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4351. integral-constant-like needs more remove_cvref_t

Section: 23.7.2.1 [span.syn] Status: New Submitter: Jonathan Wakely Opened: 2025-09-05 Last modified: 2025-09-07

Priority: Not Prioritized

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Discussion:

P2781R9 tweaked the definition of integral-constant-like to work with constant_wrapper, like so:

template<class T>
    concept integral-constant-like =                    // exposition only
      is_integral_v<remove_cvref_t<decltype(T::value)>> &&
      !is_same_v<bool, remove_const_t<decltype(T::value)>> &&
      convertible_to<T, decltype(T::value)> &&
      equality_comparable_with<T, decltype(T::value)> &&
      bool_constant<T() == T::value>::value &&
      bool_constant<static_cast<decltype(T::value)>(T()) == T::value>::value;

This was done so that cw<5> models the concept, but it needs an additional tweak so that cw<true> does not model it.

Proposed resolution:

This wording is relative to N5014.

1. Modify 23.7.2.1 [span.syn] as indicated:

   template<class T>
       concept integral-constant-like =                    // exposition only
         is_integral_v<remove_cvref_t<decltype(T::value)>> &&
         !is_same_v<bool, remove_cvrefconst_t<decltype(T::value)>> &&
         convertible_to<T, decltype(T::value)> &&
         equality_comparable_with<T, decltype(T::value)> &&
         bool_constant<T() == T::value>::value &&
         bool_constant<static_cast<decltype(T::value)>(T()) == T::value>::value;