[Bug c++/122070] [14/15/16 Regression] ICE in C++23 type deduction since r15-2864

[egas.g.ribeiro at tecnico dot ulisboa.pt via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122070

Egas  Ribeiro <egas.g.ribeiro at tecnico dot ulisboa.pt> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|needs-reduction             |

--- Comment #3 from Egas  Ribeiro <egas.g.ribeiro at tecnico dot ulisboa.pt> ---
i made a reduced test case:

// { dg-do compile { target c++23 } }

namespace std {
    template<typename T, T v> struct integral_constant { static constexpr T
value = v; };
    using size_t = decltype(sizeof(0));

    template<typename CharT>
    struct basic_string_view {
        const CharT* ptr;
        size_t len;
        constexpr basic_string_view(const CharT* p) : ptr(p), len(0) { while (p
&& p[len]) ++len; }
    };
    using string_view = basic_string_view<char>;
}

template<std::size_t N>
struct sized_string_view: std::string_view {
    using std::string_view::string_view;
};
template<std::size_t N>
sized_string_view(const char (&str)[N]) -> sized_string_view<N - 1>;


constexpr auto string_builder(auto first, auto second, auto... trailing) {
    constexpr auto is_last = sizeof...(trailing) == 0;
    auto buffer = 1;
    if constexpr (is_last) {
        return buffer;
    } else
        return string_builder(buffer, trailing...);
}

constexpr auto copyright = string_builder(sized_string_view("a"),
sized_string_view("b"), sized_string_view("c"));