Constants with type declarations

[HertzDevil]

This is not allowed:

FOO : Int64 = 123

I think it should, because this allows constant initializers to use autocasting. In this case FOO = 0_i64 would also suffice, but things change when the integer type does not have a fixed size, e.g. it is platform-specific:

FOO : LibC::SizeT = 123

It is better than the following:

FOO = LibC::SizeT.new(123)

because it is easier for the compiler to infer in the first case that FOO is a compile-time constant and skip the generation of the run-time initializer (~FOO:init here).

Naturally this would allow Crystal::Macros::TypeDeclaration#var to be a Path node. Constant declarations with a type and without an initializer would still be disallowed, unless we further define them like in #14085 (comment).

[nobodywasishere]

Is there anything that would prohibit this from being implemented? I think this could be really useful, and would be happy to try implementing this.

[straight-shoota]

No, I don't think there are any obstacles. Just needs someone to pick it up. You're welcome to =)