Expander warns about unbound variables.

* eval.c (eval_exception): New static function.
(eval_error): Reduced to wrapper around eval_exception.
(eval_warn): New function.
(me_op): Bind the rest symbol in a shadowing env to suppress
watnings about unbound rest.
(do_expand): Throw a warning when a bindable symbol is
traversed that has no binding.
(expand): Don't install atoms as last_form_expanded.

* lib.c (warning_s, restart_s, continue_s): New symbol
variables.
(obj_init): Initialize new symbol variables.

* lib.h (warning_s, restart_s, continue_s): Declared.

* lisplib.c (except_set_entries): New entries for
ignwarn and macro-time-ignwarn.

* parser.c (repl_warning): New static function.
(repl): Use repl_warning function as a handler for
warning exceptions: to print their message and then
continue by throwing a continue exception.

* parser.y (warning_continue): New static function.
(parse_once): Use warning_continue to ignore warnings.
In other words, we suppress warnings from Lisp that is
mixed into TXR pattern language code, because this
produces too many false positives.

* share/txr/stdlib/except.tl (ignwarn, macro-time-ignwarn):
New macros.

* share/txr/stdlib/place.tl (call-update-expander,
call-clobber-expander, call-delete-expander): Ignore warnings
around calls to sys:expand, because of some gensym-related
false positives (we expand code into which we inserted some
gensyms, without having inserted the constructs which
bind them.

* tests/011/macros-2.txr: Suppress unbound variable
warnings from a test case.

* tests/012/ifa.tl: Bind unbound x y variables in one
test case.

* tests/012/struct.tl: Suppress unbound variable
warnings in some test cases.

* uwind.c (uw_throw): If a warning is unhandled, then
print its message with a "warning" prefix and then
throw a continue exception.
(uw_register_subtype): Eliminate the check for sub
already being a subtype of sup. This allows us to
officially register new types against t.
(uw_late_init): Register continue exception type as a
subtype of the restart type.
Formally register warning type.

* txr.1: Documented ignwarn.

1 files changed, 36 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index f01e2537..cdebfa4c 100644
--- a/txr.1
+++ b/txr.1
@@ -32183,6 +32183,42 @@ form terminates without evaluating the remaining
 forms, and yields
 .codn nil .
 
+.coNP Macro @ ignwarn
+.synb
+.mets (ignwarn << form *)
+.syne
+.desc
+The
+.code ignwarn
+macro resembles
+.codn ignerr .
+It arranges for the evaluation of each
+.meta form
+in left-to-right order. If all the forms are evaluated, then the
+value of the last one is returned. If no forms are present, then
+.code nil
+is returned.
+
+If any
+.meta form
+throws an exception of type
+.code warning
+then this exception is intercepted by a handler established by
+.codn ignwarn .
+This handler reacts by throwing an exception of type
+.codn continue .
+
+The effect is that the warning is ignored, since the handler
+doesn't issue any diagnostic, and passes control to the warning's
+continue point.
+
+Note: all sites within \*(TX which throw a
+.code warning
+also provide a nearby catch for a
+.code continue
+exception, for resuming evaluation at the point where the warning
+was issued.
+
 .coNP Operator @ handler-bind
 .synb
 .mets (handler-bind < function-form < symbol-list << body-form *)