lib/DX/Step/ConsiderProposition.pm

   1 package DX::Step::ConsiderProposition;
   2
   3 use DX::Class;
   4
   5 with 'DX::Role::Step';
   6
   7 has proposition => (is => 'ro', isa => Proposition, required => 1);
   8
   9 sub apply_to {
  10   my ($self, $ss) = @_;
  11   my $hyp = $ss->current_hypothesis;
  12   trace consider => [
  13     statement => [
  14       [ symbol => 'consider' ],
  15       @{$self->proposition->for_deparse->[1]},
  16     ],
  17   ];
  18   my $old_scope = (my $old_hyp = $ss->current_hypothesis)->scope;
  19   my @old_locals = @{$old_scope->locals};
  20   my $top_level = $#old_locals;
  21   my $top = pop @old_locals;
  22   my $top_members = $top->members;
  23   my @new_names = grep !exists $top_members->{$_},
  24                     keys %{$self->proposition->introduced_names};
  25   my $new_scope = $old_scope->but(
  26     locals => [
  27       @old_locals,
  28       $top->but(members => {
  29         %{$top_members},
  30         map +($_ => DX::Value::Unset->new(
  31                       action_builder => DX::ActionBuilder::UnsetValue->new(
  32                         target_path => [ $top_level, $_ ],
  33                       )
  34                     )
  35         ), @new_names
  36       }),
  37     ],
  38     lex_map => {
  39       %{$old_scope->lex_map},
  40       map +($_ => [ $top_level, $_ ]), @new_names
  41     }
  42   );
  43   my $new_hyp = $old_hyp->but(scope => $new_scope);
  44   return $ss->but(
  45     current_hypothesis => $new_hyp,
  46     next_step => $self->proposition->resolve_for($new_scope)
  47   );
  48 }
  49
  50 1;