translate remaining fasta scanner error codes

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;
+import 'package:front_end/src/scanner/token.dart' show Token, TokenType;
 import 'package:front_end/src/fasta/scanner/token_constants.dart';
 
 /**
  * The error codes used for errors detected by the scanner.
  */
 class ScannerErrorCode extends ErrorCode {
   /**
    * Parameters:
+   * 0: the token that was expected but not found
+   */
+  static const ScannerErrorCode EXPECTED_TOKEN =
+      const ScannerErrorCode('EXPECTED_TOKEN', "Expected to find '{0}'.");
+
+  /**
+   * Parameters:
    * 0: the illegal character
    */
   static const ScannerErrorCode ILLEGAL_CHARACTER =
       const ScannerErrorCode('ILLEGAL_CHARACTER', "Illegal character '{0}'.");
 
   static const ScannerErrorCode MISSING_DIGIT =
       const ScannerErrorCode('MISSING_DIGIT', "Decimal digit expected.");
 
   static const ScannerErrorCode MISSING_HEX_DIGIT = const ScannerErrorCode(
       'MISSING_HEX_DIGIT', "Hexidecimal digit expected.");
 
+  static const ScannerErrorCode MISSING_IDENTIFIER =
+      const ScannerErrorCode('MISSING_IDENTIFIER', "Expected an identifier.");
+
   static const ScannerErrorCode MISSING_QUOTE =
       const ScannerErrorCode('MISSING_QUOTE', "Expected quote (' or \").");
 
   /**
    * Parameters:
    * 0: the path of the file that cannot be read
    */
   static const ScannerErrorCode UNABLE_GET_CONTENT = const ScannerErrorCode(
       'UNABLE_GET_CONTENT', "Unable to get content of '{0}'.");
 
@@ skipping 74 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 ||
-          errorCode == codeUnexpectedDollarInString) {
-        return null;
+      if (errorCode == codeUnmatchedToken) {
+        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, [')']);
+        }
+      } 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.
   }
 }