KT-316 Members of traits must be open by default

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

@@ -190,9 +190,12 @@ public class ClassDescriptorResolver {
         }
         Modality defaultModality;
         if (containingDescriptor instanceof ClassDescriptor) {
-            boolean isDefinitelyAbstract = ((ClassDescriptor) containingDescriptor).getKind() == ClassKind.TRAIT && function.getBodyExpression() == null;
+            boolean isTrait = ((ClassDescriptor) containingDescriptor).getKind() == ClassKind.TRAIT;
-            defaultModality = isDefinitelyAbstract ? Modality.ABSTRACT : Modality.FINAL;
+            boolean isDefinitelyAbstract = isTrait && function.getBodyExpression() == null;
-        } else {
+            Modality basicModality = isTrait ? Modality.OPEN : Modality.FINAL;
+            defaultModality = isDefinitelyAbstract ? Modality.ABSTRACT : basicModality;
+        }
+        else {
             defaultModality = Modality.FINAL;
         }
         Modality modality = resolveModalityFromModifiers(function.getModifierList(), defaultModality);

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

@@ -28,7 +28,9 @@ public class OverridingUtil {
     public static <D extends CallableDescriptor> Set<D> filterOverrides(Set<D> candidateSet) {
         Set<D> candidates = Sets.newLinkedHashSet(candidateSet);
         for (D descriptor : candidateSet) {
-            candidates.removeAll(descriptor.getOverriddenDescriptors());
+            Set<CallableDescriptor> overriddenDescriptors = Sets.newHashSet();
+            getAllOverriddenDescriptors(descriptor.getOriginal(), overriddenDescriptors);
+            candidates.removeAll(overriddenDescriptors);
         }
         return candidates;
     }

idea/testData/checkerWithErrorTypes/quick/regressions/kt316.jet

@@ -0,0 +1,10 @@
+// KT-316 Members of traits must be open by default
+
+trait B {
+    fun bar() {}
+    fun foo() {}
+}
+
+open class A() : B{
+    override fun foo() {}
+}