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.

2 files changed, 6 insertions, 3 deletions

diff --git a/share/txr/stdlib/except.tl b/share/txr/stdlib/except.tl
index ad5cb0b9..addc3a66 100644
--- a/share/txr/stdlib/except.tl
+++ b/share/txr/stdlib/except.tl
@@ -44,3 +44,6 @@
                                  syms-fragments)))
                    ,[mapcar car syms-fragments]
                    ,try-form)))
+
+(defmacro ignwarn (. forms)
+  ^(handler-bind (lambda (exc-sym arg) (throw 'continue)) (warning) ,*forms))
diff --git a/share/txr/stdlib/place.tl b/share/txr/stdlib/place.tl
index 20650ad0..b18fddbf 100644
--- a/share/txr/stdlib/place.tl
+++ b/share/txr/stdlib/place.tl
@@ -183,7 +183,7 @@
            (expander (get-update-expander place))
            (sys:*pl-env* env)
            (expansion [expander getter setter place body])
-           (expansion-ex (sys:expand expansion env)))
+           (expansion-ex (ignwarn (sys:expand expansion env))))
       (sys:cp-origin expansion-ex place)))
 
   (defun call-clobber-expander (ssetter unex-place env body)
@@ -191,7 +191,7 @@
            (expander (get-clobber-expander place))
            (sys:*pl-env* env)
            (expansion [expander ssetter place body])
-           (expansion-ex (sys:expand expansion env)))
+           (expansion-ex (ignwarn (sys:expand expansion env))))
       (sys:cp-origin expansion-ex place)))
 
   (defun call-delete-expander (deleter unex-place env body)
@@ -199,7 +199,7 @@
            (expander (get-delete-expander place))
            (sys:*pl-env* env)
            (expansion [expander deleter place body])
-           (expansion-ex (sys:expand expansion env)))
+           (expansion-ex (ignwarn (sys:expand expansion env))))
       (sys:cp-origin expansion-ex place))))
 
 (defmacro with-update-expander ((getter setter) unex-place env body)