extract backtrack decisions out into steps

[scpubgit/DX.git] / lib / DX / Step / InvokeNextPredicate.pm

diff --git a/lib/DX/Step/InvokeNextPredicate.pm b/lib/DX/Step/InvokeNextPredicate.pm
index dc9aab1..55bee44 100644 (file)
--- a/lib/DX/Step/InvokeNextPredicate.pm
+++ b/lib/DX/Step/InvokeNextPredicate.pm
@@ -12,7 +12,7 @@ sub apply_to {
   if (my $step = $self->proposition->resolve_for($hyp->scope)) {
     return $ss->but(next_step => $step);
   }
-  return undef;
+  return $ss->but(next_step => DX::Step::Backtrack->new);
 }
 
 1;