rust-lang / rust-lang/rust-clippy
[lint request] transmute_raw_to_boxed_trait
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Description
People transmute all sort of things into a Box<T: ?Sized> where T is a trait. The layout of this type is unspecified and there is not stable way to do this AFAICT.
@SimonSapin wrote an RFC here: https://github.com/rust-lang/rfcs/pull/2580
And there is some nightly functionality for it in core::raw::TraitObject (https://doc.rust-lang.org/core/raw/struct.TraitObject.html). We should definitely warn that the behavior of code that does this is unspecified, and maybe tell those on nightly to prefer core::raw::TraitObject instead.
Also, if we ever support multi-trait trait-objects (or different trait-object layouts), this code could break.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
No repository file or test is named. Start by reading RFC 2580 and the core::raw::TraitObject documentation, then inspect Clippy's existing transmute-related lint patterns. Done means the requested conversion is warned about and the stable versus nightly guidance is settled with tests.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- tooling
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100