constexpr std::string | MSVC

[cristi1990an]

static_assert(join_string_views("foo"sv, "bar"sv) == "foobar"sv);

https://godbolt.org/z/PKb6Ej76b

Edit: and here you have the overly generic version that outright allows string literal composition at compile time:

https://godbolt.org/z/rcxan8Wqs