Filtered out incorrect suggestion of extension methods in smart completion

idea/testData/completion/smart/NoExtensionMethodFromClassObject.kt

@@ -0,0 +1,13 @@
+class X {
+    class object {
+        fun String.f(): X = X()
+        fun g(): X = X()
+    }
+}
+
+fun foo(): X {
+    return <caret>
+}
+
+// ABSENT: X.f
+// EXIST: X.g