[Caml-list] char/line-numbers in error-messages from data-structures bulit via ocamllex?

[Chet Murthy <murthy.chet@gmail.com>]

Ages (decades) ago, I recall (perhaps incorrectly) that there was a
somewhat well-known way of using ocamllex and {ocamlyacc, PP streams}
together, in order to decorate a parse-tree with line-number
information -- so that later (e.g. type-checking) passes could emit
that line-number information as part of error-messages.

As I rack my brain trying to imagine what that method might be,
several approaches come to mind:

(1) with PP streams, I could define the token-type to be a tuple of
the real token-type and a lexing position, e.g.

type token = real_token * Lexing.position

(2) with camlyacc, I'd have to stuff the position into every branch of
the algebraic datatype, e.g.

type token =
| LIT of Lexing.position * literal
| ID of Lexing.position * identifier
| OP of Lexing.position * operator
...

Both of these seem workable, but I don't remember either of them as
being "the" way to do it, back in the day.

Does anybody have any memory of this "Echte" way of doing it?

Thanks,
--chet--