Export proc-macros directly from main crate

[TedDriggs]

There's a trick that can export traits and proc macros from one crate. Using this would make the dependency declaration cleaner, and could be gated on a default feature for people who don't need the macros.

[withoutboats]

Can you link to the trick?

[TedDriggs]

Here is @dtolnay's awesome writeup on it.

You can see it in action here in one of my own projects.

I believe the trick is that you can reexport proc macros, you just can't declare them locally.

[withoutboats]

Interesting! This is technically an unstable feature we accidentally allowed through on stable. I'll think about doing this.