Reject tail calls of #[track_caller] functions

[WaffleLapkin]

To make tail calls possible either both functions need to be #[track_caller], or neither can. For simplicity I propose to just disallow using tail calling #[track_caller] functions / tail calling from #[track_caller] functions. I don't think #[track_caller] is useful with tail calls anyway.

However, we do need to have a quite late check, after monopolization (as otherwise you don't necessarily know if the callee has #[track_caller]).

I'm not very happy with this implementation -- error'ing in the backend seems like a hack and will probably lead to disagreements between backends. Ideally we'd have a mir specific check (that would also probably make getting the span easier...).

Fixes #144755

[rustbot]

r? @SparrowLii

rustbot has assigned @SparrowLii.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[WaffleLapkin]

Hm. Alternatively, instead of rejecting callee being #[track_caller], we could use a shim (similarly to what happens when casting a #[track_caller] fn to a function pointer). I'm not sure how to do that though 🤔

[bjorn3]

nit in PR description: s/monopolization/monomorphization