This is a tracking issue for the trait methods Extend::extend_one and extend_reserve.
The feature gate for the issue is #![feature(extend_one)].

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also uses 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.

Steps

• Implement the API
• Adjust documentation (see instructions on rustc-dev-guide)
• Stabilization PR (see instructions on rustc-dev-guide)

Unresolved Questions

• Are these method names appropriate?
  • Note that Extend is in the prelude, so the explicit extend_ prefix avoids ambiguity.
• Is Extend the best place for just methods?
  • One goal is to improve Iterator::unzip, which only has Default + Extend, so there's not really much choice.

Implementation history

• Initial implementation in Add Extend::{extend_one,extend_reserve} #72162.