There was already a static assert above that checked this:

```D
    static assert(bits == 32 || bits == 64 || bits == 96 || bits == 128 || bits == 160 || bits == 192,
                  "Supporting bits are 32, 64, 96, 128, 160 and 192. " ~ to!string(bits) ~ " is not supported.");
```

While an explicit check for 192 is always clearer and makes the code more robust, the only diagnostic here worth throwing would be: "Phobos Error". Because if we hit that line, that's what it is.