Removes incorrect override check on overloaded methods

mypy/checker.py

@@ -610,7 +610,9 @@ def _visit_func_def(self, defn: FuncDef) -> None:
         """Type check a function definition."""
         self.check_func_item(defn, name=defn.name())
         if defn.info:
-            if not defn.is_dynamic():
+            if not defn.is_dynamic() and not defn.is_overload:
+                # If the definition is the implementation for an overload, the legality
+                # of the override has already been typechecked.
                 self.check_method_override(defn)
             self.check_inplace_operator_method(defn)
         if defn.original_def:

test-data/unit/check-overloading.test

@@ -1399,3 +1399,94 @@ def g(x: Tuple[A, B]) -> D: ...
 def g(x: Any) -> Any:...
 
 [builtins fixtures/tuple.pyi]
+
+[case testOverloadWithMethodOverrideAndImplementation]
+from typing import overload, Union, Any
+
+class Parent:
+    @overload
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: str) -> str: ...
+    def f(self, arg: Any) -> Any: ...
+
+class Child1(Parent):
+    @overload
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: str) -> str: ...
+    def f(self, arg: Union[int, str]) -> Union[int, str]: ...
+
+class Child2(Parent):
+    @overload
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: str) -> str: ...
+    def f(self, arg: Union[int, str]) -> int: ... # E: Overloaded function implementation cannot produce return type of signature 2
+
+class Child3(Parent):
+    @overload
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: str) -> str: ...
+    def f(self, arg: Any) -> Any: ...
+
+class Child4(Parent):
+    @overload
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: str) -> str: ...
+    def f(self, arg: Union[int, str]) -> Union[int, str]:
+        return True  # E: Incompatible return value type (got "bool", expected "Union[int, str]")
+
+[builtins fixtures/tuple.pyi]
+
+[case testOverloadWithIncompatibleMethodOverrideAndImplementation]
+from typing import overload, Union, Any
+
+class StrSub: pass
+
+class ParentWithTypedImpl:
+    @overload
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: str) -> str: ...
+    def f(self, arg: Union[int, str]) -> Union[int, str]: ...
+
+class Child1(ParentWithTypedImpl):
+    @overload # E: Signature of "f" incompatible with supertype "ParentWithTypedImpl"
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: StrSub) -> str: ...
+    def f(self, arg: Union[int, StrSub]) -> Union[int, str]: ...
+
+class Child2(ParentWithTypedImpl):
+    @overload # E: Signature of "f" incompatible with supertype "ParentWithTypedImpl"
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: StrSub) -> str: ...
+    def f(self, arg: Any) -> Any: ...
+
+class ParentWithDynamicImpl:
+    @overload
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: str) -> str: ...
+    def f(self, arg: Any) -> Any: ...
+
+class Child3(ParentWithDynamicImpl):
+    @overload # E: Signature of "f" incompatible with supertype "ParentWithDynamicImpl"
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: StrSub) -> str: ...
+    def f(self, arg: Union[int, StrSub]) -> Union[int, str]: ...
+
+class Child4(ParentWithDynamicImpl):
+    @overload # E: Signature of "f" incompatible with supertype "ParentWithDynamicImpl"
+    def f(self, arg: int) -> int: ...
+    @overload
+    def f(self, arg: StrSub) -> str: ...
+    def f(self, arg: Any) -> Any: ...
+
+[builtins fixtures/tuple.pyi]
+