CodeContracts: ccrewrite fails with Object reference not set to an instance of an object

Question

The below code makes ccrewrite blow up! Ideas? BTW, If you comment out the ActualClass, ccrewrite succeeds...

    [ContractClass(typeof(TestContracts))]
    interface ITestInterface
    {
        bool IsStarted { get; set; }
        void Begin();
    }

    class ActualClass : ITestInterface
    {
        public bool IsStarted { get; set; }
        public void Begin()
        {
            this.IsStarted = true;
        }
    }

    [ContractClassFor(typeof(ITestInterface))]
    class TestContracts : ITestInterface
    {
        ITestInterface Current { get; set; }

        private TestContracts()
        {
            Current = this;
        }

        #region ITestInterface Members

        bool ITestInterface.IsStarted
        {
            get; set;
        }

        void ITestInterface.Begin()
        {
            Contract.Requires(!Current.IsStarted);
            Contract.Ensures(Current.IsStarted);
        }

Thanks in advance!

Answer 1

Well, serves me right for not reading Jon Skeet well enough ;) The bit about how rewriter takes the contracts and puts them in your actual class...

   [ContractClassFor(typeof(ITestInterface))] 
    class TestContracts : ITestInterface 
    { 

        private TestContracts() 
        { 
        } 

        #region ITestInterface Members 

        bool ITestInterface.IsStarted 
        { 
            get; set; 
        } 

        void ITestInterface.Begin() 
        { 
            ITestInterface iface = this;
            Contract.Requires(!iface.IsStarted); 
            Contract.Ensures(iface.IsStarted); 
        } 
    }

http://social.msdn.microsoft.com/Forums/en-US/codecontracts/thread/853227bf-56e6-427b-8e9e-162c129e87ce/