The value NIL is not of type SB-C::LVAR (type-incorrect structure accessor)

[Paul F. Dietz]

(defstruct (foo (:type list))
  (x nil)
  (y 0))

(lambda (a)
  (setf (foo-x :b) nil ;; :b is type-incorrect here
        (foo-y a) 0))

===>

The value
  NIL
is not of type
  SB-C::LVAR
   [Condition of type TYPE-ERROR]
[...]
  0: (SB-C::LAMBDA-VAR-REF-LVAR #<SB-C::REF :%SOURCE-NAME STRUCTURE :LEAF #<SB-C::LAMBDA-VAR :%SOURCE-NAME STRUCTURE :TYPE #<SB-KERNEL:UNION-TYPE LIST> :WHERE-FROM :DECLARED {10064A9B93}> {10064AAA53}>)
  1: (SB-C::MAY-DELETE-MODIFYING-CAST #<SB-C::MODIFYING-CAST :%TYPE-CHECK T :VALUE #<SB-C::LVAR 1 {10064AA933}> :ASSERTED-TYPE #1=#<SB-KERNEL:UNION-TYPE SEQUENCE> :TYPE-TO-CHECK #1# {10064AAEA3}>)
  2: (SB-C::MAYBE-DELETE-CAST #<SB-C::MODIFYING-CAST :%TYPE-CHECK T :VALUE #<SB-C::LVAR 1 {10064AA933}> :ASSERTED-TYPE #1=#<SB-KERNEL:UNION-TYPE SEQUENCE> :TYPE-TO-CHECK #1# {10064AAEA3}>)
  3: (SB-C::IR1-OPTIMIZE-CAST #<SB-C::MODIFYING-CAST :%TYPE-CHECK T :VALUE #<SB-C::LVAR 1 {10064AA933}> :ASSERTED-TYPE #1=#<SB-KERNEL:UNION-TYPE SEQUENCE> :TYPE-TO-CHECK #1# {10064AAEA3}>)
 [...]

[Stas Boukarev (stassats)]

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