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Fix crash in match statement with unmatchable ClassPattern #13731

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Merged
merged 3 commits into from
Sep 26, 2022
Merged

Fix crash in match statement with unmatchable ClassPattern #13731

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21755ad
test
hauntsaninja Sep 25, 2022
40edd4d
fix
hauntsaninja Sep 25, 2022
079a73d
okay try this
hauntsaninja Sep 25, 2022
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13 changes: 4 additions & 9 deletions mypy/checkpattern.py
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Original file line number Diff line number Diff line change
Expand Up @@ -257,16 +257,13 @@ def visit_sequence_pattern(self, o: SequencePattern) -> PatternType:
contracted_inner_types = self.contract_starred_pattern_types(
inner_types, star_position, required_patterns
)
can_match = True
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):
can_match = False
else:
contracted_new_inner_types.append(typ)
contracted_rest_inner_types.append(rest)
contracted_new_inner_types.append(typ)
contracted_rest_inner_types.append(rest)
self.update_type_map(captures, type_map)

new_inner_types = self.expand_starred_pattern_types(
contracted_new_inner_types, star_position, len(inner_types)
)
Expand All @@ -279,9 +276,7 @@ def visit_sequence_pattern(self, o: SequencePattern) -> PatternType:
#
new_type: Type
rest_type: Type = current_type
if not can_match:
new_type = UninhabitedType()
elif isinstance(current_type, TupleType):
if isinstance(current_type, TupleType):
narrowed_inner_types = []
inner_rest_types = []
for inner_type, new_inner_type in zip(inner_types, new_inner_types):
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15 changes: 15 additions & 0 deletions test-data/unit/check-python310.test
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Original file line number Diff line number Diff line change
Expand Up @@ -317,6 +317,21 @@ match x:
case [str()]:
pass

[case testMatchSequencePatternWithInvalidClassPattern]
class Example:
__match_args__ = ("value",)
def __init__(self, value: str) -> None:
self.value = value

SubClass: type[Example]

match [SubClass("a"), SubClass("b")]:
case [SubClass(value), *rest]: # E: Expected type in class pattern; found "Type[__main__.Example]"
reveal_type(value) # E: Cannot determine type of "value" \
# N: Revealed type is "Any"
reveal_type(rest) # N: Revealed type is "builtins.list[__main__.Example]"
[builtins fixtures/tuple.pyi]

[case testMatchSequenceUnion-skip]
from typing import List, Union
m: Union[List[List[str]], str]
Expand Down