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.

2 files changed, 33 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)) {
diff --git a/tests/012/case.tl b/tests/012/case.tl
new file mode 100644
index 00000000..856ac56c
--- /dev/null
+++ b/tests/012/case.tl
@@ -0,0 +1,32 @@
+(load "../common")
+
+(mtest
+  (caseq 0 (1 :match)) nil
+  (caseq 0 ((1) :match)) nil
+  (caseq 1 (1 :match)) :match
+  (caseq 1 ((1) :match)) :match
+  (caseq 1 ((0 1) :match)) :match
+  (caseq 1 ((0 2) :match)) nil
+  (caseq 1 (t :match)) :match
+  (caseq 1 ((t) :match)) nil
+  (caseq t ((t) :match)) :match)
+
+(defvar o 1)
+(defvar y t)
+
+(mtest
+  (caseq* 0 (o :match)) nil
+  (caseq* 0 ((o) :match)) nil
+  (caseq* 1 (o :match)) :match
+  (caseq* 1 ((o) :match)) :match
+  (caseq* 1 ((0 o) :match)) :match
+  (caseq* 1 ((0 2) :match)) nil
+  (caseq* 1 (t :match)) :match
+  (caseq* 1 (y :match)) nil
+  (caseq* 1 ((t) :match)) nil
+  (caseq* t ((t) :match)) :match
+  (caseq* t ((y) :match)) :match)
+
+(test (casequal '(a b c d)
+        (((a b c d)) :match))
+      :match)