Use Syntax.deleted_in for error

Signed-off-by: Rudi Grinberg <me@rgrinberg.com>

src/dune/dune_file.ml

@@ -1993,18 +1993,13 @@ module Alias_conf = struct
        and+ package = field_o "package" Pkg.decode
        and+ action =
          field_o "action"
-           (let* syntax_version = Dune_lang.Syntax.get_exn Stanza.syntax
-            and+ loc = loc in
-            let deleted_in_version = (2, 0) in
-            if syntax_version < deleted_in_version then
-              located Action_dune_lang.decode
-            else
-              let what = "action field" in
-              let repl =
-                [ Pp.text "Use a rule stanza with the alias field instead" ]
-              in
-              Dune_lang.Syntax.Error.deleted_in loc Stanza.syntax
-                deleted_in_version ~what ~repl)
+           (let repl =
+              [ Pp.text "Use a rule stanza with the alias field instead" ]
+            in
+            let* () =
+              Dune_lang.Syntax.deleted_in ~repl Stanza.syntax (2, 0)
+            in
+            located Action_dune_lang.decode)
        and+ loc = loc
        and+ locks = field "locks" (repeat String_with_vars.decode) ~default:[]
        and+ deps =

src/dune_lang/syntax.ml

@@ -170,14 +170,14 @@ let desc () =
   | Values (loc, Some s) -> (loc, sprintf "'%s'" s)
   | Fields (loc, Some s) -> (loc, sprintf "Field '%s'" s)
 
-let deleted_in ?(extra_info = "") t ver =
+let deleted_in ?(extra_info = "") ?repl t ver =
   let open Version.Infix in
   let* current_ver = get_exn t in
   if current_ver < ver then
     return ()
   else
     let* loc, what = desc () in
-    Error.deleted_in ~extra_info loc t ver ~what
+    Error.deleted_in ?repl ~extra_info loc t ver ~what
 
 let deprecated_in ?(extra_info = "") t ver =
   let open Version.Infix in

src/dune_lang/syntax.mli

@@ -78,7 +78,11 @@ val greatest_supported_version : t -> Version.t
 (** Indicate the field/constructor being parsed was deleted in the given
     version *)
 val deleted_in :
-  ?extra_info:string -> t -> Version.t -> (unit, _) Decoder.parser
+     ?extra_info:string
+  -> ?repl:User_message.Style.t Pp.t list
+  -> t
+  -> Version.t
+  -> (unit, _) Decoder.parser
 
 (** Indicate the field/constructor being parsed was deprecated in the given
     version *)