warning: the feature `unsafe_binders` is incomplete and may not be safe to use and/or cause compiler crashes
  --> $DIR/expr.rs:3:12
   |
LL | #![feature(unsafe_binders)]
   |            ^^^^^^^^^^^^^^
   |
   = note: see issue #130516 <https://github.com/rust-lang/rust/issues/130516> for more information
   = note: `#[warn(incomplete_features)]` on by default

warning: 1 warning emitted