using a reverse iterator instead of reversing the array

Author: Janther

src/slang-nodes/SlangNode.ts

@@ -23,7 +23,24 @@ export function clearOffsets(): void {
   offsets.clear();
 }
 
-function getLeadingOffset(children: Edge[]): number {
+function reversedIterator(children: Edge[]): Iterable<Edge> {
+  return {
+    [Symbol.iterator](): Iterator<Edge> {
+      let index = children.length;
+      return {
+        next: function (): IteratorResult<Edge, Edge> {
+          index--;
+          return {
+            done: index < 0,
+            value: children[index]
+          };
+        }
+      };
+    }
+  };
+}
+
+function getLeadingOffset(children: Edge[] | Iterable<Edge>): number {
   let offset = 0;
   for (const { node } of children) {
     if (node.isNonterminalNode() || !isCommentOrWhiteSpace(node)) {
@@ -110,7 +127,10 @@ export class SlangNode {
 
     const [leadingOffset, trailingOffset] = enclosePeripheralComments
       ? [0, 0]
-      : [getLeadingOffset(children), getLeadingOffset(children.reverse())];
+      : [
+          getLeadingOffset(children),
+          getLeadingOffset(reversedIterator(children))
+        ];
 
     this.loc = {
       start: initialOffset + leadingOffset,