interpreter: correct semantics of special var args.

In this patch we eliminate the special operator
sys:with-dyn-rebinds, and implement correct semantics for
dynamically scoped variables that occur in argument
lists.

* eval.c (with_dyn_rebinds_s): Symbol variable removed.
(bind_args): Handle special variables dynamically:
for each symbol that appears, check whether it is a special
and treat accordingly by allocating a new dynamic environment
if necessary, and binding in that environment.
This adds overhead, which is why I moved away from this
approach in the past. But now that there is a compiler,
overhead in the interpreter matters less. Correct semantics
is more important.
(expand_params): Greatly simplified for not having to wrap the
sys:with-dyn-rebinds operator around the body.
(funcall_interp): Since bind_args can now extend the dynamic
environment, it is necessary to save and restore dyn_env
around it. Another call to bind_args occurs in op_catch;
that already saves and restores dyn_env.
(op_with_dyn_rebinds): Static function removed.
(do_expand): with-dyn-rebinds-s case removed.
(eval_init): Removed interning of sys:with-dyn-rebinds
symbol and registration of special op.

* protsym.c: Regenerated.

* compiler.tl (compiler compile): Remove case which handles
sys:with-dyn-rebinds.

1 files changed, 0 insertions, 1 deletions

diff --git a/share/txr/stdlib/compiler.tl b/share/txr/stdlib/compiler.tl
index 4275daf0..2d8962e3 100644
--- a/share/txr/stdlib/compiler.tl
+++ b/share/txr/stdlib/compiler.tl
@@ -320,7 +320,6 @@
             (defsymacro me.(compile oreg env (expand-defsymacro form)))
             (sys:upenv me.(compile oreg env.up (cadr form)))
             (sys:dvbind me.(compile oreg env (caddr form)))
-            (sys:with-dyn-rebinds me.(comp-progn oreg env (cddr form)))
             (sys:load-time-lit me.(comp-load-time-lit oreg env form))
             ((macrolet symacrolet macro-time)
              (compile-error form "unexpanded ~s encountered" sym))