From f18c207d115a5d2bf350c6ec555bd74e35f0c303 Mon Sep 17 00:00:00 2001
From: Ben Greenman <benjaminlgreenman@gmail.com>
Date: Sun, 12 Jun 2016 15:17:15 -0400
Subject: [PATCH] [private] rx: allow \ between [...]

---
 test/regexp-pass.rkt       | 7 +++++++
 trivial/private/regexp.rkt | 8 ++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/test/regexp-pass.rkt b/test/regexp-pass.rkt
index d2c7a97..1e42ac8 100644
--- a/test/regexp-pass.rkt
+++ b/test/regexp-pass.rkt
@@ -13,6 +13,13 @@
 
   ;; -- regexps, from the world
 
+  (let ([str "dont care"]) ;; from `tests/racket/contract/multi-file.rkt`
+    (check-equal?
+      (ann
+        (regexp-match: #rx"[/\\]([-a-z0-9.]*)[^/\\]*$" str)
+        (U #f (List String String)))
+      #f))
+
   (let ([l "dont care"]) ;; from `morse-code-table.rkt`
     (check-equal?
       (ann
diff --git a/trivial/private/regexp.rkt b/trivial/private/regexp.rkt
index e287729..e68a28f 100644
--- a/trivial/private/regexp.rkt
+++ b/trivial/private/regexp.rkt
@@ -149,6 +149,7 @@
   (define (unescaped-pos* str c*)
     (define L (string-length str))
     (define escaped? (box #f))
+    (define most-recent-char (box #f))
     (define (have-char-at-index? c i hist)
       (memv i (hash-ref hist c)))
     (define h-rev
@@ -157,7 +158,8 @@
         (define char (unsafe-string-ref str i))
         (cond
          [(unbox escaped?)
-          (unless (eq? #\\ char)
+          (when (or (not (eq? #\\ char))
+                    (eq? #\[ (unbox most-recent-char)))
             (set-box! escaped? #f))
           hist]
          [(eq? #\\ char)
@@ -173,7 +175,9 @@
          [else
           (let ([i* (hash-ref hist char #f)])
             (if i*
-              (hash-set hist char (cons i i*))
+              (begin
+                (set-box! most-recent-char char)
+                (hash-set hist char (cons i i*)))
               hist))])))
     ;; -- reverse all saved lists
     (for/hasheq ([(c i*) (in-hash h-rev)])