#[cfg(target(os = "x"))] //~ ERROR compact `cfg(target(..))` is experimental
struct Foo(u64, u64);

#[cfg_attr(target(os = "x"), x)] //~ ERROR compact `cfg(target(..))` is experimental
struct Bar(u64, u64);

#[cfg(not(any(all(target(os = "x")))))] //~ ERROR compact `cfg(target(..))` is experimental
fn foo() {}

fn main() {
    cfg!(target(os = "x"));
    //~^ ERROR compact `cfg(target(..))` is experimental and subject to change
}