error[E0121]: the placeholder `_` is not allowed within types on item signatures for functions
  --> $DIR/issue-95307.rs:7:28
   |
LL |     async fn new() -> [u8; _];
   |                            ^ not allowed in type signatures

error[E0658]: using `_` for array lengths is unstable
  --> $DIR/issue-95307.rs:7:28
   |
LL |     async fn new() -> [u8; _];
   |                            ^
   |
   = note: see issue #85077 <https://github.com/rust-lang/rust/issues/85077> for more information
   = help: add `#![feature(generic_arg_infer)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0121, E0658.
For more information about an error, try `rustc --explain E0121`.