Merge branch 'master' into implement-lru-cache-support

Author: machin0r

.github/workflows/test.yml

@@ -94,8 +94,8 @@ jobs:
         # This is broken. See
         # - https://github.com/python/mypy/issues/17819
         # - https://github.com/python/mypy/pull/17822
-        # - name: mypyc runtime tests with py38-debug-build-ubuntu
-        #   python: '3.9.21'
+        # - name: mypyc runtime tests with py310-debug-build-ubuntu
+        #   python: '3.10'
         #   os: ubuntu-latest
         #   toxenv: py
         #   tox_extra_args: "-n 4 mypyc/test/test_run.py mypyc/test/test_external.py"
@@ -106,12 +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
+        # Skip Windows tests until we publish ast_serialize wheels on PyPI.
+        # - 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'"
 
         - name: Type check our own code (py310-ubuntu)
           python: '3.10'
@@ -134,6 +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
@@ -152,24 +161,15 @@ jobs:
       with:
         persist-credentials: false
 
-    - name: Debug build
-      if: ${{ matrix.debug_build }}
-      run: |
-        PYTHONVERSION=${{ matrix.python }}
-        PYTHONDIR=~/python-debug/python-$PYTHONVERSION
-        VENV=$PYTHONDIR/env
-        ./misc/build-debug-python.sh $PYTHONVERSION $PYTHONDIR $VENV
-        # TODO: does this do anything? env vars aren't passed to the next step right
-        source $VENV/bin/activate
     - name: Latest dev build
       if: ${{ endsWith(matrix.python, '-dev') }}
       run: |
           git clone --depth 1 https://github.com/python/cpython.git /tmp/cpython --branch $( echo ${{ matrix.python }} | sed 's/-dev//' )
           cd /tmp/cpython
           echo git rev-parse HEAD; git rev-parse HEAD
           git show --no-patch
-          sudo apt-get update
-          sudo apt-get install -y --no-install-recommends \
+          sudo apt-get update -q
+          sudo apt-get install -q -y --no-install-recommends \
             build-essential gdb lcov libbz2-dev libffi-dev libgdbm-dev liblzma-dev libncurses5-dev \
             libreadline6-dev libsqlite3-dev libssl-dev lzma lzma-dev tk-dev uuid-dev zlib1g-dev
           ./configure --prefix=/opt/pythondev
@@ -178,6 +178,23 @@ jobs:
           sudo ln -s /opt/pythondev/bin/python3 /opt/pythondev/bin/python
           sudo ln -s /opt/pythondev/bin/pip3 /opt/pythondev/bin/pip
           echo "/opt/pythondev/bin" >> $GITHUB_PATH
+    - name: Debug build
+      if: ${{ matrix.debug_build }}
+      run: |
+          git clone --depth 1 https://github.com/python/cpython.git /tmp/cpython --branch ${{ matrix.python }}
+          cd /tmp/cpython
+          echo git rev-parse HEAD; git rev-parse HEAD
+          git show --no-patch
+          sudo apt-get update -q
+          sudo apt-get install -q -y --no-install-recommends \
+            build-essential gdb lcov libbz2-dev libffi-dev libgdbm-dev liblzma-dev libncurses5-dev \
+            libreadline6-dev libsqlite3-dev libssl-dev lzma lzma-dev tk-dev uuid-dev zlib1g-dev
+          ./configure CFLAGS="-DPy_DEBUG -DPy_TRACE_REFS -DPYMALLOC_DEBUG" --with-pydebug -with-trace-refs --prefix=/opt/pythondev
+          make -j$(nproc)
+          sudo make install
+          sudo ln -s /opt/pythondev/bin/python3 /opt/pythondev/bin/python
+          sudo ln -s /opt/pythondev/bin/pip3 /opt/pythondev/bin/pip
+          echo "/opt/pythondev/bin" >> $GITHUB_PATH
     - uses: actions/setup-python@v5
       if: ${{ !(matrix.debug_build || endsWith(matrix.python, '-dev')) }}
       with:
@@ -200,6 +217,30 @@ 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: Checkout pinned ast_serialize
+      if: ${{ matrix.dev_ast_serialize }}
+      uses: actions/checkout@v4
+      with:
+        persist-credentials: false
+        repository: mypyc/ast_serialize
+        ref: da5a16cf268dbec63ed6b2e6b715470576e2d1a6
+        path: ast_serialize
+
+    - if: ${{ matrix.dev_ast_serialize }}
+      uses: PyO3/maturin-action@v1
+      with:
+        target: aarch64
+        args: --release --out dist
+        working-directory: ast_serialize
+
+    - if: ${{ matrix.dev_ast_serialize }}
+      run: |
+        pip install ast_serialize/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
+        echo 'no way' > test_ast_serialize.py
+        python3 -c 'import ast_serialize; print(ast_serialize.parse("test_ast_serialize.py")[1])'
+        rm test_ast_serialize.py
+
     - name: Setup tox environment
       run: |
         tox run -e ${{ matrix.toxenv }} --notest

.pre-commit-config.yaml

@@ -6,7 +6,7 @@ repos:
       - id: trailing-whitespace
       - id: end-of-file-fixer
   - repo: https://github.com/psf/black-pre-commit-mirror
-    rev: 25.9.0
+    rev: 26.1.0
     hooks:
       - id: black
         exclude: '^(test-data/)'

CHANGELOG.md

@@ -11,6 +11,18 @@ Support for this will be dropped in the first half of 2026!
 
 Contributed by Marc Mueller (PR [20156](https://github.com/python/mypy/pull/20156)).
 
+### Mypyc Accelerated Mypy Wheels for ARM Windows and Free Threading
+
+For best performance, mypy can be compiled to C extension modules using mypyc. This makes
+mypy 3-5x faster than when interpreted with pure Python. We now build and upload mypyc
+accelerated mypy wheels for `win_arm64` and `cp314t-...` to PyPI, making it easy for Windows
+users on ARM and those using the free theading builds for Python 3.14 to realise this speedup
+-- just `pip install` the latest mypy.
+
+Contributed by Marc Mueller
+(PR [mypy_mypyc-wheels#106](https://github.com/mypyc/mypy_mypyc-wheels/pull/106),
+PR [mypy_mypyc-wheels#110](https://github.com/mypyc/mypy_mypyc-wheels/pull/110)).
+
 ### Removed flags `--force-uppercase-builtins` and `--force-union-syntax`
 
 The `--force-uppercase-builtins` flag was deprecated and has been a no-op since mypy 1.17.0.

docs/source/command_line.rst

@@ -537,13 +537,15 @@ potentially problematic or redundant in some way.
                 print(x + "bad")
 
     To help prevent mypy from generating spurious warnings, the "Statement is
-    unreachable" warning will be silenced in exactly two cases:
+    unreachable" warning will be silenced in exactly three cases:
 
     1.  When the unreachable statement is a ``raise`` statement, is an
         ``assert False`` statement, or calls a function that has the :py:data:`~typing.NoReturn`
         return type hint. In other words, when the unreachable statement
         throws an error or terminates the program in some way.
-    2.  When the unreachable statement was *intentionally* marked as unreachable
+    2.  When the unreachable statement is ``return NotImplemented``. This
+        is allowed by mypy due to its use in operator overloading.
+    3.  When the unreachable statement was *intentionally* marked as unreachable
         using :ref:`version_and_platform_checks`.
 
     .. note::
@@ -596,8 +598,8 @@ of the above sections.
 .. option:: --allow-redefinition-new
 
     By default, mypy won't allow a variable to be redefined with an
-    unrelated type. This *experimental* flag enables the redefinition of
-    unannotated variables with an arbitrary type. You will also need to enable
+    unrelated type. This flag enables the redefinition of unannotated
+    variables with an arbitrary type. You will also need to enable
     :option:`--local-partial-types <mypy --local-partial-types>`.
     Example:
 
@@ -629,12 +631,31 @@ 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.
 
 .. option:: --allow-redefinition
 
+    This is an alias to :option:`--allow-redefinition-old <mypy --allow-redefinition-old>`.
+    In mypy v2.0 this will point to
+    :option:`--allow-redefinition-new <mypy --allow-redefinition-new>`, and will
+    eventually became the default.
+
+.. option:: --allow-redefinition-old
+
     This is an older variant of
     :option:`--allow-redefinition-new <mypy --allow-redefinition-new>`.
     This flag enables redefinition of a variable with an
@@ -687,7 +708,7 @@ of the above sections.
         reveal_type(Foo().bar)  # 'int | None' without --local-partial-types
 
     Note: this option is always implicitly enabled in mypy daemon and will become
-    enabled by default for mypy in a future release.
+    enabled by default in mypy v2.0 release.
 
 .. option:: --no-implicit-reexport
 

docs/source/common_issues.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/config_file.rst

@@ -719,8 +719,8 @@ section of the command line docs.
     :default: False
 
     By default, mypy won't allow a variable to be redefined with an
-    unrelated type. This *experimental* flag enables the redefinition of
-    unannotated variables with an arbitrary type. You will also need to enable
+    unrelated type. This flag enables the redefinition of unannotated
+    variables with an arbitrary type. You will also need to enable
     :confval:`local_partial_types`.
     Example:
 
@@ -748,10 +748,22 @@ 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`.
 
-.. confval:: allow_redefinition
+.. confval:: allow_redefinition_old
 
     :type: boolean
     :default: False
@@ -777,14 +789,22 @@ section of the command line docs.
            items = "100"  # valid, items now has type str
            items = int(items)  # valid, items now has type int
 
+.. confval:: allow_redefinition
+
+    :type: boolean
+    :default: False
+
+    An alias to :confval:`allow_redefinition_old`, in mypy v2.0 this will point to
+    :confval:`allow_redefinition_new`, and will eventually became the default.
+
 .. confval:: local_partial_types
 
     :type: boolean
     :default: False
 
     Disallows inferring variable type for ``None`` from two assignments in different scopes.
     This is always implicitly enabled when using the :ref:`mypy daemon <mypy_daemon>`.
-    This will be enabled by default in a future mypy release.
+    This will be enabled by default in mypy v2.0 release.
 
 .. confval:: disable_error_code
 

docs/source/error_code_list2.rst

@@ -32,7 +32,7 @@ Example:
 
     # mypy: disallow-any-generics
 
-    # Error: Missing type parameters for generic type "list"  [type-arg]
+    # Error: Missing type arguments for generic type "list"  [type-arg]
     def remove_dups(items: list) -> list:
         ...
 

docs/source/stubs.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/type_inference_and_annotations.rst

@@ -159,7 +159,7 @@ on the declared type of ``arg`` in ``foo``:
 .. code-block:: python
 
     def foo(arg: list[int]) -> None:
-        print('Items:', ''.join(str(a) for a in arg))
+        print('Items:', ', '.join(str(a) for a in arg))
 
     foo([])  # OK
 
@@ -170,7 +170,7 @@ in the following statement:
 .. code-block:: python
 
     def foo(arg: list[int]) -> None:
-        print('Items:', ', '.join(arg))
+        print('Items:', ', '.join(str(a) for a in arg))
 
     a = []  # Error: Need type annotation for "a"
     foo(a)

misc/apply-cache-diff.py

@@ -3,6 +3,8 @@
 
 With some infrastructure, this can allow for distributing small cache diffs to users in
 many cases instead of full cache artifacts.
+
+Use diff-cache.py to generate a cache diff.
 """
 
 from __future__ import annotations
@@ -13,6 +15,10 @@
 
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
+from librt import base64
+from librt.internal import ReadBuffer
+
+from mypy.cache import CacheMeta
 from mypy.metastore import FilesystemMetadataStore, MetadataStore, SqliteMetadataStore
 from mypy.util import json_dumps, json_loads
 
@@ -35,10 +41,19 @@ def apply_diff(cache_dir: str, diff_file: str, sqlite: bool = False) -> None:
         if data is None:
             cache.remove(file)
         else:
-            cache.write(file, data)
-            if file.endswith(".meta.json") and "@deps" not in file:
-                meta = json_loads(data)
-                old_deps["snapshot"][meta["id"]] = meta["hash"]
+            if file.endswith(".ff"):
+                data_bytes = base64.b64decode(data)
+            else:
+                data_bytes = data.encode() if isinstance(data, str) else data
+            cache.write(file, data_bytes)
+            if file.endswith(".meta.ff") and "@deps" not in file:
+                buf = ReadBuffer(data_bytes[2:])
+                meta = CacheMeta.read(buf, data_file="")
+                assert meta is not None
+                old_deps["snapshot"][meta.id] = meta.hash
+            elif file.endswith(".meta.json") and "@deps" not in file:
+                meta_dict = json_loads(data_bytes)
+                old_deps["snapshot"][meta_dict["id"]] = meta_dict["hash"]
 
     cache.write("@deps.meta.json", json_dumps(old_deps))