translate missing ">" fasta error code to analyzer error

pkg/front_end/lib/src/scanner/errors.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/fasta/fasta_codes.dart';
 import 'package:front_end/src/fasta/scanner/error_token.dart';
 import 'package:front_end/src/scanner/token.dart' show Token, TokenType;
 import 'package:front_end/src/fasta/scanner/token_constants.dart';
 
@@ skipping 111 matching lines @@
     case "MISSING_HEX_DIGIT":
       // TODO(paulberry,ahe): Fasta reports the error location as the entire
       // number; analyzer expects the end of the number.
       charOffset = endOffset - 1;
       return _makeError(ScannerErrorCode.MISSING_HEX_DIGIT, null);
 
     case "ILLEGAL_CHARACTER":
       return _makeError(ScannerErrorCode.ILLEGAL_CHARACTER, [token.character]);
 
     default:
       if (errorCode == codeUnmatchedToken) {

[ahe, 2017/08/09 07:04:41]

Perhaps we should start thinking about how to simplify this translation by
adding more error codes to pkg/front_end/messages.yaml.

My hope for the analyzer error codes in messages.yaml is that all the cases in
"default" could move up and have their own "case".

Another thing we could do is generate an enum and use that instead of strings.

[danrubel, 2017/08/11 18:06:50]

Good ideas. I will address these in a future CL.

         TokenType type = token.begin?.type;
         if (type == TokenType.OPEN_CURLY_BRACKET ||
             type == TokenType.STRING_INTERPOLATION_EXPRESSION) {
           return _makeError(ScannerErrorCode.EXPECTED_TOKEN, ['}']);
         }
         if (type == TokenType.OPEN_SQUARE_BRACKET) {
           return _makeError(ScannerErrorCode.EXPECTED_TOKEN, [']']);
         }
         if (type == TokenType.OPEN_PAREN) {
           return _makeError(ScannerErrorCode.EXPECTED_TOKEN, [')']);
         }
+        if (type == TokenType.LT) {
+          return _makeError(ScannerErrorCode.EXPECTED_TOKEN, ['>']);
+        }
       } else if (errorCode == codeUnexpectedDollarInString) {
         return _makeError(ScannerErrorCode.MISSING_IDENTIFIER, null);
       }
       throw new UnimplementedError('$errorCode');
   }
 }
 
 /**
  * Determines whether the given [charOffset], which came from the non-EOF token
  * [token], represents the end of the input.
  */
 bool _isAtEnd(Token token, int charOffset) {
   while (true) {
     // Skip to the next token.
     token = token.next;
     // If we've found an EOF token, its charOffset indicates where the end of
     // the input is.
     if (token.isEof) return token.charOffset == charOffset;
     // If we've found a non-error token, then we know there is additional input
     // text after [charOffset].
     if (token.type.kind != BAD_INPUT_TOKEN) return false;
     // Otherwise keep looking.
   }
 }