fix: TypeGuard becomes bool instead of Any when passed as TypeVar

Author: sloboegen

mypy/constraints.py

@@ -1018,21 +1018,25 @@ def visit_callable_type(self, template: CallableType) -> list[Constraint]:
             param_spec = template.param_spec()
 
             template_ret_type, cactual_ret_type = template.ret_type, cactual.ret_type
+            bool_type = UnionType(
+                [LiteralType(True, cactual_ret_type), LiteralType(False, cactual_ret_type)]  # type: ignore[arg-type]
+            )
+
             if template.type_guard is not None and cactual.type_guard is not None:
                 template_ret_type = template.type_guard
                 cactual_ret_type = cactual.type_guard
             elif template.type_guard is not None:
                 template_ret_type = AnyType(TypeOfAny.special_form)
             elif cactual.type_guard is not None:
-                cactual_ret_type = AnyType(TypeOfAny.special_form)
+                cactual_ret_type = bool_type
 
             if template.type_is is not None and cactual.type_is is not None:
                 template_ret_type = template.type_is
                 cactual_ret_type = cactual.type_is
             elif template.type_is is not None:
                 template_ret_type = AnyType(TypeOfAny.special_form)
             elif cactual.type_is is not None:
-                cactual_ret_type = AnyType(TypeOfAny.special_form)
+                cactual_ret_type = bool_type
 
             res.extend(infer_constraints(template_ret_type, cactual_ret_type, self.direction))
 

test-data/unit/check-typeguard.test

@@ -87,6 +87,15 @@ def main(a: Tuple[T, ...]):
         reveal_type(a)  # N: Revealed type is "Tuple[T`-1, T`-1]"
 [builtins fixtures/tuple.pyi]
 
+[case testTypeGuardPassedAsTypeVarIsBool]
+from typing import Callable, TypeVar
+from typing_extensions import TypeGuard
+T = TypeVar('T')
+def is_str(x: object) -> TypeGuard[str]: ...
+def main(f: Callable[[object], T]) -> T: ...
+reveal_type(main(is_str))  # N: Revealed type is "builtins.bool"
+[builtins fixtures/tuple.pyi]
+
 [case testTypeGuardNonOverlapping]
 from typing import List
 from typing_extensions import TypeGuard

test-data/unit/check-typeis.test

@@ -104,6 +104,15 @@ def main(x: object, type_check_func: Callable[[object], TypeIs[T]]) -> T:
 reveal_type(main("a", is_str))  # N: Revealed type is "builtins.str"
 [builtins fixtures/exception.pyi]
 
+[case testTypeIsPassedAsTypeVarIsBool]
+from typing import Callable, TypeVar
+from typing_extensions import TypeIs
+T = TypeVar('T')
+def is_str(x: object) -> TypeIs[str]: pass
+def main(f: Callable[[object], T]) -> T: pass
+reveal_type(main(is_str))  # N: Revealed type is "builtins.bool"
+[builtins fixtures/tuple.pyi]
+
 [case testTypeIsUnionIn]
 from typing import Union
 from typing_extensions import TypeIs