Treat nested class of header class as header

Note that the quick fix to implement header class works incorrectly when
that class has nested classes at the moment; this should be fixed
separately

 #KT-15494 Fixed
 #KT-18573 Fixed

idea/testData/multiModuleQuickFix/enum/header/header.kt

@@ -6,12 +6,4 @@ header enum class <caret>MyEnum {
     LAST;
 
     val num: Int
-
-    companion object {
-        fun byNum(num: Int): MyEnum = when (num) {
-            1 -> FIRST
-            2 -> SECOND
-            else -> LAST
-        }
-    }
-}
+}

idea/testData/multiModuleQuickFix/enum/header/header.kt.after

@@ -6,12 +6,4 @@ header enum class MyEnum {
     LAST;
 
     val num: Int
-
-    companion object {
-        fun byNum(num: Int): MyEnum = when (num) {
-            1 -> FIRST
-            2 -> SECOND
-            else -> LAST
-        }
-    }
-}
+}

idea/testData/multiModuleQuickFix/enum/js/MyEnum.kt.after

@@ -4,14 +4,7 @@ impl enum class MyEnum {
     SECOND,
     LAST;
 
-    companion object {
-        fun byNum(num: Int): MyEnum = when (num) {
-            1 -> FIRST
-            2 -> SECOND
-            else -> LAST
-        }
-    }
-
     impl val num: Int
         get() = TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
+
 }

idea/testData/multiModuleQuickFix/nested/header/header.kt

@@ -4,10 +4,10 @@ header class <caret>WithNested {
     fun foo(): Int
 
     class Nested {
-        fun bar() = "Nested"
+        fun bar()
     }
 
     inner class Inner {
-        fun baz() = "Inner"
+        fun baz()
     }
-}
+}

idea/testData/multiModuleQuickFix/nested/header/header.kt.after

@@ -4,10 +4,10 @@ header class WithNested {
     fun foo(): Int
 
     class Nested {
-        fun bar() = "Nested"
+        fun bar()
     }
 
     inner class Inner {
-        fun baz() = "Inner"
+        fun baz()
     }
-}
+}

idea/testData/multiModuleQuickFix/nested/jvm/WithNested.kt.after

@@ -2,11 +2,11 @@
 impl class WithNested {
 
     class Nested {
-        fun bar() = "Nested"
+        fun bar()
     }
 
     inner class Inner {
-        fun baz() = "Inner"
+        fun baz()
     }
 
     impl fun foo(): Int {

idea/testData/multiModuleQuickFix/sealed/header/header.kt

@@ -1,7 +1,7 @@
 // "Create header class implementation for platform JS" "true"
 
 header sealed class <caret>Sealed {
-    object Obj : Sealed()
+    object Obj : Sealed
 
-    class Klass(val x: Int) : Sealed()
+    class Klass(x: Int) : Sealed
 }

idea/testData/multiModuleQuickFix/sealed/header/header.kt.after

@@ -1,7 +1,7 @@
 // "Create header class implementation for platform JS" "true"
 
 header sealed class Sealed {
-    object Obj : Sealed()
+    object Obj : Sealed
 
-    class Klass(val x: Int) : Sealed()
+    class Klass(x: Int) : Sealed
 }

idea/testData/multiModuleQuickFix/sealed/js/Sealed.kt.after

@@ -1,6 +1,6 @@
 // Sealed: to be implemented
 impl sealed class Sealed {
-    object Obj : Sealed()
+    object Obj : Sealed
 
-    class Klass(val x: Int) : Sealed()
+    class Klass(x: Int) : Sealed
 }