zc: add the defer statement

defer expr; and defer { ... } register code that runs when the enclosing
block ends: at the end of the block, and at return, break and continue
that leave it. the tokens are kept at the defer and compiled again at each
exit (block_close, body, kw_return, kw_break, kw_continue), newest first,
before the block's variables are released, so the analyzer sees a deferred
rt.free(p) as the transfer of p where it runs. names mean what they meant
at the defer; values are read when it runs. return, break and continue
inside a deferred statement are errors, reported once. works in unchecked
code and closures (own base per function context).

1 files changed, 1 insertions, 0 deletions

diff --git a/src/compiler/check.zc b/src/compiler/check.zc
index a22bcdd..f3374b1 100644
--- a/src/compiler/check.zc
+++ b/src/compiler/check.zc
@@ -29,6 +29,7 @@ int chk_reset() {
 	tline = 1;
 	toff = 0 - 1; toklen = 0; tpend = 0 - 1; tpline = 1;
 	infn = 0;
+	defer_drop(0); dfr_base = 0; dfr_on = 0;
 	fdepth = 0;
 	fslots = 0;
 	fchk = 0;