error: compilation successful
  --> $DIR/borrowing.rs:15:1
   |
LL | / fn main() { #![rustc_error] // rust-lang/rust#49855
LL | |     let _b = {
LL | |         let a = 3;
LL | |         unsafe { (|| yield &a).resume() }
...  |
LL | |     };
LL | | }
   | |_^

error: aborting due to previous error