anchor.diff:  /// state of the synchronization object, is full at any time.
   ///
   /// Note that `MVar` is a subtype of `Alt` and `xM :> Alt<'x>` is equivalent to
  -/// `MVar.Alt.take xM`.
  +/// `MVar.take xM`.
   type MVar<'x> :> Alt<'x>
   #endif
   
  
positive.code: /// like channels do.  When simple rendezvous is necessary, a channel should be
  /// used instead.
  ///
  /// Note that `IVar` is a subtype of `Promise` and `IVar.Alt.read xI` is
  /// equivalent to `xI :> Alt<'x>`.
  type IVar<'x> :> Promise<'x>
  #endif
  
  
negative.code: /// passing mechanism is likely to perform better.
  ///
  /// Note that `Ch` is a subtype of `Alt` and `xCh :> Alt<'x>` is equivalent to
  /// `Ch.take xCh`.
  type Ch<'x> :> Alt<'x>
  #endif
  
  