ices/53448.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#53448

#![feature(unboxed_closures)]

trait Lt<'a> {
    type T;
}
impl<'a> Lt<'a> for () {
    type T = ();
}

fn main() {
    let v:<() as Lt<'_>>::T = ();
    let f:&mut FnMut<(_,),Output=()> = &mut |_:<() as Lt<'_>>::T|{};
    f(v);
}

=== stdout ===
=== stderr ===
warning: trait objects without an explicit `dyn` are deprecated
  --> /home/runner/work/glacier/glacier/ices/53448.rs:12:16
   |
12 |     let f:&mut FnMut<(_,),Output=()> = &mut |_:<() as Lt<'_>>::T|{};
   |                ^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn FnMut<(_,),Output=()>`
   |
   = note: `#[warn(bare_trait_objects)]` on by default

error[E0277]: the size for values of type `<() as Lt<'_>>::T` cannot be known at compilation time
  --> /home/runner/work/glacier/glacier/ices/53448.rs:12:46
   |
12 |     let f:&mut FnMut<(_,),Output=()> = &mut |_:<() as Lt<'_>>::T|{};
   |                                              ^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `<() as Lt<'_>>::T`
   = help: unsized locals are gated as an unstable feature
help: consider further restricting the associated type
   |
10 | fn main() where <() as Lt<'_>>::T: Sized {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: function arguments must have a statically known size, borrowed types always have a known size
   |
12 |     let f:&mut FnMut<(_,),Output=()> = &mut |_:&<() as Lt<'_>>::T|{};
   |                                                ^

error: aborting due to previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0277`.
==============