The value NIL is not of type SB-C::TAIL-SET (in IR1)

[Paul F. Dietz]

(declaim (special *s2* *s6* *s9*))
(compile nil
         '(lambda (a)
           (dotimes
               (iv1 0
                (block b3
                  (let ((*s2*
                         (cons
                          (ash
                           (flet ((%f2 (&optional (f2-4 a) (f2-5 a))
                                    f2-4))
                             (progv '(*s6*) (list 0) a)
                             )
                           (min 81 (return-from b3 0)))
                          0)))
                    (progv '(*s9*) (list 0) 0))))
             (unwind-protect 0))))

==>

The value
  NIL
is not of type
  SB-C::TAIL-SET
   [Condition of type TYPE-ERROR]

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

Backtrace:
  0: (SB-C::MERGE-TAIL-SETS #<SB-C::COMBINATION :FUN #<SB-C::REF :LEAF #<SB-C::CLAMBDA :%SOURCE-NAME SB-C::.ANONYMOUS. :%DEBUG-NAME # :KIND :DELETED :TYPE #<SB-KERNEL:BUILT-IN-CLASSOID FUNCTION (read-only..
  1: (SB-C::DELETE-FILTER #<SB-EXT:EXIT :ENTRY #<SB-C::ENTRY {1006715AD3}> :VALUE #<SB-C::LVAR 1 {10067210D3}> {1006721113}> #<SB-C::LVAR 2 {1006715183}> #<SB-C::LVAR 1 {10067210D3}>)
  2: (SB-C::IR1-OPTIMIZE #<SB-C:COMPONENT :NAME (LAMBDA (&OPTIONAL #:NEXT5 #:START6 #:COUNT7 &REST #:G8) :IN #:DROP-THRU-TAG-3) :REANALYZE T {100675FC83}> NIL)
  3: (SB-C::IR1-OPTIMIZE-UNTIL-DONE #<SB-C:COMPONENT :NAME (LAMBDA (&OPTIONAL #:NEXT5 #:START6 #:COUNT7 &REST #:G8) :IN #:DROP-THRU-TAG-3) :REANALYZE T {100675FC83}>)
  4: (SB-C::IR1-PHASES #<SB-C:COMPONENT :NAME (LAMBDA (&OPTIONAL #:NEXT5 #:START6 #:COUNT7 &REST #:G8) :IN #:DROP-THRU-TAG-3) :REANALYZE T {100675FC83}>)
  5: (SB-C::COMPILE-COMPONENT #<SB-C:COMPONENT :NAME (LAMBDA (&OPTIONAL #:NEXT5 #:START6 #:COUNT7 &REST #:G8) :IN #:DROP-THRU-TAG-3) :REANALYZE T {100675FC83}>)

[Stas Boukarev (stassats)]

In 442d898a9f427d6ed36e8d916ee4ad0f8a3e0b15