[Sbcl-help] The binding of SB-C::Y is not a REAL

[Steven Nunez via Sbcl-help]

Does anyone know why the warning in the subject line is thrown from this code?  I've isolated the error (show below), and looked at the macro expansion, and it seems like this should not be a warning.

(defun %product-vector-array (vector array &optional result)
  "Return the result of the array premultiplied by the vector."
  (loop

    ;; with m-rows = (aops:nrow array) and n-columns = (aops:ncol array) ;; this works

    with (m-rows n-columns) = (array-dimensions array) ;; ERROR IS HERE

    with result = (or result (zero-vector n-columns (array-element-type vector)))
    for column below n-columns
    do (setf (aref result column) (loop
                    for row below m-rows
                    sum (* (aref vector row) (aref array row column))))
    finally (return result)))

    Steve