Fix for issue 22178

pkg/analyzer/lib/src/generated/parser.dart

Index: pkg/analyzer/lib/src/generated/parser.dart
diff --git a/pkg/analyzer/lib/src/generated/parser.dart b/pkg/analyzer/lib/src/generated/parser.dart
index 2d94dd0aafff19c4dd7c3edb1a9a053e390a6b6e..3787d756636318153da51c7b98d43558ed379b59 100644
--- a/pkg/analyzer/lib/src/generated/parser.dart
+++ b/pkg/analyzer/lib/src/generated/parser.dart
@@ -6084,6 +6084,9 @@ class Parser {
     } else {
       name = _createSyntheticIdentifier();
     }
+    if (commentAndMetadata.metadata.isNotEmpty) {
+      _reportErrorForNode(ParserErrorCode.ANNOTATION_ON_ENUM_CONSTANT, commentAndMetadata.metadata[0]);
+    }
     return new EnumConstantDeclaration(
         commentAndMetadata.comment,
         commentAndMetadata.metadata,
@@ -6110,7 +6113,7 @@ class Parser {
     Token rightBracket = null;
     if (_matches(TokenType.OPEN_CURLY_BRACKET)) {
       leftBracket = _expect(TokenType.OPEN_CURLY_BRACKET);
-      if (_matchesIdentifier()) {
+      if (_matchesIdentifier() || _matches(TokenType.AT)) {
         constants.add(_parseEnumConstantDeclaration());
       } else if (_matches(TokenType.COMMA) &&
           _tokenMatchesIdentifier(_peek())) {
@@ -10015,6 +10018,10 @@ class ParserErrorCode extends ErrorCode {
       'ABSTRACT_TYPEDEF',
       "Type aliases cannot be declared to be 'abstract'");
 
+  static const ParserErrorCode ANNOTATION_ON_ENUM_CONSTANT = const ParserErrorCode(
+      'ANNOTATION_ON_ENUM_CONSTANT',
+      "Enum constants cannot have annotations");
+
   static const ParserErrorCode ASSERT_DOES_NOT_TAKE_ASSIGNMENT =
       const ParserErrorCode(
           'ASSERT_DOES_NOT_TAKE_ASSIGNMENT',