span: Implement resolution to LWG-3320

[miscco]

Description

In the resolution of LWG-3320 the const_iterator and const_reverse_iterator typedefs were removed together with the respective methods c{r}begin() and c{r}end().

Adopt the tests accordingly and skip the tests from libc++ until they remove them.

This addresses #542

Checklist

Be sure you've read README.md and understand the scope of this repo.

If you're unsure about a box, leave it unchecked. A maintainer will help you.

• Identifiers in product code changes are properly _Ugly as per
  https://eel.is/c++draft/lex.name#3.1 or there are no product code changes.
• The STL builds successfully and all tests have passed (must be manually
  verified by an STL maintainer before automated testing is enabled on GitHub,
  leave this unchecked for initial submission).
• These changes introduce no known ABI breaks (adding members, renaming
  members, adding virtual functions, changing whether a type is an aggregate
  or trivially copyable, etc.).
• These changes were written from scratch using only this repository,
  the C++ Working Draft (including any cited standards), other WG21 papers
  (excluding reference implementations outside of proposed standard wording),
  and LWG issues as reference material. If they were derived from a project
  that's already listed in NOTICE.txt, that's fine, but please mention it.
  If they were derived from any other project (including Boost and libc++,
  which are not yet listed in NOTICE.txt), you must mention it here,
  so we can determine whether the license is compatible and what else needs
  to be done.

[StephanTLavavej]

Please also regex-search for span.*const_iterator in tests/std. I see at least tests/std/tests/Dev10_709168_marking_iterators_as_checked/test.cpp and tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp . Then this should be ready to go; thanks!

[CaseyCarter]

@miscco: Would you mind posting an /azp run comment in this review thread? We believe we've allowed arbitrary users to trigger Azure Pipelines but we need someone who's not a member of VC Libraries to test it.

[miscco]

The sacrifices I make ...

/azp run

[miscco]

/azp run

[azure-pipelines]

Commenter does not have sufficient privileges for PR 548 in repo microsoft/STL

[BillyONeal]

Hmmmm now to figure out where in the labyrinth to poke it...

[BillyONeal]

I tried granting "readers" permission to queue builds. Can you try once more? If this doesn't work I don't know if Pipelines can do that...

[miscco]

/azp run

[azure-pipelines]

Commenter does not have sufficient privileges for PR 548 in repo microsoft/STL

[miscco]

Hm, I am listed as Author and Contributor.

That said I really believe that running the tests should be something that you do when the PR is actually ready not me when I think I might want to test some more.

[BillyONeal]

We want you (or anyone else) to be able to poke the service if your build fails due to a spurious failure like "the HTTP request to restore the vcpkg cache got unhappy".

[BillyONeal]

"Contributors" already had access so maybe we're toast :/. Thanks for helping test!

[StephanTLavavej]

Looks good now, thanks! I'll port this to the Microsoft-internal repo.

[StephanTLavavej]

Thanks again for this interface update - it will ship in VS 2019 16.7 Preview 1.