Fix issue 20577

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 3084970abd65999132f168ad7129cc78526a5fba..d4001e839c5f58602668194d206d0a0895aaf69c 100644
--- a/pkg/analyzer/lib/src/generated/parser.dart
+++ b/pkg/analyzer/lib/src/generated/parser.dart
@@ -4413,6 +4413,9 @@ class Parser {
           initializers.add(_parseConstructorFieldInitializer());
         }
       } while (_optional(TokenType.COMMA));
+      if (factoryKeyword != null) {
+        _reportErrorForToken(ParserErrorCode.FACTORY_WITH_INITIALIZERS, factoryKeyword, []);
+      }
     }
     ConstructorName redirectedConstructor = null;
     FunctionBody body;
@@ -7944,6 +7947,13 @@ class ParserErrorCode extends ErrorCode {
 
   static const ParserErrorCode FACTORY_TOP_LEVEL_DECLARATION = const ParserErrorCode('FACTORY_TOP_LEVEL_DECLARATION', "Top-level declarations cannot be declared to be 'factory'");
 
+  static const ParserErrorCode FACTORY_WITH_INITIALIZERS
+      = const ParserErrorCode(
+          'FACTORY_WITH_INITIALIZERS',
+          "A 'factory' constructor cannot have initializers",
+          "Either remove the 'factory' keyword to make this a generative "
+          "constructor or remove the initializers.");
+
   static const ParserErrorCode FACTORY_WITHOUT_BODY = const ParserErrorCode('FACTORY_WITHOUT_BODY', "A non-redirecting 'factory' constructor must have a body");
 
   static const ParserErrorCode FIELD_INITIALIZER_OUTSIDE_CONSTRUCTOR = const ParserErrorCode('FIELD_INITIALIZER_OUTSIDE_CONSTRUCTOR', "Field initializers can only be used in a constructor");