[ty] Add support for Optional and Annotated in implicit type aliases
#21321
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Diagnostic diff on typing conformance testsChanges were detected when running ty on typing conformance tests--- old-output.txt 2025-11-10 09:08:35.361270274 +0000
+++ new-output.txt 2025-11-10 09:08:38.671305041 +0000
@@ -1,4 +1,4 @@
-fatal[panic] Panicked at /home/runner/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/05a9af7/src/function/execute.rs:451:17 when checking `/home/runner/work/ruff/ruff/typing/conformance/tests/aliases_typealiastype.py`: `infer_definition_types(Id(18b71)): execute: too many cycle iterations`
+fatal[panic] Panicked at /home/runner/.cargo/git/checkouts/salsa-e6f3bb7c2a062968/05a9af7/src/function/execute.rs:451:17 when checking `/home/runner/work/ruff/ruff/typing/conformance/tests/aliases_typealiastype.py`: `infer_definition_types(Id(18f71)): execute: too many cycle iterations`
_directives_deprecated_library.py:15:31: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `int`
_directives_deprecated_library.py:30:26: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `str`
_directives_deprecated_library.py:36:41: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `Self@__add__`
@@ -856,7 +856,11 @@
qualifiers_annotated.py:48:18: error[invalid-type-form] Boolean operations are not allowed in type expressions
qualifiers_annotated.py:49:18: error[fstring-type-annotation] Type expressions cannot use f-strings
qualifiers_annotated.py:59:8: error[invalid-type-form] Special form `typing.Annotated` expected at least 2 arguments (one type and at least one metadata element)
+qualifiers_annotated.py:71:1: error[invalid-assignment] Object of type `<typing.Annotated special form>` is not assignable to `type[Any]`
+qualifiers_annotated.py:72:1: error[invalid-assignment] Object of type `<typing.Annotated special form>` is not assignable to `type[Any]`
qualifiers_annotated.py:86:1: error[call-non-callable] Object of type `typing.Annotated` is not callable
+qualifiers_annotated.py:87:1: error[call-non-callable] Object of type `GenericAlias` is not callable
+qualifiers_annotated.py:88:1: error[call-non-callable] Object of type `GenericAlias` is not callable
qualifiers_final_annotation.py:18:7: error[invalid-type-form] Type qualifier `typing.Final` expected exactly 1 argument, got 2
qualifiers_final_annotation.py:52:9: error[invalid-assignment] Cannot assign to final attribute `ID4` on type `Self@__init__`
qualifiers_final_annotation.py:54:9: error[invalid-assignment] Cannot assign to final attribute `ID5` on type `Self@__init__`
@@ -1001,5 +1005,5 @@
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 1003 diagnostics
+Found 1007 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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Contributor
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Contributor
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| Lint rule | Added | Removed | Changed |
|---|---|---|---|
invalid-argument-type |
31 | 0 | 27 |
invalid-return-type |
14 | 0 | 0 |
unused-ignore-comment |
0 | 8 | 0 |
invalid-type-form |
4 | 0 | 0 |
call-non-callable |
2 | 0 | 0 |
not-iterable |
2 | 0 | 0 |
invalid-assignment |
1 | 0 | 0 |
| Total | 54 | 8 | 27 |
sharkdp
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sharkdp
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dcreager
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AlexWaygood
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Nov 8, 2025
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| KnownInstanceType::Literal(_) => f.write_str("typing.Literal"), | ||
| KnownInstanceType::Annotated(_) => f.write_str("typing.Annotated"), |
Member
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I'm not wild about the displays for these two, because int as a type display means "instance of int", and list[int] means "inhabitant of the type list[int]"... but KnownInstance types here that would be displayed as typing.Literal or typing.Annotated aren't actually instances/inhabitants of typing.Literal or typing.Annotated. Neither of those symbols are classes at runtime, so it would be impossible to create an "instance of typing.Literal".
What about something like <subscripted typing.Literal> or <typing.Literal special form>?
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typing.Never is also not an "instance of (a class) Never". I don't really see what's different for Literal and Annotated, when compared to some other special form / known instance types, but I changed it to your suggestion for now.
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Summary
Add support for
OptionalandAnnotatedin implicit type aliasespart of astral-sh/ty#221
Typing conformance changes
New expected diagnostics.
Ecosystem
A lot of true positives, some known limitations unrelated to this PR.
Test Plan
New Markdown tests