Scanner can include comments in the token stream.

lib/compiler/implementation/scanner/array_based_scanner.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class ArrayBasedScanner<S extends SourceString> extends AbstractScanner<S> {
   int get charOffset() => byteOffset + extraCharOffset;
   final Token tokens;
   Token tail;
   int tokenStart;
   int byteOffset;
+  final bool includeComments;
 
   /** Since the input is UTF8, some characters are represented by more
    * than one byte. [extraCharOffset] tracks the difference. */
   int extraCharOffset;
   Link<BeginGroupToken> groupingStack = const EmptyLink<BeginGroupToken>();
 
-  ArrayBasedScanner()
+  ArrayBasedScanner(this.includeComments)
     : this.extraCharOffset = 0,
       this.tokenStart = -1,
       this.byteOffset = -1,
       this.tokens = new Token(EOF_INFO, -1) {
     this.tail = this.tokens;
   }
 
   int advance() {
     int next = nextByte();
     return next;
@@ skipping 129 matching lines @@
     if (groupingStack.head.kind === LT_TOKEN) {
       groupingStack = groupingStack.tail;
     }
     if (groupingStack.isEmpty()) return;
     if (groupingStack.head.kind === LT_TOKEN) {
       groupingStack.head.endGroup = tail;
       groupingStack = groupingStack.tail;
     }
   }
 
+  void appendComment() {
+    if (!includeComments) return;
+    SourceString value = utf8String(tokenStart, -1);
+    appendByteStringToken(COMMENT_INFO, value);
+  }
+
   void discardOpenLt() {
     while (!groupingStack.isEmpty() && groupingStack.head.kind === LT_TOKEN) {
       groupingStack = groupingStack.tail;
     }
   }
 
   // TODO(ahe): make class abstract instead of adding an abstract method.
   abstract peek();
 }