Pop Quiz what is wrong with this code?

[Danni Coy]

...
foreach (y, ref row; offsetMap)
{
   auto run = 0;
    auto nPixels = 0;
    foreach (x; 0..size.x)
    {
         immutable SDL_FPair offset  = { center.x - x, y - center.y };
...

and why does it violate the principle of making the right thing the
easy thing to do?