Merge branch 'master' into warn_unreachable_in_mypy

Author: wyattscarpenter

.github/ISSUE_TEMPLATE/crash.md

@@ -15,7 +15,7 @@ labels: "crash"
 
 **Traceback**
 
-```
+```python-traceback
 (Insert traceback and other messages from mypy here -- use `--show-traceback`.)
 ```
 
@@ -25,6 +25,11 @@ labels: "crash"
 appreciated.  We also very much appreciate it if you try to narrow the
 source down to a small stand-alone example.)
 
+```python
+# Ideally, a small sample program that demonstrates the problem.
+# Or even better, a reproducible playground link https://mypy-play.net/ (use the "Gist" button)
+```
+
 **Your Environment**
 
 <!-- Include as many relevant details about the environment you experienced the bug in -->

.github/workflows/mypy_primer.yml

@@ -28,7 +28,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        shard-index: [0, 1, 2, 3, 4]
+        shard-index: [0, 1, 2, 3, 4, 5]
       fail-fast: false
     timeout-minutes: 60
     steps:
@@ -63,7 +63,7 @@ jobs:
             mypy_primer \
             --repo mypy_to_test \
             --new $GITHUB_SHA --old base_commit \
-            --num-shards 5 --shard-index ${{ matrix.shard-index }} \
+            --num-shards 6 --shard-index ${{ matrix.shard-index }} \
             --debug \
             --additional-flags="--debug-serialize" \
             --output concise \

.github/workflows/test.yml

@@ -37,11 +37,6 @@ jobs:
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
-        - name: Test suite with py39-windows-64
-          python: '3.9'
-          os: windows-latest
-          toxenv: py39
-          tox_extra_args: "-n 4"
         - name: Test suite with py310-ubuntu
           python: '3.10'
           os: ubuntu-24.04-arm
@@ -64,6 +59,11 @@ jobs:
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
+        - name: Test suite with py313-windows-64
+          python: '3.13'
+          os: windows-latest
+          toxenv: py
+          tox_extra_args: "-n 4"
 
         - name: Test suite with py314-dev-ubuntu
           python: '3.14-dev'

CHANGELOG.md

@@ -2,11 +2,70 @@
 
 ## Next Release
 
-### Remove Support for targeting Python 3.8
+## Mypy 1.17
 
-Mypy now requires `--python-version 3.9` or greater. Support for only Python 3.8 is
-fully removed now. Given an unsupported version, mypy will default to the oldest
-supported one, currently 3.9.
+We’ve just uploaded mypy 1.17 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
+Mypy is a static type checker for Python. This release includes new features and bug fixes.
+You can install it as follows:
+
+    python3 -m pip install -U mypy
+
+You can read the full documentation for this release on [Read the Docs](http://mypy.readthedocs.io).
+
+### Optionally Check That Match Is Exhaustive
+
+Mypy can now optionally generate an error if a match statement does not
+match exhaustively, without having to use `assert_never(...)`. Enable
+this by using `--enable-error-code exhaustive-match`.
+
+Example:
+
+```python
+# mypy: enable-error-code=exhaustive-match
+
+import enum
+
+class Color(enum.Enum):
+    RED = 1
+    BLUE = 2
+
+def show_color(val: Color) -> None:
+    # error: Unhandled case for values of type "Literal[Color.BLUE]"
+    match val:
+        case Color.RED:
+            print("red")
+```
+
+This feature was contributed by Donal Burns (PR [19144](https://github.com/python/mypy/pull/19144)).
+
+### Further Improvements to Attribute Resolution
+
+This release includes additional improvements to how attribute types
+and kinds are resolved. These fix many bugs and overall improve consistency.
+
+* Handle corner case: protocol/class variable/descriptor (Ivan Levkivskyi, PR [19277](https://github.com/python/mypy/pull/19277))
+* Fix a few inconsistencies in protocol/type object interactions (Ivan Levkivskyi, PR [19267](https://github.com/python/mypy/pull/19267))
+* Refactor/unify access to static attributes (Ivan Levkivskyi, PR [19254](https://github.com/python/mypy/pull/19254))
+* Remove inconsistencies in operator handling (Ivan Levkivskyi, PR [19250](https://github.com/python/mypy/pull/19250))
+* Make protocol subtyping more consistent (Ivan Levkivskyi, PR [18943](https://github.com/python/mypy/pull/18943))
+
+### Fixes to Nondeterministic Type Checking
+
+Previous mypy versions could infer different types for certain expressions
+across different runs (typically depending on which order certain types
+were processed, and this order was nondeterministic). This release includes
+fixes to several such issues.
+
+* Fix nondeterministic type checking by making join with explicit Protocol and type promotion commute (Shantanu, PR [18402](https://github.com/python/mypy/pull/18402))
+* Fix nondeterministic type checking caused by nonassociative of None joins (Shantanu, PR [19158](https://github.com/python/mypy/pull/19158))
+* Fix nondeterministic type checking caused by nonassociativity of joins (Shantanu, PR [19147](https://github.com/python/mypy/pull/19147))
+* Fix nondeterministic type checking by making join between `type` and TypeVar commute (Shantanu, PR [19149](https://github.com/python/mypy/pull/19149))
+
+### Remove Support for Targeting Python 3.8
+
+Mypy now requires `--python-version 3.9` or greater. Support for targeting Python 3.8 is
+fully removed now. Since 3.8 is an unsupported version, mypy will default to the oldest
+supported version (currently 3.9) if you still try to target 3.8.
 
 This change is necessary because typeshed stopped supporting Python 3.8 after it
 reached its End of Life in October 2024.
@@ -17,18 +76,133 @@ Contributed by Marc Mueller
 ### Initial Support for Python 3.14
 
 Mypy is now tested on 3.14 and mypyc works with 3.14.0b3 and later.
-Mypyc compiled wheels of mypy itself will be available for new versions after 3.14.0rc1 is released.
+Binary wheels compiled with mypyc for mypy itself will be available for 3.14
+some time after 3.14.0rc1 has been released.
 
-Note that not all new features might be supported just yet.
+Note that not all features are supported just yet.
 
 Contributed by Marc Mueller (PR [19164](https://github.com/python/mypy/pull/19164))
 
-### Deprecated Flag: \--force-uppercase-builtins
+### Deprecated Flag: `--force-uppercase-builtins`
 
-Mypy only supports Python 3.9+. The \--force-uppercase-builtins flag is now deprecated and a no-op. It will be removed in a future version.
+Mypy only supports Python 3.9+. The `--force-uppercase-builtins` flag is now
+deprecated as unnecessary, and a no-op. It will be removed in a future version.
 
 Contributed by Marc Mueller (PR [19176](https://github.com/python/mypy/pull/19176))
 
+### Mypyc: Improvements to Generators and Async Functions
+
+This release includes both performance improvements and bug fixes related
+to generators and async functions (these share many implementation details).
+
+* Fix exception swallowing in async try/finally blocks with await (Chainfire, PR [19353](https://github.com/python/mypy/pull/19353))
+* Fix AttributeError in async try/finally with mixed return paths (Chainfire, PR [19361](https://github.com/python/mypy/pull/19361))
+* Make generated generator helper method internal (Jukka Lehtosalo, PR [19268](https://github.com/python/mypy/pull/19268))
+* Free coroutine after await encounters StopIteration (Jukka Lehtosalo, PR [19231](https://github.com/python/mypy/pull/19231))
+* Use non-tagged integer for generator label (Jukka Lehtosalo, PR [19218](https://github.com/python/mypy/pull/19218))
+* Merge generator and environment classes in simple cases (Jukka Lehtosalo, PR [19207](https://github.com/python/mypy/pull/19207))
+
+### Mypyc: Partial, Unsafe Support for Free Threading
+
+Mypyc has minimal, quite memory-unsafe support for the free threaded
+builds of 3.14. It is also only lightly tested. Bug reports and experience
+reports are welcome!
+
+Here are some of the major limitations:
+* Free threading only works when compiling a single module at a time.
+* If there is concurrent access to an object while another thread is mutating the same
+  object, it's possible to encounter segfaults and memory corruption.
+* There are no efficient native primitives for thread synthronization, though the
+  regular `threading` module can be used.
+* Some workloads don't scale well to multiple threads for no clear reason.
+
+Related PRs:
+
+* Enable partial, unsafe support for free-threading (Jukka Lehtosalo, PR [19167](https://github.com/python/mypy/pull/19167))
+* Fix incref/decref on free-threaded builds (Jukka Lehtosalo, PR [19127](https://github.com/python/mypy/pull/19127))
+
+### Other Mypyc Fixes and Improvements
+
+* Derive .c file name from full module name if using multi_file (Jukka Lehtosalo, PR [19278](https://github.com/python/mypy/pull/19278))
+* Support overriding the group name used in output files (Jukka Lehtosalo, PR [19272](https://github.com/python/mypy/pull/19272))
+* Add note about using non-native class to subclass built-in types (Jukka Lehtosalo, PR [19236](https://github.com/python/mypy/pull/19236))
+* Make some generated classes implicitly final (Jukka Lehtosalo, PR [19235](https://github.com/python/mypy/pull/19235))
+* Don't simplify module prefixes if using separate compilation (Jukka Lehtosalo, PR [19206](https://github.com/python/mypy/pull/19206))
+
+### Stubgen Improvements
+
+* Add import for `types` in `__exit__` method signature (Alexey Makridenko, PR [19120](https://github.com/python/mypy/pull/19120))
+* Add support for including class and property docstrings (Chad Dombrova, PR [17964](https://github.com/python/mypy/pull/17964))
+* Don't generate `Incomplete | None = None` argument annotation (Sebastian Rittau, PR [19097](https://github.com/python/mypy/pull/19097))
+* Support several more constructs in stubgen's alias printer (Stanislav Terliakov, PR [18888](https://github.com/python/mypy/pull/18888))
+
+### Miscellaneous Fixes and Improvements
+
+* Combine the revealed types of multiple iteration steps in a more robust manner (Christoph Tyralla, PR [19324](https://github.com/python/mypy/pull/19324))
+* Improve the handling of "iteration dependent" errors and notes in finally clauses (Christoph Tyralla, PR [19270](https://github.com/python/mypy/pull/19270))
+* Lessen dmypy suggest path limitations for Windows machines (CoolCat467, PR [19337](https://github.com/python/mypy/pull/19337))
+* Fix type ignore comments erroneously marked as unused by dmypy (Charlie Denton, PR [15043](https://github.com/python/mypy/pull/15043))
+* Fix misspelled `exhaustive-match` error code (johnthagen, PR [19276](https://github.com/python/mypy/pull/19276))
+* Fix missing error context for unpacking assignment involving star expression (Brian Schubert, PR [19258](https://github.com/python/mypy/pull/19258))
+* Fix and simplify error de-duplication (Ivan Levkivskyi, PR [19247](https://github.com/python/mypy/pull/19247))
+* Disallow `ClassVar` in type aliases (Brian Schubert, PR [19263](https://github.com/python/mypy/pull/19263))
+* Add script that prints list of compiled files when compiling mypy (Jukka Lehtosalo, PR [19260](https://github.com/python/mypy/pull/19260))
+* Fix help message url for "None and Optional handling" section (Guy Wilson, PR [19252](https://github.com/python/mypy/pull/19252))
+* Display fully qualified name of imported base classes in errors about incompatible overrides (Mikhail Golubev, PR [19115](https://github.com/python/mypy/pull/19115))
+* Avoid false `unreachable`, `redundant-expr`, and `redundant-casts` warnings in loops more robustly and efficiently, and avoid multiple `revealed type` notes for the same line (Christoph Tyralla, PR [19118](https://github.com/python/mypy/pull/19118))
+* Fix type extraction from `isinstance` checks (Stanislav Terliakov, PR [19223](https://github.com/python/mypy/pull/19223))
+* Erase stray type variables in `functools.partial` (Stanislav Terliakov, PR [18954](https://github.com/python/mypy/pull/18954))
+* Make inferring condition value recognize the whole truth table (Stanislav Terliakov, PR [18944](https://github.com/python/mypy/pull/18944))
+* Support type aliases, `NamedTuple` and `TypedDict` in constrained TypeVar defaults (Stanislav Terliakov, PR [18884](https://github.com/python/mypy/pull/18884))
+* Move dataclass `kw_only` fields to the end of the signature (Stanislav Terliakov, PR [19018](https://github.com/python/mypy/pull/19018))
+* Provide a better fallback value for the `python_version` option (Marc Mueller, PR [19162](https://github.com/python/mypy/pull/19162))
+* Avoid spurious non-overlapping equality error with metaclass with `__eq__` (Michael J. Sullivan, PR [19220](https://github.com/python/mypy/pull/19220))
+* Narrow type variable bounds (Ivan Levkivskyi, PR [19183](https://github.com/python/mypy/pull/19183))
+* Add classifier for Python 3.14 (Marc Mueller, PR [19199](https://github.com/python/mypy/pull/19199))
+* Capitalize syntax error messages (Charulata, PR [19114](https://github.com/python/mypy/pull/19114))
+* Infer constraints eagerly if actual is Any (Ivan Levkivskyi, PR [19190](https://github.com/python/mypy/pull/19190))
+* Include walrus assignments in conditional inference (Stanislav Terliakov, PR [19038](https://github.com/python/mypy/pull/19038))
+* Use PEP 604 syntax when converting types to strings (Marc Mueller, PR [19179](https://github.com/python/mypy/pull/19179))
+* Use more lower-case builtin types in error messages (Marc Mueller, PR [19177](https://github.com/python/mypy/pull/19177))
+* Fix example to use correct method of Stack (Łukasz Kwieciński, PR [19123](https://github.com/python/mypy/pull/19123))
+* Forbid `.pop` of `Readonly` `NotRequired` TypedDict items (Stanislav Terliakov, PR [19133](https://github.com/python/mypy/pull/19133))
+* Emit a friendlier warning on invalid exclude regex, instead of a stacktrace (wyattscarpenter, PR [19102](https://github.com/python/mypy/pull/19102))
+* Enable ANSI color codes for dmypy client in Windows (wyattscarpenter, PR [19088](https://github.com/python/mypy/pull/19088))
+* Extend special case for context-based type variable inference to unions in return position (Stanislav Terliakov, PR [18976](https://github.com/python/mypy/pull/18976))
+
+### Mypy 1.17.1
+* Retain `None` as constraints bottom if no bottoms were provided (Stanislav Terliakov, PR [19485](https://github.com/python/mypy/pull/19485))
+* Fix "ignored exception in `hasattr`" in dmypy (Stanislav Terliakov, PR [19428](https://github.com/python/mypy/pull/19428))
+* Prevent a crash when InitVar is redefined with a method in a subclass (Stanislav Terliakov, PR [19453](https://github.com/python/mypy/pull/19453))
+
+### Acknowledgements
+
+Thanks to all mypy contributors who contributed to this release:
+
+* Alexey Makridenko
+* Brian Schubert
+* Chad Dombrova
+* Chainfire
+* Charlie Denton
+* Charulata
+* Christoph Tyralla
+* CoolCat467
+* Donal Burns
+* Guy Wilson
+* Ivan Levkivskyi
+* johnthagen
+* Jukka Lehtosalo
+* Łukasz Kwieciński
+* Marc Mueller
+* Michael J. Sullivan
+* Mikhail Golubev
+* Sebastian Rittau
+* Shantanu
+* Stanislav Terliakov
+* wyattscarpenter
+
+I’d also like to thank my employer, Dropbox, for supporting mypy development.
+
 ## Mypy 1.16
 
 We’ve just uploaded mypy 1.16 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).

docs/source/command_line.rst

@@ -812,6 +812,14 @@ of the above sections.
     Note: the exact list of flags enabled by running :option:`--strict` may change
     over time.
 
+    .. include:: strict_list.rst
+    ..
+        The above file is autogenerated and included during html generation.
+        (That's an include directive, and this is a comment.)
+        It would be fine to generate it at some other time instead,
+        theoretically, but we already had a convenient hook during html gen.
+
+
 .. option:: --disable-error-code
 
     This flag allows disabling one or multiple error codes globally.

docs/source/common_issues.rst

@@ -218,6 +218,14 @@ daemon <mypy_daemon>`, which can speed up incremental mypy runtimes by
 a factor of 10 or more. :ref:`Remote caching <remote-cache>` can
 make cold mypy runs several times faster.
 
+Furthermore: as of `mypy 1.13 <https://mypy-lang.blogspot.com/2024/10/mypy-113-released.html>`_,
+mypy allows use of the orjson library for handling the cache instead of the stdlib json, for
+improved performance. You can ensure the presence of orjson using the faster-cache extra:
+
+    python3 -m pip install -U mypy[faster-cache]
+
+Mypy may depend on orjson by default in the future.
+
 Types of empty collections
 --------------------------
 
@@ -505,11 +513,15 @@ to see the types of all local variables at once. Example:
    #     b: builtins.str
 .. note::
 
-   ``reveal_type`` and ``reveal_locals`` are only understood by mypy and
-   don't exist in Python. If you try to run your program, you'll have to
-   remove any ``reveal_type`` and ``reveal_locals`` calls before you can
-   run your code. Both are always available and you don't need to import
-   them.
+    ``reveal_type`` and ``reveal_locals`` are handled specially by mypy during
+    type checking, and don't have to be defined or imported.
+
+    However, if you want to run your code,
+    you'll have to remove any ``reveal_type`` and ``reveal_locals``
+    calls from your program or else Python will give you an error at runtime.
+
+    Alternatively, you can import ``reveal_type`` from ``typing_extensions``
+    or ``typing`` (on Python 3.11 and newer)
 
 .. _silencing-linters:
 

docs/source/conf.py

@@ -278,9 +278,9 @@
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3", None),
     "attrs": ("https://www.attrs.org/en/stable/", None),
-    "cython": ("https://docs.cython.org/en/latest", None),
+    "cython": ("https://cython.readthedocs.io/en/stable", None),
     "monkeytype": ("https://monkeytype.readthedocs.io/en/latest", None),
-    "setuptools": ("https://setuptools.readthedocs.io/en/latest", None),
+    "setuptools": ("https://setuptools.pypa.io/en/latest", None),
 }
 
 

docs/source/dynamic_typing.rst

@@ -1,6 +1,5 @@
 .. _dynamic-typing:
 
-
 Dynamically typed code
 ======================
 
@@ -94,6 +93,8 @@ third party libraries that mypy does not know about. This is particularly the ca
 when using the :option:`--ignore-missing-imports <mypy --ignore-missing-imports>`
 flag. See :ref:`fix-missing-imports` for more information about this.
 
+.. _any-vs-object:
+
 Any vs. object
 --------------
 

docs/source/error_code_list.rst

@@ -215,6 +215,35 @@ You can use :py:class:`~collections.abc.Callable` as the type for callable objec
         for x in objs:
             f(x)
 
+.. _code-metaclass:
+
+Check the validity of a class's metaclass [metaclass]
+-----------------------------------------------------
+
+Mypy checks whether the metaclass of a class is valid. The metaclass
+must be a subclass of ``type``. Further, the class hierarchy must yield
+a consistent metaclass. For more details, see the
+`Python documentation <https://docs.python.org/3.13/reference/datamodel.html#determining-the-appropriate-metaclass>`_
+
+Note that mypy's metaclass checking is limited and may produce false-positives.
+See also :ref:`limitations`.
+
+Example with an error:
+
+.. code-block:: python
+
+    class GoodMeta(type):
+        pass
+
+    class BadMeta:
+        pass
+
+    class A1(metaclass=GoodMeta):  # OK
+        pass
+
+    class A2(metaclass=BadMeta):  # Error:  Metaclasses not inheriting from "type" are not supported  [metaclass]
+        pass
+
 .. _code-var-annotated:
 
 Require annotation if variable type is unclear [var-annotated]

docs/source/error_code_list2.rst

@@ -616,7 +616,7 @@ Example:
 
 .. _code-exhaustive-match:
 
-Check that match statements match exhaustively [match-exhaustive]
+Check that match statements match exhaustively [exhaustive-match]
 -----------------------------------------------------------------------
 
 If enabled with :option:`--enable-error-code exhaustive-match <mypy --enable-error-code>`,