expander bug: sequential vars with no init forms.

The test case for this is (let* (a (b a))) which raises
suspicion by diagnosing an "unbound variable a" error against
the (b a) var-init pair. The error goes away if we make it
(let* ((a nil) (b a))), a perfectly equivalent form. The
diagnostic is just a symptom; the problem is that in the case
when a doesn't have an initform, the (b a) var-init pair is
being incorrectly expanded in an environment that hasn't been
extended with the a variable.

* eval.c (expand_vars): In the sequential binding situation
(let*), we must extend the environment for each variable in
the no-init-form case exactly as we do in the with-init-form
case.

1 files changed, 2 insertions, 1 deletions

diff --git a/eval.c b/eval.c
index 4731c046..85ede40c 100644
--- a/eval.c
+++ b/eval.c
@@ -3355,7 +3355,8 @@ static val expand_vars(val vars, val menv, val form, int seq_p)
     return vars;
   } else if (symbolp(sym = car(vars))) {
     val rest_vars = rest(vars);
-    val rest_vars_ex = expand_vars(rest_vars, menv, form, seq_p);
+    val menv_new = seq_p ? make_var_shadowing_env(menv, cons(sym, nil)) : menv;
+    val rest_vars_ex = expand_vars(rest_vars, menv_new, form, seq_p);
 
     if (!bindable(sym))
       not_bindable_error(form, sym);