anchor.diff:      open System.Windows
       open System
   
  -    let mutable FileSystem = 
  -        { new IFileSystem with 
  +    type DefaultFileSystem() =
  +        interface IFileSystem with
               member this.ReadAllBytesShim (fileName:string) = 
                   use stream = this.FileStreamReadShim fileName
                   let len = stream.Length
  
positive.code: 
              member __.GetLastWriteTimeShim (fileName:string) = File.GetLastWriteTime fileName
              member __.SafeExists (fileName:string) = System.IO.File.Exists fileName 
              member __.FileDelete (fileName:string) = System.IO.File.Delete fileName }       
  #endif
  
      type System.Text.Encoding with 
  
negative.code:                 System.Text.Encoding.GetEncoding(n)
  #endif                
  
      let mutable FileSystem = DefaultFileSystem() :> IFileSystem 