Merge branch 'master' into stubtest-private-typecheckonly

Author: brianschubert

.github/workflows/test.yml

@@ -106,17 +106,20 @@ jobs:
           os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
+          dev_ast_serialize: true
         - name: Parallel tests with py314-ubuntu, mypyc-compiled
           python: '3.14'
           os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
           test_mypyc: true
+          dev_ast_serialize: true
         - name: Parallel tests with py314-windows-64, interpreted
           python: '3.14'
           os: windows-latest
           toxenv: py
           tox_extra_args: "-n 2 --mypy-num-workers=2 mypy/test/testcheck.py -k 'incremental or modules or classes'"
+          dev_ast_serialize: true
 
         - name: Type check our own code (py310-ubuntu)
           python: '3.10'
@@ -139,6 +142,7 @@ jobs:
     timeout-minutes: 60
     env:
       TOX_SKIP_MISSING_INTERPRETERS: False
+      VIRTUALENV_SYSTEM_SITE_PACKAGES: ${{ matrix.dev_ast_serialize && 1 || 0 }}
       # Rich (pip) -- Disable color for windows + pytest
       FORCE_COLOR: ${{ !(startsWith(matrix.os, 'windows-') && startsWith(matrix.toxenv, 'py')) && 1 || 0 }}
       # Tox
@@ -213,6 +217,11 @@ jobs:
         pip install -r test-requirements.txt
         CC=clang MYPYC_OPT_LEVEL=0 MYPY_USE_MYPYC=1 pip install -e .
 
+    # To speed-up process until ast_serialize is on PyPI.
+    - name: Install pinned ast-serialize
+      if: ${{ matrix.dev_ast_serialize }}
+      run: pip install ast-serialize@git+https://github.com/mypyc/ast_serialize.git@052c5bfa3b2a5bf07c0b163ccbe2c5ccbfae9ac5
+
     - name: Setup tox environment
       run: |
         tox run -e ${{ matrix.toxenv }} --notest

CHANGELOG.md

@@ -631,6 +631,18 @@ of the above sections.
                 # Type of "x" is "str" here.
                 ...
 
+    Function arguments are special, changing their type within function body
+    is allowed even if they are annotated, but that annotation is used to infer
+    types of r.h.s. of all subsequent assignments. Such middle-ground semantics
+    provides good balance for majority of common use cases. For example:
+
+    .. code-block:: python
+
+        def process(values: list[float]) -> None:
+            if not values:
+                values = [0, 0, 0]
+            reveal_type(values)  # Revealed type is list[float]
+
     Note: We are planning to turn this flag on by default in a future mypy
     release, along with :option:`--local-partial-types <mypy --local-partial-types>`.
     The feature is still experimental, and the semantics may still change.

docs/source/command_line.rst

@@ -148,6 +148,14 @@ error:
 The second line is now fine, since the ignore comment causes the name
 ``frobnicate`` to get an implicit ``Any`` type.
 
+The type ignore comment must be at the start of the comments on a line.
+This type ignore will not take effect:
+
+.. code-block:: python
+
+    import frobnicate  #example other comment # type: ignore
+    frobnicate.start()
+
 .. note::
 
     You can use the form ``# type: ignore[<code>]`` to only ignore

docs/source/common_issues.rst

@@ -748,6 +748,18 @@ section of the command line docs.
                 # Type of "x" is "str" here.
                 ...
 
+    Function arguments are special, changing their type within function body
+    is allowed even if they are annotated, but that annotation is used to infer
+    types of r.h.s. of all subsequent assignments. Such middle-ground semantics
+    provides good balance for majority of common use cases. For example:
+
+    .. code-block:: python
+
+        def process(values: list[float]) -> None:
+            if not values:
+                values = [0, 0, 0]
+            reveal_type(values)  # Revealed type is list[float]
+
     Note: We are planning to turn this flag on by default in a future mypy
     release, along with :confval:`local_partial_types`.
 

docs/source/config_file.rst

@@ -126,7 +126,7 @@ For example:
             """Some docstring"""
             pass
 
-        # Error: Incompatible default for argument "foo" (default has
-        # type "ellipsis", argument has type "list[str]")
+        # Error: Incompatible default for parameter "foo" (default has
+        # type "ellipsis", parameter has type "list[str]")
         def not_ok(self, foo: list[str] = ...) -> None:
             print(foo)

docs/source/stubs.rst

@@ -143,6 +143,7 @@ def main() -> None:
         action="store_true",
         help="Whether to make a PR with the changes (default to no)",
     )
+    parser.add_argument("--no-branch", action="store_true", help="Skip creating a new branch")
     args = parser.parse_args()
 
     check_state()
@@ -158,7 +159,8 @@ def main() -> None:
         shutil.copytree(typeshed_patches, tmp_patches)
 
         branch_name = "mypybot/sync-typeshed"
-        subprocess.run(["git", "checkout", "-B", branch_name, "origin/master"], check=True)
+        if not args.no_branch:
+            subprocess.run(["git", "checkout", "-B", branch_name, "origin/master"], check=True)
 
         # Copy the stashed patches back
         shutil.rmtree(typeshed_patches, ignore_errors=True)

misc/sync-typeshed.py

@@ -0,0 +1,37 @@
+From 5c922a2484f2e18c7f901e62bb499b6414cf1090 Mon Sep 17 00:00:00 2001
+From: Marc Mueller <30130371+cdce8p@users.noreply.github.com>
+Date: Wed, 18 Feb 2026 13:11:02 +0100
+Subject: [PATCH] Adjust stubs to fix mypy lookup error due to circular
+ dependencies in stubs
+
+---
+ mypy/typeshed/stdlib/time.pyi | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/mypy/typeshed/stdlib/time.pyi b/mypy/typeshed/stdlib/time.pyi
+index 64a009318..d0853792b 100644
+--- a/mypy/typeshed/stdlib/time.pyi
++++ b/mypy/typeshed/stdlib/time.pyi
+@@ -1,16 +1,16 @@
+ import sys
+ from _typeshed import structseq
+-from typing import Any, Final, Literal, Protocol, SupportsFloat, SupportsIndex, final, type_check_only
++from typing import Any, Final, Literal, Protocol, SupportsFloat, SupportsIndex, Union, final, type_check_only
+ from typing_extensions import TypeAlias
+ 
+ _TimeTuple: TypeAlias = tuple[int, int, int, int, int, int, int, int, int]
+ 
+ if sys.version_info >= (3, 15):
+     # anticipate on https://github.com/python/cpython/pull/139224
+-    _SupportsFloatOrIndex: TypeAlias = SupportsFloat | SupportsIndex
++    _SupportsFloatOrIndex: TypeAlias = Union[SupportsFloat, SupportsIndex]
+ else:
+     # before, time functions only accept (subclass of) float, *not* SupportsFloat
+-    _SupportsFloatOrIndex: TypeAlias = float | SupportsIndex
++    _SupportsFloatOrIndex: TypeAlias = Union[float, SupportsIndex]
+ 
+ altzone: int
+ daylight: int
+-- 
+2.53.0
+

misc/typeshed_patches/0001-Adjust-stubs-to-fix-mypy-lookup-error-due-to-circula.patch

@@ -1,14 +1,14 @@
-From ed11d7e0204868ef1a43c17ed950372b1d78f497 Mon Sep 17 00:00:00 2001
+From b3021cdc4b4c2cf547c5bc2d1d21a5a00ffea001 Mon Sep 17 00:00:00 2001
 From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
 Date: Mon, 26 Sep 2022 12:55:07 -0700
 Subject: [PATCH] Remove use of LiteralString in builtins (#13743)
 
 ---
- mypy/typeshed/stdlib/builtins.pyi | 100 +-----------------------------
- 1 file changed, 1 insertion(+), 99 deletions(-)
+ mypy/typeshed/stdlib/builtins.pyi | 98 -------------------------------
+ 1 file changed, 98 deletions(-)
 
 diff --git a/mypy/typeshed/stdlib/builtins.pyi b/mypy/typeshed/stdlib/builtins.pyi
-index 693dd0b77..8acdeadff 100644
+index efc51fe25..8600a372b 100644
 --- a/mypy/typeshed/stdlib/builtins.pyi
 +++ b/mypy/typeshed/stdlib/builtins.pyi
 @@ -64,7 +64,6 @@ from typing import (  # noqa: Y022,UP035
@@ -163,10 +163,9 @@ index 693dd0b77..8acdeadff 100644
      def __eq__(self, value: object, /) -> bool: ...
      def __ge__(self, value: str, /) -> bool: ...
 -    @overload
--    def __getitem__(self: LiteralString, key: SupportsIndex | slice, /) -> LiteralString: ...
+-    def __getitem__(self: LiteralString, key: SupportsIndex | slice[SupportsIndex | None], /) -> LiteralString: ...
 -    @overload
--    def __getitem__(self, key: SupportsIndex | slice, /) -> str: ...  # type: ignore[misc]
-+    def __getitem__(self, key: SupportsIndex | slice, /) -> str: ...
+     def __getitem__(self, key: SupportsIndex | slice[SupportsIndex | None], /) -> str: ...  # type: ignore[misc]
      def __gt__(self, value: str, /) -> bool: ...
      def __hash__(self) -> int: ...
 -    @overload

misc/typeshed_patches/0001-Remove-use-of-LiteralString-in-builtins-13743.patch

@@ -0,0 +1,37 @@
+From 274a77fe74d961e9885036ed31e5ed46f8d91daa Mon Sep 17 00:00:00 2001
+From: Marc Mueller <30130371+cdce8p@users.noreply.github.com>
+Date: Mon, 23 Feb 2026 12:00:18 +0100
+Subject: [PATCH] Revert Use contravariant type variable in Container
+
+---
+ mypy/typeshed/stdlib/typing.pyi | 9 +++------
+ 1 file changed, 3 insertions(+), 6 deletions(-)
+
+diff --git a/mypy/typeshed/stdlib/typing.pyi b/mypy/typeshed/stdlib/typing.pyi
+index 83e114aac..e9f67877c 100644
+--- a/mypy/typeshed/stdlib/typing.pyi
++++ b/mypy/typeshed/stdlib/typing.pyi
+@@ -640,17 +640,14 @@ class AsyncGenerator(AsyncIterator[_YieldT_co], Protocol[_YieldT_co, _SendT_cont
+     ) -> Coroutine[Any, Any, _YieldT_co]: ...
+     def aclose(self) -> Coroutine[Any, Any, None]: ...
+ 
+-_ContainerT_contra = TypeVar("_ContainerT_contra", contravariant=True, default=Any)
+-
+ @runtime_checkable
+-class Container(Protocol[_ContainerT_contra]):
++class Container(Protocol[_T_co]):
+     # This is generic more on vibes than anything else
+     @abstractmethod
+-    def __contains__(self, x: _ContainerT_contra, /) -> bool: ...
++    def __contains__(self, x: object, /) -> bool: ...
+ 
+ @runtime_checkable
+-class Collection(Iterable[_T_co], Container[Any], Protocol[_T_co]):
+-    # Note: need to use Container[Any] instead of Container[_T_co] to ensure covariance.
++class Collection(Iterable[_T_co], Container[_T_co], Protocol[_T_co]):
+     # Implement Sized (but don't have it as a base class).
+     @abstractmethod
+     def __len__(self) -> int: ...
+-- 
+2.53.0
+