Fix panic with closure inside array len

[HKalbasi]

I was working on #15947 and found out that we panic on this test:

fn main() {
    let x = [(); &(&'static: loop { |x| {}; }) as *const _ as usize]
}

This PR fixes the panic. Closures in array len are still broken, but closure in const eval is not stable anyway.

[HKalbasi]

@bors r+

[bors]

📌 Commit c11a002 has been approved by HKalbasi

It is now in the queue for this repository.

[bors]

⌛ Testing commit c11a002 with merge 4196675...

[bors]

☀️ Test successful - checks-actions
Approved by: HKalbasi
Pushing 4196675 to master...