allow more dups

Author: ikonst

mypy/messages.py

@@ -1157,7 +1157,9 @@ def signature_incompatible_with_supertype(
         # note:          def f(self) -> str
         # note:      Subclass:
         # note:          def f(self, x: str) -> None
-        self.note("Superclass:", context, offset=ALIGN_OFFSET + OFFSET, code=code)
+        self.note(
+            "Superclass:", context, offset=ALIGN_OFFSET + OFFSET, allow_dups=ALLOW_DUPS, code=code
+        )
         if isinstance(original, (CallableType, Overloaded)):
             self.pretty_callable_or_overload(
                 original,
@@ -1168,9 +1170,17 @@ def signature_incompatible_with_supertype(
                 code=code,
             )
         else:
-            self.note(original_str, context, offset=ALIGN_OFFSET + 2 * OFFSET, code=code)
+            self.note(
+                original_str,
+                context,
+                offset=ALIGN_OFFSET + 2 * OFFSET,
+                allow_dups=ALLOW_DUPS,
+                code=code,
+            )
 
-        self.note("Subclass:", context, offset=ALIGN_OFFSET + OFFSET, code=code)
+        self.note(
+            "Subclass:", context, offset=ALIGN_OFFSET + OFFSET, allow_dups=ALLOW_DUPS, code=code
+        )
         if isinstance(override, (CallableType, Overloaded)):
             self.pretty_callable_or_overload(
                 override,
@@ -1181,7 +1191,13 @@ def signature_incompatible_with_supertype(
                 code=code,
             )
         else:
-            self.note(override_str, context, offset=ALIGN_OFFSET + 2 * OFFSET, code=code)
+            self.note(
+                override_str,
+                context,
+                offset=ALIGN_OFFSET + 2 * OFFSET,
+                allow_dups=ALLOW_DUPS,
+                code=code,
+            )
 
     def pretty_callable_or_overload(
         self,

test-data/unit/check-classes.test

@@ -588,6 +588,32 @@ class B(A):
     @dec
     def h(self) -> str: pass
 
+[case testOverrideIncompatibleWithMultipleSupertypes]
+class A:
+    def f(self, *, a: int) -> None:
+        return
+
+class B(A):
+    def f(self, *, b: int) -> None:  # E: Signature of "f" incompatible with supertype "A" \
+                                     # N:      Superclass: \
+                                     # N:          def f(self, *, a: int) -> None \
+                                     # N:      Subclass: \
+                                     # N:          def f(self, *, b: int) -> None
+        return
+
+class C(B):
+    def f(self, *, c: int) -> None:  # E: Signature of "f" incompatible with supertype "B" \
+                                     # N:      Superclass: \
+                                     # N:          def f(self, *, b: int) -> None \
+                                     # N:      Subclass: \
+                                     # N:          def f(self, *, c: int) -> None \
+                                     # E: Signature of "f" incompatible with supertype "A" \
+                                     # N:      Superclass: \
+                                     # N:          def f(self, *, a: int) -> None \
+                                     # N:      Subclass: \
+                                     # N:          def f(self, *, c: int) -> None
+        return
+
 [case testOverrideStaticMethodWithStaticMethod]
 class A:
     @staticmethod