rust-lang / rust-lang/rfcs

Extending deref/index with ownership transfer: DerefMove, IndexMove, IndexSet

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Description

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It is clear that there is a need for the ability to move out of smart pointers and indexable things (DerefMove, IndexMove). The other frequently desired option is to IndexSet, which would be a special-cased version for indexing in this situation:

map[key] = value

currently, this is handled via IndexMut, but that is sub-optimal, because if the key is not already part of the map, the result is a panic.

Basic plan

DerefMove/IndexMove/IndexSet should layer on top of the traits we have now. One needs to be careful here because of subtle interactions with autoref and so forth.

Postponed RFCs

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

No implementation files or tests are named. Start by reading the issue discussion and the linked postponed RFCs, especially RFC 1129, to understand the unresolved interactions between DerefMove, IndexMove, IndexSet, autoref, and existing traits. Done would require a settled design and an accepted RFC before implementation can be scoped.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
15/100

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