Class struct_with_empty

test/test_alignment.cpp:51–55

struct empty {};

struct struct_with_empty {
    alignas(sizeof(int) * 2) int a;
    TUPLET_NO_UNIQUE_ADDRESS empty b;
    int c;
};

#if TUPLET_HAS_NO_UNIQUE_ADDRESS && !(defined _MSC_VER)
static_assert(offsetof(struct_with_empty, b) == 0);