Use iterator concept in vector's range constructor

[Adam Bucior (AdamBucior)]

Fixes #1709.

[Michael Schellenberger Costa (miscco)]

Welcome to container hell, please take a seat

[Michael Schellenberger Costa (miscco)]

You might also have a look at _Assign_range

[Adam Bucior (AdamBucior)]

Could someone explain to me why move_iterator's iterator_concept is input_iterator_tag?

[Stephan T. Lavavej (StephanTLavavej)]

After merging #1771, there are non-trivial merge conflicts in <vector>.

[Alex Guteniev (AlexGuteniev)]

Also counts towards #189

[Stephan T. Lavavej (StephanTLavavej)]

Could someone explain to me why move_iterator's iterator_concept is input_iterator_tag?

I believe this is because a Forward Iterator can be read multiple times (the idea is that they're like forward_list - they support only forward traversal, but otherwise point to persistent objects in memory). Input Iterators can be read only once (like an istream_iterator, you can't store multiple "locations" to read previous values). move_iterator is weird because although it can wrap something with very strong traversal (up to and including random access), the automatic-moving breaks multi-read behavior. Thus, describing move_iterator with input_iterator_tag is the strictly correct thing to do.

Apologies for the year-long delay in answering this question 😹

[Adam Bucior (AdamBucior)]

Stephan T. Lavavej (@StephanTLavavej) It seems that it might change with P2520.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks, this looks great! I found only minor issues while video reviewing, so I went ahead and validated and pushed changes.

[Casey Carter (CaseyCarter)]

This is an interesting extension, since it's almost exactly the change WG21-P2408 will have us making to the non-permuting std algorithms for C++23. I think we're going to be seeing a lot of similar relaxations for "old" standard library code in C++26 as WG21 is getting our brains wrapped around where and how we can make these integrations without breaking programs in the wild.

[Stephan T. Lavavej (StephanTLavavej)]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks for improving the performance of the STL's most important data structure! 😻 🚀 🚀

[drsnuggles8]

Youtube Link to the Code Review of this PR