[@@deriving sexp] record-field attribute, [@sexp.omit_nil], for a field that is omitted if its sexp representation is ().[%sexp_of: 'a] and [%of_sexp: 'a] to not expose variable names intended for internal use.type 't t = ...ppx_sexp_conv, and breaking up the documentation between sexplib and ppx_sexp_conv. Also changed the formatting to use org-mode, so it will render properly on github. Markdown doesn't render well by default, unless you use quite different conventions about linebeaks.Type_conv and Ppx_core evolution.Make ppx_sexp_conv correctly handle aliases to polymorphic variants:
type t = A @@deriving sexptype u = t@@deriving sexptype v = u | B @@deriving sexp
Before, v_of_sexp would never manage to read B. This problem is now fixed if you use sexp_polyonuinstead ofsexp, and if you don't, you get an "unbound value __u_of_sexp__". People should use sexp_polywhen they have a polymorphic variant type that is not syntactically a polymorphic variant, but in practice it's simpler to replacesexpbysexp_poly` when faced with the error above.
The need for sexp_poly should happen only in one new case: an implementation says type u = t @@deriving sexpbut the interface says `type u =A @@deriving sexp. (the old case where it was already needed is when you have an interface that says `type u = t `@@deriving sexp and in some other implementation you try to say type t = That_module.t | A `@@deriving sexp``).