Type-Safe/Non-Boxing Global

[martindevans]

Used the same mechanisms implemented for type-safe/non-boxing functions to wrap Global in the same way. I expected this to take longer to implement, but everything just fell into place perfectly 🎉

[martindevans]

Some open questions with how this is implemented:

• Name: Currently it's Global.Accessor<T> but Global.Wrapper<T> may be more consistent?
• Mutability: Currently Set(T) does a runtime check and throws if the global is immutable. Some alternatives:
  • WrapGetter<T> and WrapSetter<T> methods, with WrapSetter returning null if the global is immutable.
  • Wrap<T> method which returns (Getter<T>, Setter<T>?) i.e. the setter is null if the global is immutable.

[peterhuene]

Thanks for putting this up! Just the one nit comment, but everything else looks good to go!

[martindevans]

I've filled in that doc comment :)

[peterhuene]

Ignoring transient CI failure.

[peterhuene]

@martindevans thanks again for all these great contributions!