Complain about built-in identifiers.

pkg/front_end/lib/src/fasta/scanner/token.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.
 
 library fasta.scanner.token;
 
 import 'keyword.dart' show Keyword;
 
 import 'precedence.dart' show BAD_INPUT_INFO, EOF_INFO, PrecedenceInfo;
 
@@ skipping 108 matching lines @@
     }
   }
 
   /// The character offset of the end of this token within the source text.
   int get charEnd => charOffset + charCount;
 
   bool get isEof => false;
 
   @override
   bool get isOperator => info.isOperator;
+
+  bool get isBuiltInIdentifier => false;
 }
 
 /**
  * A [SymbolToken] represents the symbol in its precedence info.
  * Also used for end of file with EOF_INFO.
  */
 class SymbolToken extends Token {
   final PrecedenceInfo info;
 
   SymbolToken(this.info, int charOffset) : super(charOffset);
@@ skipping 31 matching lines @@
   KeywordToken(this.keyword, int charOffset) : super(charOffset);
 
   PrecedenceInfo get info => keyword.info;
 
   String get lexeme => keyword.syntax;
 
   String get stringValue => keyword.syntax;
 
   bool isIdentifier() => keyword.isPseudo || keyword.isBuiltIn;
 
+  bool get isBuiltInIdentifier {
+    // TODO(ahe): Remove special case for "deferred" once dartbug.com/29069 is
+    // fixed.
+    return keyword.isBuiltIn || identical("deferred", lexeme);
+  }
+
   String toString() => "KeywordToken($lexeme)";
 }
 
 /**
  * A String-valued token. Represents identifiers, string literals,
  * number literals, comments, and error tokens, using the corresponding
  * precedence info.
  */
 class StringToken extends Token {
   /**
@@ skipping 181 matching lines @@
       identical(value, "<=") ||
       identical(value, "<") ||
       identical(value, "&") ||
       identical(value, "^") ||
       identical(value, "|");
 }
 
 bool isTernaryOperator(String value) => identical(value, "[]=");
 
 bool isMinusOperator(String value) => identical(value, "-");