with-resources: undocumented nil skip behavior.

Paul A. Patience discovered the hidden "feature" of
with-resourcers, that the three-argument form of the binding
(var init cleanup) causes the with-resources form to terminate
if init returns nil. The (var init) syntax doesn't generate
this logic.

* stdlib/with-resources.tl (with-resources): Do not emit the
when form unless <= 265 compatibility is in effect.

* tests/012/oop-mac.tl: New file.

* txr.1: Compat note added.

1 files changed, 7 insertions, 2 deletions

diff --git a/stdlib/with-resources.tl b/stdlib/with-resources.tl
index 9d4a89c9..e95ed4f9 100644
--- a/stdlib/with-resources.tl
+++ b/stdlib/with-resources.tl
@@ -30,8 +30,13 @@
      ^(let ((,sym ,init))
         (with-resources ,rest ,*body)))
     (((sym init . cleanup) . rest)
-     ^(let ((,sym ,init))
-        (when ,sym
+     (if (and (plusp sys:compat) (<= sys:compat 265))
+       ^(let ((,sym ,init))
+          (when ,sym
+            (unwind-protect
+              (with-resources ,rest ,*body)
+              ,*cleanup)))
+       ^(let ((,sym ,init))
           (unwind-protect
             (with-resources ,rest ,*body)
             ,*cleanup))))