do not generate delegates when the class already has such method either declared or delegated (report an ambiguity in this case)

Merge conflict resolved by committer

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

@@ -32,6 +32,8 @@ import org.jetbrains.jet.lang.types.TypeUtils;
 import java.util.Collection;
 import java.util.Collections;
 
+import static org.jetbrains.jet.lang.diagnostics.Errors.MANY_IMPL_MEMBER_NOT_IMPLEMENTED;
+
 /**
  * @author abreslav
  */
@@ -60,7 +62,18 @@ public class DelegationResolver {
                          });
 
                     Collection<CallableMemberDescriptor> generatedDescriptors = generateDelegatedMembers(classDescriptor, descriptorsToDelegate);
+                    outer:
                     for (CallableMemberDescriptor descriptor : generatedDescriptors) {
+                        for (CallableMemberDescriptor existingDescriptor : classDescriptor.getAllCallableMembers()) {
+                            if (OverridingUtil.isOverridableBy(existingDescriptor, descriptor).getResult() == OverridingUtil.OverrideCompatibilityInfo.Result.OVERRIDABLE) {
+                                if (existingDescriptor.getKind() == CallableMemberDescriptor.Kind.DELEGATION) {
+                                    //trying to delegate to many traits with the same methods
+                                    trace.report(MANY_IMPL_MEMBER_NOT_IMPLEMENTED.on(jetClass.getNameIdentifier(), jetClass, existingDescriptor));
+                                }
+                                continue outer;
+                            }
+                        }
+
                         if (descriptor instanceof PropertyDescriptor) {
                             PropertyDescriptor propertyDescriptor = (PropertyDescriptor) descriptor;
                             classDescriptor.getBuilder().addPropertyDescriptor(propertyDescriptor);

compiler/testData/codegen/classes/delegation3.kt

@@ -0,0 +1,35 @@
+trait One {
+  public open fun foo() : Int
+  public open fun faz() : Int = 10
+}
+trait Two {
+  public open fun foo() : Int
+  public open fun quux() : Int = 100
+}
+
+class OneImpl : One {
+  public override fun foo() = 1
+}
+class TwoImpl : Two {
+  public override fun foo() = 2
+}
+
+class Test2(a : One, b : Two) : Two by b, One by a {
+  public override fun foo() = 0
+}
+
+fun box() : String {
+    var t2 = Test2(OneImpl(), TwoImpl())
+    if (t2.foo() != 0)
+        return "Fail #1"
+    if (t2.faz() != 10)
+        return "Fail #2"
+    if (t2.quux() != 100)
+        return "Fail #3"
+    if (t2 !is One)
+        return "Fail #4"
+    if (t2 !is Two)
+        return "Fail #5"
+
+    return "OK"
+}

compiler/testData/diagnostics/tests/Delegation_MultipleDelegates.kt

@@ -0,0 +1,18 @@
+trait One {
+  public open fun foo() : Int
+  private fun boo() = 10
+}
+trait Two {
+  public open fun foo() : Int
+}
+
+trait OneImpl : One {
+  public override fun foo() = 1
+}
+trait TwoImpl : Two {
+  public override fun foo() = 2
+}
+
+class <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>Test1<!>() : TwoImpl, OneImpl {}
+class Test2(a : One) : One by a, Two {}
+class <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>Test3<!>(a : One, b : Two) : Two by b, One by a {}

compiler/tests/org/jetbrains/jet/codegen/ClassGenTest.java

@@ -68,6 +68,11 @@ public class ClassGenTest extends CodegenTestCase {
         blackBoxFile("classes/delegation2.kt");
     }
 
+    public void testInheritanceAndDelegation3() throws Exception {
+        createEnvironmentWithMockJdkAndIdeaAnnotations(ConfigurationKind.JDK_ONLY);
+        blackBoxFile("classes/delegation3.kt");
+    }
+
     public void testFunDelegation() throws Exception {
         createEnvironmentWithMockJdkAndIdeaAnnotations(ConfigurationKind.JDK_ONLY);
         blackBoxFile("classes/funDelegation.jet");