[libc++][docs] Mark LWG3420 complete

[jloser]

Summary

Mark LWG3420 as complete. Currently, the cpp17_iterator concept
checks that the type looks like an iterator first before checking if it
is copyable.

[• Quuxplusone]

Confirmed, we already implement the resolution here. LGTM! (Please wait for a second libc++ approver before landing.)

[ldionne]

LGTM, but can you confirm we have a test for that? Also, the commit you linked to isn't the right one, 120fa8293e22f760374a5757d081dc674046e0f0 is just moving stuff around. You should fix the commit message.

[ldionne]

libcxx/docs/Status/Cxx2bIssues.csv

26–27

Also, this wasn't done in LLVM 11 since we didn't implement concepts then, 14 is when we'll ship them for the first time.

[jloser]

[NFC] Update commit message

[jloser]

In D111598#3058500, @ldionne wrote:

LGTM, but can you confirm we have a test for that? Also, the commit you linked to isn't the right one, 120fa8293e22f760374a5757d081dc674046e0f0 is just moving stuff around. You should fix the commit message.

__cpp17_iterator seems to get used pretty heavily in libcxx/test/libcxx/iterators/iterator.requirements/iterator.assoc.types/iterator.traits/legacy_iterator.compile.pass.cpp. Is this what you had in mind or something more specific?

libcxx/docs/Status/Cxx2bIssues.csv

26–27

Fixed, thanks!

[jloser]

[NFC] Fix commit message

[jloser]

In D111598#3060264, @jloser wrote:

In D111598#3058500, @ldionne wrote:

LGTM, but can you confirm we have a test for that? Also, the commit you linked to isn't the right one, 120fa8293e22f760374a5757d081dc674046e0f0 is just moving stuff around. You should fix the commit message.

__cpp17_iterator seems to get used pretty heavily in libcxx/test/libcxx/iterators/iterator.requirements/iterator.assoc.types/iterator.traits/legacy_iterator.compile.pass.cpp. Is this what you had in mind or something more specific?

@ldionne I just landed this, but if you think of a test you'd like to see (beyond what we have now), let me know.

libcxx/docs/Status/Cxx2bIssues.csv

 "`3170 <https://wg21.link/LWG3170>`__","``is_always_equal`` added to ``std::allocator`` makes the standard library treat derived types as always equal","November 2020","",""
 "`3036 <https://wg21.link/LWG3036>`__","``polymorphic_allocator::destroy`` is extraneous","November 2020","",""
 "`3171 <https://wg21.link/LWG3171>`__","LWG2989 breaks ``directory_entry`` stream insertion","November 2020","",""
 "`3306 <https://wg21.link/LWG3306>`__","``ranges::advance`` violates its preconditions","November 2020","","","|ranges|"
 "`3403 <https://wg21.link/LWG3403>`__","Domain of ``ranges::ssize(E)`` doesn't ``match ranges::size(E)``","November 2020","","","|ranges|"
 "`3404 <https://wg21.link/LWG3404>`__","Finish removing subrange's conversions from pair-like","November 2020","","","|ranges|"
 "`3405 <https://wg21.link/LWG3405>`__","``common_view``'s converting constructor is bad, too","November 2020","","","|ranges|"
 "`3406 <https://wg21.link/LWG3406>`__","``elements_view::begin()`` and ``elements_view::end()`` have incompatible constraints","November 2020","","","|ranges|"
 "`3419 <https://wg21.link/LWG3419>`__","[algorithms.requirements]/15 doesn't reserve as many rights as it intends to","November 2020","",""
-"`3420 <https://wg21.link/LWG3420>`__","cpp17-iterator should check that the type looks like an iterator first","November 2020","","","|ranges|"
+"`3420 <https://wg21.link/LWG3420>`__","cpp17-iterator should check that the type looks like an iterator first","November 2020","|Complete|","14.0","|ranges|"
 "`3421 <https://wg21.link/LWG3421>`__","Imperfect ADL emulation for boolean-testable","November 2020","","","|ranges|"
 "`3425 <https://wg21.link/LWG3425>`__","``condition_variable_any`` fails to constrain its Lock parameters","November 2020","",""
 "`3426 <https://wg21.link/LWG3426>`__","``operator<=>(const unique_ptr<T, D>&, nullptr_t)`` can't get no satisfaction","November 2020","","","|spaceship|"
 "`3427 <https://wg21.link/LWG3427>`__","``operator<=>(const shared_ptr<T>&, nullptr_t)`` definition ill-formed","November 2020","","","|spaceship|"
 "`3428 <https://wg21.link/LWG3428>`__","``single_view``'s in place constructor should be explicit","November 2020","","","|ranges|"
 "`3434 <https://wg21.link/LWG3434>`__","``ios_base`` never reclaims memory for iarray and parray","November 2020","",""
 "`3437 <https://wg21.link/LWG3437>`__","``__cpp_lib_polymorphic_allocator`` is in the wrong header","November 2020","",""
 "`3446 <https://wg21.link/LWG3446>`__","``indirectly_readable_traits`` ambiguity for types with both ``value_type`` and ``element_type``","November 2020","","","|ranges|"