Meta LWG issue: 2023-11 meeting

[StephanTLavavej]

(Previous meta-issue: #3778)

At the November 2023 meeting, the following LWG issues were resolved in the C++ Working Paper.

❔ Not yet analyzed

• Remaining issues:
  • All done!

❌ Not applicable

If an issue requires no action from implementers, we mark it as N/A. Categories:

• Pure wording clarifications with nothing to implement (these can be changes to non-normative text like examples and informative notes, or wording cleanups to normative text that don't impact observable behavior)

  • LWG-2392 "character type" is used but not defined
  • LWG-3203 span element access invalidation
  • LWG-3957 [container.alloc.reqmts] The value category of v should be claimed
  • LWG-3965 Incorrect example in [format.string.escaped]/3 for formatting of combining characters
    • Our implementation agrees with the corrected example.

• Something that increases the restrictions placed on users, but implementers aren't expected to enforce those restrictions

  • LWG-3990 Program-defined specializations of tuple and variant can't be properly supported

• Fixes for obviously broken wording, where implementers would have done the right thing anyways

  • LWG-3431 <=> for containers should require three_way_comparable<T> instead of <=>
  • LWG-3951 [expected.object.swap]: Using value() instead of has_value()

😸 Already implemented

Sometimes we cite LWG issues in product code comments as we're implementing their proposed resolutions. When the resolutions are officially accepted, we should remove the citations (as the default assumption is that we're implementing what the Standard says). If something is especially subtle, we can convert the citation to mention the relevant Standard section. Sometimes we should add test coverage - e.g. when the Standard begins requiring something that we were already doing, but weren't explicitly testing for.

• Already implemented, comments need to be removed and messages need to cite the Standard
  • LWG-3949 atomic<bool>'s trivial destructor dropped in C++17 spec wording
    • Filed LWG-3949 atomic<bool>'s trivial destructor dropped in C++17 spec wording #4164.
• Implemented without comments
  • LWG-3305 any_cast<void>
    • We implemented dedicated static_asserts for this.
  • LWG-3948 possibly-const-range and as-const-pointer should be noexcept
  • LWG-3973 Monadic operations should be ADL-proof

🩹 Patches an unimplemented feature

We should record this LWG issue in the GitHub issue tracking the feature. That way, we'll remember to verify it, but it doesn't represent net new work.

• LWG-3892 Incorrect formatting of nested ranges and tuples
  • Recorded in P2286R8 Formatting Ranges #2919.
• LWG-3970 [mdspan.syn] Missing definition of full_extent_t and full_extent
  • Recorded in P2630R4 submdspan #3807.
• LWG-3987 Including <flat_meow> doesn't provide std::begin/end
  • Recorded in P0429R9 <flat_map> #2910 and P1222R4 <flat_set> #2912.

🐞 Not yet implemented

• Filed a GitHub issue labeled LWG

  • LWG-3749 common_iterator should handle integer-class difference types
    • Filed LWG-3749 common_iterator should handle integer-class difference types #4163.
  • LWG-3809 Is subtract_with_carry_engine<uint16_t> supposed to work?
    • Filed LWG-3809 Is subtract_with_carry_engine<uint16_t> supposed to work? #4162.
  • LWG-3897 inout_ptr will not update raw pointer to null
    • Filed LWG-3897 inout_ptr will not update raw pointer to null #4160.
  • LWG-3946 The definition of const_iterator_t should be reworked
    • Filed LWG-3946 The definition of const_iterator_t should be reworked #4161.
  • LWG-3947 Unexpected constraints on adjacent_transform_view::base()
    • Filed LWG-3947 Unexpected constraints on adjacent_transform_view::base() #4165.
  • LWG-3953 iter_move for common_iterator and counted_iterator should return decltype(auto)
    • Filed LWG-3953 iter_move for common_iterator and counted_iterator should return decltype(auto) #4157.
  • LWG-3974 mdspan::operator[] should not copy OtherIndexTypes
    • Might already be implemented, filed LWG-3974 mdspan::operator[] should not copy OtherIndexTypes #4166 to double-check.
  • LWG-4001 iota_view should provide empty
    • Filed LWG-4001 iota_view should provide empty #4159.

• PR out for review