Stop testing scanner error lengths.

pkg/front_end/test/scanner_fasta_test.dart

 // Copyright (c) 2017, 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/fasta/analyzer/token_utils.dart';
 import 'package:front_end/src/fasta/scanner/error_token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/keyword.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/string_scanner.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token_constants.dart' as fasta;
@@ skipping 206 matching lines @@
   void test_string_simple_unterminated_interpolation_identifier() {
     // TODO(paulberry,ahe): bad error recovery.
     super.test_string_simple_unterminated_interpolation_identifier();
   }
 
   TestError _translateErrorToken(fasta.ErrorToken token, int inputLength) {
     int charOffset = token.charOffset;
     // TODO(paulberry,ahe): why is endOffset sometimes null?
     int endOffset = token.endOffset ?? charOffset;
     TestError _makeError(ScannerErrorCode errorCode, List<Object> arguments) {
-      int errorLength = endOffset - charOffset;
       if (charOffset == inputLength) {
         // Analyzer never generates an error message past the end of the input,
         // since such an error would not be visible in an editor.
         // TODO(paulberry,ahe): would it make sense to replicate this behavior
         // in fasta, or move it elsewhere in analyzer?
         charOffset--;
       }
-      if (errorLength == 0) {
-        // Analyzer never generates an error message of length zero,
-        // since such an error would not be visible in an editor.
-        // TODO(paulberry,ahe): would it make sense to replicate this behavior
-        // in fasta, or move it elsewhere in analyzer?
-        errorLength = 1;
-      }
-      return new TestError(charOffset, errorLength, errorCode, arguments);
+      return new TestError(charOffset, errorCode, arguments);
     }
 
     var errorCode = token.errorCode;
     switch (errorCode) {
       case fasta.ErrorKind.UnterminatedString:
         // TODO(paulberry,ahe): Fasta reports the error location as the entire
         // string; analyzer expects the end of the string.
         charOffset = endOffset;
         return _makeError(ScannerErrorCode.UNTERMINATED_STRING_LITERAL, null);
       case fasta.ErrorKind.UnmatchedToken:
@@ skipping 18 matching lines @@
       case fasta.ErrorKind.NonAsciiWhitespace:
         return _makeError(
             ScannerErrorCode.ILLEGAL_CHARACTER, [token.character]);
       case fasta.ErrorKind.UnexpectedDollarInString:
         return null;
       default:
         throw new UnimplementedError('$errorCode');
     }
   }
 }