expander: expand must only ignores unbound warnings.

The expand function must not muffle all deferred warnings.
That causes the problem that a form like (inc var a.bar) fails
to produce a warning due to bar not being the slot of any
structure. The expand function must only muffle warnings about
undefined functions and variables.

* eval.c (muffle_unbound_warning): New static function.
(no_warn_expand): Use muffle_unbound_warning as handler,
rather than uw_muffle_warning.

* tests/012/struct.tl: Fix two test cases here which test the
expand function using a form that references a nonexistent
slot. These now generate a warning, so we use the slot name b
rather than d, which is defined.

* txr.1: Documented change to expand.

1 files changed, 20 insertions, 1 deletions

diff --git a/eval.c b/eval.c
index bf0dc246..2d840160 100644
--- a/eval.c
+++ b/eval.c
@@ -5088,12 +5088,31 @@ val expand(val form, val menv)
   return ret;
 }
 
+static val muffle_unbound_warning(val exc, struct args *args)
+{
+  (void) exc;
+
+  args_normalize_least(args, 2);
+
+  if (args->fill >= 2) {
+    val tag = args->arg[1];
+
+    if (consp(tag)) {
+      val type = car(tag);
+      if (type == var_s || type == fun_s || type == sym_s)
+        uw_rthrow(continue_s, nil);
+    }
+  }
+
+  return nil;
+}
+
 static val no_warn_expand(val form, val menv)
 {
   val ret;
   uw_frame_t uw_handler;
   uw_push_handler(&uw_handler, cons(defr_warning_s, nil),
-                  func_n1v(uw_muffle_warning));
+                  func_n1v(muffle_unbound_warning));
   ret = expand(form, menv);
   uw_pop_frame(&uw_handler);
   return ret;