include Hash_set_gen.S with type key = Ident.t;
let remove: t => key => unit;
let add: t => key => unit;
let of_array: array(key) => t;
let check_add: t => key => bool;
let mem: t => key => bool;
let iter: t => (key => unit) => unit;
let fold: t => 'b => (key => 'b => 'b) => 'b;
let to_list: t => list(key);