diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index 5c6c0440243..b39131b770e 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -584,15 +584,24 @@ namespace ts {
     }
 
     /**
-     * Extract comments from text prefixing the token closest following `pos`.
-     * The return value is an array containing a TextRange for each comment.
-     * Single-line comment ranges include the beginning '//' characters but not the ending line break.
-     * Multi - line comment ranges include the beginning '/* and ending '<asterisk>/' characters.
-     * The return value is undefined if no comments were found.
-     * @param trailing
-     * If false, whitespace is skipped until the first line break and comments between that location
-     * and the next token are returned.
-     * If true, comments occurring between the given position and the next line break are returned.
+     * Invokes a callback for each comment range following the provided position.
+     *
+     * Single-line comment ranges include the leading double-slash characters but not the ending
+     * line break. Multi-line comment ranges include the leading slash-asterisk and trailing
+     * asterisk-slash characters.
+     *
+     * @param reduce If true, accumulates the result of calling the callback in a fashion similar
+     *      to reduceLeft. If false, iteration stops when the callback returns a truthy value.
+     * @param text The source text to scan.
+     * @param pos The position at which to start scanning.
+     * @param trailing If false, whitespace is skipped until the first line break and comments
+     *      between that location and the next token are returned. If true, comments occurring
+     *      between the given position and the next line break are returned.
+     * @param cb The callback to execute as each comment range is encountered.
+     * @param state A state value to pass to each iteration of the callback.
+     * @param initial An initial value to pass when accumulating results (when "reduce" is true).
+     * @returns If "reduce" is true, the accumulated value. If "reduce" is false, the first truthy
+     *      return value of the callback.
      */
     function iterateCommentRanges<T, U>(reduce: boolean, text: string, pos: number, trailing: boolean, cb: (pos: number, end: number, kind: SyntaxKind, hasTrailingNewLine: boolean, state: T, memo: U) => U, state: T, initial?: U): U {
         let pendingPos: number;