coverage: Discard spans that fill the entire function body by Zalathar · Pull Request #121135 · rust-lang/rust (original) (raw)

I thought about adding a special-case to detect functions with a non-empty body span and no extracted spans, in order to explicitly add a span that covers the whole body. But currently it doesn't seem to be necessary, so I haven't bothered.

For fn foo() {}, I believe the way it currently works is that we generate a span for the signature, and there's another zero-width span right at the end of the body (representing the return), and the span refiner then merges those together into something that covers the whole body.

(None of this is ideal, but sadly that's the reality of trying to heuristically extract coverage spans from MIR. Right now I'm happy to be able to make any progress in simplifying the span refiner into something a bit more maintainable.)