improve parser recovery when top level function is missing 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.parser;
 
 import "dart:math" as math;
@@ skipping 5720 matching lines @@
     }
     SimpleIdentifier name = parseSimpleIdentifier();
     FormalParameterList parameters = null;
     if (!isGetter) {
       if (_matches(TokenType.OPEN_PAREN)) {
         parameters = parseFormalParameterList();
         _validateFormalParameterList(parameters);
       } else {
         _reportErrorForCurrentToken(
             ParserErrorCode.MISSING_FUNCTION_PARAMETERS);
+        parameters = new FormalParameterList(
+            _createSyntheticToken(TokenType.OPEN_PAREN), null, null, null,
+            _createSyntheticToken(TokenType.CLOSE_PAREN));
       }
     } else if (_matches(TokenType.OPEN_PAREN)) {
       _reportErrorForCurrentToken(ParserErrorCode.GETTER_WITH_PARAMETERS);
       parseFormalParameterList();
     }
     FunctionBody body;
     if (externalKeyword == null) {
       body = _parseFunctionBody(
           false, ParserErrorCode.MISSING_FUNCTION_BODY, false);
     } else {
@@ skipping 4789 matching lines @@
   }
 
   /**
    * Copy resolution data from the [fromNode] to the [toNode].
    */
   static void copyResolutionData(AstNode fromNode, AstNode toNode) {
     ResolutionCopier copier = new ResolutionCopier();
     copier._isEqualNodes(fromNode, toNode);
   }
 }