Update listener error handling.

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

Index: pkg/fasta/lib/src/source/diet_parser.dart
diff --git a/pkg/fasta/lib/src/source/diet_parser.dart b/pkg/fasta/lib/src/source/diet_parser.dart
index 028e7cd2bc3fc73371250440b9b5340452c96b98..5f1640a64a4df470f2bdffac5c53c25a7eb56fd8 100644
--- a/pkg/fasta/lib/src/source/diet_parser.dart
+++ b/pkg/fasta/lib/src/source/diet_parser.dart
@@ -31,7 +31,7 @@ class DietParser extends ClassMemberParser {
     listener.beginOptionalFormalParameters(token);
     if (!optional('(', token)) {
       if (optional(';', token)) {
-        listener.reportError(token, ErrorKind.EXPECTED_OPEN_PARENS);
+        listener.reportError(token, ErrorKind.ExpectedOpenParens);
         return token;
       }
       return listener.unexpected(token);