built-in-class,
class,
standard-object,
t
A built-in class is a class whose instances have
restricted capabilities or special representations.
Attempting to use
defclass to define subclasses of a built-in class
signals an error of type error.
Calling make-instance to create an instance
of a built-in class signals an error of type error.
Calling slot-value on an instance of a built-in class
signals an error of type error. Redefining a built-in class
or using change-class to change the class of an instance
to or from a built-in class signals an error of type error.
However, built-in classes can be used as parameter specializers
in methods.