Another way to do it

Author: shulhi

jscomp/syntax/src/res_parsetree_viewer.ml

@@ -25,7 +25,7 @@ let print_ct ct =
   | {ptyp_desc = Ptyp_variant _} -> print_endline "Ptyp_variant"
   | _ -> print_endline "Something else"
 
-let arrow_type ?(arity = max_int) ct =
+let arrow_type ?(arity = max_int) ?(attrs = []) ct =
   let has_as_attr attrs =
     Ext_list.exists attrs (fun (x, _) -> x.Asttypes.txt = "as")
   in
@@ -70,10 +70,11 @@ let arrow_type ?(arity = max_int) ct =
     | typ -> (attrs_before, List.rev acc, typ)
   in
   match ct with
-  | {ptyp_desc = Ptyp_arrow (Nolabel, _typ1, _typ2); ptyp_attributes = attrs} as
-    typ ->
+  | {ptyp_desc = Ptyp_arrow (Nolabel, _typ1, _typ2); ptyp_attributes = attrs1}
+    as typ ->
+    let attrs = List.concat [attrs; attrs1] in
     process attrs [] {typ with ptyp_attributes = []} arity
-  | typ -> process [] [] typ arity
+  | typ -> process attrs [] typ arity
 
 let functor_type modtype =
   let rec process acc modtype =

jscomp/syntax/src/res_parsetree_viewer.mli

@@ -3,6 +3,7 @@
    * we restructure the tree into (a, b, c) and its returnType d *)
 val arrow_type :
   ?arity:int ->
+  ?attrs:Parsetree.attributes ->
   Parsetree.core_type ->
   Parsetree.attributes
   * (Parsetree.attributes * Asttypes.arg_label * Parsetree.core_type) list

jscomp/syntax/src/res_printer.ml

@@ -1591,17 +1591,13 @@ and print_label_declaration ~state (ld : Parsetree.label_declaration) cmt_tbl =
        ])
 
 and print_typ_expr ~(state : State.t) (typ_expr : Parsetree.core_type) cmt_tbl =
-  let parent_has_attrs =
+  let parent_attrs =
     let attrs = ParsetreeViewer.filter_parsing_attrs typ_expr.ptyp_attributes in
-    if Ast_uncurried.core_type_is_uncurried_fun typ_expr && not (attrs = [])
-    then
-      let arity, _ = Ast_uncurried.core_type_extract_uncurried_fun typ_expr in
-      arity > 0
-    else false
+    if Ast_uncurried.core_type_is_uncurried_fun typ_expr then attrs else []
   in
   let print_arrow ?(arity = max_int) typ_expr =
     let attrs_before, args, return_type =
-      ParsetreeViewer.arrow_type ~arity typ_expr
+      ParsetreeViewer.arrow_type ~arity ~attrs:parent_attrs typ_expr
     in
     let return_type_needs_parens =
       match return_type.ptyp_desc with
@@ -1634,7 +1630,7 @@ and print_typ_expr ~(state : State.t) (typ_expr : Parsetree.core_type) cmt_tbl =
            [
              Doc.group attrs;
              Doc.group
-               (if has_attrs_before || parent_has_attrs then
+               (if has_attrs_before then
                   Doc.concat
                     [
                       Doc.lparen;
@@ -1849,6 +1845,8 @@ and print_typ_expr ~(state : State.t) (typ_expr : Parsetree.core_type) cmt_tbl =
   in
   let should_print_its_own_attributes =
     match typ_expr.ptyp_desc with
+    | Ptyp_constr _ when Ast_uncurried.core_type_is_uncurried_fun typ_expr ->
+      true
     | Ptyp_arrow _ (* es6 arrow types print their own attributes *) -> true
     | _ -> false
   in