fix

Author: hauntsaninja

mypy/erasetype.py

@@ -101,11 +101,12 @@ def visit_unpack_type(self, t: UnpackType) -> ProperType:
     def visit_callable_type(self, t: CallableType) -> ProperType:
         # We must preserve the fallback type for overload resolution to work.
         any_type = AnyType(TypeOfAny.special_form)
+        ret_type = t.ret_type if t.is_type_obj() else any_type
         return CallableType(
             arg_types=[any_type, any_type],
             arg_kinds=[ARG_STAR, ARG_STAR2],
             arg_names=[None, None],
-            ret_type=any_type,
+            ret_type=ret_type,
             fallback=t.fallback,
             is_ellipsis_args=True,
             implicit=True,

mypy/meet.py

@@ -588,7 +588,7 @@ def _type_object_overlap(left: Type, right: Type) -> bool:
 def is_overlapping_erased_types(
     left: Type, right: Type, *, ignore_promotions: bool = False
 ) -> bool:
-    """The same as 'is_overlapping_erased_types', except the types are erased first."""
+    """The same as 'is_overlapping_types', except the types are erased first."""
     return is_overlapping_types(
         erase_type(left),
         erase_type(right),

test-data/unit/check-functools.test

@@ -592,7 +592,8 @@ def f1(cls: type[A]) -> None:
 
 def f2() -> None:
     A()  # E: Cannot instantiate abstract class "A" with abstract attribute "method"
-    partial_cls = partial(A)  # E: Cannot instantiate abstract class "A" with abstract attribute "method"
+    partial_cls = partial(A)  # E: Cannot instantiate abstract class "A" with abstract attribute "method" \
+                              # E: Argument 1 to "partial" has incompatible type "Type[A]"; expected "Callable[..., A]"
     partial_cls()  # E: Cannot instantiate abstract class "A" with abstract attribute "method"
 [builtins fixtures/tuple.pyi]
 

test-data/unit/check-optional.test

@@ -1343,3 +1343,19 @@ def f(x: object) -> None:
         with C():
             pass
 [builtins fixtures/tuple.pyi]
+
+[case testRefineAwayNoneCallbackProtocol]
+# Regression test for issue encountered in https://github.com/python/mypy/pull/18347#issuecomment-2564062070
+from __future__ import annotations
+from typing import Protocol
+
+class CP(Protocol):
+    def __call__(self, parameters: str) -> str: ...
+
+class NotSet: ...
+
+class Task:
+    def with_opt(self, trn: CP | type[NotSet] | None):
+        if trn is not NotSet:
+            reveal_type(trn)  # N: Revealed type is "Union[__main__.CP, Type[__main__.NotSet], None]"
+[builtins fixtures/tuple.pyi]