[ty] Fix excess subscript argument inference for non-generic types#24354
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AlexWaygood merged 1 commit intomainfrom Apr 9, 2026
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[ty] Fix excess subscript argument inference for non-generic types#24354AlexWaygood merged 1 commit intomainfrom
AlexWaygood merged 1 commit intomainfrom
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…on-generic types In `list[int][0]`, the `[0]` subscript was incorrectly parsed as a type expression because `infer_explicit_callable_specialization_impl` always called `infer_type_expression` for excess type arguments. When the type has no type variables (i.e. is fully specialized), excess arguments should be inferred as regular expressions instead. https://claude.ai/code/session_01Kte64hrkmjVtduw18NpToE
Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 86.76%. The percentage of expected errors that received a diagnostic held steady at 81.53%. The number of fully passing files held steady at 70/132. |
Memory usage reportMemory usage unchanged ✅ |
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| Lint rule | Added | Removed | Changed |
|---|---|---|---|
invalid-await |
0 | 40 | 0 |
invalid-return-type |
0 | 1 | 0 |
invalid-type-form |
0 | 1 | 0 |
| Total | 0 | 42 | 0 |
Changes in flaky projects detected. Raw diff output excludes flaky projects; see the HTML report for details.
Raw diff:
sympy (https://github.com/sympy/sympy)
- sympy/vector/implicitregion.py:130:49 error[invalid-type-form] Int literals are not allowed in this context in a type expression
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This one is purely Claude-authored but I think it's correct? I've stared at it for quite a while now, anyway. |
sharkdp
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I guess this might need to be reworked once we add support for TypeVarTuple, but it looks good for now. Thanks.
ibraheemdev
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Apr 15, 2026
…24354) ## Summary When a non-generic type (like `list[int]`) is subscripted with excess arguments (e.g., `list[int][0]`), the excess arguments should be inferred as regular expressions, not type expressions. This prevents spurious "Int literals are not allowed in this context" errors. The fix checks if the base type has any type variables. If `typevars_len == 0`, we know it's not a generic type, so excess subscript arguments are inferred using `infer_expression()` with a default context instead of `infer_type_expression()`. This allows us to properly handle non-type values in excess subscripts while still reporting the primary error that the type is not subscriptable. This change also eliminates a duplicate error message in the test case `list[int][0]`, reducing the error count from two to one. ## Test Plan mdtests updated Co-authored-by: Claude <noreply@anthropic.com>
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Summary
When a non-generic type (like
list[int]) is subscripted with excess arguments (e.g.,list[int][0]), the excess arguments should be inferred as regular expressions, not type expressions. This prevents spurious "Int literals are not allowed in this context" errors.The fix checks if the base type has any type variables. If
typevars_len == 0, we know it's not a generic type, so excess subscript arguments are inferred usinginfer_expression()with a default context instead ofinfer_type_expression(). This allows us to properly handle non-type values in excess subscripts while still reporting the primary error that the type is not subscriptable.This change also eliminates a duplicate error message in the test case
list[int][0], reducing the error count from two to one.Test Plan
mdtests updated