Urgau

> @Urgau one I just ran into with `env_logger` is `rustbuild`. Unsure if its still used today but it looks like its for when you are a dependency of rustc....

> Another in the camp of "is this really worth a `build.rs` is a `--cfg nightly` as sometimes that is used for diagnostics like `warn(rustdoc::missing_doc_code_examples)` which are internal facing. Maybe...

# `-Zcheck-cfg` Stabilization Report :tada: ## Summary This enables rustc's checking of conditional compilation at compile time. Internally, cargo will be passing a new command line option `--check-cfg` to all...

I've tested the latest nightly and it produces the right warnings. I also updated the diagnostics output to the latest update. This is now ready to be merged.

Let's not derail this PR but it is written under "Frequently asked questions": > ### Can it be disabled? > > For Cargo users, the feature is **always on** and...

I see allowing the lint as disabling the effect of the feature but the feature is still there, Cargo is still passing the `--check-cfg` args to rustc, you can still...

This is not a false-positive, the `impl` (definition) is non-local, it has an effect outside of the function. See this sample code for a direct proof. ```rust pub trait Trait...

> 1. The suggested resolution, moving the `impl`, does not work. So the compiler output is wrong. It is implied by the suggestion that not only the `impl` but also...

> This is an ambiguous case which the RFC does not address directly. I don't think so, the `impl` is clearly visible outside the function. The RFC text is IMO...

> If the lint cannot explain itself to @ijackson why it applies, it is a bug. I agree, the lint should better explain it's reasons. T-compiler touch this in the...