Returning Result<T, Box<dyn std::error::Error>> from async task crashes rust compiler

[aodhneine]

Platform

:: uname -a
Linux voyager 5.6.4-gentoo #1 SMP Sun Apr 26 14:39:09 UTC 2020 x86_64 Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz GenuineIntel GNU/Linux

rustc version:

:: rustc --version
rustc 1.45.0-nightly (f93bb2a50 2020-05-25)

cargo version:

:: cargo --version
cargo 1.45.0-nightly (500b2bd01 2020-05-18)

Code

type NewResult<T> = Result<T, Box<dyn std::error::Error>>;

fn main() -> NewResult<()> {
    async_std::task::block_on(async {
        let handle = async_std::task::spawn(async move {
            return NewResult::<()>::Ok(());
         });
         handle.await?;
         return NewResult::<()>::Ok(());
    })?;

    return Ok(());
}

Bug
This code results in following internal compiler error:

:: cargo build -j16 --verbose
   Compiling issue_test_return_async_std v0.1.0 (/home/julia/tmp/issue_test_return_async_std)
     Running `rustc --crate-name issue_test_return_async_std --edition=2018 src/main.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type bin --emit=dep-info,link -Cembed-bitcode=no -C debuginfo=2 -C metadata=6995fa926d1dae26 -C extra-filename=-6995fa926d1dae26 --out-dir /home/julia/tmp/issue_test_return_async_std/target/debug/deps -C incremental=/home/julia/tmp/issue_test_return_async_std/target/debug/incremental -L dependency=/home/julia/tmp/issue_test_return_async_std/target/debug/deps --extern async_std=/home/julia/tmp/issue_test_return_async_std/target/debug/deps/libasync_std-c7ce65bf6fabb5ef.rlib`
error: internal compiler error: src/librustc_middle/ich/impls_ty.rs:94: StableHasher: unexpected region '_#3r

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:907:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.45.0-nightly (f93bb2a50 2020-05-25) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

error: aborting due to previous error

error: could not compile `issue_test_return_async_std`.

Caused by:
  process didn't exit successfully: `rustc --crate-name issue_test_return_async_std --edition=2018 src/main.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type bin --emit=dep-info,link -Cembed-bitcode=no -C debuginfo=2 -C metadata=6995fa926d1dae26 -C extra-filename=-6995fa926d1dae26 --out-dir /home/julia/tmp/issue_test_return_async_std/target/debug/deps -C incremental=/home/julia/tmp/issue_test_return_async_std/target/debug/incremental -L dependency=/home/julia/tmp/issue_test_return_async_std/target/debug/deps --extern async_std=/home/julia/tmp/issue_test_return_async_std/target/debug/deps/libasync_std-c7ce65bf6fabb5ef.rlib` (exit code: 101)
::

Cargo.toml:

[package]
name = "issue_test_return_async_std"
version = "0.1.0"
authors = ["aodhneine <aodhneine@protonmail.ch>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

[dependencies.async-std]
version = "1.6.0"

Everything above can be found here: https://paste.debian.net/1150415/

[aodhneine]

This issue is apparently solved in the latest nightly, so I'm closing it. I should've updated rustc in the first place.