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Incorrect redundant-expr error for isinstance on constrained TypeVars #724

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Loch64 opened this issue Aug 1, 2024 · 1 comment · May be fixed by #754
Open

Incorrect redundant-expr error for isinstance on constrained TypeVars #724

Loch64 opened this issue Aug 1, 2024 · 1 comment · May be fixed by #754
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@Loch64
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Loch64 commented Aug 1, 2024 •
edited by KotlinIsland
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Describe the problem, ie expected/actual result (if it's not blatantly obvious)

def f[T: (int, str)](t: T):
    if isinstance(t, int):  # always true and always false
        ...

Gist to reproduce

https://mypy-play.net/?mypy=basedmypy-latest&python=3.12&gist=fd75669322cbcbe6bb7c20b985768813

Basedmypy version

basedmypy 2.5.0 (compiled: yes)
@Loch64 Loch64 added the bug Something isn't working label Aug 1, 2024
@KotlinIsland
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KotlinIsland commented Aug 1, 2024 •
edited
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additionally:

def true() -> True: ...
def false() -> False: ...

if bool() and true(): ...
if bool() and false(): ...

#725

@KotlinIsland KotlinIsland changed the title Incorrect redundant-expr error for narrowing constrained TypeVars Incorrect redundant-expr error for isinstance on constrained TypeVars Aug 1, 2024
@Loch64 Loch64 removed their assignment Nov 17, 2024
@DetachHead DetachHead linked a pull request Mar 18, 2025 that will close this issue
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724 fix incorrect redundant-expr error for isinstance on constra… Loch64/basedmypy
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@Loch64 @KotlinIsland