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Fix forward references in type parameters of overparameterized PEP 695 type aliases #19725

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Aug 29, 2025
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Fix forward references in type parameters of overparameterized PEP 695 type aliases #19725

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3 changes: 2 additions & 1 deletion mypy/semanal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5597,7 +5597,8 @@ def visit_type_alias_stmt(self, s: TypeAliasStmt) -> None:
else:
incomplete_target = has_placeholder(res)

if self.found_incomplete_ref(tag) or incomplete_target:
incomplete_tv = any(has_placeholder(tv) for tv in alias_tvars)
if self.found_incomplete_ref(tag) or incomplete_target or incomplete_tv:
# Since we have got here, we know this must be a type alias (incomplete refs
# may appear in nested positions), therefore use becomes_typeinfo=True.
self.mark_incomplete(s.name.name, s.value, becomes_typeinfo=True)
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9 changes: 9 additions & 0 deletions test-data/unit/check-python312.test
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Expand Up @@ -2111,3 +2111,12 @@ if T(x) is str: # E: "TypeAliasType" not callable
reveal_type(x) # N: Revealed type is "builtins.object"
[builtins fixtures/tuple.pyi]
[typing fixtures/typing-full.pyi]

[case testPEP695TypeAliasForwardReferenceInUnusedTypeVar]
# https://discuss.python.org/t/103305
type Alias1[T: "A"] = int
type Alias2[T: ("A", int)] = int
class A: ...

x1: Alias1[A] # ok
x2: Alias2[A] # ok
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