set allowDiffPatterns = true.

channel c.

process
      in(c, in_t: bitstring);
      let diff[y,z] = in_t in
      out(c, (y,z))

(* EXPECTPV
Error: diff or choice pattern in phase 0 but diff/choice terms occur only in phase at least 4611686018427387903.
xtime: error in child process (status : 2)
END *)
