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Fix crash on recursive alias in indirection.py #19845

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Merged
merged 1 commit into from
Sep 15, 2025
Merged

Fix crash on recursive alias in indirection.py #19845

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5 changes: 3 additions & 2 deletions mypy/indirection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -39,8 +39,9 @@ def find_modules(self, typs: Iterable[types.Type]) -> set[str]:
def _visit(self, typ: types.Type) -> None:
if isinstance(typ, types.TypeAliasType):
# Avoid infinite recursion for recursive type aliases.
if typ not in self.seen_aliases:
self.seen_aliases.add(typ)
if typ in self.seen_aliases:
return
self.seen_aliases.add(typ)
typ.accept(self)

def _visit_type_tuple(self, typs: tuple[types.Type, ...]) -> None:
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7 changes: 7 additions & 0 deletions test-data/unit/check-incremental.test
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Expand Up @@ -2577,6 +2577,13 @@ C(1)[0]
[builtins fixtures/list.pyi]
[out]

[case testSerializeRecursiveAlias]
from typing import Callable, Union

Node = Union[str, int, Callable[[], "Node"]]
n: Node
[out]

[case testSerializeRecursiveAliases1]

from typing import Type, Callable, Union
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