The Rust style system code is warning-free. We previously enforced this at compile time, but it was turned off in bug 1373878, so that newer compilers (with newer warnings) would not choke on old branches. It seems like we ought to still be able to trigger failures for warnings on CI builds. Ideally this would be a non-fatal failure (orange, not red), so that other jobs could still conclude.

(In reply to Bobby Holley (:bholley) from comment #0) > The Rust style system code is warning-free. We previously enforced this at > compile time, but it was turned off in bug 1373878, so that newer compilers > (with newer warnings) would not choke on old branches. I wrote about the topic of fatal warnings here: https://blog.mozilla.org/nnethercote/2017/07/05/how-we-made-compiler-warnings-fatal-in-firefox/ > It seems like we ought to still be able to trigger failures for warnings on > CI builds. Ideally this would be a non-fatal failure (orange, not red), so > that other jobs could still conclude. We should do the same thing that we already do for C and C++ warnings. From the post: "Set things up so that fatal warnings are off by default, but enabled on continuous integration (CI). This means the primary coverage is via CI. You don’t want fatal warnings on by default because it causes problems for developers who use non-standard compilers (e.g. pre-release versions with new warning classes). Developers using the same compilers as CI can turn it on locally if they want without problem."

(In reply to Nicholas Nethercote [:njn] from comment #1) > "Set things up so that fatal warnings are off by default, but enabled on > continuous integration (CI). This means the primary coverage is via CI. You > don’t want fatal warnings on by default because it causes problems for > developers who use non-standard compilers (e.g. pre-release versions with > new warning classes). Developers using the same compilers as CI can turn it > on locally if they want without problem." This is basically what I'm proposing in comment 0, no? I do think it would be nice if we could make compiler warnings turn the build yellow rather than red, so that when warnings do hit CI, subsequent unrelated changesets can still get their test runs. I don't know how hard that is in practice though.