Upstream integration with cargo

[joshtriplett]

In today's @rust-lang/cargo meeting, we discussed some of the issues and false positives with the upstream lint for unused crates. We're interested in trying to get Cargo to natively issue this lint, initially as something that can be enabled, and eventually something enabled by default.

See rust-lang/cargo#6669 (comment) - we agreed to try the experiment of adding an option for --all-targets-including-doc (which may become --all-targets in a future edition). That solves part of the problem.

It seems like that plus dep-info should give enough information to compute this without false positives.

@est31 Given the experience you have with cargo-udeps, we wondered if you'd be interested in prototyping adding this support natively to Cargo.

[joshtriplett]

Also, if you'd be interested in discussing this further, please feel free to either come by the Cargo office hours or the Cargo meeting.

[est31]

we wondered if you'd be interested in prototyping adding this support natively to Cargo.

I would really love to do that! In fact I already have a PR to add such support to Cargo, the main blocker for it was a flag like --all-targets-including-doc.

feel free to either come by the Cargo office hours or the Cargo meeting.

I'll definitely try to get in touch with the greater Cargo team :).