Fix missing error for "str" | None union with string literals#2828
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fangyi-zhou wants to merge 8 commits intofacebook:mainfrom
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Fix missing error for "str" | None union with string literals#2828fangyi-zhou wants to merge 8 commits intofacebook:mainfrom
"str" | None union with string literals#2828fangyi-zhou wants to merge 8 commits intofacebook:mainfrom
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`NoneType` is a plain type at runtime that doesn't support `__or__` with string arguments, so `"Foo" | None` raises a TypeError just like `"Foo" | int`. The `is_plain_type` check was missing the `Type::None` case. Fixes facebook#1005 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Add test cases covering more Type variants (Any, builtin parameterized generics) and a runtime validation script for reviewers. The Any case was already handled correctly. Builtin parameterized generics like list[int] are a known false negative documented with a bug marker. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
…ble, LiteralString TypedDict, NamedTuple, and Protocol are class definitions that correctly get flagged. Literal[1], Callable[[int], str], and LiteralString are typing special forms that correctly pass through. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
…, LiteralString, Type[Any], Never, NoReturn Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Moved to a gist for PR reviewers instead. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
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@yangdanny97 has imported this pull request. If you are a Meta employee, you can view this in D97631848. |
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Summary
At runtime,
"Foo" | NoneraisesTypeErrorbecauseNoneTypedoesn't support__or__with string operands. Pyrefly'sis_plain_typecheck was missingType::None, so this case wasn't flagged.Fix: Add
Type::None => truetois_plain_typein theForwardRefUnioncheck.Tests: Add cases covering
None,Any,TypedDict,NamedTuple,Protocol,Literal[1],Callable,LiteralString, and builtin parameterized generics (list[int],dict[str, int]).Known gap: Builtin parameterized generics like
list[int](types.GenericAlias) error at runtime butList[int](typing._GenericAlias) does not. Pyrefly represents both identically, so it can't distinguish them. This is documented with abugmarker.Runtime validation script: https://gist.github.com/fangyi-zhou/ce153247db2e6b71e985f27e9e31c03b
Fixes #1005
Test plan
cargo test -p pyrefly test_union— all 44 tests passpython3 test.py --no-test --no-conformance— formatting and linting clean🤖 Generated with Claude Code