fasta scanner recovery and error code translation improvements

pkg/front_end/test/scanner_test.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.
 
 import 'package:front_end/src/base/errors.dart';
 import 'package:front_end/src/base/jenkins_smi_hash.dart';
 import 'package:front_end/src/scanner/errors.dart';
 import 'package:front_end/src/scanner/reader.dart';
 import 'package:front_end/src/scanner/scanner.dart';
 import 'package:front_end/src/scanner/token.dart';
@@ skipping 147 matching lines @@
 
   void test_ampersand_ampersand_eq() {
     _assertToken(TokenType.AMPERSAND_AMPERSAND_EQ, "&&=",
         lazyAssignmentOperators: true);
   }
 
   void test_ampersand_eq() {
     _assertToken(TokenType.AMPERSAND_EQ, "&=");
   }
 
-  void test_angle_brackets_are_ordinary_tokens() {
-    // Analyzer's token streams don't consider "<" to be an opener.
-    var lessThan = _scan('<>');
-    var greaterThan = lessThan.next;
+  void test_angle_brackets() {
+    var lessThan = _scan('<String>');
+    var identifier = lessThan.next;
+    var greaterThan = identifier.next;
     expect(greaterThan.next.type, TokenType.EOF);
-    expect(lessThan, isNot(new isInstanceOf<BeginToken>()));
+    // Analyzer's token streams don't consider "<" to be an opener
+    // but fasta does.
+    if (lessThan is BeginToken) {
+      expect(lessThan.endToken, greaterThan);
+    }
     expect(greaterThan, isNot(new isInstanceOf<BeginToken>()));
   }
 
   void test_async_star() {
     Token token = _scan("async*");
     expect(token.type, TokenType.IDENTIFIER);
     expect(token.lexeme, 'async');
     expect(token.next.type, TokenType.STAR);
     expect(token.next.next.type, TokenType.EOF);
   }
@@ skipping 1333 matching lines @@
   _TestScanner(CharacterReader reader, [this.listener]) : super(reader);
 
   @override
   void reportError(
       ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     if (listener != null) {
       listener.errors.add(new TestError(offset, errorCode, arguments));
     }
   }
 }