IDEA-122661 "Method overloads method of superclass" inspection missing default methods in Java 8 interfaces

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/visibility/MethodOverloadsParentMethodInspectionBase.java

@@ -17,6 +17,7 @@ package com.siyeh.ig.visibility;
 
 import com.intellij.codeInspection.ui.SingleCheckboxOptionsPanel;
 import com.intellij.psi.*;
+import com.intellij.psi.util.PsiUtil;
 import com.siyeh.InspectionGadgetsBundle;
 import com.siyeh.ig.BaseInspection;
 import com.siyeh.ig.BaseInspectionVisitor;
@@ -85,18 +86,36 @@ public class MethodOverloadsParentMethodInspectionBase extends BaseInspection {
       if (MethodUtils.hasSuper(method)) {
         return;
       }
-      PsiClass ancestorClass = aClass.getSuperClass();
       final Set<PsiClass> visitedClasses = new HashSet<PsiClass>();
-      while (ancestorClass != null) {
-        if (!visitedClasses.add(ancestorClass)) {
-          return;
-        }
-        if (methodOverloads(method, ancestorClass)) {
-          registerMethodError(method);
-          return;
-        }
-        ancestorClass = ancestorClass.getSuperClass();
+      processSupers(method, aClass, aClass, visitedClasses);
+    }
+
+    private boolean processSupers(final PsiMethod method,
+                                  final PsiClass psiClass,
+                                  final PsiClass initialClass,
+                                  final Set<PsiClass> visitedClasses) {
+      if (!visitedClasses.add(psiClass)) {
+        return false;
       }
+      if (initialClass != psiClass && methodOverloads(method, psiClass)) {
+        registerMethodError(method);
+        return true;
+      } 
+      else {
+        if (PsiUtil.isLanguageLevel8OrHigher(method)) {
+          for (PsiClass superClass : psiClass.getSupers()) {
+            if (processSupers(method, superClass, initialClass, visitedClasses)) {
+              return true;
+            }
+          }
+        } else {
+          final PsiClass superClass = psiClass.getSuperClass();
+          if (superClass != null) {
+            return processSupers(method, superClass, initialClass, visitedClasses);
+          }
+        }
+      }
+      return false;
     }
 
     private boolean methodOverloads(PsiMethod method, PsiClass ancestorClass) {
@@ -107,6 +126,7 @@ public class MethodOverloadsParentMethodInspectionBase extends BaseInspection {
       for (final PsiMethod testMethod : methods) {
         if (!testMethod.hasModifierProperty(PsiModifier.PRIVATE) &&
             !testMethod.hasModifierProperty(PsiModifier.STATIC) &&
+            !testMethod.hasModifierProperty(PsiModifier.ABSTRACT) &&
             !isOverriddenInClass(testMethod, method.getContainingClass())) {
           final PsiParameterList testParameterList = testMethod.getParameterList();
           final PsiParameter[] testParameters = testParameterList.getParameters();

plugins/InspectionGadgets/test/com/siyeh/igtest/visibility/method_overloads_parent_method/MethodOverloadsParentMethod.java

@@ -24,4 +24,25 @@ class Parent {
   Object bla(double d) {
     return null;
   }
+}
+
+class DefaultMethod {
+  public static interface IFoo {
+    default void foo(int i) {
+      System.out.println("IFoo.foo(int): " + i);
+    }
+
+    void bar(int i);
+    
+  }
+
+  public static class Foo implements IFoo {
+    public void foo(long l) {
+      System.out.println("Foo.foo(long): " + l);
+    }
+
+    public void bar(long l) {
+      System.out.println("Foo.bar(long): " + l);
+    }
+  }
 }

plugins/InspectionGadgets/test/com/siyeh/igtest/visibility/method_overloads_parent_method/expected.xml

@@ -21,4 +21,11 @@
     <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Method overloads method of superclass</problem_class>
     <description>Method &lt;code&gt;bla()&lt;/code&gt; overloads a compatible method of a superclass, when overriding might have been intended #loc</description>
   </problem>
+
+  <problem>
+    <file>MethodOverloadsParentMethod.java</file>
+    <line>40</line>
+    <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Method overloads method of superclass</problem_class>
+    <description>Method &lt;code&gt;foo()&lt;/code&gt; overloads a compatible method of a superclass, when overriding might have been intended #loc</description>
+  </problem>
 </problems>

plugins/InspectionGadgets/testsrc/com/siyeh/ig/visibility/MethodOverloadsParentMethodInspectionTest.java

@@ -1,5 +1,9 @@
 package com.siyeh.ig.visibility;
 
+import com.intellij.openapi.projectRoots.Sdk;
+import com.intellij.openapi.roots.LanguageLevelProjectExtension;
+import com.intellij.pom.java.LanguageLevel;
+import com.intellij.testFramework.IdeaTestUtil;
 import com.siyeh.ig.IGInspectionTestCase;
 
 public class MethodOverloadsParentMethodInspectionTest extends IGInspectionTestCase {
@@ -7,4 +11,12 @@ public class MethodOverloadsParentMethodInspectionTest extends IGInspectionTestC
   public void test() throws Exception {
     doTest("com/siyeh/igtest/visibility/method_overloads_parent_method", new MethodOverloadsParentMethodInspection());
   }
+
+  @Override
+  protected Sdk getTestProjectSdk() {
+    final Sdk sdk = IdeaTestUtil.getMockJdk17();
+    LanguageLevelProjectExtension.getInstance(getProject()).setLanguageLevel(LanguageLevel.HIGHEST);
+    return sdk;
+  }
+  
 }