Use msvc-x64 mode with a C file, because designated initializers aren't supported in clang/gcc modes until 0.17.8.

Hover over .x in the following example (from #2363 ):

struct foo {
    int x;
};

struct bar {
    struct foo;
    int y;
};

int main() {
    struct bar bar = {.x=12, .y=13};
    return 0;
}