anchor.diff:      ast.Expression expression = node.value.accept(this);
       return new ast.Return(
           new KeywordToken(Keyword.keywords['return'], -1),
  -        new SymbolToken(SEMICOLON_INFO, -1),
  +        semicolon,
           expression);
     }
   
  
positive.code:   ast.Identifier assignIdentifier() {
      assert(identifier == null);
      String name = _newName();
      identifier = new ast.Identifier(
          new StringToken.fromString(IDENTIFIER_INFO, name, -1));
      return identifier;
    }
  
  
negative.code:       ast.Expression value = (body as ast.Return).expression;
        if (value is ast.LiteralNull) {
          // '{ return null; }' is '{}'.
          body = makeBlock([]);
        } else {
          // '{ return e; }' is '=> e;'.
          body = new ast.Return(new SymbolToken(FUNCTION_INFO, -1),
                                semicolon,
                                value);
        }
      }
  