package Class::Virtually::Abstract;
use base qw(Class::Virtual);
use Carp::Assert;

assert( prototype('CORE::bless') eq '$;$' );
sub bless ($;$) {
    my $class = $_[1] || caller;

    if( grep { $_ eq 'Class::Virtually::Abstract' } @{$class.'::ISA'} ) {
        confess("Connot bless objects into abstract class $class");
    }
    else {
         CORE::bless(shift, $class);
    }
}


sub import {
    shift;

    my $base = caller();

    *{$base.'::bless'} = \&bless;

    *{$base.'::import'} = sub {
        my $class = shift;
        return if $class eq $base;

        foreach my $missing_meth ($class->missing_methods) {
            require Carp;
            Carp::croak("Class $class must define $missing_meth for class ".
                        "$base");
        }
        
        $class->SUPER::import(@_);
    };

    1;
}

##</code><code>##

    package Foo;
    require Some::Abstract::Class;
    @ISA = qw(Some::Abstract::Class);

##</code><code>##

    package Foo;
    use base qw(Some::Abstract::Class);