1 error[E0321]: cross-crate traits with a default impl, like `std::marker::Send`, can only be implemented for a struct/enum type, not `&'static main::Foo`
2 --> $DIR/empty_span.rs:17:5
4 17 | unsafe impl Send for &'static Foo { }
5 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
7 error: aborting due to previous error(s)