Try to fix the hangs that implementing backtracking into subrules introduced.

Author: jnthn

src/QAST/Compiler.nqp

@@ -271,12 +271,14 @@ class QAST::Compiler is HLL::Compiler {
 
     method pass($node) {
         my $ops := self.post_new('Ops', :result(%*REG<cur>));
+        my @backtrack := ["'backtrack'=>1"]
+            if $node.backtrack ne 'r';
         if $node.name() {
             my $name := $*PASTCOMPILER.as_post($node.name(), :rtype<~>);
-            $ops.push_pirop('callmethod', '"!cursor_pass"', %*REG<cur>, %*REG<pos>, $name);
+            $ops.push_pirop('callmethod', '"!cursor_pass"', %*REG<cur>, %*REG<pos>, $name, |@backtrack);
         }
         else {
-            $ops.push_pirop('callmethod', '"!cursor_pass"', %*REG<cur>, %*REG<pos>);
+            $ops.push_pirop('callmethod', '"!cursor_pass"', %*REG<cur>, %*REG<pos>, |@backtrack);
         }
         $ops.push_pirop('return', %*REG<cur>);
         $ops;

src/QRegex/Cursor.nqp

@@ -99,10 +99,11 @@ role NQPCursorRole {
     }
 
     my $pass_mark := 1; # NQP has no constant table yet
-    method !cursor_pass($pos, $name?) {
+    method !cursor_pass($pos, $name?, :$backtrack) {
         $!match := $pass_mark;
         $!pos := $pos;
-        $!restart := $!regexsub;
+        $!restart := $!regexsub
+            if $backtrack;
         self.'!reduce'($name) if $name;
     }