anchor.diff:  (defn copy-buffer-backed-gpu-array-to-texture-backed-gpu-array
       ((src gpu-array-bb) (dst gpu-array-t))
       gpu-array-t
  -  (upload-gpu-array-bb-to-gpu-array-t
  -   dst src
  -   (gpu-array-bb-element-pixel-format src))
  +  (upload-gpu-array-bb-to-gpu-array-t dst src)
     dst)
   
   
  
positive.code:               (texture-type (or (establish-texture-type rank nil nil nil po2p nil t nil)
                                  (error "Could not extablish a buffer-texture-type with dimensions ~a"
                                         dimensions))))
           (assert-valid-args-for-buffer-backend-texture
            image-format cubes rectangle multisample mipmap layer-count
            texture-type)
           (values (make-gpu-array nil :dimensions dimensions :element-type element-type)
  
negative.code:       (t (error "not currently supported for upload: ~a" tex-type)))))
  
  
  ;;------------------------------------------------------------
  
  (define-const +valid-texture-storage-options+
  