allow parameterized types to customize their messages

The same arguments that are passed to the where block are also passed to
the message block to allow the error message to be customized.

lib/MooseX/Meta/TypeConstraint/Parameterizable.pm

@@ -192,7 +192,7 @@ sub parameterize {
                     constraining_value => $args,
                     parent_type_constraint=>$self->parent_type_constraint,
                     constraining_value_type_constraint => $self->constraining_value_type_constraint,
-                    ($self->has_message ? (message => $self->message) : ()),
+                    ($self->has_message ? (message => sub { $self->message->( @_, $args ) } ) : ()),
                 );
             }
         }

t/08-custom-messages.t

@@ -0,0 +1,24 @@
+use strict;
+use warnings;
+
+use Test::More;
+use MooseX::Types -declare=>[qw( SizedArray )];
+use MooseX::Types::Parameterizable qw(Parameterizable);
+use MooseX::Types::Moose qw( Int ArrayRef );
+
+ok subtype(
+    SizedArray,
+    as Parameterizable[ArrayRef,Int],
+    where {
+        my ($value, $max) = @_;
+        @$value > $max
+    },
+    message {
+        my($value, $max) = @_;
+        return sprintf('%d > %d', scalar(@$value), $max);
+    }
+), 'Created parameterized type';
+
+is SizedArray([3])->get_message([1..4]), q{4 > 3}, 'custom message';
+
+done_testing;