futures-util-preview doesn't compile on the recent nightly

[tirr-c]

It suddenly complains about Pins, maybe the upstream API has changed.

error[E0277]: the size for values of type `<&mut future::maybe_done::MaybeDone<Fut> as std::ops::Deref>::Target` cannot be known at compilation time
   --> futures-util/src/future/maybe_done.rs:110:9
    |
110 |         Pin::set(self, MaybeDone::Done(res));
    |         ^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `std::marker::Sized` is not implemented for `<&mut future::maybe_done::MaybeDone<Fut> as std::ops::Deref>::Target`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where <&mut future::maybe_done::MaybeDone<Fut> as std::ops::Deref>::Target: std::marker::Sized` bound
    = note: all function arguments must have a statically known size
    = help: unsized locals are gated as an unstable feature

(...)

error: aborting due to 38 previous errors

$ rustc -V
rustc 1.32.0-nightly (6acbb5b65 2018-11-25)

It was okay until edaac35d6 2018-11-24.

[aturon]

cc @cramertj @withoutboats

[Nemo157]

Seems like a rustc inference issue, it should know that <typeof(self)>::Deref = Self here, and Self: Sized.

Here's all the commits to rust-lang/rust between those versions. I think there's some tool that can pull bors' try builds into rustup to be able to check the individual PRs?

[withoutboats]

This is a regression in rustc. Filed an issue at rust-lang/rust#56237. Closing the issue on this repo.

[cramertj]

#1351 contains a workaround.