Static None

[catharinejm]

Minor optimization:

Rather than dealing with Box<Option<T>>, which requires a fresh allocation for everything, we can pretend to store Option<Box<T>>. We allocate a single static object, denoted EMPTY, and store its address when the channel is empty. Then, when we load the address, if it matches EMPTY we return None, otherwise we convert the pointer to a Box<T> and return Some(...) containing the box.

[catharinejm]

I'm gonna close this. The merge conflict is pretty extensive, and honestly this is probably a useless optimization. Based on rust-lang/rust#6001 and rust-lang/rust#1271, the compiler is already doing something similar. At some point we can profile some running code to see whether it makes needless allocations in practice or not.