Uncaught compiler error for FTYPE with invalid function name

[Paul F. Dietz]

 (lambda () (declare (ftype (function () t) (foo))))

===>

Invalid function name: (FOO)
   [Condition of type SIMPLE-TYPE-ERROR]
[...]
  0: (FBOUNDP (FOO))
  1: (SB-C::PROCESS-FTYPE-DECL (FUNCTION NIL T) #S(SB-KERNEL:LEXENV :FUNS NIL :VARS NIL :BLOCKS NIL :TAGS NIL :TYPE-RESTRICTIONS NIL :LAMBDA NIL ...) ((FOO)) NIL :COMPILE)
  2: (SB-C::PROCESS-1-DECL (FTYPE (FUNCTION NIL T) (FOO)) #S(SB-KERNEL:LEXENV :FUNS NIL :VARS NIL :BLOCKS NIL :TAGS NIL :TYPE-RESTRICTIONS NIL :LAMBDA NIL ...) NIL NIL T :COMPILE)
[...]