case macros: bug in singleton key optimization.

* eval.c (me_case): Reduce (key) to key only if key is
an atom. Otherwise we reduce ((a b c)), which
is a single list-valued key to (a b c), which looks like
three keys. This was introduced on Oct 25, 2017 in
commit b72c9309c8d8f1af320dce616a69412510531b48,
making it a regression.

* tests/012/case.tl: New file. The last test
case fails without this bugfix. The others pass either way.

1 files changed, 1 insertions, 1 deletions

diff --git a/eval.c b/eval.c
index 4e640923..066a8f2a 100644
--- a/eval.c
+++ b/eval.c
@@ -4166,7 +4166,7 @@ static val me_case(val form, val menv)
         hash_keys = keys = expand_eval(cons(list_s, keys), nil, menv);
     }
 
-    if (consp(keys) && !cdr(keys))
+    if (consp(keys) && atom(car(keys)) && !cdr(keys))
       keys = car(keys);
 
     if (atom(keys)) {