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Transform the inner expression of StarExpr - #22131
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Cherith1222 wants to merge 2 commits into
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Cherith1222 wants to merge 2 commits into
Cherith1222 wants to merge 2 commits into
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Functions using value-constrained type variables are checked as copies made by TreeTransform. visit_star_expr reused the original inner expression, so in '(*result,)' the NameExpr kept pointing at the original Var, which is never inferred because only the copies are checked. That produced a spurious has-type error and an Any tuple. Transform the inner expression and preserve the 'valid' flag. Fixes python#21693. AI-assisted (Cursor). Not yet reviewed by a human.
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Diff from mypy_primer, showing the effect of this PR on open source code: scipy-stubs (https://github.com/scipy/scipy-stubs)
- tests/misc/test_submodules_empty.pyi:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
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dibrinsofor
approved these changes
Oct 7, 2026
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Summary
Functions that use value-constrained type variables are checked as copies made by
TreeTransform.visit_star_exprreused the original inner expression, so in(*result,)theNameExprstill pointed at the originalVar. That variable is never inferred, because only the copies are checked. The result was a spurious[has-type]error and anAnytuple. The inner expression is now transformed, and thevalidflag is preserved.Fixes #21693.
Test Plan
Before the change, the new test failed. After it, the new test passed.
check-typevar-tuple.testandcheck-typevar-values.testtogether: 212 passed. Resource Sentinel, 1 CPU, 2.5 GiB.Not run: the full mypy suite and mypy_primer.
AI assistance
Drafted with Cursor. The account owner authorized opening this pull request. A human has not reviewed the diff. There is no
Co-authored-by,Reviewed-by, orSigned-off-bytrailer.