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Fix false unreachable warning in tuple patterns #22165

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Fix false unreachable warning in tuple patterns #22165

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4e37da5
fix: stop sequence patterns after impossible items
jstar0 Oct 10, 2026
64d5f60
fix: preserve empty starred pattern matches
jstar0 Oct 10, 2026
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2 changes: 2 additions & 0 deletions mypy/checkpattern.py
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Original file line number Diff line number Diff line change
Expand Up @@ -337,6 +337,8 @@ def visit_sequence_pattern(self, o: SequencePattern) -> PatternType:
for p, t in zip(o.patterns, contracted_inner_types):
pattern_type = self.accept(p, t)
typ, rest, type_map = pattern_type
if is_uninhabited(typ) and not isinstance(p, StarredPattern):
return self.early_non_match()
contracted_new_inner_types.append(typ)
contracted_rest_inner_types.append(rest)
self.update_type_map(captures, type_map)
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12 changes: 12 additions & 0 deletions test-data/unit/check-python310.test
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Expand Up @@ -315,6 +315,18 @@ match m:
reveal_type(m) # N: Revealed type is "tuple[Literal[1], Literal['str']]"
[builtins fixtures/list.pyi]

[case testMatchSequencePatternTupleUnionStopsAfterUnmatchedItem]
# flags: --strict-equality --warn-unreachable
from typing import Literal

m: tuple[Literal["a"], None] | tuple[Literal["b"], int] = ("a", None)
match m:
case "a", None:
pass
case _:
pass
[builtins fixtures/tuple.pyi]

[case testMatchSequencePatternTupleStarred]
# flags: --strict-equality --warn-unreachable
from typing import Tuple
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