error[E0658]: unsized tuple coercion is not stable enough for use and is subject to change
  --> $DIR/feature-gate-unsized_tuple_coercion.rs:2:28
   |
LL |     let _ : &(dyn Send,) = &((),);
   |                            ^^^^^^
   |
   = note: see issue #42877 <https://github.com/rust-lang/rust/issues/42877> for more information
   = help: add `#![feature(unsized_tuple_coercion)]` 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   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date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 1 previous error

For more information about this error, try `rustc --explain E0658`.