matcher: fix broken @(let @a @(some @a)) test case.

This is caused by the way the loop match compiler moves the
matching logic into a guard, which causes a re-ordering of the
variable assignments which interferes with backreferencing
when @(some) is embedded into a @(let), and probably other
situations. The issues is that the backreferencing equal
tests can be reordered to occur before the assignment which
sets the intial value of the backreferenced variable:
cart before the horse kind of thing.

* share/txr/stdlib/match.tl (compile-loop-match): Do not add
the submatch into the guard sequence. Thus guard1's vars and
var-exprs, move into into the main compiled-match,
and guard1's guard-expr moves into guard0. Thus guard1
disappears, guard0 becomes guard.

* tests/011/patmatch.tl: New test case that is also fixed,
and which was not fixed by a different approach to the problem
that I scrapped.

1 files changed, 2 insertions, 0 deletions

diff --git a/tests/011/patmatch.tl b/tests/011/patmatch.tl
index 7d0482b2..84d59381 100644
--- a/tests/011/patmatch.tl
+++ b/tests/011/patmatch.tl
@@ -88,3 +88,5 @@
 (set *print-circle* t)
 
 (test (when-match @(let a @(some @a)) '#1=(1 2 #1# 3) :yes) :yes)
+
+(test (when-match (@a @(let a @(some @a))) '(#1=(1 2 #1# 3) #1#) :yes) :yes)