Compilation error on latest nightly

[Bunogi]

As far as I can tell, this is a regression in the rust compiler. rust-lang/rust#64433. Recommend using nightly-2019-09-10 or earlier for now.

[Bunogi]

Not a regression -- See discussion in the upstream issue. Will leave it as-is until it's
been resolved. Use nightly-2019-09-10 or earlier for now.

[Bunogi]

Now fixed on latest nightly.