Consider adding option for utilizing extern_types

[crumblingstatue]

The extern types RFC has been implemented for a while now, but it's not very well baked yet.

Adding an unstable option to utilize extern types for opaque types might be a nice way to get some real world use out of extern types, before they get stabilized.

This option would -of course- be only available on the nightly rust target.

[emilio]

Sorry for the huge lag here.

What do you mean with for "opaque" types? Opaque types need to maintain their layout and such, so I don't see how they map. You mean for empty types / forward declarations and such?

If so, it should be doable, I can mentor it if needed.

[crumblingstatue]

By "opaque types", I was trying to refer to what are apparently called opaque pointers.

Many C libraries employ a technique where the API only forward declares a type (T), but never defines it. Then, the users interact with T by calling functions that deal with pointers to T.

I guess I could try implementing it, no promises though.

[emilio]

By "opaque types", I was trying to refer to what are apparently called opaque pointers.

Ok, yeah, that's the forward declaration I meant above :)