Multiple coercions ?

[Alexis Sukrieh]

Hello there,

I'm a bit puzzled by something I found when hacking on Coat and I'd like 
to have your point of view on this.

Let's say we have the folloiwng types:

  subtype 'Date'
      => as 'Str'
      => where { /^\d\d\d\d-\d\d-\d\d$/ };

  subtype 'DateTime'
      => as 'Str'
      => where { /^\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d$/ };


  coerce 'DateTime'
      => from 'Date'
      => via { "$_ 00:00:00" };


And a class that has two attributes:

{
    package Foo;
    use Moose;

    has 'date' => (
        is => 'rw',
        isa => 'Date',
    );

    has 'date_time' => (
        is => 'rw',
        isa => 'DateTime',
        coerce => 1,
    );
}

This works pretty well: as expected, I can coerce date_time from a 
Date-valid value :

Perl> my $f = Foo->new
Foo=HASH(0x85567d0)

Perl> $f->date_time('2008-02-11')
2008-02-11 00:00:00


Now - and that's where the issue gets in the scene - if I add another 
coercion for the DateTime subtype, but from another source, it won't work :

coerce 'DateTime'
    => from 'Int'
    => via { time_to_datetime($_) };

Perl> use Foo
[!] The type coercion for 'DateTime' has already been registered at 
/usr/share/perl5/Moose/Util/TypeConstraints.pm line 289

Moose::Util::TypeConstraints::_install_type_coercions('DateTime', 
'ARRAY(0x862add0)') called at 
/usr/share/perl5/Moose/Util/TypeConstraints.pm line 218
        Moose::Util::TypeConstraints::coerce('DateTime', 'Date', 
'CODE(0x862a8b4)') called at Foo.pm line 37
        require Foo.pm called at (eval 2) line 3



So it looks like, with Moose, when you define a coercion, a subtype is 
defined under the table, hence it's not possible to define more than one 
coercion for a given type.

Am I doing something wrong here? Is it supposed to be possible? If not, why?

For the record this works pretty well with Coat/Coat::Types and I think 
it should with Moose.

Thanks.

        Alexis.