Variable AttachmentDescription.stencilOps

the operations to be performed on the attachment color and depth attachments may only need to define the ops member depth-stencil attachments must define both ops (for depth) and stencilOps members.

struct AttachmentDescription
{
  // ...
  AttachmentOps stencilOps = AttachmentOps(cast(LoadOp)2, cast(StoreOp)1);
  // ...
}