rustc crashes with exit code 101 and no error - 2018 edition + futures-await + automatic extern crate

[Arnavion]

$ rustc -vV

rustc 1.28.0-nightly (84804c387 2018-06-26)
binary: rustc
commit-hash: 84804c3874a15f55a905c0b53d820372003b0c24
commit-date: 2018-06-26
host: x86_64-pc-windows-msvc
release: 1.28.0-nightly
LLVM version: 6.0

Cargo.toml

cargo-features = ["edition"]

[package]
name = "rust-test"
version = "0.1.0"
authors = ["Arnavion <arnavion@gmail.com>"]
edition = "2018"

[dependencies]
futures-await = "0.1.x"

Cargo.lock

[[package]]
name = "futures"
version = "0.1.21"
source = "registry+https://github.com/rust-lang/crates.io-index"

[[package]]
name = "futures-await"
version = "0.1.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
 "futures 0.1.21 (registry+https://github.com/rust-lang/crates.io-index)",
 "futures-await-async-macro 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "futures-await-await-macro 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
name = "futures-await-async-macro"
version = "0.1.4"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
 "proc-macro2 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
 "quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "syn 0.14.4 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
name = "futures-await-await-macro"
version = "0.1.1"
source = "registry+https://github.com/rust-lang/crates.io-index"

[[package]]
name = "proc-macro2"
version = "0.4.6"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
 "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
name = "quote"
version = "0.6.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
 "proc-macro2 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
name = "rust-test"
version = "0.1.0"
dependencies = [
 "futures-await 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
name = "syn"
version = "0.14.4"
source = "registry+https://github.com/rust-lang/crates.io-index"
dependencies = [
 "proc-macro2 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
 "quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
]

[[package]]
name = "unicode-xid"
version = "0.1.0"
source = "registry+https://github.com/rust-lang/crates.io-index"

[metadata]
"checksum futures 0.1.21 (registry+https://github.com/rust-lang/crates.io-index)" = "1a70b146671de62ec8c8ed572219ca5d594d9b06c0b364d5e67b722fc559b48c"
"checksum futures-await 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "d76972f0c250aadc9c3e521023e769b097f838a2d9a71e5139c4fdf0c7657463"
"checksum futures-await-async-macro 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "fdd257a06a5fd1f31adcbddb8068678b2ae534fb6eb282df010ae41db59ddf84"
"checksum futures-await-await-macro 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f3b8bd34e4f4d1bf0e3fe3f22ad22475429f594221472216e34b942f912ec4a4"
"checksum proc-macro2 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "effdb53b25cdad54f8f48843d67398f7ef2e14f12c1b4cb4effc549a6462a4d6"
"checksum quote 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)" = "e44651a0dc4cdd99f71c83b561e221f714912d11af1a4dff0631f923d53af035"
"checksum syn 0.14.4 (registry+https://github.com/rust-lang/crates.io-index)" = "2beff8ebc3658f07512a413866875adddd20f4fd47b2a4e6c9da65cd281baaea"
"checksum unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fc72304796d0818e357ead4e000d19c9c174ab23dc11093ac919054d20a6a7fc"

lib.rs

// extern crate futures_await;

use futures_await as futures;
use crate::futures::{ Future, IntoFuture };

fn foo() -> impl Future<Item = (), Error = ()> {
	Ok(()).into_future()
}

$ cargo build --verbose

<snip>
     Running `rustc --edition=2018 --crate-name rust_test src\lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=dab8a58d770a200f -C extra-filename=-dab8a58d770a200f --out-dir C:\Stuff\Sources\rust-test\target\debug\deps -C linker=lld-link -C incremental=C:\Stuff\Sources\rust-test\target\debug\incremental -L dependency=C:\Stuff\Sources\rust-test\target\debug\deps --extern futures_await=C:\Stuff\Sources\rust-test\target\debug\deps\libfutures_await-de83e6f62427976c.rlib -C target-feature=+crt-static`
warning: unused import: `IntoFuture`
 --> src\lib.rs:4:31
  |
4 | use crate::futures::{ Future, IntoFuture };
  |                               ^^^^^^^^^^
  |
  = note: #[warn(unused_imports)] on by default

error: Could not compile `rust-test`.

Caused by:
  process didn't exit successfully: `rustc --edition=2018 --crate-name rust_test src\lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=dab8a58d770a200f -C extra-filename=-dab8a58d770a200f --out-dir C:\Stuff\Sources\rust-test\target\debug\deps -C linker=lld-link -C incremental=C:\Stuff\Sources\rust-test\target\debug\incremental -L dependency=C:\Stuff\Sources\rust-test\target\debug\deps --extern futures_await=C:\Stuff\Sources\rust-test\target\debug\deps\libfutures_await-de83e6f62427976c.rlib -C target-feature=+crt-static` (exit code: 101)

• Uncommenting the extern crate futures_await; line makes it compile successfully.

• Using the futures 0.1.x crate directly instead of futures_await compiles successfully, without needing to add an extern crate futures; line.

[Arnavion]

It seems rustc doesn't like the use futures_await as futures; if there is no extern crate futures_await; Replacing it with

mod futures {
	pub use futures_await::*;
}

compiles fine.

Perhaps the original code isn't actually supposed to compile with edition 2018, and the bug is just a missing error message?

[aturon]

cc @petrochenkov

[eddyb]

Can't reproduce on nightly. Can you confirm this, @Arnavion?
(I suspect #52923 fixed this by replacing "the finalize_import hack")

[Arnavion]

Looks like it. rustc 1.30.0-nightly (6e0f1cc15 2018-09-05) compiles it successfully.