Merge remote-tracking branch 'upstream/master' into experiments/typecheck-unreachable

Author: A5rocks

.github/workflows/test.yml

@@ -33,7 +33,7 @@ jobs:
         # the oldest and newest supported Python versions
         - name: Test suite with py39-ubuntu, mypyc-compiled
           python: '3.9'
-          os: ubuntu-22.04-arm
+          os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
@@ -44,31 +44,31 @@ jobs:
           tox_extra_args: "-n 4"
         - name: Test suite with py310-ubuntu
           python: '3.10'
-          os: ubuntu-22.04-arm
+          os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4"
         - name: Test suite with py311-ubuntu, mypyc-compiled
           python: '3.11'
-          os: ubuntu-22.04-arm
+          os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
         - name: Test suite with py312-ubuntu, mypyc-compiled
           python: '3.12'
-          os: ubuntu-22.04-arm
+          os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
         - name: Test suite with py313-ubuntu, mypyc-compiled
           python: '3.13'
-          os: ubuntu-22.04-arm
+          os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
 
         # - name: Test suite with py314-dev-ubuntu
         #   python: '3.14-dev'
-        #   os: ubuntu-22.04-arm
+        #   os: ubuntu-24.04-arm
         #   toxenv: py
         #   tox_extra_args: "-n 4"
         #   allow_failure: true

.pre-commit-config.yaml

@@ -11,7 +11,7 @@ repos:
       - id: black
         exclude: '^(test-data/)'
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.8.6
+    rev: v0.9.10
     hooks:
       - id: ruff
         args: [--exit-non-zero-on-fix]

CREDITS

@@ -15,7 +15,7 @@ Dropbox core team:
 
 Non-Dropbox core team members:
 
-  Ethan Smith
+  Emma Harper Smith <[email protected]>
   Guido van Rossum <[email protected]>
   Jelle Zijlstra <[email protected]>
   Michael J. Sullivan <[email protected]>

docs/source/metaclasses.rst

@@ -34,12 +34,14 @@ Mypy supports the lookup of attributes in the metaclass:
 
 .. code-block:: python
 
-    from typing import ClassVar, Self
+    from typing import ClassVar, TypeVar
+
+    S = TypeVar("S")
 
     class M(type):
         count: ClassVar[int] = 0
 
-        def make(cls) -> Self:
+        def make(cls: type[S]) -> S:
             M.count += 1
             return cls()
 
@@ -55,9 +57,6 @@ Mypy supports the lookup of attributes in the metaclass:
     b: B = B.make()  # metaclasses are inherited
     print(B.count + " objects were created")  # Error: Unsupported operand types for + ("int" and "str")
 
-.. note::
-    In Python 3.10 and earlier, ``Self`` is available in ``typing_extensions``.
-
 .. _limitations:
 
 Gotchas and limitations of metaclass support
@@ -88,3 +87,6 @@ so it's better not to combine metaclasses and class hierarchies:
   such as ``class A(metaclass=f()): ...``
 * Mypy does not and cannot understand arbitrary metaclass code.
 * Mypy only recognizes subclasses of :py:class:`type` as potential metaclasses.
+* ``Self`` is not allowed as annotation in metaclasses as per `PEP 673`_.
+
+.. _PEP 673: https://peps.python.org/pep-0673/#valid-locations-for-self

docs/source/type_narrowing.rst

@@ -8,6 +8,15 @@ techniques which are supported by mypy.
 
 Type narrowing is when you convince a type checker that a broader type is actually more specific, for instance, that an object of type ``Shape`` is actually of the narrower type ``Square``.
 
+The following type narrowing techniques are available:
+
+- :ref:`type-narrowing-expressions`
+- :ref:`casts`
+- :ref:`type-guards`
+- :ref:`typeis`
+
+
+.. _type-narrowing-expressions:
 
 Type narrowing expressions
 --------------------------
@@ -356,40 +365,6 @@ What happens here?
 
   The same will work with ``isinstance(x := a, float)`` as well.
 
-Limitations
------------
-
-Mypy's analysis is limited to individual symbols and it will not track
-relationships between symbols. For example, in the following code
-it's easy to deduce that if :code:`a` is None then :code:`b` must not be,
-therefore :code:`a or b` will always be an instance of :code:`C`,
-but Mypy will not be able to tell that:
-
-.. code-block:: python
-
-    class C:
-        pass
-
-    def f(a: C | None, b: C | None) -> C:
-        if a is not None or b is not None:
-            return a or b  # Incompatible return value type (got "C | None", expected "C")
-        return C()
-
-Tracking these sort of cross-variable conditions in a type checker would add significant complexity
-and performance overhead.
-
-You can use an ``assert`` to convince the type checker, override it with a :ref:`cast <casts>`
-or rewrite the function to be slightly more verbose:
-
-.. code-block:: python
-
-    def f(a: C | None, b: C | None) -> C:
-        if a is not None:
-            return a
-        elif b is not None:
-            return b
-        return C()
-
 
 .. _typeis:
 
@@ -555,3 +530,38 @@ You can use the assignment expression operator ``:=`` with ``TypeIs`` to create
             reveal_type(x)  # Revealed type is 'float'
             # x is narrowed to float in this block
             print(x + 1.0)
+
+
+Limitations
+-----------
+
+Mypy's analysis is limited to individual symbols and it will not track
+relationships between symbols. For example, in the following code
+it's easy to deduce that if :code:`a` is None then :code:`b` must not be,
+therefore :code:`a or b` will always be an instance of :code:`C`,
+but Mypy will not be able to tell that:
+
+.. code-block:: python
+
+    class C:
+        pass
+
+    def f(a: C | None, b: C | None) -> C:
+        if a is not None or b is not None:
+            return a or b  # Incompatible return value type (got "C | None", expected "C")
+        return C()
+
+Tracking these sort of cross-variable conditions in a type checker would add significant complexity
+and performance overhead.
+
+You can use an ``assert`` to convince the type checker, override it with a :ref:`cast <casts>`
+or rewrite the function to be slightly more verbose:
+
+.. code-block:: python
+
+    def f(a: C | None, b: C | None) -> C:
+        if a is not None:
+            return a
+        elif b is not None:
+            return b
+        return C()