Traits are not implemented for functions with higher-ranked lifetime bounds

[wthrowe]

Also the error is really confusing, because the compiler omits the troublesome bound in the error message.

trait IsClone: Clone {}
impl IsClone for fn(&()) {}
//~^ error: the trait `core::clone::Clone` is not implemented for the type `fn(&())`
impl IsClone for for<'a> fn(&'a ()) {}
//~^ error: the trait `core::clone::Clone` is not implemented for the type `fn(&'a ())`
impl<'a> IsClone for fn(&'a ()) {} // OK

[petrochenkov]

Duplicate of #24000

[wthrowe]

Yep.