I've found a strange bug related to proc macros, which I have hard time reproducing. The simplest steps are:

1. Clone futures_rs (https://github.com/rust-lang-nursery/futures-rs)
2. Check out version tagged as 0.1.18 (it does not fail on the newest version)
3. Run cargo check - it passes
4. Add #![feature(proc_macro)] on the beginning of src/lib.rs
5. Run cargo check - it fails:

error[E0432]: unresolved import --> src/future/mod.rs:34:16 | 34 | pub use self::{result as done, FutureResult as Done}; | ^^^^^^^^^^^^^^ error: aborting due to previous error 

I'm sorry for convoluted instructions, I could not reproduce the issue from the scratch or by reducing futures-rs to a failing bare minimum.

The failing code looks really casual, just reexports of a simple function. If anybody could find the root cause, that would probably help a lot.

I'm using rustc 1.27.0-nightly (ac3c2288f 2018-04-18) on Ubuntu 17.10.