Add `=` as default-value separator for named parameters.

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 2762 matching lines @@
   /**
    * Parse a formal parameter. At most one of `isOptional` and `isNamed` can be
    * `true`. The [kind] is the kind of parameter being expected based on the
    * presence or absence of group delimiters. Return the formal parameter that
    * was parsed.
    *
    *     defaultFormalParameter ::=
    *         normalFormalParameter ('=' expression)?
    *
    *     defaultNamedParameter ::=
+   *         normalFormalParameter ('=' expression)?
    *         normalFormalParameter (':' expression)?
    */
   FormalParameter parseFormalParameter(ParameterKind kind) {
     NormalFormalParameter parameter = parseNormalFormalParameter();
     TokenType type = _currentToken.type;
     if (type == TokenType.EQ) {
       Token separator = getAndAdvance();
       Expression defaultValue = parseExpression2();
-      if (kind == ParameterKind.NAMED) {
-        _reportErrorForToken(
-            ParserErrorCode.WRONG_SEPARATOR_FOR_NAMED_PARAMETER, separator);
-      } else if (kind == ParameterKind.REQUIRED) {
+      if (kind == ParameterKind.REQUIRED) {
         _reportErrorForNode(
             ParserErrorCode.POSITIONAL_PARAMETER_OUTSIDE_GROUP, parameter);
       }
       return new DefaultFormalParameter(
           parameter, kind, separator, defaultValue);
     } else if (type == TokenType.COLON) {
       Token separator = getAndAdvance();
       Expression defaultValue = parseExpression2();
       if (kind == ParameterKind.POSITIONAL) {
         _reportErrorForToken(
@@ skipping 5294 matching lines @@
    */
   Parser_SyntheticKeywordToken(Keyword keyword, int offset)
       : super(keyword, offset);
 
   @override
   int get length => 0;
 
   @override
   Token copy() => new Parser_SyntheticKeywordToken(keyword, offset);
 }