fix: no fallback

Signed-off-by: Antonio Nuno Monteiro <anmonteiro@gmail.com>

bin/describe/describe_pp.ml

@@ -158,30 +158,23 @@ let get_pped_file super_context file =
     ml_kind
   in
   let* module_for_file = module_for_file ~sctx:super_context ~ml_kind file_in_build_dir in
-  let build_fallback =
-    Memo.lazy_ (fun () ->
-      Build_system.file_exists file_in_build_dir
-      >>= function
-      | false ->
-        User_error.raise
-          [ Pp.textf "%s does not exist" (Path.to_string_maybe_quoted file_in_build_dir) ]
-      | true ->
-        let+ () = Build_system.build_file file_in_build_dir in
-        Error file_in_build_dir)
+  let file_not_found () =
+    User_error.raise
+      [ Pp.textf "%s does not exist" (Path.to_string_maybe_quoted file_in_build_dir) ]
   in
   match module_for_file with
   | Some (`Module m) ->
     let pp_file =
       m |> Dune_rules.Module.source ~ml_kind |> Option.map ~f:Dune_rules.Module.File.path
     in
     (match pp_file with
-     | None -> Memo.Lazy.force build_fallback
+     | None -> file_not_found ()
      | Some pp_file ->
        let+ () = Build_system.build_file pp_file in
        Ok pp_file)
   | Some (`Staged_pps loc) ->
     User_error.raise ~loc [ Pp.text "staged_pps are not supported." ]
-  | None -> Memo.Lazy.force build_fallback
+  | None -> file_not_found ()
 ;;
 
 let term =