tighten up SearchState new() signature slightly

diff --git a/lib/DX/SearchState.pm b/lib/DX/SearchState.pm
index 0702168..4966512 100644 (file)
--- a/lib/DX/SearchState.pm
+++ b/lib/DX/SearchState.pm
@@ -8,7 +8,7 @@ use DX::Class;
 
 has current_hypothesis => (is => 'ro', isa => Hypothesis, required => 1);
 
-has next_step => (is => 'ro', isa => Maybe[Step]);
+has next_step => (is => 'ro', isa => Maybe[Step], required => 1);
 
 has propositions => (is => 'ro', isa => PropositionSequence, required => 1);
 
@@ -16,9 +16,9 @@ has alternatives => (is => 'ro', isa => AlternativeList, required => 1);
 
 has is_solution_state => (is => 'ro', required => 1);
 
-has on_exhaustion_step => (is => 'ro', required => 1);
+has on_exhaustion_step => (is => 'ro', isa => Maybe[Step], required => 1);
 
-has on_solution_step => (is => 'ro', required => 1);
+has on_solution_step => (is => 'ro', isa => Maybe[Step], required => 1);
 
 sub next_proposition {
   my ($self, $hyp) = @_;
@@ -41,7 +41,7 @@ sub new_for {
           ),
           is_solution_state => 0,
         )
-      : ( is_solution_state => 1 )
+      : ( next_step => undef, is_solution_state => 1 )
     ),
     on_exhaustion_step => undef,
     on_solution_step => DX::Step::MarkAsSolution->new,