Proposed resolution:

This wording is relative to N4901.

1. Modify [basic.string.general], as indicated:

   -3- In all cases, [data(), data() + size()] is a valid range, data() + size() points at an object with value charT() (a "null terminator"), and size() <= capacity() is true.

   -4- A size_type parameter type in a basic_string deduction guide refers to the size_type member type of the type deduced by the deduction guide.

   -?- The types iterator and const_iterator meet the constexpr iterator requirements ([iterator.requirements.general]).

[ 2022-02-10 Approved at February 2022 virtual plenary. Status changed: Tentatively Ready → WP. ]

[ 2022-01-30; Reflector poll ]

Set status to Tentatively Ready after six votes in favour during reflector poll.

std::vector's iterator and const_iterator are required to meet constexpr iterator requirements in C++20 per P1004R2, but it seems that the similar wording is missing for std::basic_string in both P0980R1 and the current working draft.

I think we should add a bullet "The types iterator and const_iterator meet the constexpr iterator requirements ([iterator.requirements.general])." to [basic.string.general].