-- Eww -- this feature is completely unsafe (by design).
PROC send (CHAN OF INT32 out)
  CHAN OF REAL32 r RETYPES out:
  r ! 3.14159
:
PROC recv (CHAN OF INT32 in)
  CHAN OF REAL32 r RETYPES in:
  REAL32 n:
  SEQ
    r ? n
    ASSERT (n > 3.1)
    ASSERT (n < 3.2)
:
PROC P ()
  CHAN OF INT32 c:
  PAR
    send (c)
    recv (c)
: