Missing ambiguity error for impl trait

[Veykril]

          While we are here, this one can also be triggered with `impl` syntax

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=d43383743ffef4b512c74809eb38bbca

fn f(_: &impl 'a + Sized) {}

Originally posted by @Veykril in #19265 (comment)

[Shourya742]

@rustbot claim