src/test/ui/issues/issue-16994.stderr

error: compilation successful
  --> $DIR/issue-16994.rs:18:1
   |
LL | / fn main() { //~ ERROR compilation successful
LL | |     cb(Box::new(|(k, &(ref v, b))| (*k, v.clone(), b)));
LL | | }
   | |_^

error: aborting due to previous error