Merge branch 'master' into patch-10

Author: wyattscarpenter

.github/workflows/docs.yml

@@ -44,7 +44,7 @@ jobs:
         with:
           python-version: '3.12'
       - name: Install tox
-        run: pip install tox==4.26.0
+        run: pip install tox==4.53.1
       - name: Setup tox environment
         run: tox run -e ${{ env.TOXENV }} --notest
       - name: Test

.github/workflows/test.yml

@@ -59,6 +59,12 @@ jobs:
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
+        - name: Test suite with py315-ubuntu, mypyc-compiled
+          python: '3.15'
+          os: ubuntu-24.04-arm
+          toxenv: py
+          tox_extra_args: "-n 4"
+          test_mypyc: true
         - name: Test suite with py314t-ubuntu, mypyc-compiled
           python: '3.14t'
           os: ubuntu-24.04-arm
@@ -139,6 +145,7 @@ jobs:
     timeout-minutes: 60
     env:
       TOX_SKIP_MISSING_INTERPRETERS: False
+      VIRTUALENV_SYSTEM_SITE_PACKAGES: ${{ matrix.test_mypyc && 1 || 0 }}
       # Rich (pip) -- Disable color for windows + pytest
       FORCE_COLOR: ${{ !(startsWith(matrix.os, 'windows-') && startsWith(matrix.toxenv, 'py')) && 1 || 0 }}
       # Tox
@@ -195,6 +202,7 @@ jobs:
       if: ${{ !(matrix.debug_build || endsWith(matrix.python, '-dev')) }}
       with:
         python-version: ${{ matrix.python }}
+        allow-prereleases: true
 
     - name: Install tox
       run: |
@@ -205,12 +213,14 @@ jobs:
         echo debug build; python -c 'import sysconfig; print(bool(sysconfig.get_config_var("Py_DEBUG")))'
         echo os.cpu_count; python -c 'import os; print(os.cpu_count())'
         echo os.sched_getaffinity; python -c 'import os; print(len(getattr(os, "sched_getaffinity", lambda *args: [])(0)))'
-        pip install tox==4.26.0
+        pip install tox==4.53.1
 
     - name: Compiled with mypyc
       if: ${{ matrix.test_mypyc }}
+      # Use local version of librt during self-compilation in tests.
       run: |
         pip install -r test-requirements.txt
+        pip install -U mypyc/lib-rt
         CC=clang MYPYC_OPT_LEVEL=0 MYPY_USE_MYPYC=1 pip install -e .
 
     - name: Setup tox environment
@@ -268,7 +278,7 @@ jobs:
           default: 3.11.1
           command: python -c "import platform; print(f'{platform.architecture()=} {platform.machine()=}');"
       - name: Install tox
-        run: pip install tox==4.26.0
+        run: pip install tox==4.53.1
       - name: Setup tox environment
         run: tox run -e py --notest
       - name: Test

CHANGELOG.md

@@ -123,6 +123,18 @@ tox -e dev --override testenv:dev.allowlist_externals+=env -- env  # inspect the
 If you don't already have `tox` installed, you can use a virtual environment as
 described above to install `tox` via `pip` (e.g., ``python -m pip install tox``).
 
+## LLM-assisted contributions
+
+In general, mypy takes a neutral stance on using various LLM code assistants to
+make contributions. LLMs are just another tool, and contributors bear full
+responsibility for the code they are submitting. Disclosing the use of LLMs in
+pull request description is recommended, but not required.
+
+However, we discourage use of LLMs by *new* contributors. We are interested in
+growing long-term contributors who have good understanding of mypy code.
+Pull requests from new contributors that are mostly generated by LLMs
+with little human input will be closed.
+
 ## First time contributors
 
 If you're looking for things to help with, browse our [issue tracker](https://github.com/python/mypy/issues)!

CONTRIBUTING.md

@@ -40,8 +40,7 @@ See :ref:`dynamic-typing` for more details.
 Generic types
 .............
 
-In Python 3.9 and later, built-in collection type objects support
-indexing:
+Built-in collection type objects support indexing:
 
 ====================== ===============================
 Type                   Description
@@ -65,13 +64,11 @@ strings and ``dict[Any, Any]`` is a dictionary of dynamically typed
 Python protocols. For example, a ``str`` object or a ``list[str]`` object is
 valid when ``Iterable[str]`` or ``Sequence[str]`` is expected.
 You can import them from :py:mod:`collections.abc` instead of importing from
-:py:mod:`typing` in Python 3.9.
+:py:mod:`typing`.
 
-See :ref:`generic-builtins` for more details, including how you can
-use these in annotations also in Python 3.7 and 3.8.
+See :ref:`generic-builtins` for more details.
 
-These legacy types defined in :py:mod:`typing` are needed if you need to support
-Python 3.8 and earlier:
+These legacy types defined in :py:mod:`typing` are also supported:
 
 ====================== ===============================
 Type                   Description
@@ -80,17 +77,5 @@ Type                   Description
 ``Tuple[int, int]``    tuple of two ``int`` objects (``Tuple[()]`` is the empty tuple)
 ``Tuple[int, ...]``    tuple of an arbitrary number of ``int`` objects
 ``Dict[str, int]``     dictionary from ``str`` keys to ``int`` values
-``Iterable[int]``      iterable object containing ints
-``Sequence[bool]``     sequence of booleans (read-only)
-``Mapping[str, int]``  mapping from ``str`` keys to ``int`` values (read-only)
 ``Type[C]``            type object of ``C`` (``C`` is a class/type variable/union of types)
 ====================== ===============================
-
-``List`` is an alias for the built-in type ``list`` that supports
-indexing (and similarly for ``dict``/``Dict`` and
-``tuple``/``Tuple``).
-
-Note that even though ``Iterable``, ``Sequence`` and ``Mapping`` look
-similar to abstract base classes defined in :py:mod:`collections.abc`
-(formerly ``collections``), they are not identical, since the latter
-don't support indexing prior to Python 3.9.

docs/source/builtin_types.rst

@@ -43,18 +43,18 @@ Useful built-in types
    x: str = "test"
    x: bytes = b"test"
 
-   # For collections on Python 3.9+, the type of the collection item is in brackets
+   # For collections, the type of the collection item is in brackets
    x: list[int] = [1]
    x: set[int] = {6, 7}
 
    # For mappings, we need the types of both keys and values
-   x: dict[str, float] = {"field": 2.0}  # Python 3.9+
+   x: dict[str, float] = {"field": 2.0}
 
    # For tuples of fixed size, we specify the types of all the elements
-   x: tuple[int, str, float] = (3, "yes", 7.5)  # Python 3.9+
+   x: tuple[int, str, float] = (3, "yes", 7.5)
 
    # For tuples of variable size, we use one type and ellipsis
-   x: tuple[int, ...] = (1, 2, 3)  # Python 3.9+
+   x: tuple[int, ...] = (1, 2, 3)
 
    # On Python 3.8 and earlier, the name of the collection type is
    # capitalized, and the type is imported from the 'typing' module
@@ -67,13 +67,12 @@ Useful built-in types
 
    from typing import Union, Optional
 
-   # On Python 3.10+, use the | operator when something could be one of a few types
-   x: list[int | str] = [3, 5, "test", "fun"]  # Python 3.10+
-   # On earlier versions, use Union
+   # Use the | operator when something could be one of a few types
+   x: list[int | str] = [3, 5, "test", "fun"]
+   # Union is equivalent
    x: list[Union[int, str]] = [3, 5, "test", "fun"]
 
-   # Use X | None for a value that could be None on Python 3.10+
-   # Use Optional[X] on 3.9 and earlier; Optional[X] is the same as 'X | None'
+   # Use X | None for a value that could be None; Optional[X] is the same as X | None
    x: str | None = "something" if some_condition() else None
    if x is not None:
        # Mypy understands x won't be None here because of the if-statement

docs/source/cheat_sheet_py3.rst

@@ -595,13 +595,13 @@ of the above sections.
     This flag causes mypy to suppress errors caused by not being able to fully
     infer the types of global and class variables.
 
-.. option:: --allow-redefinition-new
+.. option:: --allow-redefinition
 
     By default, mypy won't allow a variable to be redefined with an
     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:
+    variables with an arbitrary type. This also requires
+    :option:`--local-partial-types <mypy --no-local-partial-types>`, which is
+    enabled by default starting from mypy 2.0. Example:
 
     .. code-block:: python
 
@@ -613,7 +613,7 @@ of the above sections.
             # Type of "x" is "int | str" here.
             return x
 
-    Without the new flag, mypy only supports inferring optional types
+    Without this flag, mypy only supports inferring optional types
     (``X | None``) from multiple assignments. With this option enabled,
     mypy can infer arbitrary union types.
 
@@ -644,26 +644,23 @@ of the above sections.
             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>`.
+    release.
 
-.. option:: --allow-redefinition
+.. option:: --allow-redefinition-new
 
-    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.
+    Deprecated alias for :option:`--allow-redefinition <mypy --allow-redefinition>`.
 
 .. option:: --allow-redefinition-old
 
-    This is an older variant of
-    :option:`--allow-redefinition-new <mypy --allow-redefinition-new>`.
+    This is an older, more limited variant of
+    :option:`--allow-redefinition <mypy --allow-redefinition>`.
     This flag enables redefinition of a variable with an
     arbitrary type *in some contexts*: only redefinitions within the
     same block and nesting depth as the original definition are allowed.
 
-    We have no plans to remove this flag, but we expect that
-    :option:`--allow-redefinition-new <mypy --allow-redefinition-new>`
-    will replace this flag for new use cases eventually.
+    We have no plans to remove this flag, but
+    :option:`--allow-redefinition <mypy --allow-redefinition>`
+    is recommended for new use cases.
 
     Example where this can be useful:
 
@@ -684,30 +681,26 @@ of the above sections.
            items = "100"  # valid, items now has type str
            items = int(items)  # valid, items now has type int
 
-.. option:: --local-partial-types
+.. option:: --no-local-partial-types
 
-    In mypy, the most common cases for partial types are variables initialized using ``None``,
-    but without explicit ``X | None`` annotations. By default, mypy won't check partial types
-    spanning module top level or class top level. This flag changes the behavior to only allow
-    partial types at local level, therefore it disallows inferring variable type for ``None``
-    from two assignments in different scopes. For example:
+    Disable local partial types to enable legacy type inference mode for
+    containers.
 
-    .. code-block:: python
+    Local partial types prevent inferring a container type for a variable, when
+    the initial assignment happens at module top level or in a class body, and
+    the container item type is only set in a function. Example:
 
-        a = None  # Need type annotation here if using --local-partial-types
-        b: int | None = None
+    .. code-block:: python
 
-        class Foo:
-            bar = None  # Need type annotation here if using --local-partial-types
-            baz: int | None = None
+        a = []  # Need type annotation unless using --no-local-partial-types
 
-            def __init__(self) -> None:
-                self.bar = 1
+        def func() -> None:
+            a.append(1)
 
-        reveal_type(Foo().bar)  # 'int | None' without --local-partial-types
+        reveal_type(a)  # "list[int]" if using --no-local-partial-types
 
-    Note: this option is always implicitly enabled in mypy daemon and will become
-    enabled by default in mypy v2.0 release.
+    Local partial types are enabled by default starting from mypy 2.0. The
+    mypy daemon requires local partial types.
 
 .. option:: --no-implicit-reexport
 
@@ -764,11 +757,11 @@ of the above sections.
     Note that :option:`--strict-equality-for-none <mypy --strict-equality-for-none>`
     only works in combination with :option:`--strict-equality <mypy --strict-equality>`.
 
-.. option:: --strict-bytes
+.. option:: --no-strict-bytes
 
-    By default, mypy treats ``bytearray`` and ``memoryview`` as subtypes of ``bytes`` which
-    is not true at runtime. Use this flag to disable this behavior. ``--strict-bytes`` will
-    be enabled by default in *mypy 2.0*.
+    Treat ``bytearray`` and ``memoryview`` as subtypes of ``bytes``. This is not true
+    at runtime and can lead to unexpected behavior. This was the default behavior prior
+    to mypy 2.0.
 
     .. code-block:: python
 
@@ -777,10 +770,12 @@ of the above sections.
            with open("binary_file", "wb") as fp:
                fp.write(buf)
 
-       f(bytearray(b""))  # error: Argument 1 to "f" has incompatible type "bytearray"; expected "bytes"
-       f(memoryview(b""))  # error: Argument 1 to "f" has incompatible type "memoryview"; expected "bytes"
+       # Using --no-strict-bytes disables the following errors
+       f(bytearray(b""))  # Argument 1 to "f" has incompatible type "bytearray"; expected "bytes"
+       f(memoryview(b""))  # Argument 1 to "f" has incompatible type "memoryview"; expected "bytes"
 
-       # If `f` accepts any object that implements the buffer protocol, consider using:
+       # If `f` accepts any object that implements the buffer protocol,
+       # consider using Buffer instead:
        from collections.abc import Buffer  # "from typing_extensions" in Python 3.11 and earlier
 
        def f(buf: Buffer) -> None:
@@ -1037,6 +1032,43 @@ beyond what incremental mode can offer, try running mypy in
     Skip cache internal consistency checks based on mtime.
 
 
+.. _parallel:
+
+Parallel type-checking
+**********************
+
+By default, mypy checks all modules in the same Python process. This can be slow
+for large code bases. Mypy offers experimental parallel type-checking mode using
+multiple worker processes. In parallel mode, modules that do not depend om each
+other are type-checked in parallel. :ref:`Incremental cache <incremental>` is
+used to manage most of the shared state. Parallel type-checking also requires
+:option:`--local-partial-types <mypy --no-local-partial-types>`, which is
+enabled by default starting from mypy 2.0.
+
+.. option:: -n NUMBER, --num-workers NUMBER
+
+    Use ``NUMBER`` parallel worker processes (in addition to the coordinator
+    process) to perform type-checking. Specifying ``--num-workers 0`` (default)
+    disables parallel checking. Automatic detection of the optimal number
+    of workers is not supported yet.
+
+    This setting will override the ``MYPY_NUM_WORKERS`` environment
+    variable if it is set.
+
+Notes:
+
+* An import cycle is always processed as a whole by a worker process. Thus,
+  avoiding large import cycles in your code will *significantly* improve
+  type-checking speed.
+
+* Specifying a number of workers that is larger than the number of *physical*
+  CPU cores is not beneficial, since mypy is usually CPU bound. Best way to
+  tune the number of workers on a given machine is to start from 3-4 workers
+  and increase the number while you see a performance improvement.
+
+* Parallel mode requires and automatically enables :option:`--native-parser`.
+
+
 Advanced options
 ****************
 
@@ -1110,6 +1142,11 @@ in developing or debugging mypy internals.
     cause mypy to type check the contents of ``temp.py`` instead of  ``original.py``,
     but error messages will still reference ``original.py``.
 
+.. option:: --native-parser
+
+    This enables fast Rust-based parser that parses directly to mypy AST.
+    It will become the default parser in one of the next mypy releases.
+
 
 Report generation
 *****************
@@ -1174,7 +1211,7 @@ format into the specified directory.
 Enabling incomplete/experimental features
 *****************************************
 
-.. option:: --enable-incomplete-feature {PreciseTupleTypes,InlineTypedDict,TypeForm}
+.. option:: --enable-incomplete-feature {PreciseTupleTypes,InlineTypedDict}
 
     Some features may require several mypy releases to implement, for example
     due to their complexity, potential for backwards incompatibility, or
@@ -1229,8 +1266,6 @@ List of currently incomplete/experimental features:
      def test_values() -> {"width": int, "description": str}:
          return {"width": 42, "description": "test"}
 
-* ``TypeForm``: this feature enables ``TypeForm``, as described in
-  `PEP 747 – Annotating Type Forms <https://peps.python.org/pep-0747/>_`.
 
 
 Miscellaneous

docs/source/command_line.rst

@@ -232,8 +232,7 @@ improved performance. You can ensure the presence of orjson using the ``faster-c
 
     python3 -m pip install -U mypy[faster-cache]
 
-Mypy may depend on orjson by default in the future. To use faster, native parser, use the
-``native-parse`` extra. Native parser will be default in near future.
+Mypy may depend on orjson by default in the future.
 
 Types of empty collections
 --------------------------
@@ -671,7 +670,7 @@ subtly different, and it's important to understand how they differ to avoid pitf
 
    .. code-block:: python
 
-     from typing import TypeAlias  # "from typing_extensions" in Python 3.9 and earlier
+     from typing import TypeAlias
 
      class A: ...
      Alias: TypeAlias = A