In Rust, closures don't need to be boxed, because they're just bytes like everything else. In this case, they can be stored by-value as a generic type in the fu

In Rust, closures don't need to be boxed, because they're just bytes like everything else. In this case, they can be stored by-value as a generic type in the future itself, which can be stored on the stack. The one time that you do tend to see closures get boxed is when returning them, because you can't write out their type. In the future you'll be able to get around that by using the `impl Trait` syntax mentioned in the post (https://github.com/rust-lang/rfcs/pull/1522 https://github.com/rust-lang/rfcs/pull/1522).