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Make frozendict covariant in its value type #16669

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Make frozendict covariant in its value type #16669

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14 changes: 14 additions & 0 deletions stdlib/@tests/test_cases/builtins/check_frozendict-py315.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,3 +13,17 @@
assert_type(frozendict({"x": 1}), frozendict[str, int])
assert_type(frozendict([("k", 2)]), frozendict[str, int])
assert_type(frozendict({"x": 1}, y=2), frozendict[str, int])

# gh-16668: like ``Mapping``, ``frozendict`` is covariant in its value type
# (but not in its key type).
def takes_optional_values(d: frozendict[str, int | None]) -> None: ...

int_values: frozendict[str, int] = frozendict(a=1)
takes_optional_values(int_values)
assert_type(int_values.get("a"), int | None)
assert_type(int_values.get("a", 0), int)
assert_type(int_values.get("a", "x"), int | str)

def takes_object_keys(d: frozendict[object, int]) -> None: ...

takes_object_keys(int_values) # type: ignore
25 changes: 13 additions & 12 deletions stdlib/builtins.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -78,6 +78,7 @@ _T_contra = TypeVar("_T_contra", contravariant=True)
_R_co = TypeVar("_R_co", covariant=True)
_KT = TypeVar("_KT")
_VT = TypeVar("_VT")
_VT_co = TypeVar("_VT_co", covariant=True)
_S = TypeVar("_S")
_T1 = TypeVar("_T1")
_T2 = TypeVar("_T2")
Expand Down Expand Up @@ -1378,7 +1379,7 @@ class dict(MutableMapping[_KT, _VT]):

if sys.version_info >= (3, 15):
@disjoint_base
class frozendict(Mapping[_KT, _VT]):
class frozendict(Mapping[_KT, _VT_co]):
@overload
def __new__(cls, /) -> frozendict[Any, Any]: ...
@overload
Expand All @@ -1396,7 +1397,7 @@ if sys.version_info >= (3, 15):
cls: type[frozendict[str, _VT]], iterable: Iterable[tuple[str, _VT]], /, **kwargs: _VT
) -> frozendict[str, _VT]: ...

def copy(self) -> frozendict[_KT, _VT]: ...
def copy(self) -> frozendict[_KT, _VT_co]: ...

@overload
@classmethod
Expand All @@ -1406,27 +1407,27 @@ if sys.version_info >= (3, 15):
def fromkeys(cls, iterable: Iterable[_T], value: _S, /) -> frozendict[_T, _S]: ...

@overload # type: ignore[override]
def get(self, key: _KT, default: None = None, /) -> _VT | None: ...
def get(self, key: _KT, default: None = None, /) -> _VT_co | None: ...
@overload
def get(self, key: _KT, default: _VT, /) -> _VT: ...
def get(self, key: _KT, default: _VT_co, /) -> _VT_co: ... # type: ignore[misc] # pyright: ignore[reportGeneralTypeIssues] # Covariant type as parameter # pyrefly: ignore [invalid-variance]
@overload
def get(self, key: _KT, default: _T, /) -> _VT | _T: ...
def get(self, key: _KT, default: _T, /) -> _VT_co | _T: ...

def keys(self) -> dict_keys[_KT, _VT]: ...
def values(self) -> dict_values[_KT, _VT]: ...
def items(self) -> dict_items[_KT, _VT]: ...
def keys(self) -> dict_keys[_KT, _VT_co]: ...
def values(self) -> dict_values[_KT, _VT_co]: ...
def items(self) -> dict_items[_KT, _VT_co]: ...
def __len__(self) -> int: ...
def __getitem__(self, key: _KT, /) -> _VT: ...
def __getitem__(self, key: _KT, /) -> _VT_co: ...
def __reversed__(self) -> Iterator[_KT]: ...
def __iter__(self) -> Iterator[_KT]: ...
def __hash__(self) -> int: ...
def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
def __or__(self, value: dict[_T1, _T2] | frozendict[_T1, _T2], /) -> frozendict[_KT | _T1, _VT | _T2]: ...
def __or__(self, value: dict[_T1, _T2] | frozendict[_T1, _T2], /) -> frozendict[_KT | _T1, _VT_co | _T2]: ...

@overload
def __ror__(self, value: dict[_T1, _T2], /) -> dict[_KT | _T1, _VT | _T2]: ...
def __ror__(self, value: dict[_T1, _T2], /) -> dict[_KT | _T1, _VT_co | _T2]: ...
@overload
def __ror__(self, value: frozendict[_T1, _T2], /) -> frozendict[_KT | _T1, _VT | _T2]: ...
def __ror__(self, value: frozendict[_T1, _T2], /) -> frozendict[_KT | _T1, _VT_co | _T2]: ...

@disjoint_base
class set(MutableSet[_T]):
Expand Down
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