// edition:2021 // FIXME(async_closures): This needs a better error message! #![feature(async_closure, async_fn_traits)] use std::ops::AsyncFn; fn main() { fn needs_async_fn(_: impl AsyncFn()) {} let mut x = 1; needs_async_fn(async || { //~^ ERROR i16: ops::async_function::internal_implementation_detail::AsyncFnKindHelper // FIXME: Should say "closure is AsyncFnMut but it needs AsyncFn" or sth. x += 1; }); }