inherit unrelated abstract/default through hierarchy: don't merge methods with not override equivalent signatures (IDEA-146135)

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/GenericsHighlightUtil.java

@@ -457,8 +457,8 @@ public class GenericsHighlightUtil {
         if (aClass.findMethodsBySignature(method, false).length > 0) continue;
         final PsiClass containingClass = method.getContainingClass();
         if (containingClass == null) continue;
-        final PsiSubstitutor containingClassSubstitutor =
-          TypeConversionUtil.getSuperClassSubstitutor(containingClass, aClass, PsiSubstitutor.EMPTY);
+        final PsiSubstitutor containingClassSubstitutor = TypeConversionUtil.getClassSubstitutor(containingClass, aClass, PsiSubstitutor.EMPTY);
+        if (containingClassSubstitutor == null) continue;
         final PsiSubstitutor finalSubstitutor =
           PsiSuperMethodImplUtil.obtainFinalSubstitutor(containingClass, containingClassSubstitutor, hms.getSubstitutor(), false);
         final MethodSignatureBackedByPsiMethod signature = MethodSignatureBackedByPsiMethod.create(method, finalSubstitutor, false);
@@ -499,7 +499,11 @@ public class GenericsHighlightUtil {
         final PsiClass unrelatedMethodContainingClass = unrelatedMethod.getContainingClass();
         if (unrelatedMethodContainingClass == null) continue;
         if (!aClass.hasModifierProperty(PsiModifier.ABSTRACT) && astracts != null && unrelatedMethodContainingClass.isInterface()) {
-          if (defaultMethodContainingClass.isInheritor(unrelatedMethodContainingClass, true)) continue;
+          if (defaultMethodContainingClass.isInheritor(unrelatedMethodContainingClass, true) && 
+              MethodSignatureUtil.isSubsignature(unrelatedMethod.getSignature(PsiSubstitutor.EMPTY), 
+                                                 defaultMethod.getSignature(PsiSubstitutor.EMPTY))) {
+            continue;
+          }
           final String key = aClass instanceof PsiEnumConstantInitializer ? "enum.constant.should.implement.method" : "class.must.be.abstract";
           final String message = JavaErrorMessages.message(key, HighlightUtil.formatClass(aClass, false), JavaHighlightUtil.formatMethod(astracts.get(0)), 
                                                            HighlightUtil.formatClass(unrelatedMethodContainingClass, false));

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/interfaceMethods/SubsignatureCheckWhen2DifferentMethodsBecomeOverrideEquivalent.java

@@ -0,0 +1,85 @@
+
+class Test1 {
+  interface A {
+    void foo(String x);
+  }
+
+  interface C<T> extends A {
+
+    default void foo(T x) { }
+  }
+
+  class <error descr="Class 'D' must either be declared abstract or implement abstract method 'foo(String)' in 'A'">D</error> implements C<String> { }
+  interface E extends C<String> { }
+}
+
+class Test2 {
+  interface A {
+    default void foo(String x) {}
+  }
+
+  interface C<T> extends A {
+
+    void foo(T x);
+  }
+
+  <error descr="Class 'D' must either be declared abstract or implement abstract method 'foo(T)' in 'C'">class <error descr="Class 'D' must either be declared abstract or implement abstract method 'foo(T)' in 'C'">D</error> implements C<String></error> {}
+  interface E extends C<String> {}
+}
+
+class Test3 {
+  interface A {
+    default void foo(String x) {}
+  }
+
+  interface C<T> extends A {
+
+    default void foo(T x) {}
+  }
+
+  class D implements C<String> { }
+  interface E extends C<String> { }
+}
+
+class Test4 {
+  interface A {
+    void foo(String x);
+  }
+
+  interface C<T> extends A {
+
+    void foo(T x);
+  }
+
+  abstract class D implements C<String>, A { }
+  interface E extends C<String>, A {}
+}
+
+class Test5 {
+  interface A {
+    void foo(String x);
+  }
+
+  abstract class B implements A { }
+
+  interface C<T> extends A {
+    default void foo(T x) { }
+  }
+
+  class <error descr="Class 'D' must either be declared abstract or implement abstract method 'foo(String)' in 'A'">D</error> extends B implements C<String> { }
+}
+
+
+class Test6 {
+  interface A {
+    default void foo(String s) { }
+  }
+
+  interface B extends A {}
+
+  interface C<T> extends A {
+    default void foo(T t) {}
+  }
+  abstract static class D implements C<String>, B { }
+  static class E extends D {}
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/Interface8MethodsHighlightingTest.java

@@ -93,6 +93,10 @@ public class Interface8MethodsHighlightingTest extends LightCodeInsightFixtureTe
     doTest();
   }
 
+  public void testSubsignatureCheckWhen2DifferentMethodsBecomeOverrideEquivalent() throws Exception {
+    doTest();
+  }
+
   private void doTest() {
     doTest(false, false);
   }