correct super method hierarchy for multiple inheritance

java/java-psi-impl/src/com/intellij/psi/impl/PsiSuperMethodImplUtil.java

@@ -215,15 +215,15 @@ public class PsiSuperMethodImplUtil {
       LOG.assertTrue(copy.getMethod().isValid());
       map.put(signature, copy);
     }
-    else if (isSuperMethod(aClass, existing, hierarchicalMethodSignature)) {
-      mergeSupers(existing, hierarchicalMethodSignature);
-    }
     else if (isReturnTypeIsMoreSpecificThan(hierarchicalMethodSignature, existing) && isSuperMethod(aClass, hierarchicalMethodSignature, existing)) {
       HierarchicalMethodSignatureImpl newSuper = copy(hierarchicalMethodSignature);
       mergeSupers(newSuper, existing);
       LOG.assertTrue(newSuper.getMethod().isValid());
       map.put(signature, newSuper);
     }
+    else if (isSuperMethod(aClass, existing, hierarchicalMethodSignature)) {
+      mergeSupers(existing, hierarchicalMethodSignature);
+    }
     // just drop an invalid method declaration there - to highlight accordingly
     else if (!result.containsKey(signature)) {
       LOG.assertTrue(hierarchicalMethodSignature.getMethod().isValid());
@@ -234,7 +234,7 @@ public class PsiSuperMethodImplUtil {
   private static boolean isReturnTypeIsMoreSpecificThan(@NotNull HierarchicalMethodSignature thisSig, @NotNull HierarchicalMethodSignature thatSig) {
     PsiType thisRet = thisSig.getSubstitutor().substitute(thisSig.getMethod().getReturnType());
     PsiType thatRet = thatSig.getSubstitutor().substitute(thatSig.getMethod().getReturnType());
-    return thatRet != null && thisRet != null && !thatRet.equals(thisRet) && TypeConversionUtil.isAssignable(thatRet, thisRet);
+    return thatRet != null && thisRet != null && !thatRet.equals(thisRet) && TypeConversionUtil.isAssignable(thatRet, thisRet, false);
   }
 
   private static void mergeSupers(final HierarchicalMethodSignatureImpl existing, final HierarchicalMethodSignature superSignature) {

java/java-tests/testData/codeInsight/overrideImplement/afterMultipleInterfaceInheritance.java

@@ -0,0 +1,16 @@
+interface A
+{
+    abstract String foo();
+}
+
+interface B
+{
+    abstract Object foo();
+}
+
+class C implements A, B
+{
+    public String foo() {
+        <selection>return null;  //To change body of implemented methods use File | Settings | File Templates.</selection>
+    }
+}

java/java-tests/testData/codeInsight/overrideImplement/beforeMultipleInterfaceInheritance.java

@@ -0,0 +1,14 @@
+interface A
+{
+    abstract String foo();
+}
+
+interface B
+{
+    abstract Object foo();
+}
+
+class C implements A, B
+{
+    <caret>
+}

java/java-tests/testSrc/com/intellij/codeInsight/OverrideImplementTest.java

@@ -62,6 +62,7 @@ public class OverrideImplementTest extends LightCodeInsightTestCase {
   public void testOnTheLineWithExistingExpression() { doTest(false); }
   public void testSimplifyObjectWildcard() { doTest(false); }
   public void testErasureWildcard() { doTest(false); }
+  public void testMultipleInterfaceInheritance() { doTest(false); }
 
   public void testImplementExtensionMethods() { doTest8(false, true); }
   public void testDoNotImplementExtensionMethods() { doTest8(false, true); }