The fixes for #54716 and #60236 introduced `__arg` variables that, presently, are accessible to the user ([playground](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018)): ```rust #![feature(async_await)] async fn foo(_: usize) { println!("{}", __arg0); } fn main() { } ``` This code compiles, but it should error.