#! /usr/bin/env perl

use strict;
use warnings;
use 5.10.0;

package Foo;

use Moose;
use Moose::Util::TypeConstraints;
use namespace::autoclean;
use Path::Class qw / file /;

subtype 'AFile' =>
    as 'Path::Class::File' =>
    message { 'Item is not a Path::Class::File' };

coerce  'AFile' =>
    from 'Str' =>
    via { file($_) };

subtype 'ExistingFile' =>
	as 'AFile' =>
	where { say "In subtype where clause: $_[0]"; -f $_[0] },
	message { "$_[0] does not exist" };

has file => ( isa => 'ExistingFile', is => 'ro', required => 1 );

__PACKAGE__->meta->make_immutable;

package main;
use Path::Class qw / file /;

say $0;
eval { my $foo = Foo->new(file => file($0)); }; say ":::".$@.":::";
eval { my $foo = Foo->new(file => $0); }; say ":::".$@.":::";

##</code><code>##

subtype_madness.pl
In subtype where clause: subtype_madness.pl
::::::
:::Attribute (file) does not pass the type constraint because: subtype_madness.pl does not exist at constructor Foo::new (defined at subtype_madness.pl line 29) line 34
	Foo::new('Foo', 'file', 'subtype_madness.pl') called at subtype_madness.pl line 36
	eval {...} at subtype_madness.pl line 36
:::