The design docs are full of good things that we simply can't get done in the next couple of months, and that are simply not worth delaying 6.christmas for. This is an initial attempt to list some things we're going to explicitly put off for a future Perl 6.
We have a fairly good idea of where we want to go with these, and what needs doing to get there. Getting there will need a good amount of compiler engineering work, with some quite substantial refactors to a few bits of the internals (and avoiding that will likely lead to a whole bunch of "interesting" inconsistencies). We just don't have the resources to do that ahead of Christmas. And, while macros and slangs will be great, they're hardly a blocker for getting lots of useful stuff done in the language.
We'll support both fixed-size and multi-dimensional arrays in 6.christmas:
my @weekdays[52;7];
my num @a[3;3;3] @intensity;
But making certain dimensions have an unlimited number of elements is deferred.
See S09 for the details, but this is deferred.
We'll certainly provide multi-dimensional arrays (that work is nearly completed), but the various other bits mentioned in S09 should be explored in module space first. If the results lead us to wanting to add to the core language, than can happen in the future.
Details in S09, if you're curious.
We'll only support coercion types in signatures:
sub foo(Int() $x) { }
But that's all. Not on variables, not as generic arguments, and so forth. Same goes for definedness types (the :D and :U type modifiers).
Read the design docs to understand why it's non-trivial, but there's all kinds of fun (like being able to jump into any zero-arg block, provided all on the way is also zero arg). We already support labelled loops, and have a rich set of control flow structures. I suspect more people will learn we didn't do goto by reading this post than by actually wanting it and finding it missing, anyway.
Basically, don't expect anything that isn't in Rakudo already to be there in 6.christmas. (Given what's there is enough to parse Perl 6 itself, that's hardly a disappointing feature set!)
Buf and Uni support for regexes is desirable, but we won't get there in time for 6.christmas.
I'm not sure this will survive in the design anyway, but it certainly won't make it for 6.christmas. Details in S06.
See S10 for details. It turns out that the FALLBACK method in objects covers enough interesting use cases for us not to worry too much about this bit of S10.
S12 speculates about things like:
use oo :closed :final;
We won't be doing anything about this in 6.christmas, and we'll see about beyond that. If it's interesting for semantic reasons, it stands a chance of making it into a future version of the Perl 6 language. If it was just there for performance reasons, we need to know it will actually help (because dynamic optimization that knows how to de-optimize can get plenty of the benefits without such a declaration).
The lazy/infinite string type for stream matching. Will be valuable, but only really after we wire it into the grammar engine.
For 6.christmas, the Complex type will always be a pair of native nums. Being able to type-parameterize it is conjectured in the design docs, and can be provided in a future Perl 6.
int1, uint1, int2, uint2, int4, and uint4, along with their aliases (like bit), will not be provided in 6.christmas.
Speculated about in the design docs, but will almost certainly need design work. May, in a post-slang/macro world, be better handled in module space. Either way, given taint mode's low use in Perl 5, this isn't going to really be a significant blocker.
You could use the lack of
gotoas an advertised feature to create a sense of urgency. “It’s a language that doesn’t let you create spaghetti! But we plan to allow that – so get in on it NOW, while the going’s good!”