Changing how binding of special variables works.

The old way: process, at expansion time, bindings in lambda
lists and all binding constructs to find special variables
(symbols marked special). Replace these bindings with
an annotation. Then when the interpreter performs binding,
the binding helper functions process these annotations.
Also, if specials occur, wrap the construct in
sys:with-save-specials to set up the necessary dynamic
environment frame.

The new way: process, at expansion time, bindings in
lambda lists and binding constructs (which have been reduced
to just let and let*). If special variables occur, then
wrap the body in in sys:with-dyn-rebinds which re-binds
specific symbols in the dynamic namespace, copying their
value from their lexical binding.  The lexical bindings are
then replaced with the value sys:unbound, which indicates that
the value should be resolved in the dynamic environment.

* eval.c (with_saved_vars_s): Symbol variable removed.
(with_dyn_rebinds_s): New symbol variable.
(lookup_var, lookup_sym_lisp1): If a lexical binding contains
the value sys:unbound, then continue the search through the
dynamic environment; ignore the remaining lexical
environments.
(expand_params_rec): Bugfix: neglected collect of
special variable in fallback case.
(expand_params): Takes body environment, and returns two
values as a cons cell. The additional return value is a body
that is either the original body, or else is wrapped with
sys:with-dyn-rebinds. Removed is the special variable
hack inserted into the syntax.
(expand_macrolet, expand_tree_cases): Adjust to new
expand_params interface.
(op_with_saved_vars): Static function removed.
(op_with_dyn_rebinds): New static function.
(expand_vars): Return list of special variables via pointer
argument, rather than just a Boolean which indicates that
specials are present. Transformation to special representation
is removed.
(expand_catch_clause): Adjust to new expand_params interface.
(expand_save_specials): Static function removed.
(do_expand): Adjust let/let* expansion to new expand_vars
interface. Generate the sys:with-dyn-rebinds wrapping around
the body. Adjust the defun, lambda and mac-param-bind
expanders to the new expand_params interface.
Recognize sys:with-dyn-rebinds and don't expand it;
all places which generate this form have to expand the
internals themselves.
(eval_init): Remove initialization of with_saved_var_s,
and its registration as an operator.
Initialize with_dyn_rebinds_s with interned symbol,
and register as operator.

0 files changed, 0 insertions, 0 deletions