and aux_capture_var env (name, ty_opt) = (aux env name, aux_opt env ty_opt)
and aux_branch env (pattern, term) =
(aux_pattern env pattern, aux env term)
and aux_capture_var env (name, ty_opt) = (aux env name, aux_opt env ty_opt)
and aux_branch env (pattern, term) =
(aux_pattern env pattern, aux env term)