Pre-RFC - Add compile_warning! macro

[Kampfkarren]

@dtolnay

Println formatting is evaluated at runtime, not at compile time. The implementation would need to be substantially different given that warnings need to appear at compile time, not runtime

You're right, this seems like something that makes an implementation demonstrably harder. I'm going to remove that part unless you feel it is necessary.

@dtolnay

#[allow] is not covered. It is mentioned in the summary, but the summary is supposed to summarize what is covered by the rest of the document.

I plan on adding onto that, but thanks for the tip on the summary.

@dtolnay

Compiler plugins are not the only alternative.

My bad, I thought this section was asking for alternatives already in Rust, but I understand now it is asking for alternative solutions as well.

@dtolnay

This would be surprising to me. It does not match the normal behavior of deny(warnings) .

Agh, I'm dumb. I forgot what #[deny(warnings)] actually did. Fixing this

@dtolnay

For example I don’t see how const fn could emit conditional warnings under this proposal.

I need to test to see if compile_error! works with const fn, I just assumed. Update: It doesn't, strange.