(setf (find-class x) nil) doesn't completely remove the class

[Stas Boukarev]

(progn (defclass abc () ())
       (lambda (x) (typep x 'abc))
       (setf (find-class 'abc) nil)
       (lambda (x) (typep x 'abc)))

can't compile TYPEP of anonymous or undefined class:
  #<STANDARD-CLASSOID anonymous {1007EE8B73}>

This is because specifier-type caches the result

(progn (defclass abc () ())
       (sb-kernel:specifier-type 'abc)
       (setf (find-class 'abc) nil)
       (sb-kernel:specifier-type 'abc))
=>
#<STANDARD-CLASSOID anonymous {10093AF653}>

[Stas Boukarev (stassats)]

sb-kernel:%clear-classoid should probably call values-specifier-type-cache-clear, but how many other caches are there where it can hide?

[Stas Boukarev (stassats)]

Did just that in 1f3c06ef4d1e1d61cea3156ce76e637c4c6a4225.