Generated field for classObject is now final

EA-38323 Fixed - Illegal field modifiers in class

compiler/backend/src/org/jetbrains/jet/codegen/ImplementationBodyCodegen.java

@@ -596,7 +596,7 @@ public class ImplementationBodyCodegen extends ClassBodyCodegen {
             final ClassDescriptor descriptor1 = bindingContext.get(BindingContext.CLASS, classObject.getObjectDeclaration());
             assert descriptor1 != null;
             Type type = Type.getObjectType(typeMapper.mapType(descriptor1).getInternalName());
-            v.newField(classObject, ACC_PUBLIC | ACC_STATIC, "$classobj", type.getDescriptor(), null, null);
+            v.newField(classObject, ACC_PUBLIC | ACC_STATIC | ACC_FINAL, "$classobj", type.getDescriptor(), null, null);
 
             staticInitializerChunks.add(new CodeChunk() {
                 @Override

compiler/testData/codegen/classes/classObjectInTrait.jet

@@ -0,0 +1,12 @@
+// EA-38323 - Illegal field modifiers in class: classObject field in C must be static and final 
+
+trait C {
+  class object {
+    public val FOO: String = "OK"
+  }
+}
+
+fun box(): String {
+  return C.FOO
+}
+

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

@@ -217,6 +217,11 @@ public class ClassGenTest extends CodegenTestCase {
         blackBoxFile("classes/classObject.jet");
     }
 
+    public void testClassObjectInTrait() throws Exception {
+        createEnvironmentWithMockJdkAndIdeaAnnotations(ConfigurationKind.JDK_ONLY);
+        blackBoxFile("classes/classObjectInTrait.jet");
+    }
+
     public void testClassObjectMethod() throws Exception {
         createEnvironmentWithMockJdkAndIdeaAnnotations(ConfigurationKind.JDK_ONLY);
         // todo to be implemented after removal of type info