Tracking issue for feature `extern_crate_self`

[petrochenkov]

With this feature extern crate NAME as RENAME; now accepts NAME=self and interprets it as referring to the local crate.

As with other extern crate items, RENAME in this case gets into extern prelude and therefore can be used from absolute paths and imports on 2018 edition.

extern crate self as serde; // Adds local crate to extern prelude as `serde`

mod foo { ... }

// Anywhere in this crate
use serde::foo; // OK
::serde::foo; // OK

The feature's primary purpose is to resolve #54647 and support migration of proc macro crates to 2018 edition.

Implementation PR - #55275.

[mehcode]

This would be excellent. Is there something blocking stabilization here?

The "work-around" described in a related issue gets significantly more awkward if you're expanding proc-macros in doctests. See my recent edition upgrade on diesel: https://github.com/diesel-rs/diesel/blob/af1ff2476f997d6eb04fffd58260705d77ff6b6f/diesel_derives/src/util.rs#L81-L96

[petrochenkov]

@mehcode

Is there something blocking stabilization here?

I don't think so, someone just needs to submit a stabilization PR, and then it should go through the "official" approval by the lang team.