Skip to content

Fix regression involving dict or on recursive dict #21148

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
hauntsaninja wants to merge 3 commits into from
+17 −12
Closed

Fix regression involving dict or on recursive dict #21148

Show file tree
Hide file tree
Changes from 2 commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
37d2ee4
Fix regression involving dict or on recursive dict
hauntsaninja Apr 2, 2026
7f48f4d
fix fixture
hauntsaninja Apr 2, 2026
31a61a2
use is_same_type for symmetry
hauntsaninja Apr 2, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 5 additions & 3 deletions mypy/constraints.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -506,9 +506,11 @@ def handle_recursive_union(template: UnionType, actual: Type, direction: int) ->
# the union in two parts, and try inferring sequentially.
non_type_var_items = [t for t in template.items if not isinstance(t, TypeVarType)]
type_var_items = [t for t in template.items if isinstance(t, TypeVarType)]
return infer_constraints(
UnionType.make_union(non_type_var_items), actual, direction
) or infer_constraints(UnionType.make_union(type_var_items), actual, direction)
ret = infer_constraints(UnionType.make_union(non_type_var_items), actual, direction)
if ret or any(mypy.subtypes.is_subtype(t, actual) for t in non_type_var_items):
Copy link
Copy Markdown
Member

@ilevkivskyi ilevkivskyi Apr 2, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Using is_subtype() independently of direction is suspicious.

return ret
ret = infer_constraints(UnionType.make_union(type_var_items), actual, direction)
return ret


def any_constraints(options: list[list[Constraint] | None], *, eager: bool) -> list[Constraint]:
Expand Down
9 changes: 9 additions & 0 deletions test-data/unit/check-recursive-types.test
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1040,3 +1040,12 @@ def f(obj: OneClass) -> None:
else:
reveal_type(obj) # N: Revealed type is "builtins.list[...]"
[builtins fixtures/isinstancelist.pyi]

[case testRecursiveDictOr]
from typing_extensions import TypeAlias
A: TypeAlias = "dict[str, A | int]"

def f(d1: A, d2: A) -> None:
d3: A = {**d1, **d2}
d4: A = d1 | d2
[builtins fixtures/dict-full.pyi]
12 changes: 3 additions & 9 deletions test-data/unit/fixtures/dict-full.pyi
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ from typing import (
)

T = TypeVar('T')
T1 = TypeVar('T1')
T2 = TypeVar('T2')
KT = TypeVar('KT')
VT = TypeVar('VT')
Expand Down Expand Up @@ -39,15 +40,8 @@ class dict(Mapping[KT, VT]):
def get(self, key: KT, default: T, /) -> Union[VT, T]: pass
def __len__(self) -> int: ...

# This was actually added in 3.9:
@overload
def __or__(self, __value: dict[KT, VT]) -> dict[KT, VT]: ...
@overload
def __or__(self, __value: dict[T, T2]) -> dict[Union[KT, T], Union[VT, T2]]: ...
@overload
def __ror__(self, __value: dict[KT, VT]) -> dict[KT, VT]: ...
@overload
def __ror__(self, __value: dict[T, T2]) -> dict[Union[KT, T], Union[VT, T2]]: ...
def __or__(self, value: dict[T1, T2], /) -> dict[KT | T1, VT | T2]: ...
def __ror__(self, value: dict[T1, T2], /) -> dict[KT | T1, VT | T2]: ...
# dict.__ior__ should be kept roughly in line with MutableMapping.update()
@overload # type: ignore[misc]
def __ior__(self, __value: _typeshed.SupportsKeysAndGetItem[KT, VT]) -> Self: ...
Expand Down
Loading