src/test/ui/used.rs

#[used]
static FOO: u32 = 0; // OK

#[used] //~ ERROR attribute must be applied to a `static` variable
fn foo() {}

#[used] //~ ERROR attribute must be applied to a `static` variable
struct Foo {}

#[used] //~ ERROR attribute must be applied to a `static` variable
trait Bar {}

#[used] //~ ERROR attribute must be applied to a `static` variable
impl Bar for Foo {}

fn main() {}