Sexp_with_layout.Parsedparsing produces absolute positions
type t = | Atom of Src_pos.Absolute.t * string * string option | 
| List of Src_pos.Absolute.t * t_or_comment list * Src_pos.Absolute.t | 
S-expressions annotated with relative source positions and comments
and comment = | Plain_comment of Src_pos.Absolute.t * string | 
| Sexp_comment of Src_pos.Absolute.t * comment list * t | 
val sexp_of_t_or_comment : t_or_comment -> Type.t