ambiguous constants references: shadowing (IDEA-146058)

java/java-psi-impl/src/com/intellij/psi/scope/conflictResolvers/JavaVariableConflictResolver.java

@@ -69,10 +69,10 @@ public class JavaVariableConflictResolver implements PsiConflictResolver{
         Boolean oldClassIsInheritor = null;
         if (newClass != null && oldClass != null) {
           if (newClass.isInheritor(oldClass, true)) {
-            if (!(scope instanceof PsiClass) ||
-                scope.equals(oldClass) ||
+            if (scope != null &&
+                (scope.equals(oldClass) ||
                 scope.equals(newClass) ||
-                !((PsiClass)scope).isInheritorDeep(oldClass, newClass)) {
+                !((PsiClass)scope).isInheritorDeep(oldClass, newClass))) {
               // candidate is better
               conflicts.remove(currentResult);
               currentResult = candidate;

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting/AmbiguousConstants.java

@@ -0,0 +1,28 @@
+
+class MultipleInheritance {
+  interface A {
+    int X = 1;
+  }
+
+  interface B extends A {
+    int X = 2;
+  }
+
+  interface C extends A, B {
+    int Y = C.<error descr="Reference to 'X' is ambiguous, both 'A.X' and 'B.X' match">X</error>;
+  }
+}
+
+class Shadowing {
+  interface A {
+    int X = 1;
+  }
+
+  interface B extends A {
+    int X = 2;
+  }
+
+  interface C extends B {
+    int Y = C.X;
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/LightAdvHighlightingTest.java

@@ -379,6 +379,10 @@ public class LightAdvHighlightingTest extends LightDaemonAnalyzerTestCase {
     doTest(false, false);
   }
 
+  public void testAmbiguousConstants() throws Exception {
+    doTest(false, false);
+  }
+
   public void testInsane() throws IOException {
     configureFromFileText("x.java", "class X { \nx_x_x_x\n }");
     List<HighlightInfo> infos = highlightErrors();