error[E0720]: opaque type expands to a recursive type
  --> $DIR/issue-67166.rs:7:19
   |
LL |     let _foo: Box<impl Copy + '_> = Box::new(()); // FIXME: The error doesn't much make sense.
   |                   ^^^^^^^^^^^^^^ expands to a recursive type
   |
   = note: type resolves to itself

error: aborting due to previous error

For more information about this error, try `rustc --explain E0720`.