P2988R12 `optional<T&>`
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- Dominant language
- C++
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Description
WG21-P2988R12 optional<T&>
WG21-P3836R2 Make optional<T&> Trivially Copyable
LWG-4299 Missing Mandates: part in optional<T&>::transform
LWG-4300 Missing Returns: element in optional<T&>::emplace
LWG-4304 std::optional<NonReturnable&> is ill-formed due to value_or
LWG-4308 std::optional<T&>::iterator can't be a contiguous iterator for some T
LWG-4439 std::optional<T&>::swap possibly selects ADL-found swap
Also note #5871 tracking:
LWG-4015 LWG-3973 broke const overloads of std::optional monadic operations
INCREASED feature-test macros:
#define __cpp_lib_freestanding_optional 202506L
#define __cpp_lib_optional 202506L
Note: We are not yet accepting PRs for C++26 features.
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
The issue lists WG21-P2988R12, WG21-P3836R2, and LWG-4299, LWG-4300, LWG-4304, LWG-4308, and LWG-4439, with #5871 as related tracking. Start by reading those references and checking the requested feature-test macro changes; the payload names no files or tests, and notes that PRs for C++26 features are not yet being accepted.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- tooling
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 15/100