anchor.diff:        error :> CO
   
       let setupConstructor (env:Env) (name:string) (proto:CO) update =
  -      let ctor = new Func<FunctionObject, CommonObject, BoxedValue, CommonObject>(constructor' proto)
  +      let ctor = new Func<FO, CO, BV, CO>(constructor' proto)
         let ctor = Utils.createHostFunction env ctor
         
         ctor.Prototype <- env.Prototypes.Function
  
positive.code:   let private name = "Error"
    let private updater (ctors:Constructors) ctor = {ctors with Error=ctor} 
  
    let toString (o:CommonObject) =
      name + ": " + TypeConverter.ToString(o.Get "message")
  
    let createPrototype (env:Environment) proto =
      let prototype = env.NewError()
      prototype.Prototype <- proto
      prototype
  
    let setupConstructor (env:Environment) =
      let proto = env.Prototypes.Error
      Utils.setupConstructor env name proto updater
  
    let setupPrototype (env:Environment) =
      let proto = env.Prototypes.Error
      let ctor = env.Constructors.Error
      
      let toString = new Func<CommonObject, string>(toString)
      let toString = Utils.createHostFunction env toString
      proto.Put("toString", toString, DontEnum)
  
  
negative.code:   let private name = "ReferenceError" 
    let private updater (ctors:Constructors) ctor = {ctors with ReferenceError=ctor} 
    
    let setupConstructor (env:Env) =
      let proto = env.Prototypes.ReferenceError
      Error.Utils.setupConstructor env name proto updater
  
    let setupPrototype (env:Env) =
      let proto = env.Prototypes.ReferenceError
      let ctor = env.Constructors.ReferenceError
      Error.Utils.setupPrototype name ctor proto
  