Simplify findContainingList (#22128)

Author: Andy

src/services/utilities.ts

@@ -619,13 +619,7 @@ namespace ts {
         // be parented by the container of the SyntaxList, not the SyntaxList itself.
         // In order to find the list item index, we first need to locate SyntaxList itself and then search
         // for the position of the relevant node (or comma).
-        const syntaxList = forEach(node.parent.getChildren(), c => {
-            // find syntax list that covers the span of the node
-            if (isSyntaxList(c) && c.pos <= node.pos && c.end >= node.end) {
-                return c;
-            }
-        });
-
+        const syntaxList = find(node.parent.getChildren(), (c): c is SyntaxList => isSyntaxList(c) && rangeContainsRange(c, node));
         // Either we didn't find an appropriate list, or the list must contain us.
         Debug.assert(!syntaxList || contains(syntaxList.getChildren(), node));
         return syntaxList;