Allow using Object and similar types as instance variable types

[asterite]

Object, Reference, Enum, Enumerable and many other types that are currently disallowed should be able to be used as the type of instance, class and global variables.

This is a current limitation of the language but it's doable. It will come with time.

[lbguilherme]

struct Foo
  @thing : Object
end

Object is a superclass of any struct. That mean @thing can contain any struct or the program. So sizeof(@thing) is the size of the largest struct known plus 4 bytes for the type id. Does that mean @thing can contain Foo itself? It gets cyclic.

[asterite]

Objects larger than 64 bits will be boxed in heap memory.

[asterite]

Mmm... but for that case, I'm not sure. Object wlll be represented as a 64 bits raw pointer... I guess that can be codegen'd, not sure. Maybe it'll be an error.

[lbguilherme]

I can be unexpected that some times it is copied by value and some others it is copied by reference (boxed). Maybe it could be always boxed when the type is Object.

[KCreate]

Hello

What priority does this issue have right now?

[zatherz]

Bump. IMO the value should always be boxed when passed as Object, so that there's less magic and unpredictability.

[zatherz]

Reason for closing?

[HertzDevil]

I just had this idea:

module ValueM; end
module ReferenceM; end

struct Value
  include ValueM
end

class Reference
  include ReferenceM
end

alias Any = ValueM | ReferenceM

Of course, doing it this way means Any must be bigger than the biggest Value type ever instantiated, which is UInt8[4096] for the standard library.

For Reference and Class this should be doable. (You can in fact already do Reference.new, you just can't cast to it explicitly.) For uninstantiated generics this is more tricky; what should the type below be?

typeof([1].as(Indexable)[0])