8000 Retain None (unreachable) when typemap is None with `type(x) is Foo` check by sterliakov · Pull Request #18486 · python/mypy · GitHub
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Retain None (unreachable) when typemap is None with type(x) is Foo check #18486

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Merged
merged 2 commits into from
Jan 27, 2025
Merged

Retain None (unreachable) when typemap is None with type(x) is Foo check #18486

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dc581d7
Retain all-None typemaps when merging in ``type(x) == SomeType`` narr…
sterliakov Jan 18, 2025
0d549ad
Add more explicit tests
sterliakov Jan 18, 2025
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Add more explicit tests
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@sterliakov
sterliakov committed Jan 18, 2025
commit 0d549ad13089d87b684fb35fcae5a3add621481c
27 changes: 27 additions & 0 deletions test-data/unit/check-isinstance.test
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Original file line number Diff line number Diff line change
Expand Up @@ -2661,6 +2661,33 @@ y: Any
if type(y) is int:
reveal_type(y) # N: Revealed type is "builtins.int"

[case testTypeEqualsCheckUsingIsNonOverlapping]
# flags: --warn-unreachable
from typing import Union

y: str
if type(y) is int: # E: Subclass of "str" and "int" cannot exist: would have incompatible method signatures
y # E: Statement is unreachable
else:
reveal_type(y) # N: Revealed type is "builtins.str"
[builtins fixtures/isinstance.pyi]

[case testTypeEqualsCheckUsingIsNonOverlappingChild-xfail]
# flags: --warn-unreachable
from typing import Union

class A: ...
class B: ...
class C(A): ...
x: Union[B, C]
# C instance cannot be exactly its parent A, we need reversed subtyping relationship
# here (type(parent) is Child).
if type(x) is A:
reveal_type(x) # E: Statement is unreachable
else:
reveal_type(x) # N: Revealed type is "Union[__main__.B, __main__.C]"
[builtins fixtures/isinstance.pyi]

[case testTypeEqualsNarrowingUnionWithElse]
from typing import Union

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1 change: 0 additions & 1 deletion test-data/unit/check-typevar-values.test
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Expand Up @@ -744,5 +744,4 @@ def fn(w: W) -> W:
elif type(w) is int:
reveal_type(w) # N: Revealed type is "builtins.int"
return w

[builtins fixtures/isinstance.pyi]
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