Missing coverage on `assert!(!...)` statements

[EFanZh]

I tried this code:

fn main() {
    assert!(!false);
}

I expected to see this happen: Run this program with cargo-llvm-cov: cargo llvm-cov run --html, I expect the source code should be fully covered.

Instead, this happened: The assert! part in the source code is not covered. But if I change !false to true, the source will be fully covered, it seems that I can’t get assert! to be covered as long as the argument starts with an ! operator.

Meta

rustc --version --verbose:

rustc 1.76.0-nightly (f967532a4 2023-12-08)
binary: rustc
commit-hash: f967532a47eb728ada44473a5c4c2eca1a45fe30
commit-date: 2023-12-08
host: x86_64-pc-windows-msvc
release: 1.76.0-nightly
LLVM version: 17.0.5

[matthiaskrgr]

Might be that llvm just optimizes it out as dead code. Do you see it with -Copt-level=0 ?

[EFanZh]

@matthiaskrgr: I think cargo-llvm-cov already uses opt-level=0 by default. Nevertheless, I have tested using env RUSTFLAGS='-Copt-level=0' cargo llvm-cov run --html, and the result is the same.

[taiki-e]

This may be a similar case to #110486. It seems that something odd is happening when the compiler gets the coverage of the code generated by the macro and maps it to the original code.

@rustbot label +A-code-coverage

[Noratrieb]

cc @Zalathar

[Zalathar]

I can reproduce this with 2023-12-08 but not with 2023-12-14.

It was probably fixed by #118198.

[Noratrieb]

Would it make sense to add a test for this specifically?

[Zalathar]

Would it make sense to add a test for this specifically?

PR filed: #119011