regexec.c: Use foldcase instead of lower/upper

The way Perl deals with folds of ASCII-range characters, is to have an
array that maps to the opposite case character.  For example, fold[a] is
A, and fold[A] is a.  To see if a character matches a pattern character
case-insensitively, you compare it against the pattern character itself,
and if that fails, against the fold[pattern character].

Unfortunately that breaks down outside of ASCII, where the folds are not
necessarily one-to-one.  This code is a vestige of that original
paradim, and I'm converting it to use the more modern.  The apparent
reason it doesn't fail in fold_grind.t is that it is for CURLY nodes,
and CURLY is not currently set on EXACTish nodes unless the node
contains a single UTF-8 invariant character.   Effectively, that means
a character in the ASCII range.

I think parts of this could be simplified further, but I don't
understand the whole context of this code to undertake that.

1 files changed, 5 insertions, 10 deletions

diff --git a/regexec.c b/regexec.c
index 46484dffce..8650654934 100644
--- a/regexec.c
+++ b/regexec.c
@@ -5290,16 +5290,11 @@ NULL
 		    }
 		    else { /* UTF_PATTERN */
 			if (IS_TEXTFU(text_node) || IS_TEXTF(text_node)) {
-			     STRLEN ulen1, ulen2;
-			     U8 tmpbuf1[UTF8_MAXBYTES_CASE+1];
-			     U8 tmpbuf2[UTF8_MAXBYTES_CASE+1];
-
-			     /* XXX probably should be using foldcase */
-			     to_utf8_lower((U8*)s, tmpbuf1, &ulen1);
-			     to_utf8_upper((U8*)s, tmpbuf2, &ulen2);
-			     ST.c1 = utf8n_to_uvchr(tmpbuf1, UTF8_MAXLEN, 0,
-						    uniflags);
-			     ST.c2 = utf8n_to_uvchr(tmpbuf2, UTF8_MAXLEN, 0,
+			     STRLEN ulen;
+			     U8 tmpbuf[UTF8_MAXBYTES_CASE+1];
+
+			     to_utf8_fold((U8*)s, tmpbuf, &ulen);
+			     ST.c1 = ST.c2 = utf8n_to_uvchr(tmpbuf, UTF8_MAXLEN, 0,
 						    uniflags);
 			}
 			else {