surprising error with opaque types

[lcnr]

fn constrain<'a, F: FnOnce(&'a ())>(_: F) {}
fn foo<'a>(_: &'a ()) -> impl Sized + use<'a> {
    constrain(foo); // adds use `opaque<'!a> = ()`
    () // adds use `opaque<'a> = ()` -> leak check error
}
fn main() {}

results in the following error in HIR typeck

error[E0277]: expected a `FnOnce(&())` closure, found `for<'a> fn(&'a ()) -> impl Sized {foo}`
 --> <source>:3:24
  |
3 |     constrain_identity(foo);
  |     ------------------ ^^^ expected an `FnOnce(&())` closure, found `for<'a> fn(&'a ()) -> impl Sized {foo}`
  |     |
  |     required by a bound introduced by this call
  |
  = help: the trait `FnOnce(&())` is not implemented for fn item `for<'a> fn(&'a ()) -> impl Sized {foo}`
note: required by a bound in `constrain_identity`
 --> <source>:1:30
  |
1 | fn constrain_identity<'a, F: FnOnce(&'a ())>(_: F) {}
  |                              ^^^^^^^^^^^^^^ required by this bound in `constrain_identity`

[lcnr]

This adds a use referencing placeholders to the opaque type storage, might be fixed #140497