package Test::HashK;

use Moose;
use Types::Standard qw( Dict Optional Int );
use Types::ReadOnly qw( Locked );

my $colour_hash = Locked[
   Dict[
      red   => Optional[Int],
      blue  => Optional[Int],
      green => Optional[Int],
   ],
];

has scores => (
   is       => 'rw',
   isa      => $colour_hash,
   default  => sub{ {} },
   coerce   => 1,
);

__PACKAGE__->meta->make_immutable;

package main;

my $thk = Test::HashK->new(scores => { green => 0 });
$thk->scores->{red}  = 2000;
$thk->scores->{bloo} = 'tobyink';  # dies