Fix over-eager regex concat optimization

Author: moritz

src/QRegex/P6Regex/Actions.nqp

@@ -59,7 +59,8 @@ class QRegex::P6Regex::Actions is HLL::Actions {
             my $ast := $_.ast;
             if $ast {
                 if $lastlit && $ast.rxtype eq 'literal'
-                        && !QAST::Node.ACCEPTS($ast[0]) {
+                        && !QAST::Node.ACCEPTS($ast[0])
+                        && $lastlit.subtype eq $ast.subtype {
                     $lastlit[0] := $lastlit[0] ~ $ast[0];
                 }
                 else {

t/qregex/rx_modifiers

@@ -25,6 +25,7 @@
 # todo :pugs<feature>
 :1i bcd			aBCDef	y	ignorecase, repetition (:1i)
 :1i bcd			aBxDef	n	ignorecase, repetition (:1i)
+A :i B			Ab		y	ignorecase in the middle, literals on both sides
 ab [:i cd ] ef		abcdef	y	ignorecase, lexical (:i)
 ab [:i cd ] ef		abCdef	y	ignorecase, lexical (:i)
 ab [:i cd ] ef		abcDef	y	ignorecase, lexical (:i)