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INTERNAL ERROR: maximum semantic analysis iteration count reached on self-referential union #17132

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kmurphy4 opened this issue Apr 17, 2024 · 1 comment · Fixed by #17350
Closed

INTERNAL ERROR: maximum semantic analysis iteration count reached on self-referential union #17132

kmurphy4 opened this issue Apr 17, 2024 · 1 comment · Fixed by #17350
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crash topic-recursive-types topic-type-alias TypeAlias and other type alias issues

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@kmurphy4
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Crash Report

Under some specific conditions, mypy crashes when creating type aliases for unions with self-referential variants.

Specifically, both of these work fine:

X: ty.TypeAlias = ty.Union[
    ty.Set["X"],
    ty.Sequence["X"],
]

Y: ty.TypeAlias = ty.Union[
    ty.Sequence[ty.Optional["Y"]],
]

but this crashes:

Z: ty.TypeAlias = ty.Union[
    ty.Set["Z"],
    ty.Sequence[ty.Optional["Z"]],
]

with

main.py: error: INTERNAL ERROR: maximum semantic analysis iteration count reached

To Reproduce

https://mypy-play.net/?mypy=1.9.0&python=3.12&flags=show-traceback&gist=5f48179cab35cd594aca11d797bf530d
@kmurphy4 kmurphy4 added the crash label Apr 17, 2024
@ilevkivskyi
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It is interesting that it looks like a slightly different version

Z = ty.Union[
    ty.Set[ty.Optional["Z"]],
    ty.Sequence[ty.Optional["Z"]],
]

hangs indefinitely, while eating memory.

@AlexWaygood AlexWaygood added the topic-type-alias TypeAlias and other type alias issues label Jun 9, 2024
@ilevkivskyi ilevkivskyi mentioned this issue Jun 9, 2024
Merged
ilevkivskyi added a commit that referenced this issue Jun 9, 2024
@ilevkivskyi @pre-commit-ci
Fix crash on recursive alias with an optional type (#17350)
428a035 
Fixes #17132

Fix is trivial, we don't need that extra `get_proper_type()`.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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crash topic-recursive-types topic-type-alias TypeAlias and other type alias issues
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Fix crash on recursive alias with an optional type ilevkivskyi/mypy
4 participants
@JelleZijlstra @ilevkivskyi @kmurphy4 @AlexWaygood