seq_info: nullify bugfix.

A change in the nullify function to support hash tables has
broken various functions which classify an object using
seq_info, obtainig a SEQ_HASHLIKE kind, and then work with
si.obj using hash functions. But si.obj has been nullified.
An example of a broken function is find-max.

Basically, this can be attributed to a careless use of nullify
in seq_info. The purpose of nullify is to support code which
treats any sequence as if it were a list. But seq_info doesn't
do that; it classifies sequences and treats them according to
their kind. Under seq_info, the only non-list objects that get
treated as lists are list-like structures. For these it makes
sense to call nullify, in case they have a nullify method.

* lib.c (seq_info): Don't unconditionally call nullify on all
COBJ objects. Only call nullify on struct objects. If that
returns nil, then treat the object as SEQ_NIL; and if it
returns an object different from the original, then recurse.

1 files changed, 19 insertions, 13 deletions

diff --git a/lib.c b/lib.c
index 522128a6..9cc20045 100644
--- a/lib.c
+++ b/lib.c
@@ -268,17 +268,12 @@ seq_info_t seq_info(val obj)
   seq_info_t ret;
   type_t to = type(obj);
 
+  ret.obj = obj;
+
   if (to != COBJ) {
-    ret.obj = obj;
     ret.type = to;
     ret.kind = seq_kind_tab[to];
     return ret;
-  }
-
-  ret.obj = obj = nullify(obj);
-
-  if (!obj || (ret.type = to = type(obj)) != COBJ) {
-    ret.kind = seq_kind_tab[to];
   } else {
     val cls = obj->co.cls;
 
@@ -287,12 +282,23 @@ seq_info_t seq_info(val obj)
     } else if (cls == carray_s) {
       ret.kind = SEQ_VECLIKE;
     } else if (obj_struct_p(obj)) {
-      if (maybe_slot(obj, length_s))
-        ret.kind = SEQ_VECLIKE;
-      if (maybe_slot(obj, car_s))
-        ret.kind = SEQ_LISTLIKE;
-      else
-        ret.kind = SEQ_NOTSEQ;
+      val sub = nullify(obj);
+
+      if (!sub) {
+        ret.kind = SEQ_NIL;
+        ret.obj = nil;
+      } else if (sub != obj) {
+        return seq_info(sub);
+      } else {
+        if (maybe_slot(obj, length_s))
+          ret.kind = SEQ_VECLIKE;
+        if (maybe_slot(obj, car_s))
+          ret.kind = SEQ_LISTLIKE;
+        if (maybe_slot(obj, car_s))
+          ret.kind = SEQ_LISTLIKE;
+        else
+          ret.kind = SEQ_NOTSEQ;
+      }
     } else {
       ret.kind = SEQ_NOTSEQ;
     }