Add attributes field to arg type in typedtree

Introduces an 'attrs' field to the 'arg' record in typedtree.ml and typedtree.mli to support attributes on function arguments. Updates related code in typetexp.ml and printtyped.ml to handle the new field, enabling attribute preservation and printing for function argument types.

Author: cristianoc

compiler/ml/printtyped.ml

@@ -152,6 +152,7 @@ let rec core_type i ppf x =
   | Ttyp_arrow (arg, ret, _) ->
     line i ppf "Ttyp_arrow\n";
     arg_label i ppf arg.lbl;
+    attributes i ppf arg.attrs;
     core_type i ppf arg.typ;
     core_type i ppf ret
   | Ttyp_tuple l ->

compiler/ml/typedtree.ml

@@ -303,7 +303,7 @@ and core_type = {
   ctyp_attributes: attribute list;
 }
 
-and arg = {lbl: Noloc.arg_label; typ: core_type}
+and arg = {attrs: attributes; lbl: Noloc.arg_label; typ: core_type}
 
 and core_type_desc =
   | Ttyp_any

compiler/ml/typedtree.mli

@@ -409,7 +409,7 @@ and core_type = {
   ctyp_attributes: attributes;
 }
 
-and arg = {lbl: Noloc.arg_label; typ: core_type}
+and arg = {attrs: attributes; lbl: Noloc.arg_label; typ: core_type}
 
 and core_type_desc =
   | Ttyp_any

compiler/ml/typetexp.ml

@@ -329,7 +329,7 @@ and transl_type_aux env policy styp =
       else ty1
     in
     let ty = newty (Tarrow ({lbl; typ = ty1}, cty2.ctyp_type, Cok, arity)) in
-    ctyp (Ttyp_arrow ({lbl; typ = cty1}, cty2, arity)) ty
+    ctyp (Ttyp_arrow ({attrs = arg.attrs; lbl; typ = cty1}, cty2, arity)) ty
   | Ptyp_tuple stl ->
     assert (List.length stl >= 2);
     let ctys = List.map (transl_type env policy) stl in