diff --git a/mypy/constraints.py b/mypy/constraints.py index 848dec07cbcb..45a96b993563 100644 --- a/mypy/constraints.py +++ b/mypy/constraints.py @@ -3,7 +3,8 @@ from __future__ import annotations from collections.abc import Iterable, Sequence -from typing import TYPE_CHECKING, Final +from typing import TYPE_CHECKING, Final, cast +from typing_extensions import TypeGuard import mypy.subtypes import mypy.typeops @@ -340,6 +341,16 @@ def _infer_constraints( if isinstance(actual, AnyType) and actual.type_of_any == TypeOfAny.suggestion_engine: return [] + # type[A | B] is always represented as type[A] | type[B] internally. + # This makes our constraint solver choke on type[T] <: type[A] | type[B], + # solving T as generic meet(A, B) which is often `object`. Force unwrap such unions + # if both sides are type[...] or unions thereof. See `testTypeVarType` test + type_type_unwrapped = False + if _is_type_type(template) and _is_type_type(actual): + type_type_unwrapped = True + template = _unwrap_type_type(template) + actual = _unwrap_type_type(actual) + # If the template is simply a type variable, emit a Constraint directly. # We need to handle this case before handling Unions for two reasons: # 1. "T <: Union[U1, U2]" is not equivalent to "T <: U1 or T <: U2", @@ -373,6 +384,11 @@ def _infer_constraints( if direction == SUPERTYPE_OF and isinstance(actual, UnionType): res = [] for a_item in actual.items: + # `orig_template` has to be preserved intact in case it's recursive. + # If we unwraped ``type[...]`` previously, wrap the item back again, + # as ``type[...]`` can't be removed from `orig_template`. + if type_type_unwrapped: + a_item = TypeType.make_normalized(a_item) res.extend(infer_constraints(orig_template, a_item, direction)) return res @@ -411,6 +427,26 @@ def _infer_constraints( return template.accept(ConstraintBuilderVisitor(actual, direction, skip_neg_op)) +def _is_type_type(tp: ProperType) -> TypeGuard[TypeType | UnionType]: + """Is ``tp`` a ``type[...]`` or a union thereof? + + ``Type[A | B]`` is internally represented as ``type[A] | type[B]``, and this + troubles the solver sometimes. + """ + return ( + isinstance(tp, TypeType) + or isinstance(tp, UnionType) + and all(isinstance(get_proper_type(o), TypeType) for o in tp.items) + ) + + +def _unwrap_type_type(tp: TypeType | UnionType) -> ProperType: + """Extract the inner type from ``type[...]`` expression or a union thereof.""" + if isinstance(tp, TypeType): + return tp.item + return UnionType.make_union([cast(TypeType, get_proper_type(o)).item for o in tp.items]) + + def infer_constraints_if_possible( template: Type, actual: Type, direction: int ) -> list[Constraint] | None: diff --git a/test-data/unit/check-typevar-unbound.test b/test-data/unit/check-typevar-unbound.test index ed6beaa100db..587ae6577328 100644 --- a/test-data/unit/check-typevar-unbound.test +++ b/test-data/unit/check-typevar-unbound.test @@ -69,3 +69,50 @@ from typing import TypeVar T = TypeVar("T") def f(t: T) -> None: a, *b = t # E: "object" object is not iterable + +[case testTypeVarType] +from typing import Mapping, Type, TypeVar, Union +T = TypeVar("T") + +class A: ... +class B: ... + +lookup_table: Mapping[str, Type[Union[A,B]]] +def load(lookup_table: Mapping[str, Type[T]], lookup_key: str) -> T: + ... +reveal_type(load(lookup_table, "a")) # N: Revealed type is "Union[__main__.A, __main__.B]" + +lookup_table_a: Mapping[str, Type[A]] +def load2(lookup_table: Mapping[str, Type[Union[T, int]]], lookup_key: str) -> T: + ... +reveal_type(load2(lookup_table_a, "a")) # N: Revealed type is "__main__.A" + +[builtins fixtures/tuple.pyi] + +[case testTypeVarTypeAssignment] +# Adapted from https://github.com/python/mypy/issues/12115 +from typing import TypeVar, Type, Callable, Union, Any + +t1: Type[bool] = bool +t2: Union[Type[bool], Type[str]] = bool + +T1 = TypeVar("T1", bound=Union[bool, str]) +def foo1(t: Type[T1]) -> None: ... +foo1(t1) +foo1(t2) + +T2 = TypeVar("T2", bool, str) +def foo2(t: Type[T2]) -> None: ... +foo2(t1) +# Rejected correctly: T2 cannot be Union[bool, str] +foo2(t2) # E: Value of type variable "T2" of "foo2" cannot be "Union[bool, str]" + +T3 = TypeVar("T3") +def foo3(t: Type[T3]) -> None: ... +foo3(t1) +foo3(t2) + +def foo4(t: Type[Union[bool, str]]) -> None: ... +foo4(t1) +foo4(t2) +[builtins fixtures/tuple.pyi]