Fix for parsing generic function types with Fasta.

pkg/analyzer/lib/dart/ast/ast_factory.dart

 // Copyright (c) 2016, 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.
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:front_end/src/scanner/token.dart';
 import 'package:meta/meta.dart';
 
 /**
@@ skipping 608 matching lines @@
       @required FormalParameterList parameters,
       Token question});
 
   /**
    * Initialize a newly created generic function type.
    */
   GenericFunctionType genericFunctionType(
       TypeAnnotation returnType,
       Token functionKeyword,
       TypeParameterList typeParameters,
-      FormalParameterList _parameters);
+      FormalParameterList parameters);
 
   /**
    * Returns a newly created generic type alias. Either or both of the
    * [comment] and [metadata] can be `null` if the variable list does not have
    * the corresponding attribute. The [typeParameters] can be `null` if there
    * are no type parameters.
    */
   GenericTypeAlias genericTypeAlias(
       Comment comment,
       List<Annotation> metadata,
@@ skipping 474 matching lines @@
    */
   WithClause withClause(Token withKeyword, List<TypeName> mixinTypes);
 
   /**
    * Returns a newly created yield expression. The [star] can be `null` if no
    * star was provided.
    */
   YieldStatement yieldStatement(
       Token yieldKeyword, Token star, Expression expression, Token semicolon);
 }