return type can be omitted when override

compiler/frontend/src/org/jetbrains/jet/lang/resolve/DeclarationsChecker.java

@@ -162,7 +162,7 @@ public class DeclarationsChecker {
             JetFunction function = (JetFunction) member;
             hasDeferredType = function.getReturnTypeRef() == null && function.getBodyExpression() != null && !function.hasBlockBody();
         }
-        if ((memberDescriptor.getVisibility().isPublicAPI()) && hasDeferredType) {
+        if ((memberDescriptor.getVisibility().isPublicAPI()) && memberDescriptor.getOverriddenDescriptors().size() == 0 && hasDeferredType) {
             trace.report(PUBLIC_MEMBER_SHOULD_SPECIFY_TYPE.on(member));
         }
     }

compiler/testData/diagnostics/tests/scopes/visibility2.jet

@@ -38,3 +38,7 @@ class Q {
     }
 }
 
+//check that 'toString' can be invoked without specifying 'public' and ': String'
+class NewClass : java.util.ArrayList<Integer>() {
+    override fun toString() = "a"
+}