missing diagnostic

[matthiaskrgr]

I tried this code:

fn constant<const C: usize>() -> impl use< Sized {}

I expected to see this happen:
anything

Instead, this happened:
nothing

Meta

rustc --version --verbose:

rustc 1.79.0-nightly (f9b161492 2024-04-19)
binary: rustc
commit-hash: f9b16149208c8a8a349c32813312716f6603eb6f
commit-date: 2024-04-19
host: x86_64-unknown-linux-gnu
release: 1.79.0-nightly
LLVM version: 18.1.4

[matthiaskrgr]

The problem here is that the compilation fails, however rustc does not issue any sort of diagnostic to tell the user what went wrong.