Tracking Issue for unqualified_local_imports lint

[RalfJung]

This is a tracking issue for the unqualified_local_imports lint.
The feature gate for the issue is #![feature(unqualified_local_imports)].

This lint helps deal with rust-lang/rustfmt#4709 by having the compiler detect imports of local items that are not syntactically distinguishable from imports from other cates. Making them syntactically distinguishable ensures rustfmt can consistently apply the desired import grouping with group_imports = "StdExternalCrate".

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.
Discussion comments will get marked as off-topic or deleted.
Repeated discussions on the tracking issue may lead to the tracking issue getting locked.

Steps

• Implement the lint: add unqualified_local_imports lint #125645
• Adjust documentation (see instructions on rustc-dev-guide)
• Formatting for new syntax has been added to the Style Guide (nightly-style-procedure)
• Stabilization PR (see instructions on rustc-dev-guide)

Unresolved Questions

• Currently this largely acts like a rustc internal lint, and the rustfmt feature that motivates the lint is unstable. Is there any path to stabilization?

Implementation history