[ty] Support legacy typing special forms in implicit type aliases
#21433
+307
−8
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Diagnostic diff on typing conformance testsChanges were detected when running ty on typing conformance tests--- old-output.txt 2025-11-13 18:52:28.399550432 +0000
+++ new-output.txt 2025-11-13 18:52:31.878582783 +0000
@@ -576,7 +576,6 @@
generics_syntax_scoping.py:124:13: error[type-assertion-failure] Argument does not have asserted type `int | float | complex`
generics_type_erasure.py:38:16: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `int | None`, found `Literal[""]`
generics_type_erasure.py:40:16: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `str | None`, found `Literal[0]`
-generics_type_erasure.py:56:1: error[type-assertion-failure] Argument does not have asserted type `bytes`
generics_typevartuple_args.py:16:34: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo(PEP 646), ...]`
generics_typevartuple_args.py:20:1: error[type-assertion-failure] Argument does not have asserted type `tuple[int, str]`
generics_typevartuple_args.py:27:77: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo(PEP 646), ...]`
@@ -1000,5 +999,5 @@
typeddicts_usage.py:28:17: error[missing-typed-dict-key] Missing required key 'name' in TypedDict `Movie` constructor
typeddicts_usage.py:28:18: error[invalid-key] Invalid key for TypedDict `Movie`: Unknown key "title"
typeddicts_usage.py:40:24: error[invalid-type-form] The special form `typing.TypedDict` is not allowed in type expressions. Did you mean to use a concrete TypedDict or `collections.abc.Mapping[str, object]` instead?
-Found 1002 diagnostics
+Found 1001 diagnostics
WARN A fatal error occurred while checking some files. Not all project files were analyzed. See the diagnostics list above for details.
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| Lint rule | Added | Removed | Changed |
|---|---|---|---|
invalid-argument-type |
75 | 2 | 8 |
unused-ignore-comment |
0 | 33 | 0 |
invalid-type-form |
7 | 0 | 0 |
possibly-missing-attribute |
1 | 4 | 2 |
invalid-assignment |
3 | 0 | 2 |
invalid-return-type |
1 | 1 | 2 |
no-matching-overload |
4 | 0 | 0 |
not-iterable |
0 | 0 | 2 |
unresolved-attribute |
2 | 0 | 0 |
unresolved-reference |
0 | 2 | 0 |
unsupported-operator |
1 | 0 | 0 |
| Total | 94 | 42 | 16 |
sharkdp
requested review from
AlexWaygood,
carljm and
dcreager
as code owners
sharkdp
commented
Nov 13, 2025
Comment on lines
+686
to
+697
| InvalidSubclassOf1 = type[1] | ||
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| # TODO: This should be an error | ||
| InvalidSubclassOfLiteral = type[Literal[42]] | ||
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| def _( | ||
| invalid_subclass_of_1: InvalidSubclassOf1, | ||
| invalid_subclass_of_literal: InvalidSubclassOfLiteral, | ||
| ): | ||
| reveal_type(invalid_subclass_of_1) # revealed: type[Unknown] | ||
| # TODO: this should be `type[Unknown]` or `Unknown` | ||
| reveal_type(invalid_subclass_of_literal) # revealed: <class 'int'> |
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This is just a follow-up from a previous PR.
dcreager
added a commit
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this pull request
Nov 14, 2025
* origin/main: (59 commits) [ty] Improve diagnostic range for `non-subscriptable` diagnostics (#21461) [ty] Improve literal promotion heuristics (#21439) [ty] Further improve details around which expressions should be deferred in stub files (#21456) [ty] Improve generic class constructor inference (#21442) [ty] Propagate type context through conditional expressions (#21443) [ty] Suppress completions when introducing names with `as` [ty] Add panic-by-default await methods to `TestServer` (#21451) [ty] name is parameter and global is a syntax error (#21312) [ty] Fixup a few details around version-specific dataclass features (#21453) [ty] Support attribute-expression `TYPE_CHECKING` conditionals (#21449) [ty] Support stringified annotations in value-position `Annotated` instances (#21447) [ty] Type inference for genererator expressions (#21437) [ty] Make `__getattr__` available for `ModuleType` instances (#21450) [ty] Increase default receive timeout in tests to 10s (#21448) [ty] Add synthetic members to completions on dataclasses (#21446) [ty] Support legacy `typing` special forms in implicit type aliases (#21433) Bump 0.14.5 (#21435) [ty] Support `type[…]` and `Type[…]` in implicit type aliases (#21421) [ty] Respect notebook cell boundaries when adding an auto import (#21322) Update PyCharm setup instructions (#21409) ...
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Summary
Support various legacy
typingspecial forms (List,Dict, …) in implicit type aliases.Ecosystem impact
A lot of true positives (e.g. on
alerta)!Test Plan
New Markdown tests