to

static struct S
{
    int a;
    string b;
    bool c;
}

static struct SS
{
    string name;
    S s;
}

assert(127.to!String == "127");
assert(S(29, "yolo", true).to!String == `S(29, "yolo", true)`);
assert(SS("ribena cow", S(69, "swag", false)).to!String == `SS("ribena cow", S(69, "swag", false))`);