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Generalise PEP 798 support to SupportsKeysAndGetItem #22021

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Merged
hauntsaninja merged 1 commit into from
Sep 22, 2026
Merged

Generalise PEP 798 support to SupportsKeysAndGetItem #22021

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4 changes: 3 additions & 1 deletion mypy/checkexpr.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6013,7 +6013,9 @@ def visit_dictionary_comprehension(self, e: DictionaryComprehension) -> Type:
)
if e.key is None:
# Logic and motivation here is similar to check_generator_or_comprehension().
arg_types = [self.chk.named_generic_type("typing.Mapping", [ktdef, vtdef])]
arg_types = [
self.chk.named_generic_type("_typeshed.SupportsKeysAndGetItem", [ktdef, vtdef])
]
arg_kinds = [nodes.ARG_POS]
arg_names = [None]
args = [e.value]
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18 changes: 15 additions & 3 deletions test-data/unit/check-python315.test
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Expand Up @@ -5,7 +5,7 @@ def test(x: list[list[int]], y: list[dict[str, int]]) -> None:
reveal_type([*i for i in x]) # N: Revealed type is "builtins.list[builtins.int]"
reveal_type({*i for i in x}) # N: Revealed type is "builtins.set[builtins.int]"
reveal_type({**d for d in y}) # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"
[builtins fixtures/isinstancelist.pyi]
[builtins fixtures/primitives.pyi]

[case testStarUnpackInComprehensionBasicsOld]
# flags: --no-native-parser
Expand All @@ -14,11 +14,23 @@ def test(x: list[list[int]], y: list[dict[str, int]]) -> None:
reveal_type([*i for i in x]) # N: Revealed type is "builtins.list[builtins.int]"
reveal_type({*i for i in x}) # N: Revealed type is "builtins.set[builtins.int]"
reveal_type({**d for d in y}) # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"
[builtins fixtures/isinstancelist.pyi]
[builtins fixtures/primitives.pyi]

[case testStarUnpackInComprehensionUnion]
def test(x: list[list[int]] | list[list[str]], y: list[dict[str, int]] | list[dict[str, str]]) -> None:
reveal_type([*i for i in x]) # N: Revealed type is "builtins.list[builtins.int | builtins.str]"
reveal_type({*i for i in x}) # N: Revealed type is "builtins.set[builtins.int | builtins.str]"
reveal_type({**d for d in y}) # N: Revealed type is "builtins.dict[builtins.str | builtins.str, builtins.int | builtins.str]"
[builtins fixtures/isinstancelist.pyi]
[builtins fixtures/primitives.pyi]

[case testDoubleStarUnpackInComprehensionStructuralMapping]
class MappingLike:
def keys(self) -> list[str]:
return ["key"]
def __getitem__(self, key: str) -> int:
return 1

def test(xs: list[MappingLike]) -> dict[str, int]:
reveal_type({**x for x in xs}) # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"
return {**x for x in xs}
[builtins fixtures/primitives.pyi]
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