Proposed resolution:
This wording is relative to N4917.
Modify [range.iota.iterator] as indicated:
[…]namespace std::ranges { template<weakly_incrementable W, semiregular Bound> requires weakly-equality-comparable-with<W, Bound> && copyable<W> struct iota_view<W, Bound>::iterator { private: W value_ = W(); // exposition only public: […] friend constexpr iterator operator-(iterator i, difference_type n) requires advanceable<W>; friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires advanceable<W> || sized_sentinel_for<W, W>; }; }friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires advanceable<W> || sized_sentinel_for<W, W>;-23- Effects: Equivalent to:
using D = difference_type; if constexpr (is-integer-like<W>) { if constexpr (is-signed-integer-like<W>) return D(D(x.value_) - D(y.value_)); else return (y.value_ > x.value_) ? D(-D(y.value_ - x.value_)) : D(x.value_ - y.value_); } else { return x.value_ - y.value_; }