Make application default to uncurried at the lambda level.

jscomp/core/lam_convert.ml

@@ -549,7 +549,7 @@ let convert (exports : Set_ident.t) (lam : Lambda.lambda) :
         (* we need do this eargly in case [aux fn] add some wrapper *)
         Lam.apply (convert_aux fn)
           (Ext_list.map args convert_aux)
-          { ap_loc = loc; ap_inlined; ap_status = App_na }
+          { ap_loc = loc; ap_inlined; ap_status = App_uncurry }
     | Lfunction { params; body; attr } ->
         let new_map, body =
           rename_optional_parameters Map_ident.empty params body

jscomp/ml/translcore.ml

@@ -1036,14 +1036,8 @@ and transl_cases_try cases =
   List.map transl_case_try cases
 
 and transl_apply ?(inlined = Default_inline) ?(uncurried_partial_application=None) lam sargs loc =
-  let lapply funct args =
-    match funct with
-    (* Attention: This may not be what we need to change the application arity*)
-    | Lapply ap -> Lapply { ap with ap_args = ap.ap_args @ args; ap_loc = loc }
-    | lexp ->
-        Lapply
-          { ap_loc = loc; ap_func = lexp; ap_args = args; ap_inlined = inlined }
-  in
+  let lapply ap_func ap_args =
+    Lapply { ap_loc = loc; ap_func; ap_args; ap_inlined = inlined } in
   let rec build_apply lam args = function
     | (None, optional) :: l ->
         let defs = ref [] in