anchor.diff:  /// the arguments, negative acknowledgment token and a channel to the server and
   /// then synchronize using a `take` operation on the channel for the reply.  See
   /// `withNackJob` for an illustrative toy example.
  -///
  -/// Note that `Alt` is a subtype of `Job`.  You can use an alternative in any
  -/// context that requires a job.
  -type Alt<'x> :> Job<'x>
  +type Alt<'x> =
  +  /// `Alt<'x>` is a subtype of `Job<'x>`.  You can use an alternative in any
  +  /// context that requires a job.
  +  inherit Job<'x>
   #endif
   
   /// Operations on first-class synchronous operations or alternatives.
  
positive.code: /// operation, but in situations where buffering is needed, some other message
  /// passing mechanism such as a bounded mailbox, `BoundedMb<_>`, or unbounded
  /// mailbox, `Mailbox<_>`, may be preferable.
  ///
  /// Note that `Ch<'x>` is a subtype of `Alt<'x>` and `xCh :> Alt<'x>` is
  /// equivalent to `Ch.take xCh`.
  type Ch<'x> :> Alt<'x>
  #endif
  
  /// Operations on synchronous channels.
  
negative.code: /// bounded, a bounded mailbox, `BoundedMb<_>`, should be preferred.  In
  /// situations where buffering is not needed, a channel, `Ch<_>`, should be
  /// preferred.
  type Mailbox<'x> =
    /// `Mailbox<'x>` is a subtype of `Alt<'x>` and `xMb :> Alt<'x>` is equivalent
    /// to `Mailbox.take xMb`.
    inherit Alt<'x>
  
    /// Creates a new mailbox.
    new: unit -> Mailbox<'x>
  #endif
  
  /// Operations on buffered mailboxes.
  