rust-lang / rust-lang/rfcs

Interaction between elision and trait objects is not ideal

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Description

As observed on https://github.com/rust-lang/rust/pull/27248, the interaction between elision and trait objects changed recently as the result of a bug fix, but in some cases the older, buggy behavior may have been preferable. In particular, trait object defaults operate by different rules per RFC 599. I have also argued that object lifetime defaults ought to be treated differently from other lifetimes for the purpose of '_, which is closely tied to elision. However, it's unclear just what the new rules ought to be.

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Research direction

Start by reading the behavior change discussed in rust-lang/rust#27248, then compare RFC 599 with the RFC 1177 comment about object lifetime defaults and '_. The issue is done only when the intended elision and trait-object rules are clearly decided and documented, likely through an accepted RFC.

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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
25/100

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