# HG changeset patch
# User Stefan Monnier <monnier@iro.umontreal.ca>
# Date 959272240 0
# Node ID c971620b680c8ffa63eaff56588211334a798e7f
# Parent  16fae460c29eea365bcd543112b56ea2f19bf0f9
(at_begline_loc_p): Also recognize the \\(?:^ case
of an anchor at the beginning of a shy-group.

diff --git a/regex.c b/regex.c
--- a/regex.c
+++ b/regex.c
@@ -3208,7 +3208,12 @@
        /* After a subexpression?  */
        (*prev == '(' && (syntax & RE_NO_BK_PARENS || prev_prev_backslash))
        /* After an alternative?	 */
-    || (*prev == '|' && (syntax & RE_NO_BK_VBAR || prev_prev_backslash));
+    || (*prev == '|' && (syntax & RE_NO_BK_VBAR || prev_prev_backslash))
+       /* After a shy subexpression?  */
+    || ((syntax & RE_SHY_GROUPS) && prev - 2 >= pattern
+	&& prev[-1] == '?' && prev[-2] == '('
+	&& (syntax & RE_NO_BK_PARENS
+	    || (prev - 3 >= pattern && prev[-3] == '\\')));
 }