package Funky::Rectangle;
use Moose;
use Types::Standard qw(InstanceOf Str);
use Data::Dump 'pp';

my $vertex_type = InstanceOf->of('Funky::Vertex')->plus_constructors(Str, "new");

has 'LL' => (is=>'rw', isa=>$vertex_type, coerce=>1);
has 'UR' => (is=>'rw', isa=>$vertex_type, coerce=>1);

# ...