Bounds in Higher-Ranked Lifetimes in trait objects don't seem to work

[arielb1]

use std::marker::CovariantLifetime as CLT;
fn does_not_compile<'b>(y: CLT<'b>) -> Box<for<'s:'b> Fn() -> CLT<'s>> {
    Box::new(move ||y)
}
fn does_compile<'b, 's:'b>(y: CLT<'b>) -> Box<Fn() -> CLT<'s>> {
    Box::new(move ||y)
}
fn main() {}

Error:

<anon>:3:21: 3:22 error: mismatched types:
 expected `core::marker::CovariantLifetime<'s>`,
    found `core::marker::CovariantLifetime<'b>`
(lifetime mismatch) [E0308]
<anon>:3     Box::new(move ||y)
                             ^
<anon>:3:21: 3:22 note: the lifetime 's as defined on the block at 3:20...
<anon>:3     Box::new(move ||y)
                             ^
<anon>:2:72: 4:2 note: ...does not necessarily outlive the lifetime 'b as defined on the block at 2:71
<anon>:2 fn does_not_compile<'b>(y: CLT<'b>) -> Box<for<'s:'b> Fn() -> CLT<'s>> {
<anon>:3     Box::new(move ||y)
<anon>:4 }
error: aborting due to previous error
playpen: application terminated with error code 101

[theemathas]

Possibly releated to #22791

[steveklabnik]

Triage: I am not sure how to reproduce this, as PhantomData is the replacement for the old *Lifetime types, and I am terrible with remembering the various variances. @arielb1 any idea about this today?

[Mark-Simulacrum]

I can't reproduce this failure today, but it might be due to a lack of understanding how to do it with PhantomData. I'm going to give this a close since I think it's no longer relevant, but please do reopen with a modern example if possible. What I came up with is below, but it doesn't work.

use std::marker::PhantomData;

fn does_not_compile<'b>(y: PhantomData<&'b ()>) -> Box<for<'s: 'b> Fn() -> PhantomData<&'s ()>> {
    Box::new(move ||y)
}
fn does_compile<'b, 's:'b>(y: PhantomData<&'b ()>) -> Box<Fn() -> PhantomData<&'s ()>> {
    Box::new(move ||y)
}
fn main() {}

error[E0582]: binding for associated type `Output` references lifetime `'s`, which does not appear in the trait input types
 --> test.rs:3:76
  |
3 | fn does_not_compile<'b>(y: PhantomData<&'b ()>) -> Box<for<'s: 'b> Fn() -> PhantomData<&'s ()>> {
  |                                                                            ^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error