reflect reviewer's comments - Memo.parallel_iter

Signed-off-by: Haochen Kotoi-Xie <[email protected]>

Author: haochenx

src/dune_rules/melange/melange_rules.ml

@@ -178,13 +178,10 @@ let build_js ~loc ~dir ~pkg_name ~mode ~module_systems ~output ~obj_dir ~sctx
    assumed. *)
 let add_deps_to_aliases ?(alias = Melange_stanzas.Emit.implicit_alias) ~dir deps
     =
-  let open Memo.O in
   let alias = Alias.make alias ~dir in
   let dune_default_alias = Alias.all ~dir in
   let attach alias = Rules.Produce.Alias.add_deps alias deps in
-  let+ () = attach alias
-  and+ () = attach dune_default_alias in
-  ()
+  Memo.parallel_iter ~f:attach [ alias; dune_default_alias ]
 
 let setup_emit_cmj_rules ~sctx ~dir ~scope ~expander ~dir_contents
     (mel : Melange_stanzas.Emit.t) =