fix #25739, incorrectly expanding a generic comment multiple times

pkg/analyzer/lib/src/generated/parser.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.src.generated.parser;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 3930 matching lines @@
   }
 
   bool _injectGenericComment(TokenType type, int prefixLen) {
     if (parseGenericMethodComments) {
       CommentToken t = _currentToken.precedingComments;
       for (; t != null; t = t.next) {
         if (t.type == type) {
           String comment = t.lexeme.substring(prefixLen, t.lexeme.length - 2);
           Token list = _scanGenericMethodComment(comment, t.offset + prefixLen);
           if (list != null) {
+            // Remove the tokens from the comment stream.
+            if (t.previous != null) {
+              t.previous.setNext(t.next);
+            } else {
+              assert(_currentToken.precedingComments == t);
+              // The implementation types all have this setter, but the Token
+              // interface does not.
+              (_currentToken as dynamic).precedingComments = t.next;

[Jennifer Messerly, 2016/02/10 19:15:07]

not enthused about this... suggestions? :)

[Bob Nystrom, 2016/02/12 17:40:47]

Yeah, this seems gross to me, but I don't know the parser well enough to suggest
an alternative.

When I was poking at this, I considered resynthesizing the token without the
comment, but that seemed like a lot of work too.

[Brian Wilkerson, 2016/02/12 17:56:55]

I just turned Token into an interface, and replaced it in the type hierarchy
with SimpleToken, which is clearly marked as internal implementation, so that
opens some options.

(1) We could add a setter to SimpleToken, although it would have to throw an
exception if the token cannot support comments.

(2) We could add an internal interface ("TokenWithComment"?), implement it in
all of the existing "*WithComment" classes, and add the setter there, which
would avoid the possibility of throwing an exception.

(3) We could define TokenWithComment as a simple class and mix it in to all of
the existing "*WithComment" classes.

+            }
             // Insert the tokens into the stream.
             _injectTokenList(list);
             return true;
           }
         }
       }
     }
     return false;
   }
 
@@ skipping 7397 matching lines @@
   }
 
   /**
    * Copy resolution data from the [fromNode] to the [toNode].
    */
   static void copyResolutionData(AstNode fromNode, AstNode toNode) {
     ResolutionCopier copier = new ResolutionCopier();
     copier._isEqualNodes(fromNode, toNode);
   }
 }