                         .name
                         .as_name_expr()
@@ -1179,7 +1214,7 @@ where
                         (Name::new(alias.name.id.split('.').next().unwrap()), false)
                     };
 
-                    let (symbol, _) = self.add_symbol(symbol_name);
+                    let symbol = self.add_symbol(symbol_name);
                     self.add_definition(
                         symbol,
                         ImportDefinitionNodeRef {
@@ -1250,7 +1285,7 @@ where
                         //
                         // For more details, see the doc-comment on `StarImportPlaceholderPredicate`.
                         for export in exported_names(self.db, referenced_module) {
-                            let (symbol_id, newly_added) = self.add_symbol(export.clone());
+                            let symbol_id = self.add_symbol(export.clone());
                             let node_ref = StarImportDefinitionNodeRef { node, symbol_id };
                             let star_import = StarImportPlaceholderPredicate::new(
                                 self.db,
@@ -1258,40 +1293,16 @@ where
                                 symbol_id,
                                 referenced_module,
                             );
-                            let pre_definition = self.flow_snapshot();
+
+                            let pre_definition =
+                                self.current_use_def_map().single_symbol_snapshot(symbol_id);
                             self.push_additional_definition(symbol_id, node_ref);
-
-                            // Fast path for if there were no previous definitions
-                            // of the symbol defined through the `*` import:
-                            // we can apply the visibility constraint to *only* the added definition,
-                            // rather than all definitions
-                            if newly_added {
-                                let constraint_id = self
-                                    .current_use_def_map_mut()
-                                    .record_star_import_visibility_constraint(
-                                        star_import,
-                                        symbol_id,
-                                    );
-
-                                let post_definition = self.flow_snapshot();
-                                self.flow_restore(pre_definition);
-
-                                self.current_use_def_map_mut()
-                                    .negate_star_import_visibility_constraint(
-                                        symbol_id,
-                                        constraint_id,
-                                    );
-
-                                self.flow_merge(post_definition);
-                            } else {
-                                let constraint_id =
-                                    self.record_visibility_constraint(star_import.into());
-                                let post_definition = self.flow_snapshot();
-                                self.flow_restore(pre_definition.clone());
-                                self.record_negated_visibility_constraint(constraint_id);
-                                self.flow_merge(post_definition);
-                                self.simplify_visibility_constraints(pre_definition);
-                            }
+                            self.current_use_def_map_mut()
+                                .record_and_negate_star_import_visibility_constraint(
+                                    star_import,
+                                    symbol_id,
+                                    pre_definition,
+                                );
                         }
 
                         continue;
@@ -1311,7 +1322,7 @@ where
                     self.has_future_annotations |= alias.name.id == "annotations"
                         && node.module.as_deref() == Some("__future__");
 
-                    let (symbol, _) = self.add_symbol(symbol_name.clone());
+                    let symbol = self.add_symbol(symbol_name.clone());
 
                     self.add_definition(
                         symbol,
@@ -1323,6 +1334,17 @@ where
                     );
                 }
             }
+
+            ast::Stmt::Assert(node) => {
+                self.visit_expr(&node.test);
+                let predicate = self.record_expression_narrowing_constraint(&node.test);
+                self.record_visibility_constraint(predicate);
+
+                if let Some(msg) = &node.msg {
+                    self.visit_expr(msg);
+                }
+            }
+
             ast::Stmt::Assign(node) => {
                 debug_assert_eq!(&self.current_assignments, &[]);
 
@@ -1583,54 +1605,76 @@ where
                     return;
                 }
 
-                let after_subject = self.flow_snapshot();
-                let mut vis_constraints = vec![];
-                let mut post_case_snapshots = vec![];
-                for (i, case) in cases.iter().enumerate() {
-                    if i != 0 {
-                        post_case_snapshots.push(self.flow_snapshot());
-                        self.flow_restore(after_subject.clone());
-                    }
+                let mut no_case_matched = self.flow_snapshot();
 
+                let has_catchall = cases
+                    .last()
+                    .is_some_and(|case| case.guard.is_none() && case.pattern.is_wildcard());
+
+                let mut post_case_snapshots = vec![];
+                let mut match_predicate;
+
+                for (i, case) in cases.iter().enumerate() {
                     self.current_match_case = Some(CurrentMatchCase::new(&case.pattern));
                     self.visit_pattern(&case.pattern);
                     self.current_match_case = None;
-                    let predicate = self.add_pattern_narrowing_constraint(
+                    // unlike in [Stmt::If], we don't reset [no_case_matched]
+                    // here because the effects of visiting a pattern is binding
+                    // symbols, and this doesn't occur unless the pattern
+                    // actually matches
+                    match_predicate = self.add_pattern_narrowing_constraint(
                         subject_expr,
                         &case.pattern,
                         case.guard.as_deref(),
                     );
-                    self.record_reachability_constraint(predicate);
-                    if let Some(expr) = &case.guard {
-                        self.visit_expr(expr);
-                    }
+                    let vis_constraint_id = self.record_reachability_constraint(match_predicate);
+
+                    let match_success_guard_failure = case.guard.as_ref().map(|guard| {
+                        let guard_expr = self.add_standalone_expression(guard);
+                        self.visit_expr(guard);
+                        let post_guard_eval = self.flow_snapshot();
+                        let predicate = Predicate {
+                            node: PredicateNode::Expression(guard_expr),
+                            is_positive: true,
+                        };
+                        self.record_negated_narrowing_constraint(predicate);
+                        let match_success_guard_failure = self.flow_snapshot();
+                        self.flow_restore(post_guard_eval);
+                        self.record_narrowing_constraint(predicate);
+                        match_success_guard_failure
+                    });
+
+                    self.record_visibility_constraint_id(vis_constraint_id);
+
                     self.visit_body(&case.body);
-                    for id in &vis_constraints {
-                        self.record_negated_visibility_constraint(*id);
-                    }
-                    let vis_constraint_id = self.record_visibility_constraint(predicate);
-                    vis_constraints.push(vis_constraint_id);
-                }
 
-                // If there is no final wildcard match case, pretend there is one. This is similar to how
-                // we add an implicit `else` block in if-elif chains, in case it's not present.
-                if !cases
-                    .last()
-                    .is_some_and(|case| case.guard.is_none() && case.pattern.is_wildcard())
-                {
                     post_case_snapshots.push(self.flow_snapshot());
-                    self.flow_restore(after_subject.clone());
 
-                    for id in &vis_constraints {
-                        self.record_negated_visibility_constraint(*id);
+                    if i != cases.len() - 1 || !has_catchall {
+                        // We need to restore the state after each case, but not after the last
+                        // one. The last one will just become the state that we merge the other
+                        // snapshots into.
+                        self.flow_restore(no_case_matched.clone());
+                        self.record_negated_narrowing_constraint(match_predicate);
+                        if let Some(match_success_guard_failure) = match_success_guard_failure {
+                            self.flow_merge(match_success_guard_failure);
+                        } else {
+                            assert!(case.guard.is_none());
+                        }
+                    } else {
+                        debug_assert!(match_success_guard_failure.is_none());
+                        debug_assert!(case.guard.is_none());
                     }
+
+                    self.record_negated_visibility_constraint(vis_constraint_id);
+                    no_case_matched = self.flow_snapshot();
                 }
 
                 for post_clause_state in post_case_snapshots {
                     self.flow_merge(post_clause_state);
                 }
 
-                self.simplify_visibility_constraints(after_subject);
+                self.simplify_visibility_constraints(no_case_matched);
             }
             ast::Stmt::Try(ast::StmtTry {
                 body,
@@ -1696,7 +1740,7 @@ where
                         // which is invalid syntax. However, it's still pretty obvious here that the user
                         // *wanted* `e` to be bound, so we should still create a definition here nonetheless.
                         if let Some(symbol_name) = symbol_name {
-                            let (symbol, _) = self.add_symbol(symbol_name.id.clone());
+                            let symbol = self.add_symbol(symbol_name.id.clone());
 
                             self.add_definition(
                                 symbol,
@@ -1772,7 +1816,7 @@ where
         let node_key = NodeKey::from_node(expr);
 
         match expr {
-            ast::Expr::Name(name_node @ ast::ExprName { id, ctx, .. }) => {
+            ast::Expr::Name(ast::ExprName { id, ctx, .. }) => {
                 let (is_use, is_definition) = match (ctx, self.current_assignment()) {
                     (ast::ExprContext::Store, Some(CurrentAssignment::AugAssign(_))) => {
                         // For augmented assignment, the target expression is also used.
@@ -1783,7 +1827,7 @@ where
                     (ast::ExprContext::Del, _) => (false, true),
                     (ast::ExprContext::Invalid, _) => (false, false),
                 };
-                let (symbol, _) = self.add_symbol(id.clone());
+                let symbol = self.add_symbol(id.clone());
 
                 if is_use {
                     self.mark_symbol_used(symbol);
@@ -1835,12 +1879,17 @@ where
                             // implemented.
                             self.add_definition(symbol, named);
                         }
-                        Some(CurrentAssignment::Comprehension { node, first }) => {
+                        Some(CurrentAssignment::Comprehension {
+                            unpack,
+                            node,
+                            first,
+                        }) => {
                             self.add_definition(
                                 symbol,
                                 ComprehensionDefinitionNodeRef {
+                                    unpack,
                                     iterable: &node.iter,
-                                    target: name_node,
+                                    target: expr,
                                     first,
                                     is_async: node.is_async,
                                 },
@@ -2111,14 +2160,37 @@ where
                                 DefinitionKind::WithItem(assignment),
                             );
                         }
-                        Some(CurrentAssignment::Comprehension { .. }) => {
-                            // TODO:
+                        Some(CurrentAssignment::Comprehension {
+                            unpack,
+                            node,
+                            first,
+                        }) => {
+                            // SAFETY: `iter` and `expr` belong to the `self.module` tree
+                            #[allow(unsafe_code)]
+                            let assignment = ComprehensionDefinitionKind {
+                                target_kind: TargetKind::from(unpack),
+                                iterable: unsafe {
+                                    AstNodeRef::new(self.module.clone(), &node.iter)
+                                },
+                                target: unsafe { AstNodeRef::new(self.module.clone(), expr) },
+                                first,
+                                is_async: node.is_async,
+                            };
+                            // Temporarily move to the scope of the method to which the instance attribute is defined.
+                            // SAFETY: `self.scope_stack` is not empty because the targets in comprehensions should always introduce a new scope.
+                            let scope = self.scope_stack.pop().expect("The popped scope must be a comprehension, which must have a parent scope");
+                            self.register_attribute_assignment(
+                                object,
+                                attr,
+                                DefinitionKind::Comprehension(assignment),
+                            );
+                            self.scope_stack.push(scope);
                         }
                         Some(CurrentAssignment::AugAssign(_)) => {
                             // TODO:
                         }
                         Some(CurrentAssignment::Named(_)) => {
-                            // TODO:
+                            // A named expression whose target is an attribute is syntactically prohibited
                         }
                         None => {}
                     }
@@ -2159,7 +2231,7 @@ where
             range: _,
         }) = pattern
         {
-            let (symbol, _) = self.add_symbol(name.id().clone());
+            let symbol = self.add_symbol(name.id().clone());
             let state = self.current_match_case.as_ref().unwrap();
             self.add_definition(
                 symbol,
@@ -2180,7 +2252,7 @@ where
             rest: Some(name), ..
         }) = pattern
         {
-            let (symbol, _) = self.add_symbol(name.id().clone());
+            let symbol = self.add_symbol(name.id().clone());
             let state = self.current_match_case.as_ref().unwrap();
             self.add_definition(
                 symbol,
@@ -2212,6 +2284,7 @@ enum CurrentAssignment<'a> {
     Comprehension {
         node: &'a ast::Comprehension,
         first: bool,
+        unpack: Option<(UnpackPosition, Unpack<'a>)>,
     },
     WithItem {
         item: &'a ast::WithItem,
@@ -2225,11 +2298,9 @@ impl CurrentAssignment<'_> {
         match self {
             Self::Assign { unpack, .. }
             | Self::For { unpack, .. }
-            | Self::WithItem { unpack, .. } => unpack.as_mut().map(|(position, _)| position),
-            Self::AnnAssign(_)
-            | Self::AugAssign(_)
-            | Self::Named(_)
-            | Self::Comprehension { .. } => None,
+            | Self::WithItem { unpack, .. }
+            | Self::Comprehension { unpack, .. } => unpack.as_mut().map(|(position, _)| position),
+            Self::AnnAssign(_) | Self::AugAssign(_) | Self::Named(_) => None,
         }
     }
 }
@@ -2284,13 +2355,17 @@ enum Unpackable<'a> {
         item: &'a ast::WithItem,
         is_async: bool,
     },
+    Comprehension {
+        first: bool,
+        node: &'a ast::Comprehension,
+    },
 }
 
 impl<'a> Unpackable<'a> {
     const fn kind(&self) -> UnpackKind {
         match self {
             Unpackable::Assign(_) => UnpackKind::Assign,
-            Unpackable::For(_) => UnpackKind::Iterable,
+            Unpackable::For(_) | Unpackable::Comprehension { .. } => UnpackKind::Iterable,
             Unpackable::WithItem { .. } => UnpackKind::ContextManager,
         }
     }
@@ -2305,6 +2380,11 @@ impl<'a> Unpackable<'a> {
                 is_async: *is_async,
                 unpack,
             },
+            Unpackable::Comprehension { node, first } => CurrentAssignment::Comprehension {
+                node,
+                first: *first,
+                unpack,
+            },
         }
     }
 }

crates/red_knot_python_semantic/src/semantic_index/definition.rs

@@ -281,8 +281,9 @@ pub(crate) struct ExceptHandlerDefinitionNodeRef<'a> {
 
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct ComprehensionDefinitionNodeRef<'a> {
+    pub(crate) unpack: Option<(UnpackPosition, Unpack<'a>)>,
     pub(crate) iterable: &'a ast::Expr,
-    pub(crate) target: &'a ast::ExprName,
+    pub(crate) target: &'a ast::Expr,
     pub(crate) first: bool,
     pub(crate) is_async: bool,
 }
@@ -374,11 +375,13 @@ impl<'db> DefinitionNodeRef<'db> {
                 is_async,
             }),
             DefinitionNodeRef::Comprehension(ComprehensionDefinitionNodeRef {
+                unpack,
                 iterable,
                 target,
                 first,
                 is_async,
             }) => DefinitionKind::Comprehension(ComprehensionDefinitionKind {
+                target_kind: TargetKind::from(unpack),
                 iterable: AstNodeRef::new(parsed.clone(), iterable),
                 target: AstNodeRef::new(parsed, target),
                 first,
@@ -474,7 +477,9 @@ impl<'db> DefinitionNodeRef<'db> {
                 unpack: _,
                 is_async: _,
             }) => DefinitionNodeKey(NodeKey::from_node(target)),
-            Self::Comprehension(ComprehensionDefinitionNodeRef { target, .. }) => target.into(),
+            Self::Comprehension(ComprehensionDefinitionNodeRef { target, .. }) => {
+                DefinitionNodeKey(NodeKey::from_node(target))
+            }
             Self::VariadicPositionalParameter(node) => node.into(),
             Self::VariadicKeywordParameter(node) => node.into(),
             Self::Parameter(node) => node.into(),
@@ -550,7 +555,7 @@ pub enum DefinitionKind<'db> {
     AnnotatedAssignment(AnnotatedAssignmentDefinitionKind),
     AugmentedAssignment(AstNodeRef<ast::StmtAugAssign>),
     For(ForStmtDefinitionKind<'db>),
-    Comprehension(ComprehensionDefinitionKind),
+    Comprehension(ComprehensionDefinitionKind<'db>),
     VariadicPositionalParameter(AstNodeRef<ast::Parameter>),
     VariadicKeywordParameter(AstNodeRef<ast::Parameter>),
     Parameter(AstNodeRef<ast::ParameterWithDefault>),
@@ -749,19 +754,24 @@ impl MatchPatternDefinitionKind {
 }
 
 #[derive(Clone, Debug)]
-pub struct ComprehensionDefinitionKind {
-    iterable: AstNodeRef<ast::Expr>,
-    target: AstNodeRef<ast::ExprName>,
-    first: bool,
-    is_async: bool,
+pub struct ComprehensionDefinitionKind<'db> {
+    pub(super) target_kind: TargetKind<'db>,
+    pub(super) iterable: AstNodeRef<ast::Expr>,
+    pub(super) target: AstNodeRef<ast::Expr>,
+    pub(super) first: bool,
+    pub(super) is_async: bool,
 }
 
-impl ComprehensionDefinitionKind {
+impl<'db> ComprehensionDefinitionKind<'db> {
     pub(crate) fn iterable(&self) -> &ast::Expr {
         self.iterable.node()
     }
 
-    pub(crate) fn target(&self) -> &ast::ExprName {
+    pub(crate) fn target_kind(&self) -> TargetKind<'db> {
+        self.target_kind
+    }
+
+    pub(crate) fn target(&self) -> &ast::Expr {
         self.target.node()
     }
 

crates/red_knot_python_semantic/src/semantic_index/re_exports.rs

@@ -26,36 +26,37 @@ use ruff_python_ast::{
     name::Name,
     visitor::{walk_expr, walk_pattern, walk_stmt, Visitor},
 };
-use rustc_hash::FxHashSet;
+use rustc_hash::FxHashMap;
 
 use crate::{module_name::ModuleName, resolve_module, Db};
 
 fn exports_cycle_recover(
     _db: &dyn Db,
-    _value: &FxHashSet<Name>,
+    _value: &[Name],
     _count: u32,
     _file: File,
-) -> salsa::CycleRecoveryAction<FxHashSet<Name>> {
+) -> salsa::CycleRecoveryAction<Box<[Name]>> {
     salsa::CycleRecoveryAction::Iterate
 }
 
-fn exports_cycle_initial(_db: &dyn Db, _file: File) -> FxHashSet<Name> {
-    FxHashSet::default()
+fn exports_cycle_initial(_db: &dyn Db, _file: File) -> Box<[Name]> {
+    Box::default()
 }
 
 #[salsa::tracked(return_ref, cycle_fn=exports_cycle_recover, cycle_initial=exports_cycle_initial)]
-pub(super) fn exported_names(db: &dyn Db, file: File) -> FxHashSet<Name> {
+pub(super) fn exported_names(db: &dyn Db, file: File) -> Box<[Name]> {
     let module = parsed_module(db.upcast(), file);
     let mut finder = ExportFinder::new(db, file);
     finder.visit_body(module.suite());
-    finder.exports
+    finder.resolve_exports()
 }
 
 struct ExportFinder<'db> {
     db: &'db dyn Db,
     file: File,
     visiting_stub_file: bool,
-    exports: FxHashSet<Name>,
+    exports: FxHashMap<&'db Name, PossibleExportKind>,
+    dunder_all: DunderAll,
 }
 
 impl<'db> ExportFinder<'db> {
@@ -64,30 +65,59 @@ impl<'db> ExportFinder<'db> {
             db,
             file,
             visiting_stub_file: file.is_stub(db.upcast()),
-            exports: FxHashSet::default(),
+            exports: FxHashMap::default(),
+            dunder_all: DunderAll::NotPresent,
         }
     }
 
-    fn possibly_add_export(&mut self, name: &Name) {
-        if name.starts_with('_') {
-            return;
+    fn possibly_add_export(&mut self, export: &'db Name, kind: PossibleExportKind) {
+        self.exports.insert(export, kind);
+
+        if export == "__all__" {
+            self.dunder_all = DunderAll::Present;
+        }
+    }
+
+    fn resolve_exports(self) -> Box<[Name]> {
+        match self.dunder_all {
+            DunderAll::NotPresent => self
+                .exports
+                .into_iter()
+                .filter_map(|(name, kind)| {
+                    if kind == PossibleExportKind::StubImportWithoutRedundantAlias {
+                        return None;
+                    }
+                    if name.starts_with('_') {
+                        return None;
+                    }
+                    Some(name.clone())
+                })
+                .collect(),
+            DunderAll::Present => self.exports.into_keys().cloned().collect(),
         }
-        self.exports.insert(name.clone());
     }
 }
 
 impl<'db> Visitor<'db> for ExportFinder<'db> {
     fn visit_alias(&mut self, alias: &'db ast::Alias) {
-        let ast::Alias { name, asname, .. } = alias;
-        if self.visiting_stub_file {
-            // If the source is a stub, names defined by imports are only exported
-            // if they use the explicit `foo as foo` syntax:
-            if asname.as_ref().is_some_and(|asname| asname.id == name.id) {
-                self.possibly_add_export(&name.id);
-            }
+        let ast::Alias {
+            name,
+            asname,
+            range: _,
+        } = alias;
+
+        let name = &name.id;
+        let asname = asname.as_ref().map(|asname| &asname.id);
+
+        // If the source is a stub, names defined by imports are only exported
+        // if they use the explicit `foo as foo` syntax:
+        let kind = if self.visiting_stub_file && asname.is_none_or(|asname| asname != name) {
+            PossibleExportKind::StubImportWithoutRedundantAlias
         } else {
-            self.possibly_add_export(&asname.as_ref().unwrap_or(name).id);
-        }
+            PossibleExportKind::Normal
+        };
+
+        self.possibly_add_export(asname.unwrap_or(name), kind);
     }
 
     fn visit_pattern(&mut self, pattern: &'db ast::Pattern) {
@@ -106,7 +136,7 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
                     // all names with leading underscores, but this will not always be the case
                     // (in the future we will want to support modules with `__all__ = ['_']`).
                     if name != "_" {
-                        self.possibly_add_export(&name.id);
+                        self.possibly_add_export(&name.id, PossibleExportKind::Normal);
                     }
                 }
             }
@@ -120,12 +150,12 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
                     self.visit_pattern(pattern);
                 }
                 if let Some(rest) = rest {
-                    self.possibly_add_export(&rest.id);
+                    self.possibly_add_export(&rest.id, PossibleExportKind::Normal);
                 }
             }
             ast::Pattern::MatchStar(ast::PatternMatchStar { name, range: _ }) => {
                 if let Some(name) = name {
-                    self.possibly_add_export(&name.id);
+                    self.possibly_add_export(&name.id, PossibleExportKind::Normal);
                 }
             }
             ast::Pattern::MatchSequence(_)
@@ -137,7 +167,7 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
         }
     }
 
-    fn visit_stmt(&mut self, stmt: &'db ruff_python_ast::Stmt) {
+    fn visit_stmt(&mut self, stmt: &'db ast::Stmt) {
         match stmt {
             ast::Stmt::ClassDef(ast::StmtClassDef {
                 name,
@@ -147,7 +177,7 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
                 body: _,        // We don't want to visit the body of the class
                 range: _,
             }) => {
-                self.possibly_add_export(&name.id);
+                self.possibly_add_export(&name.id, PossibleExportKind::Normal);
                 for decorator in decorator_list {
                     self.visit_decorator(decorator);
                 }
@@ -155,6 +185,7 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
                     self.visit_arguments(arguments);
                 }
             }
+
             ast::Stmt::FunctionDef(ast::StmtFunctionDef {
                 name,
                 decorator_list,
@@ -165,7 +196,7 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
                 range: _,
                 is_async: _,
             }) => {
-                self.possibly_add_export(&name.id);
+                self.possibly_add_export(&name.id, PossibleExportKind::Normal);
                 for decorator in decorator_list {
                     self.visit_decorator(decorator);
                 }
@@ -174,6 +205,7 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
                     self.visit_expr(returns);
                 }
             }
+
             ast::Stmt::AnnAssign(ast::StmtAnnAssign {
                 target,
                 value,
@@ -189,6 +221,7 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
                     self.visit_expr(value);
                 }
             }
+
             ast::Stmt::TypeAlias(ast::StmtTypeAlias {
                 name,
                 type_params: _,
@@ -199,20 +232,22 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
                 // Neither walrus expressions nor statements cannot appear in type aliases;
                 // no need to recursively visit the `value` or `type_params`
             }
+
             ast::Stmt::ImportFrom(node) => {
                 let mut found_star = false;
                 for name in &node.names {
                     if &name.name.id == "*" {
                         if !found_star {
                             found_star = true;
-                            self.exports.extend(
+                            for export in
                                 ModuleName::from_import_statement(self.db, self.file, node)
                                     .ok()
                                     .and_then(|module_name| resolve_module(self.db, &module_name))
                                     .iter()
                                     .flat_map(|module| exported_names(self.db, module.file()))
-                                    .cloned(),
-                            );
+                            {
+                                self.possibly_add_export(export, PossibleExportKind::Normal);
+                            }
                         }
                     } else {
                         self.visit_alias(name);
@@ -248,7 +283,7 @@ impl<'db> Visitor<'db> for ExportFinder<'db> {
         match expr {
             ast::Expr::Name(ast::ExprName { id, ctx, range: _ }) => {
                 if ctx.is_store() {
-                    self.possibly_add_export(id);
+                    self.possibly_add_export(id, PossibleExportKind::Normal);
                 }
             }
 
@@ -325,7 +360,8 @@ impl<'db> Visitor<'db> for WalrusFinder<'_, 'db> {
                     range: _,
                 }) = &**target
                 {
-                    self.export_finder.possibly_add_export(id);
+                    self.export_finder
+                        .possibly_add_export(id, PossibleExportKind::Normal);
                 }
             }
 
@@ -358,3 +394,15 @@ impl<'db> Visitor<'db> for WalrusFinder<'_, 'db> {
         }
     }
 }
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum PossibleExportKind {
+    Normal,
+    StubImportWithoutRedundantAlias,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum DunderAll {
+    NotPresent,
+    Present,
+}

crates/red_knot_python_semantic/src/semantic_index/use_def.rs

@@ -429,6 +429,14 @@ impl<'db> UseDefMap<'db> {
         self.declarations_iterator(declarations)
     }
 
+    pub(crate) fn all_public_declarations<'map>(
+        &'map self,
+    ) -> impl Iterator<Item = (ScopedSymbolId, DeclarationsIterator<'map, 'db>)> + 'map {
+        (0..self.public_symbols.len())
+            .map(ScopedSymbolId::from_usize)
+            .map(|symbol_id| (symbol_id, self.public_declarations(symbol_id)))
+    }
+
     /// This function is intended to be called only once inside `TypeInferenceBuilder::infer_function_body`.
     pub(crate) fn can_implicit_return(&self, db: &dyn crate::Db) -> bool {
         !self
@@ -551,6 +559,7 @@ impl<'db> Iterator for ConstraintsIterator<'_, 'db> {
 
 impl std::iter::FusedIterator for ConstraintsIterator<'_, '_> {}
 
+#[derive(Clone)]
 pub(crate) struct DeclarationsIterator<'map, 'db> {
     all_definitions: &'map IndexVec<ScopedDefinitionId, Option<Definition<'db>>>,
     pub(crate) predicates: &'map Predicates<'db>,
@@ -766,32 +775,76 @@ impl<'db> UseDefMapBuilder<'db> {
             .add_and_constraint(self.scope_start_visibility, constraint);
     }
 
-    #[must_use = "A `*`-import visibility constraint must always be negated after it is added"]
-    pub(super) fn record_star_import_visibility_constraint(
+    /// Snapshot the state of a single symbol at the current point in control flow.
+    ///
+    /// This is only used for `*`-import visibility constraints, which are handled differently
+    /// to most other visibility constraints. See the doc-comment for
+    /// [`Self::record_and_negate_star_import_visibility_constraint`] for more details.
+    pub(super) fn single_symbol_snapshot(&self, symbol: ScopedSymbolId) -> SymbolState {
+        self.symbol_states[symbol].clone()
+    }
+
+    /// This method exists solely for handling `*`-import visibility constraints.
+    ///
+    /// The reason why we add visibility constraints for [`Definition`]s created by `*` imports
+    /// is laid out in the doc-comment for [`StarImportPlaceholderPredicate`]. But treating these
+    /// visibility constraints in the use-def map the same way as all other visibility constraints
+    /// was shown to lead to [significant regressions] for small codebases where typeshed
+    /// dominates. (Although `*` imports are not common generally, they are used in several
+    /// important places by typeshed.)
+    ///
+    /// To solve these regressions, it was observed that we could do significantly less work for
+    /// `*`-import definitions. We do a number of things differently here to our normal handling of
+    /// visibility constraints:
+    ///
+    /// - We only apply and negate the visibility constraints to a single symbol, rather than to
+    ///   all symbols. This is possible here because, unlike most definitions, we know in advance that
+    ///   exactly one definition occurs inside the "if-true" predicate branch, and we know exactly
+    ///   which definition it is.
+    ///
+    ///   Doing things this way is cheaper in and of itself. However, it also allows us to avoid
+    ///   calling [`Self::simplify_visibility_constraints`] after the constraint has been applied to
+    ///   the "if-predicate-true" branch and negated for the "if-predicate-false" branch. Simplifying
+    ///   the visibility constraints is only important for symbols that did not have any new
+    ///   definitions inside either the "if-predicate-true" branch or the "if-predicate-false" branch.
+    ///
+    /// - We only snapshot the state for a single symbol prior to the definition, rather than doing
+    ///   expensive calls to [`Self::snapshot`]. Again, this is possible because we know
+    ///   that only a single definition occurs inside the "if-predicate-true" predicate branch.
+    ///
+    /// - Normally we take care to check whether an "if-predicate-true" branch or an
+    ///   "if-predicate-false" branch contains a terminal statement: these can affect the visibility
+    ///   of symbols defined inside either branch. However, in the case of `*`-import definitions,
+    ///   this is unnecessary (and therefore not done in this method), since we know that a `*`-import
+    ///   predicate cannot create a terminal statement inside either branch.
+    ///
+    /// [significant regressions]: https://github.com/astral-sh/ruff/pull/17286#issuecomment-2786755746
+    pub(super) fn record_and_negate_star_import_visibility_constraint(
         &mut self,
         star_import: StarImportPlaceholderPredicate<'db>,
         symbol: ScopedSymbolId,
-    ) -> StarImportVisibilityConstraintId {
+        pre_definition_state: SymbolState,
+    ) {
         let predicate_id = self.add_predicate(star_import.into());
         let visibility_id = self.visibility_constraints.add_atom(predicate_id);
-        self.symbol_states[symbol]
-            .record_visibility_constraint(&mut self.visibility_constraints, visibility_id);
-        StarImportVisibilityConstraintId(visibility_id)
-    }
+        let negated_visibility_id = self
+            .visibility_constraints
+            .add_not_constraint(visibility_id);
 
-    pub(super) fn negate_star_import_visibility_constraint(
-        &mut self,
-        symbol_id: ScopedSymbolId,
-        constraint: StarImportVisibilityConstraintId,
-    ) {
-        let negated_constraint = self
-            .visibility_constraints
-            .add_not_constraint(constraint.into_scoped_constraint_id());
-        self.symbol_states[symbol_id]
-            .record_visibility_constraint(&mut self.visibility_constraints, negated_constraint);
-        self.scope_start_visibility = self
-            .visibility_constraints
-            .add_and_constraint(self.scope_start_visibility, negated_constraint);
+        let mut post_definition_state =
+            std::mem::replace(&mut self.symbol_states[symbol], pre_definition_state);
+
+        post_definition_state
+            .record_visibility_constraint(&mut self.visibility_constraints, visibility_id);
+
+        self.symbol_states[symbol]
+            .record_visibility_constraint(&mut self.visibility_constraints, negated_visibility_id);
+
+        self.symbol_states[symbol].merge(
+            post_definition_state,
+            &mut self.narrowing_constraints,
+            &mut self.visibility_constraints,
+        );
     }
 
     /// This method resets the visibility constraints for all symbols to a previous state
@@ -1042,24 +1095,3 @@ impl<'db> UseDefMapBuilder<'db> {
         }
     }
 }
-
-/// Newtype wrapper over [`ScopedVisibilityConstraintId`] to improve type safety.
-///
-/// By returning this type from [`UseDefMapBuilder::record_star_import_visibility_constraint`]
-/// rather than [`ScopedVisibilityConstraintId`] directly, we ensure that
-/// [`UseDefMapBuilder::negate_star_import_visibility_constraint`] must be called after the
-/// visibility constraint has been added, and we ensure that
-/// [`super::SemanticIndexBuilder::record_negated_visibility_constraint`] *cannot* be called with
-/// the narrowing constraint (which would lead to incorrect behaviour).
-///
-/// This type is defined here rather than in the [`super::visibility_constraints`] module
-/// because it should only ever be constructed and deconstructed from methods in the
-/// [`UseDefMapBuilder`].
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub(super) struct StarImportVisibilityConstraintId(ScopedVisibilityConstraintId);
-
-impl StarImportVisibilityConstraintId {
-    fn into_scoped_constraint_id(self) -> ScopedVisibilityConstraintId {
-        self.0
-    }
-}

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

@@ -314,7 +314,7 @@ impl SymbolBindings {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-pub(super) struct SymbolState {
+pub(in crate::semantic_index) struct SymbolState {
     declarations: SymbolDeclarations,
     bindings: SymbolBindings,
 }

crates/red_knot_python_semantic/src/types/builder.rs

@@ -12,6 +12,11 @@
 //!     flattens into the outer one), intersections cannot contain other intersections (also
 //!     flattens), and intersections cannot contain unions (the intersection distributes over the
 //!     union, inverting it into a union-of-intersections).
+//!   * No type in a union can be a subtype of any other type in the union (just eliminate the
+//!     subtype from the union).
+//!   * No type in an intersection can be a supertype of any other type in the intersection (just
+//!     eliminate the supertype from the intersection).
+//!   * An intersection containing two non-overlapping types simplifies to [`Type::Never`].
 //!
 //! The implication of these invariants is that a [`UnionBuilder`] does not necessarily build a
 //! [`Type::Union`]. For example, if only one type is added to the [`UnionBuilder`], `build()` will
@@ -19,19 +24,100 @@
 //! union type is added to the intersection, it will distribute and [`IntersectionBuilder::build`]
 //! may end up returning a [`Type::Union`] of intersections.
 //!
-//! In the future we should have these additional invariants, but they aren't implemented yet:
-//!   * No type in a union can be a subtype of any other type in the union (just eliminate the
-//!     subtype from the union).
-//!   * No type in an intersection can be a supertype of any other type in the intersection (just
-//!     eliminate the supertype from the intersection).
-//!   * An intersection containing two non-overlapping types should simplify to [`Type::Never`].
+//! ## Performance
+//!
+//! In practice, there are two kinds of unions found in the wild: relatively-small unions made up
+//! of normal user types (classes, etc), and large unions made up of literals, which can occur via
+//! large enums (not yet implemented) or from string/integer/bytes literals, which can grow due to
+//! literal arithmetic or operations on literal strings/bytes. For normal unions, it's most
+//! efficient to just store the member types in a vector, and do O(n^2) `is_subtype_of` checks to
+//! maintain the union in simplified form. But literal unions can grow to a size where this becomes
+//! a performance problem. For this reason, we group literal types in `UnionBuilder`. Since every
+//! different string literal type shares exactly the same possible super-types, and none of them
+//! are subtypes of each other (unless exactly the same literal type), we can avoid many
+//! unnecessary `is_subtype_of` checks.
 
-use crate::types::{IntersectionType, KnownClass, Type, TypeVarBoundOrConstraints, UnionType};
+use crate::types::{
+    BytesLiteralType, IntersectionType, KnownClass, StringLiteralType, Type,
+    TypeVarBoundOrConstraints, UnionType,
+};
 use crate::{Db, FxOrderSet};
 use smallvec::SmallVec;
 
+enum UnionElement<'db> {
+    IntLiterals(FxOrderSet<i64>),
+    StringLiterals(FxOrderSet<StringLiteralType<'db>>),
+    BytesLiterals(FxOrderSet<BytesLiteralType<'db>>),
+    Type(Type<'db>),
+}
+
+impl<'db> UnionElement<'db> {
+    /// Try reducing this `UnionElement` given the presence in the same union of `other_type`.
+    ///
+    /// If this `UnionElement` is a group of literals, filter the literals present if needed and
+    /// return `ReduceResult::KeepIf` with a boolean value indicating whether the remaining group
+    /// of literals should be kept in the union
+    ///
+    /// If this `UnionElement` is some other type, return `ReduceResult::Type` so `UnionBuilder`
+    /// can perform more complex checks on it.
+    fn try_reduce(&mut self, db: &'db dyn Db, other_type: Type<'db>) -> ReduceResult<'db> {
+        // `AlwaysTruthy` and `AlwaysFalsy` are the only types which can be a supertype of only
+        // _some_ literals of the same kind, so we need to walk the full set in this case.
+        let needs_filter = matches!(other_type, Type::AlwaysTruthy | Type::AlwaysFalsy);
+        match self {
+            UnionElement::IntLiterals(literals) => {
+                ReduceResult::KeepIf(if needs_filter {
+                    literals.retain(|literal| {
+                        !Type::IntLiteral(*literal).is_subtype_of(db, other_type)
+                    });
+                    !literals.is_empty()
+                } else {
+                    // SAFETY: All `UnionElement` literal kinds must always be non-empty
+                    !Type::IntLiteral(literals[0]).is_subtype_of(db, other_type)
+                })
+            }
+            UnionElement::StringLiterals(literals) => {
+                ReduceResult::KeepIf(if needs_filter {
+                    literals.retain(|literal| {
+                        !Type::StringLiteral(*literal).is_subtype_of(db, other_type)
+                    });
+                    !literals.is_empty()
+                } else {
+                    // SAFETY: All `UnionElement` literal kinds must always be non-empty
+                    !Type::StringLiteral(literals[0]).is_subtype_of(db, other_type)
+                })
+            }
+            UnionElement::BytesLiterals(literals) => {
+                ReduceResult::KeepIf(if needs_filter {
+                    literals.retain(|literal| {
+                        !Type::BytesLiteral(*literal).is_subtype_of(db, other_type)
+                    });
+                    !literals.is_empty()
+                } else {
+                    // SAFETY: All `UnionElement` literal kinds must always be non-empty
+                    !Type::BytesLiteral(literals[0]).is_subtype_of(db, other_type)
+                })
+            }
+            UnionElement::Type(existing) => ReduceResult::Type(*existing),
+        }
+    }
+}
+
+enum ReduceResult<'db> {
+    /// Reduction of this `UnionElement` is complete; keep it in the union if the nested
+    /// boolean is true, eliminate it from the union if false.
+    KeepIf(bool),
+    /// The given `Type` can stand-in for the entire `UnionElement` for further union
+    /// simplification checks.
+    Type(Type<'db>),
+}
+
+// TODO increase this once we extend `UnionElement` throughout all union/intersection
+// representations, so that we can make large unions of literals fast in all operations.
+const MAX_UNION_LITERALS: usize = 200;
+
 pub(crate) struct UnionBuilder<'db> {
-    elements: Vec<Type<'db>>,
+    elements: Vec<UnionElement<'db>>,
     db: &'db dyn Db,
 }
 
@@ -48,27 +134,118 @@ impl<'db> UnionBuilder<'db> {
     }
 
     /// Collapse the union to a single type: `object`.
-    fn collapse_to_object(mut self) -> Self {
+    fn collapse_to_object(&mut self) {
         self.elements.clear();
-        self.elements.push(Type::object(self.db));
-        self
+        self.elements
+            .push(UnionElement::Type(Type::object(self.db)));
     }
 
     /// Adds a type to this union.
     pub(crate) fn add(mut self, ty: Type<'db>) -> Self {
+        self.add_in_place(ty);
+        self
+    }
+
+    /// Adds a type to this union.
+    pub(crate) fn add_in_place(&mut self, ty: Type<'db>) {
         match ty {
             Type::Union(union) => {
                 let new_elements = union.elements(self.db);
                 self.elements.reserve(new_elements.len());
                 for element in new_elements {
-                    self = self.add(*element);
+                    self.add_in_place(*element);
                 }
             }
             // Adding `Never` to a union is a no-op.
             Type::Never => {}
+            // If adding a string literal, look for an existing `UnionElement::StringLiterals` to
+            // add it to, or an existing element that is a super-type of string literals, which
+            // means we shouldn't add it. Otherwise, add a new `UnionElement::StringLiterals`
+            // containing it.
+            Type::StringLiteral(literal) => {
+                let mut found = false;
+                for element in &mut self.elements {
+                    match element {
+                        UnionElement::StringLiterals(literals) => {
+                            if literals.len() >= MAX_UNION_LITERALS {
+                                let replace_with = KnownClass::Str.to_instance(self.db);
+                                self.add_in_place(replace_with);
+                                return;
+                            }
+                            literals.insert(literal);
+                            found = true;
+                            break;
+                        }
+                        UnionElement::Type(existing) if ty.is_subtype_of(self.db, *existing) => {
+                            return;
+                        }
+                        _ => {}
+                    }
+                }
+                if !found {
+                    self.elements
+                        .push(UnionElement::StringLiterals(FxOrderSet::from_iter([
+                            literal,
+                        ])));
+                }
+            }
+            // Same for bytes literals as for string literals, above.
+            Type::BytesLiteral(literal) => {
+                let mut found = false;
+                for element in &mut self.elements {
+                    match element {
+                        UnionElement::BytesLiterals(literals) => {
+                            if literals.len() >= MAX_UNION_LITERALS {
+                                let replace_with = KnownClass::Bytes.to_instance(self.db);
+                                self.add_in_place(replace_with);
+                                return;
+                            }
+                            literals.insert(literal);
+                            found = true;
+                            break;
+                        }
+                        UnionElement::Type(existing) if ty.is_subtype_of(self.db, *existing) => {
+                            return;
+                        }
+                        _ => {}
+                    }
+                }
+                if !found {
+                    self.elements
+                        .push(UnionElement::BytesLiterals(FxOrderSet::from_iter([
+                            literal,
+                        ])));
+                }
+            }
+            // And same for int literals as well.
+            Type::IntLiteral(literal) => {
+                let mut found = false;
+                for element in &mut self.elements {
+                    match element {
+                        UnionElement::IntLiterals(literals) => {
+                            if literals.len() >= MAX_UNION_LITERALS {
+                                let replace_with = KnownClass::Int.to_instance(self.db);
+                                self.add_in_place(replace_with);
+                                return;
+                            }
+                            literals.insert(literal);
+                            found = true;
+                            break;
+                        }
+                        UnionElement::Type(existing) if ty.is_subtype_of(self.db, *existing) => {
+                            return;
+                        }
+                        _ => {}
+                    }
+                }
+                if !found {
+                    self.elements
+                        .push(UnionElement::IntLiterals(FxOrderSet::from_iter([literal])));
+                }
+            }
             // Adding `object` to a union results in `object`.
             ty if ty.is_object(self.db) => {
-                return self.collapse_to_object();
+                self.collapse_to_object();
             }
             _ => {
                 let bool_pair = if let Type::BooleanLiteral(b) = ty {
@@ -81,8 +258,17 @@ impl<'db> UnionBuilder<'db> {
                 let mut to_remove = SmallVec::<[usize; 2]>::new();
                 let ty_negated = ty.negate(self.db);
 
-                for (index, element) in self.elements.iter().enumerate() {
-                    if Some(*element) == bool_pair {
+                for (index, element) in self.elements.iter_mut().enumerate() {
+                    let element_type = match element.try_reduce(self.db, ty) {
+                        ReduceResult::KeepIf(keep) => {
+                            if !keep {
+                                to_remove.push(index);
+                            }
+                            continue;
+                        }
+                        ReduceResult::Type(ty) => ty,
+                    };
+                    if Some(element_type) == bool_pair {
                         to_add = KnownClass::Bool.to_instance(self.db);
                         to_remove.push(index);
                         // The type we are adding is a BooleanLiteral, which doesn't have any
@@ -92,14 +278,14 @@ impl<'db> UnionBuilder<'db> {
                         break;
                     }
 
-                    if ty.is_same_gradual_form(*element)
-                        || ty.is_subtype_of(self.db, *element)
-                        || element.is_object(self.db)
+                    if ty.is_gradual_equivalent_to(self.db, element_type)
+                        || ty.is_subtype_of(self.db, element_type)
+                        || element_type.is_object(self.db)
                     {
-                        return self;
-                    } else if element.is_subtype_of(self.db, ty) {
+                        return;
+                    } else if element_type.is_subtype_of(self.db, ty) {
                         to_remove.push(index);
-                    } else if ty_negated.is_subtype_of(self.db, *element) {
+                    } else if ty_negated.is_subtype_of(self.db, element_type) {
                         // We add `ty` to the union. We just checked that `~ty` is a subtype of an existing `element`.
                         // This also means that `~ty | ty` is a subtype of `element | ty`, because both elements in the
                         // first union are subtypes of the corresponding elements in the second union. But `~ty | ty` is
@@ -107,28 +293,43 @@ impl<'db> UnionBuilder<'db> {
                         // `element | ty` must be `object` (object has no other supertypes). This means we can simplify
                         // the whole union to just `object`, since all other potential elements would also be subtypes of
                         // `object`.
-                        return self.collapse_to_object();
+                        self.collapse_to_object();
+                        return;
                     }
                 }
                 if let Some((&first, rest)) = to_remove.split_first() {
-                    self.elements[first] = to_add;
+                    self.elements[first] = UnionElement::Type(to_add);
                     // We iterate in descending order to keep remaining indices valid after `swap_remove`.
                     for &index in rest.iter().rev() {
                         self.elements.swap_remove(index);
                     }
                 } else {
-                    self.elements.push(to_add);
+                    self.elements.push(UnionElement::Type(to_add));
                 }
             }
         }
-        self
     }
 
     pub(crate) fn build(self) -> Type<'db> {
-        match self.elements.len() {
+        let mut types = vec![];
+        for element in self.elements {
+            match element {
+                UnionElement::IntLiterals(literals) => {
+                    types.extend(literals.into_iter().map(Type::IntLiteral));
+                }
+                UnionElement::StringLiterals(literals) => {
+                    types.extend(literals.into_iter().map(Type::StringLiteral));
+                }
+                UnionElement::BytesLiterals(literals) => {
+                    types.extend(literals.into_iter().map(Type::BytesLiteral));
+                }
+                UnionElement::Type(ty) => types.push(ty),
+            }
+        }
+        match types.len() {
             0 => Type::Never,
-            1 => self.elements[0],
-            _ => Type::Union(UnionType::new(self.db, self.elements.into_boxed_slice())),
+            1 => types[0],
+            _ => Type::Union(UnionType::new(self.db, types.into_boxed_slice())),
         }
     }
 }
@@ -359,7 +560,7 @@ impl<'db> InnerIntersectionBuilder<'db> {
                 for (index, existing_positive) in self.positive.iter().enumerate() {
                     // S & T = S    if S <: T
                     if existing_positive.is_subtype_of(db, new_positive)
-                        || existing_positive.is_same_gradual_form(new_positive)
+                        || existing_positive.is_gradual_equivalent_to(db, new_positive)
                     {
                         return;
                     }
@@ -455,7 +656,9 @@ impl<'db> InnerIntersectionBuilder<'db> {
                 let mut to_remove = SmallVec::<[usize; 1]>::new();
                 for (index, existing_negative) in self.negative.iter().enumerate() {
                     // ~S & ~T = ~T    if S <: T
-                    if existing_negative.is_subtype_of(db, new_negative) {
+                    if existing_negative.is_subtype_of(db, new_negative)
+                        || existing_negative.is_gradual_equivalent_to(db, new_negative)
+                    {
                         to_remove.push(index);
                     }
                     // same rule, reverse order

crates/red_knot_python_semantic/src/types/call.rs

@@ -5,7 +5,7 @@ use crate::Db;
 mod arguments;
 mod bind;
 pub(super) use arguments::{Argument, CallArgumentTypes, CallArguments};
-pub(super) use bind::Bindings;
+pub(super) use bind::{Bindings, CallableBinding};
 
 /// Wraps a [`Bindings`] for an unsuccessful call with information about why the call was
 /// unsuccessful.

crates/red_knot_python_semantic/src/types/call/arguments.rs

@@ -109,21 +109,6 @@ impl<'a, 'db> CallArgumentTypes<'a, 'db> {
         result
     }
 
-    /// Create a new [`CallArgumentTypes`] by prepending a synthetic argument to the front of this
-    /// argument list.
-    pub(crate) fn prepend_synthetic(&self, synthetic: Type<'db>) -> Self {
-        Self {
-            arguments: CallArguments(
-                std::iter::once(Argument::Synthetic)
-                    .chain(self.arguments.iter())
-                    .collect(),
-            ),
-            types: std::iter::once(synthetic)
-                .chain(self.types.iter().copied())
-                .collect(),
-        }
-    }
-
     pub(crate) fn iter(&self) -> impl Iterator<Item = (Argument<'a>, Type<'db>)> + '_ {
         self.arguments.iter().zip(self.types.iter().copied())
     }