Compile error escaping from sb-rotate-byte:rotate-byte: bad size specified for UNSIGNED-BYTE type specifier: 0

[Paul F. Dietz]

(compile nil '(lambda (x s) (sb-rotate-byte:rotate-byte s (byte 0 1) x)))

==>

bad size specified for UNSIGNED-BYTE type specifier: 0
   [Condition of type SIMPLE-ERROR]

Restarts:
 0: [RETRY] Retry SLIME REPL evaluation request.
 1: [*ABORT] Return to SLIME's top level.
 2: [ABORT] abort thread (#<THREAD "new-repl-thread" RUNNING {10440A2463}>)

Backtrace:
  0: ((SB-IMPL::TYPE-EXPANDER UNSIGNED-BYTE) (UNSIGNED-BYTE 0))
  1: (SB-KERNEL::%PARSE-TYPE (UNSIGNED-BYTE 0) #S(SB-KERNEL::TYPE-CONTEXT :SPEC (UNSIGNED-BYTE 0) :PROTO-CLASSOID NIL :CACHEABLE T))
  2: (SB-KERNEL::BASIC-PARSE-TYPESPEC (UNSIGNED-BYTE 0) #S(SB-KERNEL::TYPE-CONTEXT :SPEC (UNSIGNED-BYTE 0) :PROTO-CLASSOID NIL :CACHEABLE T))
  3: (SB-KERNEL:SPECIFIER-TYPE (UNSIGNED-BYTE 0) NIL NIL)
  4: (SB-ROTATE-BYTE::%ROTATE-BYTE-DERIVE-TYPE-OPTIMIZER #<SB-C::COMBINATION :FUN #<SB-C::REF :LEAF #<SB-C::GLOBAL-VAR :%SOURCE-NAME SB-ROTATE-BYTE::%ROTATE-BYTE :TYPE #1=#<SB-KERNEL:FUN-TYPE #> :DEFINED-..
  5: ((FLET SB-C::PROCESS-INFO :IN SB-C::IR1-OPTIMIZE-COMBINATION))
  6: (SB-C::IR1-OPTIMIZE-COMBINATION #<SB-C::COMBINATION :FUN #<SB-C::REF :LEAF #<SB-C::GLOBAL-VAR :%SOURCE-NAME SB-ROTATE-BYTE::%ROTATE-BYTE :TYPE #1=#<SB-KERNEL:FUN-TYPE #> :DEFINED-TYPE #1# :WHERE-FROM..
  7: (SB-C::IR1-OPTIMIZE #<SB-C:COMPONENT :NAME (LAMBDA (X S)) {10440D6DD3}> NIL)
  8: (SB-C::IR1-OPTIMIZE-UNTIL-DONE #<SB-C:COMPONENT :NAME (LAMBDA (X S)) {10440D6DD3}>)