rustdoctest: no allow lints are put in doctests, contradicting Rustdoc Book

[QuietMisdreavus]

In the current Rustdoc Book, it mentions that a few lints are automatically allowed in doctests:

Some common allow attributes are inserted, including unused_variables, unused_assignments, unused_mut, unused_attributes, and dead_code. Small examples often trigger these lints.

However, as the image above demonstrates, this does not seem to be the case. I have not added any #![doc(test(attr(warn(unused))))] or similar attributes to my crate, which would override such behavior. These warnings are usually suppressed, but adding --nocapture when running tests shows these warnings. (It also shows more important warnings, like unused_must_use, which helped in a different library of mine.)

@rust-lang/docs @rust-lang/dev-tools - Is this a docs issue (which would mean removing this entry from the Rustdoc Book) or a rustdoc issue (which would mean making sure these items are added)?

[GuillaumeGomez]

I think it should be added into rustdoc instead (but I was sure it was already...).

[QuietMisdreavus]

I've opened #45764 to add a blanket #![allow(unused)] when a crate doesn't specify any attributes via #![doc(test(attr(...)))]. I also opened #45767 to document #![doc(test(attr(...)))] itself.