Cleanup Let_binding.split_annot

lib/Sugar.ml

@@ -168,25 +168,21 @@ module Let_binding = struct
           in
           Exp (Ast_helper.Exp.fun_ param exp)
         in
-        ( xargs
-        , Some (Pvc_constraint {locally_abstract_univars= []; typ})
+        ( Some (Pvc_constraint {locally_abstract_univars= []; typ})
         , sub_exp ~ctx:exp_ctx exp )
     (* The type constraint is always printed before the declaration for
        functions, for other value bindings we preserve its position. *)
     | Pexp_constraint (exp, typ) when not (List.is_empty xargs) ->
         Cmts.relocate cmts ~src:body.pexp_loc ~before:exp.pexp_loc
           ~after:exp.pexp_loc ;
-        ( xargs
-        , Some (Pvc_constraint {locally_abstract_univars= []; typ})
+        ( Some (Pvc_constraint {locally_abstract_univars= []; typ})
         , sub_exp ~ctx exp )
     | Pexp_coerce (exp, typ1, typ2)
       when Source.type_constraint_is_first typ2 exp.pexp_loc ->
         Cmts.relocate cmts ~src:body.pexp_loc ~before:exp.pexp_loc
           ~after:exp.pexp_loc ;
-        ( xargs
-        , Some (Pvc_coercion {ground= typ1; coercion= typ2})
-        , sub_exp ~ctx exp )
-    | _ -> (xargs, None, xbody)
+        (Some (Pvc_coercion {ground= typ1; coercion= typ2}), sub_exp ~ctx exp)
+    | _ -> (None, xbody)
 
   let split_fun_args cmts xpat xbody =
     let xargs, xbody =
@@ -195,9 +191,12 @@ module Let_binding = struct
           fun_ cmts ~will_keep_first_ast_node:false xbody
       | _ -> ([], xbody)
     in
-    match (xbody.ast.pexp_desc, xpat.ast.ppat_desc) with
-    | Pexp_constraint _, Ppat_constraint _ -> (xargs, None, xbody)
-    | _ -> split_annot cmts xargs xbody
+    let annot =
+      match (xbody.ast.pexp_desc, xpat.ast.ppat_desc) with
+      | Pexp_constraint _, Ppat_constraint _ -> (None, xbody)
+      | _ -> split_annot cmts xargs xbody
+    in
+    (xargs, annot)
 
   let should_desugar_args pat typ =
     match (pat.ast, typ) with
@@ -210,10 +209,10 @@ module Let_binding = struct
     let lb_exp = sub_exp ~ctx pvb_expr
     and lb_pat = sub_pat ~ctx pvb_pat
     and lb_typ = pvb_constraint in
-    let lb_args, lb_typ, lb_exp =
+    let lb_args, (lb_typ, lb_exp) =
       if should_desugar_args lb_pat lb_typ then
         split_fun_args cmts lb_pat lb_exp
-      else ([], lb_typ, lb_exp)
+      else ([], (lb_typ, lb_exp))
     in
     { lb_op= Location.{txt= (if first then "let" else "and"); loc= none}
     ; lb_pat