Automatically published version of the package `rustc_error_codes` in the rust-lang/rust repository from commit 30ca215b4e38b32aa7abdd635c5e2d56f5724494 The publishing script for this crate lives at: https://github.com/alexcrichton/rustc-auto-publish
Rust 2015 does not permit the use of `async fn`.
Example of erroneous code:
```compile_fail,E0670
async fn foo() {}
```
Switch to the Rust 2018 edition to use `async fn`.