Update comment

Author: rbuckton

src/compiler/checker.ts

@@ -17257,10 +17257,10 @@ namespace ts {
         function checkElementTypeOfArrayOrString(arrayOrStringType: Type, errorNode: Node): Type {
             Debug.assert(languageVersion < ScriptTarget.ES2015);
 
-            // After we remove all types that are StringLike, we will know if there was a string constituent
-            // based on whether the remaining type is the same as the initial type.
             let arrayType = arrayOrStringType;
             if (arrayOrStringType.flags & TypeFlags.Union) {
+                // After we remove all types that are StringLike, we will know if there was a string constituent
+                // based on whether the result of filter is a new array.
                 const arrayTypes = (arrayOrStringType as UnionType).types;
                 const filteredTypes = filter(arrayTypes, t => !(t.flags & TypeFlags.StringLike));
                 if (filteredTypes !== arrayTypes) {