Rust doesn't use niche in reference (or pointer) to slice
Nobody has claimed this yet.
- Dominant language
- Rust
- Stars
- 119k
- Forks
- 16.1k
- PR merge metrics
- PR metrics pending
Description
From reddit thread: why can't rust optimize the size of Option<Option<&str>>?
Indeed, in spite of the fact that &str doesn't all use more than half of possible bit sequences (top bit of 2nd word is always zero, plus first word can not be zero) only Option<&str> is optimized
Would it make sense to teach compiler about that niche or is it prevented by some deeper issue?
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
Start with the linked Godbolt comparison and the from_raw_parts safety documentation to verify the claimed unused bit patterns. Then trace how the Rust compiler handles niches for &str and nested Option; a useful outcome is a documented feasibility decision or a precisely scoped compiler change with tests.
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
- 28/100