KT-1985 Creating class body on override/implement if necessary

compiler/frontend/src/org/jetbrains/jet/lang/psi/JetPsiFactory.java

@@ -147,6 +147,11 @@ public class JetPsiFactory {
         return function.getBodyExpression();
     }
 
+    public static JetClassBody createEmptyClassBody(Project project) {
+        JetClass aClass = createClass(project, "class A(){}");
+        return aClass.getBody();
+    }
+
     public static JetParameter createParameter(Project project, String name, String type) {
         JetNamedFunction function = createFunction(project, "fun foo(" + name + " : " + type + ") {}");
         return function.getValueParameters().get(0);

idea/src/org/jetbrains/jet/plugin/codeInsight/OverrideImplementMethodsHandler.java

@@ -68,9 +68,10 @@ public abstract class OverrideImplementMethodsHandler implements LanguageCodeIns
             JetClassOrObject classOrObject,
             List<DescriptorClassMember> selectedElements
     ) {
-        final JetClassBody body = classOrObject.getBody();
+        JetClassBody body = classOrObject.getBody();
+        Project project = classOrObject.getProject();
         if (body == null) {
-            return;
+            body = JetPsiFactory.createEmptyClassBody(project);
         }
 
         PsiElement afterAnchor = findInsertAfterAnchor(editor, body);
@@ -86,6 +87,10 @@ public abstract class OverrideImplementMethodsHandler implements LanguageCodeIns
             afterAnchor = added;
             elementsToCompact.add((JetElement) added);
         }
+        if (!body.isPhysical()) {
+            classOrObject.add(JetPsiFactory.createWhiteSpace(project));
+            classOrObject.add(body);
+        }
         ReferenceToClassesShortening.compactReferenceToClasses(elementsToCompact);
     }