When DefaultFormalParameter, don't use ParameterKind.REQUIRED.

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

 // Copyright (c) 2014, 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.
 
 library analyzer.src.generated.parser;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 2781 matching lines @@
    */
   FormalParameter parseFormalParameter(ParameterKind kind) {
     NormalFormalParameter parameter = parseNormalFormalParameter();
     TokenType type = _currentToken.type;
     if (type == TokenType.EQ) {
       Token separator = getAndAdvance();
       Expression defaultValue = parseExpression2();
       if (kind == ParameterKind.REQUIRED) {
         _reportErrorForNode(
             ParserErrorCode.POSITIONAL_PARAMETER_OUTSIDE_GROUP, parameter);
+        kind = ParameterKind.POSITIONAL;
       }
       return new DefaultFormalParameter(
           parameter, kind, separator, defaultValue);
     } else if (type == TokenType.COLON) {
       Token separator = getAndAdvance();
       Expression defaultValue = parseExpression2();
       if (kind == ParameterKind.POSITIONAL) {
         _reportErrorForToken(
             ParserErrorCode.WRONG_SEPARATOR_FOR_POSITIONAL_PARAMETER,
             separator);
       } else if (kind == ParameterKind.REQUIRED) {
         _reportErrorForNode(
             ParserErrorCode.NAMED_PARAMETER_OUTSIDE_GROUP, parameter);
+        kind = ParameterKind.NAMED;
       }
       return new DefaultFormalParameter(
           parameter, kind, separator, defaultValue);
     } else if (kind != ParameterKind.REQUIRED) {
       return new DefaultFormalParameter(parameter, kind, null, null);
     }
     return parameter;
   }
 
   /**
@@ skipping 5295 matching lines @@
    */
   Parser_SyntheticKeywordToken(Keyword keyword, int offset)
       : super(keyword, offset);
 
   @override
   int get length => 0;
 
   @override
   Token copy() => new Parser_SyntheticKeywordToken(keyword, offset);
 }