Hash_set.For_derivingmodule type M_of_sexp = sig ... endmodule type Sexp_of_m = sig ... endmodule type Equal_m = sig ... endM is meant to be used in combination with OCaml applicative functor types:
val m__t_sexp_grammar :
(module Base__.Hash_set_intf.M_sexp_grammar with type t = 'elt) ->
'elt t Sexplib0.Sexp_grammar.t