Use Keyword.isPseudo to translate Fasta's "pseudo-keywords" properly.

pkg/front_end/lib/src/fasta/analyzer/token_utils.dart

 // Copyright (c) 2016, 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.analyzer.token_utils;
 
 import 'package:front_end/src/fasta/scanner/token.dart' show
     KeywordToken,
     Token;
 
@@ skipping 36 matching lines @@
 
     case IDENTIFIER_TOKEN:
       return makeStringToken(TokenType.IDENTIFIER);
 
     case INT_TOKEN:
       return makeStringToken(TokenType.INT);
 
     case KEYWORD_TOKEN:
       KeywordToken keywordToken = token;
       var syntax = keywordToken.keyword.syntax;
+      if (keywordToken.keyword.isPseudo) {
+        // TODO(paulberry,ahe): Fasta considers "deferred" be a "pseudo-keyword"
+        // (ordinary identifier which has special meaning under circumstances),
+        // but analyzer and the spec consider it to be a built-in identifier
+        // (identifier which can't be used in type names).
+        if (!identical(syntax, 'deferred')) {
+          return makeStringToken(TokenType.IDENTIFIER);
+        }
+      }
       // TODO(paulberry): if the map lookup proves to be too slow, consider
       // using a switch statement, or perhaps a string of
       // "if (identical(syntax, "foo"))" checks.  (Note that identical checks
       // should be safe because the Fasta scanner uses string literals for
       // the values of keyword.syntax.)
-      var keyword = _keywordMap[syntax];
-      if (keyword == null) {
-        if (_pseudoKeywords.contains(syntax)) {
-          // TODO(paulberry,ahe): fasta scans "async", "await", and "sync" as
-          // keywords.  They need to be identifiers since their meaning is only
-          // special in certain contexts.
-          return makeStringToken(TokenType.IDENTIFIER);
-        } else {
-          return internalError('Unknown keyword: $syntax');
-        }
-      }
+      var keyword =
+          _keywordMap[syntax] ?? internalError('Unknown keyword: $syntax');
       if (commentToken == null) {
         return new analyzer.KeywordToken(keyword, token.charOffset);
       } else {
         return new analyzer.KeywordTokenWithComment(
             keyword, token.charOffset, commentToken);
       }
       break;
 
     case STRING_TOKEN:
       return makeStringToken(TokenType.STRING);
@@ skipping 55 matching lines @@
   "import": analyzer.Keyword.IMPORT,
   "library": analyzer.Keyword.LIBRARY,
   "operator": analyzer.Keyword.OPERATOR,
   "part": analyzer.Keyword.PART,
   "set": analyzer.Keyword.SET,
   "static": analyzer.Keyword.STATIC,
   "typedef": analyzer.Keyword.TYPEDEF,
   "deferred": analyzer.Keyword.DEFERRED,
 };
 
-final _pseudoKeywords = new Set<String>.from(['async', 'await', 'sync']);
-
 TokenType getTokenType(Token token) {
   switch (token.kind) {
     case EOF_TOKEN: return TokenType.EOF;
     case DOUBLE_TOKEN: return TokenType.DOUBLE;
     case HEXADECIMAL_TOKEN: return TokenType.HEXADECIMAL;
     case IDENTIFIER_TOKEN: return TokenType.IDENTIFIER;
     case INT_TOKEN: return TokenType.INT;
     case KEYWORD_TOKEN: return TokenType.KEYWORD;
     // case MULTI_LINE_COMMENT_TOKEN: return TokenType.MULTI_LINE_COMMENT;
     // case SCRIPT_TAG_TOKEN: return TokenType.SCRIPT_TAG;
@@ skipping 66 matching lines @@
     case BACKSLASH_TOKEN: return TokenType.BACKSLASH;
     case PERIOD_PERIOD_PERIOD_TOKEN: return TokenType.PERIOD_PERIOD_PERIOD;
     // case GENERIC_METHOD_TYPE_LIST_TOKEN:
     //   return TokenType.GENERIC_METHOD_TYPE_LIST;
     // case GENERIC_METHOD_TYPE_ASSIGN_TOKEN:
     //   return TokenType.GENERIC_METHOD_TYPE_ASSIGN;
     default:
       return internalError("Unhandled token ${token.info}");
   }
 }