Merge branch 'master' into bugfix/gh-19186-typevar-default-crash

Author: sterliakov

.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 \

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 +76,128 @@ 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))
+
+### 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/)).

mypy/checker.py

@@ -618,7 +618,7 @@ def accept_loop(
                     if on_enter_body is not None:
                         on_enter_body()
 
-                    with IterationErrorWatcher(self.msg.errors, iter_errors) as watcher:
+                    with IterationErrorWatcher(self.msg.errors, iter_errors):
                         self.accept(body)
 
                 partials_new = sum(len(pts.map) for pts in self.partial_types)
@@ -641,10 +641,7 @@ def accept_loop(
                 if iter == 20:
                     raise RuntimeError("Too many iterations when checking a loop")
 
-            for error_info in watcher.yield_error_infos():
-                self.msg.fail(*error_info[:2], code=error_info[2])
-            for note_info in watcher.yield_note_infos(self.options):
-                self.note(*note_info)
+            self.msg.iteration_dependent_errors(iter_errors)
 
             # If exit_condition is set, assume it must be False on exit from the loop:
             if exit_condition:
@@ -3041,7 +3038,7 @@ def is_noop_for_reachability(self, s: Statement) -> bool:
             if isinstance(s.expr, EllipsisExpr):
                 return True
             elif isinstance(s.expr, CallExpr):
-                with self.expr_checker.msg.filter_errors():
+                with self.expr_checker.msg.filter_errors(filter_revealed_type=True):
                     typ = get_proper_type(
                         self.expr_checker.accept(
                             s.expr, allow_none_return=True, always_allow_any=True
@@ -3141,7 +3138,7 @@ def check_assignment(
                         else:
                             self.check_getattr_method(signature, lvalue, name)
 
-                if name == "__slots__":
+                if name == "__slots__" and self.scope.active_class() is not None:
                     typ = lvalue_type or self.expr_checker.accept(rvalue)
                     self.check_slots_definition(typ, lvalue)
                 if name == "__match_args__" and inferred is not None:
@@ -3320,6 +3317,12 @@ def get_variable_type_context(self, inferred: Var, rvalue: Expression) -> Type |
                     type_contexts.append(base_type)
         # Use most derived supertype as type context if available.
         if not type_contexts:
+            if inferred.name == "__slots__" and self.scope.active_class() is not None:
+                str_type = self.named_type("builtins.str")
+                return self.named_generic_type("typing.Iterable", [str_type])
+            if inferred.name == "__all__" and self.scope.is_top_level():
+                str_type = self.named_type("builtins.str")
+                return self.named_generic_type("typing.Sequence", [str_type])
             return None
         candidate = type_contexts[0]
         for other in type_contexts:
@@ -4969,7 +4972,7 @@ def visit_try_stmt(self, s: TryStmt) -> None:
             if s.finally_body:
                 # First we check finally_body is type safe on all abnormal exit paths
                 iter_errors = IterationDependentErrors()
-                with IterationErrorWatcher(self.msg.errors, iter_errors) as watcher:
+                with IterationErrorWatcher(self.msg.errors, iter_errors):
                     self.accept(s.finally_body)
 
         if s.finally_body:
@@ -4986,13 +4989,9 @@ def visit_try_stmt(self, s: TryStmt) -> None:
             # that follows the try statement.)
             assert iter_errors is not None
             if not self.binder.is_unreachable():
-                with IterationErrorWatcher(self.msg.errors, iter_errors) as watcher:
+                with IterationErrorWatcher(self.msg.errors, iter_errors):
                     self.accept(s.finally_body)
-
-            for error_info in watcher.yield_error_infos():
-                self.msg.fail(*error_info[:2], code=error_info[2])
-            for note_info in watcher.yield_note_infos(self.options):
-                self.msg.note(*note_info)
+            self.msg.iteration_dependent_errors(iter_errors)
 
     def visit_try_without_finally(self, s: TryStmt, try_frame: bool) -> None:
         """Type check a try statement, ignoring the finally block.
@@ -7280,7 +7279,7 @@ def named_type(self, name: str) -> Instance:
         if isinstance(node, TypeAlias):
             assert isinstance(node.target, Instance)  # type: ignore[misc]
             node = node.target.type
-        assert isinstance(node, TypeInfo)
+        assert isinstance(node, TypeInfo), node
         any_type = AnyType(TypeOfAny.from_omitted_generics)
         return Instance(node, [any_type] * len(node.defn.type_vars))
 
@@ -7299,7 +7298,7 @@ def lookup_typeinfo(self, fullname: str) -> TypeInfo:
         # Assume that the name refers to a class.
         sym = self.lookup_qualified(fullname)
         node = sym.node
-        assert isinstance(node, TypeInfo)
+        assert isinstance(node, TypeInfo), node
         return node
 
     def type_type(self) -> Instance:
@@ -7890,6 +7889,9 @@ def has_valid_attribute(self, typ: Type, name: str) -> bool:
     def get_expression_type(self, node: Expression, type_context: Type | None = None) -> Type:
         return self.expr_checker.accept(node, type_context=type_context)
 
+    def is_defined_in_stub(self, typ: Instance, /) -> bool:
+        return self.modules[typ.type.module_name].is_stub
+
     def check_deprecated(self, node: Node | None, context: Context) -> None:
         """Warn if deprecated and not directly imported with a `from` statement."""
         if isinstance(node, Decorator):

mypy/checker_shared.py

@@ -277,6 +277,10 @@ def checking_await_set(self) -> Iterator[None]:
     def get_precise_awaitable_type(self, typ: Type, local_errors: ErrorWatcher) -> Type | None:
         raise NotImplementedError
 
+    @abstractmethod
+    def is_defined_in_stub(self, typ: Instance, /) -> bool:
+        raise NotImplementedError
+
 
 class CheckerScope:
     # We keep two stacks combined, to maintain the relative order
@@ -334,6 +338,10 @@ def current_self_type(self) -> Instance | TupleType | None:
                 return fill_typevars(item)
         return None
 
+    def is_top_level(self) -> bool:
+        """Is current scope top-level (no classes or functions)?"""
+        return len(self.stack) == 1
+
     @contextmanager
     def push_function(self, item: FuncItem) -> Iterator[None]:
         self.stack.append(item)

mypy/checkpattern.py

@@ -796,9 +796,9 @@ def get_var(expr: Expression) -> Var:
     Warning: this in only true for expressions captured by a match statement.
     Don't call it from anywhere else
     """
-    assert isinstance(expr, NameExpr)
+    assert isinstance(expr, NameExpr), expr
     node = expr.node
-    assert isinstance(node, Var)
+    assert isinstance(node, Var), node
     return node