Location.Error
val createf : loc:t -> ('a, Format.formatter, unit, t) format4 -> 'a
val message : t -> string
val register_error_of_exn : (exn -> t option) -> unit
val of_exn : exn -> t option
val to_extension : t -> string Astlib.Location.loc * Parsetree.payload
val raise : t -> 'a