call-next-method bug

[Gregor.pa@Xerox.COM]

There is a bug having to do with call-next-method in the current version
of PCL.  I know I am supposed to be fixing them, not reporting them, and
this message doesn't include a patch, but I thought I would let people
know about this problem.

In the following sequence, calling (foo (class-named 't)) will return T
instead of signalling an error.  This is because the extra "next-method"
from foo leaks through and is made available to bar.  This will be fixed
properly in the next version of PCL.

(defmethod foo ((x standard-class))
  (bar x))

(defmethod foo ((x class))
  (call-next-method))

(defmethod foo ((x t))
  t)

(defmethod bar ((x standard-class))
  (call-next-method))
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