rustdoc: private_doc_tests lint no longer fires on stable

[ehuss]

As of rustc 1.47.0-beta.1, the private_doc_tests lint is no longer working.

#![warn(private_doc_tests)]
/// hi!
/// ```
/// let x = 1;
/// ```
fn f() {}

I expected to see this happen: cargo doc should issue warning: documentation test in private item

Instead, this happened: No warnings emitted.

This appears to have changed in #74855. I don't see any discussion there about this, so I'm guessing it was unintentional.

cc @jyn514.

[jyn514]

This was definitely unintentional. I thought I added a test for this ...

[jyn514]

Hmm, it tests with deny(rustdoc) but not with deny(missing_doc_code_examples). Maybe the name of the lint wasn't registered?

https://github.com/rust-lang/rust/pull/74855/files#diff-2009d75a18198cb86d168844baa3c607

[ehuss]

The issue is this line. Compiletest runs with RUSTC_BOOTSTRAP set. I don't recall off the top of my head how to force a test to be stable.

[jyn514]

Wait now I'm confused. I thought the point of this lint was that it only runs on nightly, because we're not sure if we want to stabilize it.

cc @rust-lang/rustdoc

[jyn514]

@ehuss are you sure this used to work?

[ehuss]

The private_doc_tests lint has been on stable since 1.32. It is documented here.

[jyn514]

Got it, I mixed it up with missing_doc_code_examples. Yeah this is a bug then - the two lints should be treated differently.