Keep types in signatures of function types properly instantiated as the function

runtime/lib/mirrors_impl.dart

 // Copyright (c) 2012, 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.
 
 // VM-specific implementation of the dart:mirrors library.
 
 import "dart:collection" show UnmodifiableListView, UnmodifiableMapView;
 import "dart:_internal" as internal;
 
 var _dirty = false;
@@ skipping 932 matching lines @@
   MethodMirror get callMethod {
     if (_callMethod == null) {
       _callMethod = _FunctionTypeMirror_call_method(_functionReflectee);
     }
     return _callMethod;
   }
 
   TypeMirror _returnType = null;
   TypeMirror get returnType {
     if (_returnType == null) {
-      _returnType = reflectType(
-          _FunctionTypeMirror_return_type(_functionReflectee, _instantiator));
+      _returnType =
+          reflectType(_FunctionTypeMirror_return_type(_functionReflectee));
     }
     return _returnType;
   }
 
   List<ParameterMirror> _parameters = null;
   List<ParameterMirror> get parameters {
     if (_parameters == null) {
       _parameters = _FunctionTypeMirror_parameters(_functionReflectee);
       _parameters = new UnmodifiableListView(_parameters);
     }
     return _parameters;
   }
 
   bool get isOriginalDeclaration => true;
   get originalDeclaration => this;
   get typeVariables => _emptyList;
   get typeArguments => _emptyList;
   get metadata => _emptyList;
   get location => null;
 
   String toString() => "FunctionTypeMirror on '${_n(simpleName)}'";
 
   MethodMirror _FunctionTypeMirror_call_method(functionReflectee)
       native "FunctionTypeMirror_call_method";
 
-  static Type _FunctionTypeMirror_return_type(functionReflectee, instantiator)
+  static Type _FunctionTypeMirror_return_type(functionReflectee)
       native "FunctionTypeMirror_return_type";
 
   List<ParameterMirror> _FunctionTypeMirror_parameters(functionReflectee)
       native "FunctionTypeMirror_parameters";
 }
 
 abstract class _LocalDeclarationMirror extends _LocalMirror
     implements DeclarationMirror {
   final _reflectee;
   Symbol _simpleName;
@@ skipping 656 matching lines @@
   }
 
   static Type _instantiateType(Type key, List<Type> typeArguments) {
     if (typeArguments.isEmpty) {
       throw new ArgumentError.value(typeArguments, 'typeArguments',
           'Type arguments list cannot be empty.');
     }
     return instantiateGenericType(key, typeArguments.toList(growable: false));
   }
 }