[match-case]: mapping pattern narrowing inconsistent with equivalent isinstance #2865
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from typing import reveal_type
from collections.abc import Mapping
def test_instance(x: dict | int) -> None:
if isinstance(x, Mapping):
reveal_type(x)
else:
reveal_type(x)
def test_match(x: dict | int) -> None:
match x:
case {}: # equivalent to isinstance(x, Mapping)
reveal_type(x)
case _:
reveal_type(x)Revealed type: `dict[Unknown, Unknown] | (int & Top[Mapping[Unknown, object]])` (revealed-type) [Ln 6, Col 21]
Revealed type: `int & ~Top[Mapping[Unknown, object]]` (revealed-type) [Ln 8, Col 21]
Revealed type: `dict[Unknown, Unknown] | int` (revealed-type) [Ln 13, Col 25]
Revealed type: `dict[Unknown, Unknown] | int` (revealed-type) [Ln 15, Col 25]
The isinstance(x, Mapping) and case {} are equivalent at runtime and should produce the same narrowing.
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