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Section: 25.3.4.2 [iterator.concept.readable] Status: Resolved Submitter: Eric Niebler Opened: 2019-09-09 Last modified: 2020-09-06
Priority: 1
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Discussion:
In the current spec, shared_ptr<int> is readable, but shared_ptr<int>& is not. That is because readable_traits is not stripping top-level references before testing for nested typedefs.
Either readable_traits should see through cv- and ref-qualifiers, or else the readable concept should strip top-level references when building the iter_value_t associated type (e.g., iter_value_t<remove_reference_t<In>>). Suggest priority P1 because it effects the definition of a concept which cannot change after C++20.[2019-10 Priority set to 1 after reflector discussion]
[2019-11 This should be resolved by P1878]
Previous resolution [SUPERSEDED]:
This wording is relative to N4830.
Modify 25.3.4.2 [iterator.concept.readable], concept readable synopsis, as indicated:
template<class In> concept readable = requires { typename iter_value_t<remove_reference_t<In>>; typename iter_reference_t<In>; typename iter_rvalue_reference_t<In>; } && common_reference_with<iter_reference_t<In>&&, iter_value_t<remove_reference_t<In>>&> && common_reference_with<iter_reference_t<In>&&, iter_rvalue_reference_t<In>&&> && common_reference_with<iter_rvalue_reference_t<In>&&, const iter_value_t<remove_reference_t<In>>&>;
[2019-11; Resolved by the adoption of P1878 in Belfast]
Proposed resolution:
Resolved by P1878.