find-class

(find-class symbol &optional (errorp t) environment)

Returns the class metaobject named by symbol -- a standard-class instance whose slots the class-name / closer-mop readers (class-slots, slot-definition-name, ...) consume. The answer is memoized, so two calls for the same class return the same (eq) object -- the same object class-of answers for an instance of that class. When no class is named symbol, an error is signaled unless errorp is nil, in which case nil is returned; environment is ignored. The known classes are every defclass / define-condition / defstruct in the program, the built-in condition hierarchy, and the built-in classes (integer, string, ..., t). On the compiled backends the class set is fixed at compile time; classes built from runtime data do not exist.

(setf (find-class alias) class) registers class under a second name: after it, find-class, make-instance, typep, subtypep and a handler-case clause all resolve the alias to the very same class (the metaobject is eq). Only this aliasing shape is supported -- the value must be a literal (find-class 'target) naming an already defined class -- and only at top level, because the compiled backends build their class table at compile time.