Added test

idea/testData/quickfix/migration/operatorModifier/forOverride.kt

@@ -0,0 +1,10 @@
+// "Add 'operator' modifier" "true"
+open class A {
+    open fun plus(other: A): A = A()
+}
+
+class B : A() {
+    override fun <caret>plus(other: A): A {
+        return super.plus(other)
+    }
+}

idea/testData/quickfix/migration/operatorModifier/forOverride.kt.after

@@ -0,0 +1,10 @@
+// "Add 'operator' modifier" "true"
+open class A {
+    open fun plus(other: A): A = A()
+}
+
+class B : A() {
+    override operator fun <caret>plus(other: A): A {
+        return super.plus(other)
+    }
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -4303,6 +4303,12 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("forOverride.kt")
+            public void testForOverride() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("idea/testData/quickfix/migration/operatorModifier/forOverride.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("overridden.kt")
             public void testOverridden() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("idea/testData/quickfix/migration/operatorModifier/overridden.kt");