constexpr string_view operator "" sv(const char* str, size_t len) noexcept;
Returns: string_view{str, len}.
constexpr u16string_view operator "" sv(const char16_t* str, size_t len) noexcept;
Returns: u16string_view{str, len}.
constexpr u32string_view operator "" sv(const char32_t* str, size_t len) noexcept;
Returns: u32string_view{str, len}.
constexpr wstring_view operator "" sv(const wchar_t* str, size_t len) noexcept;
Returns: wstring_view{str, len}.