Clean up callback interfaces.

service/datastore/reflect.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package datastore
 
 import (
         "reflect"
         "time"
 
         "github.com/luci/gae/service/blobstore"
 )
 
 var (
         typeOfBool              = reflect.TypeOf(true)
         typeOfBSKey             = reflect.TypeOf(blobstore.Key(""))
         typeOfCursorCB          = reflect.TypeOf(CursorCB(nil))
         typeOfGeoPoint          = reflect.TypeOf(GeoPoint{})
         typeOfInt64             = reflect.TypeOf(int64(0))
         typeOfKey               = reflect.TypeOf((*Key)(nil))
         typeOfPropertyConverter = reflect.TypeOf((*PropertyConverter)(nil)).Elem()
         typeOfPropertyLoadSaver = reflect.TypeOf((*PropertyLoadSaver)(nil)).Elem()
         typeOfString            = reflect.TypeOf("")
         typeOfTime              = reflect.TypeOf(time.Time{})
         typeOfToggle            = reflect.TypeOf(Auto)
         typeOfMGS               = reflect.TypeOf((*MetaGetterSetter)(nil)).Elem()
         typeOfPropertyMap       = reflect.TypeOf((PropertyMap)(nil))
+        typeOfError             = reflect.TypeOf((*error)(nil)).Elem()
 )