let return kf e p =
match e with
| Some e ->
begin try
let v = Macros.result_var kf in
let v = WpFol.lv_to_fol_var v in
mk_let ~fresh:false v (texpr e) p
with Types.Unsupported t ->
let msg = "unsupported type in 'return' processing: "^t in
raise (Calculus.InvalidModel msg)
end
| None -> p