The expected type vs. found type in the error `one type is more general than the other`

Code

#![feature(unboxed_closures)]
#![feature(fn_traits)]

struct A;
impl<'l> FnOnce<(&'l i32,)> for A{
    type Output = &'l i32;
    extern "rust-call" fn call_once(self, x: (&'l i32,))->Self::Output{
        x.0
    }
}
fn show<'a,F,>(_:F)
where F: for<'b> FnOnce(&'b i32)->&'a i32
{
    
}

fn main(){
    show(A);
}

Current output

error[E0308]: mismatched types
  --> src/main.rs:18:5
   |
18 |     show(A);
   |     ^^^^^^^ one type is more general than the other
   |
   = note: expected reference `&'b _`
              found reference `&_`
note: the lifetime requirement is introduced here
  --> src/main.rs:12:35
   |
12 | where F: for<'b> FnOnce(&'b i32)->&'a i32
   |                                   ^^^^^^^

Desired output

expected reference `&'a _`
found reference `&'b _`

Rationale and extra context

The trait bound where F: for<'b> FnOnce(&'b i32)->&'a i32 means we expect that the parameter is &'b i32 for any lifetime 'b and the returned type is &a i32 for a specific lifetime 'a, the implementation of FnOnce for A means the parameter and returned are &'l i32 for any lifetime 'l.

That is, for passing A, it implements for<'b> Fn(&'b i32)->&'b i32, and the trait bound expresses that we expect for<'b> Fn(&'b i32)->&'a i32

Other cases

No response

Rust Version

1.81.0-nightly

Anything else?

No response

Reproduce the example from src/main.rs with Rust 1.81.0-nightly and inspect the diagnostic produced at show(A), especially the FnOnce trait bound in show. Compare the current and desired expected/found lifetime labels; done means the diagnostic reports the intended lifetimes without regressing the relevant compiler tests.