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ghost 0.1.11

Define your own PhantomData
Documentation 
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use ghost::phantom;

#[phantom]
struct InvariantPhantom<#[invariant] T>;

fn require_covariant<'a>(phantom: InvariantPhantom<&'static str>) -> InvariantPhantom<&'a str> {
    phantom
}

fn require_contravariant<'a>(phantom: InvariantPhantom<&'a str>) -> InvariantPhantom<&'static str> {
    phantom
}

fn main() {}