let result env =
let t = match env.ret_type with Some t -> t
| None ->
let t = Kernel_function.get_return_type env.kf in
env.ret_type <- Some t ; t
in
let x = match env.result with Some x -> x
| None ->
let x = D.fresh "result" (Mdata.Vacsl (Ctype t)) in
env.result <- Some x ; x
in (x, t)