move backtrack step creation into rspace

[scpubgit/DX.git] / lib / DX / ResolutionSpace.pm

diff --git a/lib/DX/ResolutionSpace.pm b/lib/DX/ResolutionSpace.pm
index 4210b02..c2bfff6 100644 (file)
--- a/lib/DX/ResolutionSpace.pm
+++ b/lib/DX/ResolutionSpace.pm
@@ -1,6 +1,7 @@
 package DX::ResolutionSpace;
 
 use DX::Utils qw(step);
+use DX::Step::Backtrack;
 use DX::Class;
 
 has proposition => (is => 'ro');
@@ -23,7 +24,7 @@ sub remaining_resolution_space {
 
 sub next_step {
   my ($self) = @_;
-  return undef unless @{$self->members};
+  return DX::Step::Backtrack->new unless @{$self->members};
   return step(
     resolves => $self->proposition,
     resolution_space => $self,