closure rvalue not checked for WF allowing it to assume more implied bounds

[aliemjay]

The following should not compile because the bound D: 'static is not satisfied in fn test:

struct Static<D: 'static>(Option<D>);

pub fn test<D>() {
    let _ = || {
        Static(None::<D>)
    };
}

[compiler-errors]

This isn't unsound, I think? I thought that this WF obligation would be discharged at the callsite of the closure; it gives the right error for D: 'static when it's called.