POSITION miscompiles on a constant sequence containing OTHERWISE

[Paul F. Dietz]

(funcall (lambda (x) (position x '(a otherwise b))) 'a)

==>

Execution of a form compiled with errors.
Form:
  (CASE SB-C::ITEM (A 0) (OTHERWISE 1) (B 2))
Compile-time error:
  during macroexpansion of (CASE SB-C::ITEM (A 0) ...). Use *BREAK-ON-SIGNALS* to
intercept.

 Bad CASE clause:
   (OTHERWISE 1)
 OTHERWISE allowed as the key designator only in the final otherwise-clause,
 not in a normal-clause. Use (OTHERWISE) instead, or move the clause to the
 correct position.
See also:
  The ANSI Standard, Macro CASE
   [Condition of type SB-INT:COMPILED-PROGRAM-ERROR]

Restarts:
 0: [ABORT] Exit debugger, returning to top level.

Backtrace:
  0: ((LAMBDA (X)) #<unused argument>)
  1: (SB-INT:SIMPLE-EVAL-IN-LEXENV (FUNCALL (LAMBDA (X) (POSITION X #)) (QUOTE A)) #<NULL-LEXENV>)
  2: (EVAL (FUNCALL (LAMBDA (X) (POSITION X #)) (QUOTE A)))
 [...]