multiple slot descriptions of the same slot in a DEFSTRUCT

[Kahn.pa@Xerox.ARPA]

What does the following mean?

(defstruct foo (a 0) (a 1))

is it equivalent to 

(defstruct foo (a 1))


Along the same lines, is it an error when using the :include option to
"over-ride" a default as follows

(defstruct (bar (:include foo)) (a 2))

or does this work as well as the advertised:

(defstruct (bar (:include foo (a 2)))