more type system hacking and tests

[gitmo/Moose.git] / PLANS

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-- Type Constraints refactor
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- move the details of TC construction that are in Moose.pm and 
  Moose::Util::TypeConstraints into the Moose::Meta::TypeConstraint module

This will make it much easier to generate TCs on their own, without 
having to use the sugar layer. This should also clean up their APIs 
as well, which will make it easier to subclass them.

- create an official TC registry API

Right now the registration of the TC is a by-product of creation in the sugar 
layer, this is bad and make extension of TCs difficult. I am not sure if this 
registry API should exist as part of Moose::Util::TypeConstraints, or of we 
should create a complete registry object itself. 

This registry should be a singleton, but M::U::TC should enforce that lifecycle 
choice so that you can use your own registry if you really want too.

I mean parent of the registry. So that I can create my own registry
object for a given class, and any retrieval of a type constraint from
this object would automatically search parent registries as well.

- refactor the various TC internals to make it more subclassing friendly

This also includes the coercion stuff as well. This should give you what you 
need to make your object/class bound stuff.

- move the container TCs from MooseX::AttributeHelpers into Moose core

These have proven so useful for me in the latest $work project that I think 
they should really be core. 

- allow a switch of some kind to optionally turn TC checking off at runtime 

The type checks can get expensive and some people have suggested that allowing 
the checks to be turned off would be helpful for deploying into performance 
intensive systems. Perhaps this can actually be done as an option to make_immutable? 

- add support for locally scoped TC

This would borrow from MooseX::TypeLibrary to prefix the TC with the name 
of the package. It would then be accesible from the outside as the fully 
scoped name, but the local attributes would use it first. (this would need support 
in the registry for this).

- look into sugar extensions

Use roles as sugar layer function providers (ala MooseX::AttributeHelpers). This 
would allow custom metaclasses to provide roles to extend the sugar syntax with.

(NOTE: Talk to phaylon a bit more on this)

- misc. minor bits

* make the errors for TCs use ->message
* look into localizing the messages too
* make ANON TCs be lazy, so they can possibly be subsituted for the real thing later
* make ANON TCs more introspectable
* add this ...

#
#   Type Definition
#
subtype 'Username',
   from 'Str',
  where {     (/[a-z][a-z0-9]+/i or fail('Invalid character(s)'))
          and (length($_) >= 5   or fail('Too short (less than 5 chars)'))
        }
on_fail { MyException->throw(value => $_[0], message => $_[1]) };

# fail() will just return false unless the call is made via
$tc->check_or_fail($value);

* and then something like this:

subtype Foo => as Bar => where { ... } => scoped => -global;
subtype Foo => as Bar => where { ... } => scoped => -local; 

# or 

subtype Foo => as Bar => where { ... } => in __PACKAGE__ ; 

# or (not sure if it would be possible)

my $Foo = subtype Bar => where { ... };


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-- Roles refactor
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-- Immutable refactor
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