Proposed resolution:

This wording is relative to N4971.

1. Modify [range.repeat.view], class template repeat_view synopsis, as indicated:

   [Drafting note: The proposed wording has been suggested by Casey Carter, see microsoft/STL#3576]

   namespace std::ranges {
     […]
   
     template<class T, class Bound = unreachable_sentinel_t>
       repeat_view(T, Bound = Bound()) -> repeat_view<T, Bound>;
   }
   

[ Tokyo 2024-03-23; Status changed: Voting → WP. ]

[ 2024-03-12; Reflector poll ]

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

Currently, a binary call to std::views::repeat decay the arguments due to the deduction guide, but a unary call doesn't, which is inconsistent.

For example:

#include <concepts>
#include <ranges>

using RPV = std::ranges::repeat_view<const char*>;

static_assert(std::same_as<decltype(std::views::repeat("foo", std::unreachable_sentinel)), RPV>); // OK
static_assert(std::same_as<decltype(std::views::repeat(+"foo", std::unreachable_sentinel)), RPV>); // OK
static_assert(std::same_as<decltype(std::views::repeat("foo")), RPV>); // ill-formed
static_assert(std::same_as<decltype(std::views::repeat(+"foo")), RPV>); // OK

Presumably we should extend the deduction guide of std::ranges::repeat_view to cover the unary cases.