Changes how TypeGuard types are checked in subtypes

mypy/messages.py

@@ -1740,7 +1740,10 @@ def format(typ: Type) -> str:
  # return type (this always works).
  return format(TypeType.make_normalized(erase_type(func.items[0].ret_type)))
  elif isinstance(func, CallableType):
- return_type = format(func.ret_type)
+ if func.type_guard is not None:
+ return_type = f'TypeGuard[{format(func.type_guard)}]'
+ else:
+ return_type = format(func.ret_type)
  if func.is_ellipsis_args:
  return 'Callable[..., {}]'.format(return_type)
  arg_strings = []

mypy/subtypes.py

@@ -310,6 +310,13 @@ def visit_type_var(self, left: TypeVarType) -> bool:
  def visit_callable_type(self, left: CallableType) -> bool:
  right = self.right
  if isinstance(right, CallableType):
+ if left.type_guard is not None and right.type_guard is not None:
+ if not self._is_subtype(left.type_guard, right.type_guard):
+ return False
+ elif right.type_guard is not None and left.type_guard is None:
+ # This means that one function has `TypeGuard` and other does not.
+ # They are not compatible. See https://github.com/python/mypy/issues/11307
+ return False
  return is_callable_compatible(
  left, right,
  is_compat=self._is_subtype,

test-data/unit/check-typeguard.test

@@ -458,3 +458,73 @@ def foobar_typeguard(x: object):
  return
  reveal_type(x) # N: Revealed type is "__main__.<subclass of "Foo" and "Bar">"
 [builtins fixtures/tuple.pyi]
+
+[case testTypeGuardAsFunctionArgAsBoolSubtype]
+from typing import Callable
+from typing_extensions import TypeGuard
+
+def accepts_bool(f: Callable[[object], bool]): pass
+
+def with_bool_typeguard(o: object) -> TypeGuard[bool]: pass
+def with_str_typeguard(o: object) -> TypeGuard[str]: pass
+def with_bool(o: object) -> bool: pass
+
+accepts_bool(with_bool_typeguard)
+accepts_bool(with_str_typeguard)
+accepts_bool(with_bool)
+[builtins fixtures/tuple.pyi]
+
+[case testTypeGuardAsFunctionArg]
+from typing import Callable
+from typing_extensions import TypeGuard
+
+def accepts_typeguard(f: Callable[[object], TypeGuard[bool]]): pass
+def different_typeguard(f: Callable[[object], TypeGuard[str]]): pass
+
+def with_typeguard(o: object) -> TypeGuard[bool]: pass
+def with_bool(o: object) -> bool: pass
+
+accepts_typeguard(with_typeguard)
+accepts_typeguard(with_bool) # E: Argument 1 to "accepts_typeguard" has incompatible type "Callable[[object], bool]"; expected "Callable[[object], TypeGuard[bool]]"
+
+different_typeguard(with_typeguard) # E: Argument 1 to "different_typeguard" has incompatible type "Callable[[object], TypeGuard[bool]]"; expected "Callable[[object], TypeGuard[str]]"
+different_typeguard(with_bool) # E: Argument 1 to "different_typeguard" has incompatible type "Callable[[object], bool]"; expected "Callable[[object], TypeGuard[str]]"
+[builtins fixtures/tuple.pyi]
+
+[case testTypeGuardAsGenericFunctionArg]
+from typing import Callable, TypeVar
+from typing_extensions import TypeGuard
+
+T = TypeVar('T')
+
+def accepts_typeguard(f: Callable[[object], TypeGuard[T]]): pass
+
+def with_bool_typeguard(o: object) -> TypeGuard[bool]: pass
+def with_str_typeguard(o: object) -> TypeGuard[str]: pass
+def with_bool(o: object) -> bool: pass
+
+accepts_typeguard(with_bool_typeguard)
+accepts_typeguard(with_str_typeguard)
+accepts_typeguard(with_bool) # E: Argument 1 to "accepts_typeguard" has incompatible type "Callable[[object], bool]"; expected "Callable[[object], TypeGuard[bool]]"
+[builtins fixtures/tuple.pyi]
+
+[case testTypeGuardAsOverloadedFunctionArg]
+# https://github.com/python/mypy/issues/11307
+from typing import Callable, TypeVar, Generic, Any, overload
+from typing_extensions import TypeGuard
+
+_T = TypeVar('_T')
+
+class filter(Generic[_T]):
+ @overload
+ def __init__(self, function: Callable[[object], TypeGuard[_T]]) -> None: pass
+ @overload
+ def __init__(self, function: Callable[[_T], Any]) -> None: pass
+ def __init__(self, function): pass
+
+def is_int_typeguard(a: object) -> TypeGuard[int]: pass
+def returns_bool(a: object) -> bool: pass
+
+reveal_type(filter(is_int_typeguard)) # N: Revealed type is "__main__.filter[builtins.int*]"
+reveal_type(filter(returns_bool)) # N: Revealed type is "__main__.filter[builtins.object*]"
+[builtins fixtures/tuple.pyi]