abstract method overrides abstract: distinguish between covariant returns (IDEA-121930)

(cherry picked from commit 52e7e2b268ad91e5c9a23c8a4671b1a3b9db89f5)

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/inheritance/AbstractMethodOverridesAbstractMethodInspection.java

@@ -217,7 +217,7 @@ public class AbstractMethodOverridesAbstractMethodInspection extends BaseInspect
       if (aClass == null || superClass == null) return false;
       final PsiSubstitutor substitutor = TypeConversionUtil.getSuperClassSubstitutor(superClass, aClass, PsiSubstitutor.EMPTY);
       final PsiType type2 = method2.getReturnType();
-      return Comparing.equal(TypeConversionUtil.erasure(type1), TypeConversionUtil.erasure(substitutor.substitute(type2)));
+      return Comparing.equal(type1, substitutor.substitute(type2));
     }
 
     private boolean isAbstract(PsiMethod method) {

plugins/InspectionGadgets/test/com/siyeh/igtest/inheritance/abstract_method_overrides_abstract_method/AbstractMethodOverridesAbstractMethod.java

@@ -78,4 +78,17 @@ class Java8DefaultMethods {
           System.out.println("sub");
       }
   }
-}
+}
+
+class CovariantReturnTypes {
+  interface A<T> {}
+  interface Foo {
+    A<? extends Number> test();
+  }
+
+  interface Bar extends Foo {
+    @Override
+    A<Integer> test();
+  }
+}
+