Rust contravariance, Regarding the contravariance of `fn(&'a i32) -> ()`

[zirconium-n]

@phil-skillwon

in any place where fn(&'a i32) is used, we should be able to replace it with fn(&'static i32), because the Rust compiler will automatically shrink 'static to 'a

Well, you are assuming covariance here, of course you get covariance (which is the wrong result).