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Library Trait Evolution Experiment #712
Description
| Metadata | |
|---|---|
| Contact | @lcnr |
| Team(s) | lang (@tmandry), libs, types (@lcnr) |
| Goal document | 2026/library-trait-evolution-experiment |
| Funding contact | Hexcat |
Summary
Setup a Library Trait Evolution experiment. It works to unify the design of language features to make trait definitions less rigid. This includes refined trait implementations and Supertrait Auto-impl, but also more targeted features for the standard library, such as #[rustc_must_implement_one_of].
We plan to collect different use-cases and requirements here, both from the standard library and the wider ecosystem. We then use this to design, implement, and stabilize features solving these issues.
This issue is intended for status updates only.
For general questions or comments, please contact a goal owner or post in the Zulip topic.
Activity
nxsaken commentedon Jul 8, 2026
This issue is intended for status updates only.
For general questions or comments, please contact the owner(s) directly.
lcnr commentedon Jul 14, 2026
This is now an accepted Language Team Experiment rust-lang/lang-team#377 and we've started by extracting the use-cases mentioned in the existing proposals and the related issues in a shared repository: https://github.com/rust-lang/library-trait-evolution-initiative/issues
I currently don't have a great sense of all the different requirements for features here and e.g. discussing rust-lang/library-trait-evolution-initiative#4 in our weekly meeting, we realized the original approach explored in is likely not a valid use case of rust-lang/rfcs#3851 as the original idea isn't possible due to other constraints. This is something I would love to get help for, see this zulip thread.