File: invariant.rs

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rust-ghost 0.1.5-1
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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() {}