quasiquote: make new @,expr work in dot position.

Bugfix: the newly introduced @.expr fails in the
dotted position because ^(a . @,expr) turns
into (list 'a 'let ...).

* eval.c (is_meta_unquote): New static function.
(expand_qquote_rec): Replace existing shape test with
is_meta_unquote. We must also use this test in one more place:
whenever the cdr of a list has the meta unquote shape,
we must treat the result similarly to a dotted atom, by
converting to append format.

* tests/010/qquote.tl: Test cases to cover this.

1 files changed, 12 insertions, 0 deletions

diff --git a/tests/010/qquote.tl b/tests/010/qquote.tl
index e6daad3a..26d5417b 100644
--- a/tests/010/qquote.tl
+++ b/tests/010/qquote.tl
@@ -9,15 +9,27 @@
   (tree-bind (x y (op arg)) ^(a b @,sym)
     (assert (eq op 'sys:var))
     (assert (eq arg sym)))
+  (tree-bind (x y . (op arg)) ^(a b . @,sym)
+    (assert (eq op 'sys:var))
+    (assert (eq arg sym)))
   (tree-bind (x y (op arg)) ^(a b @,atom)
     (assert (eq op 'sys:var))
     (assert (eq arg atom)))
+  (tree-bind (x y . (op arg)) ^(a b . @,atom)
+    (assert (eq op 'sys:var))
+    (assert (eq arg atom)))
   (tree-bind (x y (op arg)) ^(a b @,cons)
     (assert (eq op 'sys:expr))
     (assert (eq arg cons)))
+  (tree-bind (x y . (op arg)) ^(a b . @,cons)
+    (assert (eq op 'sys:expr))
+    (assert (eq arg cons)))
   (tree-bind (x y (op arg)) ^(a b @,dwim)
     (assert (eq op 'sys:expr))
     (assert (eq arg dwim)))
+  (tree-bind (x y . (op arg)) ^(a b . @,dwim)
+    (assert (eq op 'sys:expr))
+    (assert (eq arg dwim)))
   (tree-bind (x y (op arg . tail)) ^(a b (sys:expr ,sym . foo))
     (assert (eq op 'sys:expr))
     (assert (eq arg sym))