nested not in cfg doesn't work

[klutzy]

This compiles and prints "nonesuch":

#[crate_type = "bin"];
#[cfg(not(not(nonesuch)))]
fn main() {
    if cfg!(not(not(nonesuch))) {
        println("nonesuch");
    }
}

syntax::attr::test_cfg doesn't work in a recursive way. It may be better to forbid it instead?

[klutzy]

non-issue. Maybe we have to leave a note that "not(expression) is not what you want".