Fix incorrect type inference when inherited from Any class (#8019)

Fixes #8001

Author: TH3CHARLie

mypy/checkexpr.py

@@ -2470,6 +2470,14 @@ def lookup_definer(typ: Instance, attr_name: str) -> Optional[str]:
             else:
                 return result
 
+        # We finish invoking above operators and no early return happens. Therefore,
+        # we check if either the LHS or the RHS is Instance and fallbacks to Any,
+        # if so, we also return Any
+        if ((isinstance(left_type, Instance) and left_type.type.fallback_to_any) or
+                (isinstance(right_type, Instance) and right_type.type.fallback_to_any)):
+            any_type = AnyType(TypeOfAny.special_form)
+            return any_type, any_type
+
         # STEP 4b:
         # Sometimes, the variants list is empty. In that case, we fall-back to attempting to
         # call the __op__ method (even though it's missing).

test-data/unit/check-classes.test

@@ -6575,3 +6575,24 @@ class C:
 from typing import Callable
 class C:
     x: Callable[[C], int] = lambda x: x.y.g()  # E: "C" has no attribute "y"
+
+[case testOpWithInheritedFromAny]
+from typing import Any
+C: Any
+class D(C):
+    pass
+
+class D1(C):
+    def __add__(self, rhs: float) -> D1:
+        return self
+
+reveal_type(0.5 + C)  # N: Revealed type is 'Any'
+
+reveal_type(0.5 + D())  # N: Revealed type is 'Any'
+reveal_type(D() + 0.5)  # N: Revealed type is 'Any'
+reveal_type("str" + D())  # N: Revealed type is 'builtins.str'
+reveal_type(D() + "str")  # N: Revealed type is 'Any'
+
+
+reveal_type(0.5 + D1())  # N: Revealed type is 'Any'
+reveal_type(D1() + 0.5)  # N: Revealed type is '__main__.D1'