8000 Fix type inference in pattern matching by positional argument by sobolevn · Pull Request #13618 · python/mypy · GitHub
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Fix type inference in pattern matching by positional argument #13618

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Merged
merged 2 commits into from
Sep 7, 2022
Merged

Fix type inference in pattern matching by positional argument #13618

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2f4bd29
Fix type inference in pattern matching by positional argument
sobolevn Sep 7, 2022
311e6fc
More tests
sobolevn Sep 7, 2022
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2 changes: 1 addition & 1 deletion mypy/expandtype.py
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Original file line number Diff line number Diff line change
Expand Up @@ -136,7 +136,7 @@ def visit_erased_type(self, t: ErasedType) -> Type:
def visit_instance(self, t: Instance) -> Type:
args = self.expand_types_with_unpack(list(t.args))
if isinstance(args, list):
return Instance(t.type, args, t.line, t.column)
return t.copy_modified(args=args)
else:
return args

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67 changes: 67 additions & 0 deletions test-data/unit/check-python310.test
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Expand Up @@ -1628,3 +1628,70 @@ match var:
case ("yes", b):
reveal_type(b) # N: Revealed type is "Union[builtins.int, builtins.str]"
[builtins fixtures/tuple.pyi]

[case testMatchNamedAndKeywordsAreTheSame]
from typing import Generic, TypeVar, Union
from typing_extensions import Final
from dataclasses import dataclass

T = TypeVar("T")

class Regular:
x: str
y: int
__match_args__ = ("x",)
class ReveresedOrder:
x: int
y: str
__match_args__ = ("y",)
class GenericRegular(Generic[T]):
x: T
__match_args__ = ("x",)
class GenericWithFinal(Generic[T]):
x: T
__match_args__: Final = ("x",)
class RegularSubtype(GenericRegular[str]): ...

@dataclass
class GenericDataclass(Generic[T]):
x: T

input_arg: Union[
Regular,
ReveresedOrder,
GenericRegular[str],
GenericWithFinal[str],
RegularSubtype,
GenericDataclass[str],
]

# Positional:
match input_arg:
case Regular(a):
reveal_type(a) # N: Revealed type is "builtins.str"
case ReveresedOrder(a):
reveal_type(a) # N: Revealed type is "builtins.str"
case GenericWithFinal(a):
reveal_type(a) # N: Revealed type is "builtins.str"
case RegularSubtype(a):
reveal_type(a) # N: Revealed type is "builtins.str"
case GenericRegular(a):
reveal_type(a) # N: Revealed type is "builtins.str"
case GenericDataclass(a):
reveal_type(a) # N: Revealed type is "builtins.str"

# Keywords:
match input_arg:
case Regular(x=a):
reveal_type(a) # N: Revealed type is "builtins.str"
case ReveresedOrder(x=b): # Order is different
reveal_type(b) # N: Revealed type is "builtins.int"
case GenericWithFinal(x=a):
reveal_type(a) # N: Revealed type is "builtins.str"
case RegularSubtype(x=a):
reveal_type(a) # N: Revealed type is "builtins.str"
case GenericRegular(x=a):
reveal_type(a) # N: Revealed type is "builtins.str"
case GenericDataclass(x=a):
reveal_type(a) # N: Revealed type is "builtins.str"
[builtins fixtures/dataclasses.pyi]
0