lib: access special methods via special slot mechanism.

* ffi.c (ffi_flex_struct_in): Use get_special_slot to obtain
length method.

* lib.c (nullify_s, from_list_s, lambda_set_s): Definitions
removed from here.
(seq_info, car, cdr,  rplaca, rplacd, make_like, nullify,
replace_obj, length, empty, sub, ref, refset, dwim_set): Use
get_special_slot to obtain special method from object,
rather than maybe_slot.
(obj_init): Remove initializations of nullify_s, from_list_s
and lambda_set_s from here.

* struct.c (enum special_slot): Definition removed from here.
(nullify_s, from_list_s, lambda_set_s): Definitions moved here
from lib.c.
(special_sym): New static array.
(struct_init): Initializations of nullify_s, from_list_s
and lambda_set_s moved here from lib.c.
(get_special_slot): New function.

* struct.h (lambda_set_s): Declared.
(enum special_slot): Definition moved here.
(get_special_slot): Declared.

* txr.1: Added compat note, since get_special_slot behaves
like maybe_slot under 224 compatibility.

1 files changed, 1 insertions, 1 deletions

diff --git a/ffi.c b/ffi.c
index 6891aac1..4f79dcc1 100644
--- a/ffi.c
+++ b/ffi.c
@@ -2050,7 +2050,7 @@ static void ffi_ptr_in_release(struct txr_ffi_type *tft, val obj, mem_t *dst)
 static val ffi_flex_struct_in(struct txr_ffi_type *tft, val strct, val self)
 {
   struct smemb *lastm = &tft->memb[tft->nelem - 1];
-  val length_meth = maybe_slot(strct, length_s);
+  val length_meth = get_special_slot(strct, length_m);
 
   if (length_meth) {
     val len = funcall1(length_meth, strct);