#<sb-c:tn> is not valid as the third argument to VOP: SB-KERNEL:%RAW-INSTANCE-SET/WORD

[Patrick Poitras]

We can trigger a bug using the following in a fresh session.

(funcall (lambda ()
           (DEFSTRUCT BLARG
             (A 0 :TYPE (unsigned-byte 64)))
           (MAKE-BLARG :A 123)))

#<SB-C:TN #:G320!1 :DEBUG-ENVIRONMENT> is not valid as the third argument to VOP:
  SB-KERNEL:%RAW-INSTANCE-SET/WORD
Primitive type: T
SC restrictions:
  (SB-VM::UNSIGNED-REG)
The primitive type disallows these loadable SCs:
  (SB-VM::UNSIGNED-REG)
   [Condition of type SIMPLE-ERROR]

Subsequent calls to this piece of code will not trigger the error.

SBCL Versions tested: 2.3.3 and 2.4.1.60-9863540f7

uname -a

Linux <username> 5.15.0-76-generic #83-Ubuntu SMP Thu Jun 15 19:16:32 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

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Additional notes:

This was noticed in the wild in the context of a testing suite that spawned test-related structures as part of the test.

Edit: `:type (unsigned-byte 64)` and `:type (signed-byte 64)` both throw this error, but the 8,16, and 32-bit equivalents do not.