Closure_conversion_aux.Function_declsUsed to represent information about a set of function declarations during closure conversion. (The only case in which such a set may contain more than one declaration is when processing "let rec".)
module Function_decl : sig ... endval create : Function_decl.t list -> tval to_list : t -> Function_decl.t listval all_free_idents : t -> Ident.Set.t