diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index e97ece5bf00..7b3b51c3f27 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -6841,6 +6841,11 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                 return leadingComments;
             }
 
+            /**
+             * Removes all but the pinned or triple slash comments.
+             * @param ranges The array to be filtered
+             * @param onlyPinnedOrTripleSlashComments whether the filtering should be performed.
+             */
             function filterComments(ranges: CommentRange[], onlyPinnedOrTripleSlashComments: boolean): CommentRange[] {
                 // If we're removing comments, then we want to strip out all but the pinned or
                 // triple slash comments.
diff --git a/src/services/services.ts b/src/services/services.ts
index 60796669d65..8e670268498 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -261,26 +261,25 @@ namespace ts {
         }
 
         public getFirstToken(sourceFile?: SourceFile): Node {
-            let children = this.getChildren();
-            for (let child of children) {
-                if (child.kind < SyntaxKind.FirstNode) {
-                    return child;
-                }
-
-                return child.getFirstToken(sourceFile);
+            let children = this.getChildren(sourceFile);
+            if (!children.length) {
+                return undefined;
             }
+
+            let child = children[0];
+
+            return child.kind < SyntaxKind.FirstNode ? child : child.getFirstToken(sourceFile);
         }
 
         public getLastToken(sourceFile?: SourceFile): Node {
             let children = this.getChildren(sourceFile);
-            for (let i = children.length - 1; i >= 0; i--) {
-                let child = children[i];
-                if (child.kind < SyntaxKind.FirstNode) {
-                    return child;
-                }
 
-                return child.getLastToken(sourceFile);
+            let child = lastOrUndefined(children);
+            if (!child) { 
+                return undefined; 
             }
+
+            return child.kind < SyntaxKind.FirstNode ? child : child.getLastToken(sourceFile);
         }
     }