Extracts only send rights from the given mailbox, returning a
(possibly shared) handle to the underlying mailbox containing only
send rights. Messages sent to mbox
go to the underlying
mailbox
, but messages may not be received from mbox
.
(Attempting to do so signals a <only-send-rights>
condition.)
Note: This is implemented using a proxy wrapper class for mailboxes. The send-message! primitive knows how to indirect through the proxy wrapper.
Note: This is not currently implemented.