Ergonomic ref-counting

[nikomatsakis]

Metadata
Owner(s)	@joshtriplett
Team(s)	compiler, lang, libs-api
Goal document	2024h2/ergonomic-rc

Summary

Deliver nightly support some solution to reduce the ergonomic pain of working with ref-counted and cheaply cloneable types.

Tasks and status

• Author RFC (Simplify lightweight clones, including into closures and async blocks rfcs#3680)
• Design meeting (lang )
• RFC decision (lang, libs-api )
• Nightly implementation (@spastorino) -- in progress
• Standard reviews (compiler )
• Blog post on Inside Rust

[nikomatsakis]

This issue is intended for status updates only.

For general questions or comments, please contact the owner(s) directly.

[nikomatsakis]

This issue has not seen many updates, but there has been definite progress:

• @joshtriplett opened Simplify lightweight clones, including into closures and async blocks rfcs#3680. The @rust-lang/lang team has not yet truly discussed or reached a decision on that RFC.
• @spastorino began implementation work on a prototype.

[nikomatsakis]

Year-end summary:

In 2024H2 @spastorino began work on an experimental implementation (not yet landed) and @joshtriplett authored a corresponding RFC (rust-lang/rfcs#3680), which has received substantial feedback.

We opened a proposed 2025H1 project goal to continue by (a) landing the experimental branch and (b) addressing feedback on the RFC, reading it with the lang-team, and reaching a decision.