P0551R3 Thou Shalt Not Specialize std Function Templates!

[StephanTLavavej]

P0551R3 Thou Shalt Not Specialize std Function Templates!

[StephanTLavavej]

As statementreply observed and Casey Carter (@CaseyCarter) confirmed on Discord, there's no action required for STL implementers here. I was originally confused by the paper, because it suggests that std::swap (etc.) could be implemented as a function object, but Casey Carter (@CaseyCarter) explained that this is not possible with the wording that was voted in (because swap(std_vector1, std_vector2) needs to find std::swap through ADL, but that won't work if it's a function object).

Therefore, the only action that STL implementers could take here would be to request compiler support for prohibiting user specializations. This seems both difficult (as we would have to design a mechanism, probably powered by attributes, get all of the front-ends to implement it, and then apply it to all function templates), and extremely low value for users, possibly negative value (it would help them "conform" by breaking their code, without actually providing a new system to migrate to). Speaking for myself, I am one of the strongest proponents of deprecating and removing code in a staged manner, to help users migrate to better techniques over time - but that scenario doesn't apply here, yet.

Therefore, the maintainer consensus is to close this issue as resolved - our implementation conforms to the Standard here, and currently chooses not to diagnose "unspecified (possibly ill-formed)" usage here.