Change the calling conventions for Parser.reportUnrecoverableError.

pkg/front_end/lib/src/fasta/source/diet_parser.dart

Index: pkg/front_end/lib/src/fasta/source/diet_parser.dart
diff --git a/pkg/front_end/lib/src/fasta/source/diet_parser.dart b/pkg/front_end/lib/src/fasta/source/diet_parser.dart
index 8c142581387e3fc5d755fb34325977bf1e5767a7..35b9da2b44bfd414bf077797cf6df7e07bde2950 100644
--- a/pkg/front_end/lib/src/fasta/source/diet_parser.dart
+++ b/pkg/front_end/lib/src/fasta/source/diet_parser.dart
@@ -30,7 +30,7 @@ class DietParser extends ClassMemberParser {
         reportRecoverableError(token, ErrorKind.ExpectedOpenParens, {});
         return token;
       }
-      return reportUnrecoverableError(token, ErrorKind.UnexpectedToken);
+      return reportUnrecoverableError(token, ErrorKind.UnexpectedToken)?.next;
     }
     BeginGroupToken beginGroupToken = token;
     Token endToken = beginGroupToken.endGroup;