Implement LWG-3843 std::expected<T,E>::value() & assumes E is copy constructible
#3737
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Also speculatively generalize the resolution to `expected<void, E>`.
StephanTLavavej
requested changes
May 28, 2023
StephanTLavavej
approved these changes
May 29, 2023
strega-nil-ms
approved these changes
Jun 8, 2023
|
I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
|
Thanks for improving our conformance to the latest Working Paper as expected! 😹 🎉 🚀 |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Per LWG-3843,
std::expected<int, std::unique_ptr<int>>{}.value()needs to be rejected. But currently MSVC and Clang incorrectly accept it (DevCom-1638273 and LLVM-53224).We also need to ensure that the
value() &overload also treats_Erras a const lvalue on copy.The mandating is missing in the standard wording in [expected.void.obs] currently, which is likely another LWG issue. I've mailed LWG chair for this.
Edit: the issue is now LWG-3940.