From 9b97c918e354e008a3583fcb96495e37c15494cc Mon Sep 17 00:00:00 2001
From: Nathan Trapuzzano <nbtrap@nbtrap.com>
Date: Tue, 25 Feb 2014 22:36:56 -0500
Subject: [PATCH] Create new bindings for the referenced register upon entry to
 subpattern-reference.

When entering a register x via subpattern-reference, the registers
local to x receive new dynamic bindings, which shadow the old bindings
for the duration of the subpattern call.  Previously, "local" did not
include the register itself--x in this case.  With this patch, the
referenced register now receives a new binding as well.

It's not entirely clear that this is the appropriate behavior.  In a
regex like "(.\1?)(?1)", the back-reference to '\1' now will always
fail, rather than potentially matching according to what was matched
in the first pass through the first register.
---
 closures.lisp |  4 ++--
 test/simple   | 16 ++++------------
 2 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/closures.lisp b/closures.lisp
index 4e3a67d..9e12c98 100644
--- a/closures.lisp
+++ b/closures.lisp
@@ -97,14 +97,14 @@ such that the call to NEXT-FN after the match would succeed."))
     (labels
         ((pop-offsets (offsets offsets-stacks)
            (declare (simple-vector offsets offsets-stacks))
-           (loop for idx from (1+ num) upto (+ num subregister-count)
+           (loop for idx from num upto (+ num subregister-count)
               collect (let ()
                         (declare (fixnum idx))
                         (setf (svref offsets idx)
                               (pop (svref offsets-stacks idx))))))
          (push-offsets (offsets saved-offsets offsets-stacks)
            (declare (simple-vector offsets offsets-stacks) (list saved-offsets))
-           (loop for idx from (1+ num) upto (+ num subregister-count) do
+           (loop for idx from num upto (+ num subregister-count) do
                 (let ()
                   (declare (fixnum idx))
                   (push (svref offsets idx) (svref offsets-stacks idx))
diff --git a/test/simple b/test/simple
index 5242bfa..6035f4a 100644
--- a/test/simple
+++ b/test/simple
@@ -422,15 +422,11 @@ characters if there's a match."
            (scan regex "fffffff"))
           '(0 7 #(0 4 4 6) #(1 7 5 7))))
 
-(equalp (multiple-value-list
-         (scan "^(.\\1?)(?1)$" "aba"))
-        '(0 3 #(0) #(1)))
+(null (scan "^(.\\1?)(?1)$" "aba"))
 
 (let ((*allow-named-registers* t)
       (regex "^(?<regOne>.\\k<regOne>?)(?&regOne)$"))
-  (equalp (multiple-value-list
-           (scan regex "aba"))
-          '(0 3 #(0) #(1))))
+  (null (scan regex "aba")))
 
 (equalp (multiple-value-list
          (scan "^(.\\2?)(.)(?1)$" "abcb"))
@@ -454,13 +450,9 @@ characters if there's a match."
 ;;            (scan regex "aaba"))
 ;;           '(0 4 #(nil 0 0) #(nil 1 1))))
 
-(equalp (multiple-value-list
-         (scan "^(a|\\3(?1)\\2|(?2))((b|c)(?4)?)(?1)(d(?1))$" "abbcdcabbda"))
-        '(0 11 #(0 1 1 9) #(1 2 2 11)))
+(null (scan "^(a|\\3(?1)\\2|(?2))((b|c)(?4)?)(?1)(d(?1))$" "abbcdcabbda"))
 
 ;; Cf. #17
 ;; (let ((*allow-named-registers* t)
 ;;       (regex "^(?<regOne>a|\\k<regThree>(?&regOne)\\k<regTwo>|(?&regTwo))(?<regTwo>(?<regThree>b|c)(?&regFour)?)(?&regOne)(?<regFour>d(?&regOne))$"))
-;;   (equalp (multiple-value-list
-;;            (scan regex "abbcdcabbda"))
-;;           '(0 11 #(0 1 1 9) #(1 2 2 11))))
+;;   (null (scan regex "abbcdcabbda")))