Proposed resolution:

This wording is relative to N4917.

1. Modify [flat.map.overview] as indicated:

   -7- Any sequence container ([sequence.reqmts])type C supporting Cpp17RandomAccessIteratorthat meets sequence container requirements ([sequence.reqmts]) can be used to instantiate flat_map, as long as C::iterator meets the Cpp17RandomAccessIterator requirements and invocations of member functions C::size and C::max_size do not exit via an exception. In particular, vector ([vector]) and deque ([deque]) can be used.

2. Modify [flat.multimap.overview] as indicated:

   -7- Any sequence container ([sequence.reqmts])type C supporting Cpp17RandomAccessIteratorthat meets sequence container requirements ([sequence.reqmts]) can be used to instantiate flat_multimap, as long as C::iterator meets the Cpp17RandomAccessIterator requirements and invocations of member functions C::size and C::max_size do not exit via an exception. In particular, vector ([vector]) and deque ([deque]) can be used.

[ 2022-11-12 Approved at November 2022 meeting in Kona. Status changed: Immediate → WP. ]

[ Kona 2022-11-08; Move to Immediate status ]

This is resolution of US 42-103 ([flat.map.overview] p6 [flat.multimap.overview] p6 Clearing when restoring invariants).

Currently both [flat.map.overview] p7 and [flat.multimap.overview] p7 claims that flat_(multi)map supports "Any sequence container ([sequence.reqmts]) C supporting Cpp17RandomAccessIterator", which arguably includes std::array (see LWG 617). This is incorrect as std::array does not provide operations required to restored these adaptors invariant, including clear. We should require that C meets sequence container requirements, and we state that fact explicitly in [array.overview] p3: "An array meets some of the requirements of a sequence container ([sequence.reqmts])".