[JS IR DCE] Move withNested fun to get better diff in the next commit

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/Dce.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -94,7 +94,19 @@ private fun removeUselessDeclarations(module: IrModuleFragment, usefulDeclaratio
     }
 }
 
-private fun Iterable<IrDeclaration>.withNested(): Iterable<IrDeclaration> {
+fun usefulDeclarations(roots: Iterable<IrDeclaration>, context: JsIrBackendContext): Set<IrDeclaration> {
+    val queue = ArrayDeque<IrDeclaration>()
+    val result = hashSetOf<IrDeclaration>()
+    val constructedClasses = hashSetOf<IrClass>()
+
+    fun IrDeclaration.enqueue() {
+        if ((this !is IrProperty || this.isExternal) && this !in result) {
+            result.add(this)
+            queue.addLast(this)
+        }
+    }
+
+    fun Iterable<IrDeclaration>.withNested(): Iterable<IrDeclaration> {
         val result = mutableListOf<IrDeclaration>()
 
         this.forEach {
@@ -117,18 +129,6 @@ private fun Iterable<IrDeclaration>.withNested(): Iterable<IrDeclaration> {
         return result
     }
 
-fun usefulDeclarations(roots: Iterable<IrDeclaration>, context: JsIrBackendContext): Set<IrDeclaration> {
-    val queue = ArrayDeque<IrDeclaration>()
-    val result = hashSetOf<IrDeclaration>()
-    val constructedClasses = hashSetOf<IrClass>()
-
-    fun IrDeclaration.enqueue() {
-        if ((this !is IrProperty || this.isExternal) && this !in result) {
-            result.add(this)
-            queue.addLast(this)
-        }
-    }
-
     // Add roots, including nested declarations
     stageController.withInitialIr {
         roots.withNested().forEach { it.enqueue() }