+417: Toplevel NIL expressions mess up unreachable code reporting.
+ In sbcl-1.0.10.7, COMPILE-FILE on the file
+ nil
+ (defmethod frob ((package package) stream)
+ (if (string= (package-name package) "FOO")
+ (pprint-logical-block (stream nil))
+ (print-unreadable-object (package stream))))
+ causes complaints like
+ ; in: SOME SB-C::STRANGE SB-C::PLACE
+ ; (SB-C::UNABLE SB-C::TO SB-C::LOCATE SB-C::SOURCE)
+ ;
+ ; note: deleting unreachable code
+ ;
+ ; note: deleting unreachable code
+ Deleting the toplevel NIL, or even replacing it with 3,
+ causes the system not to complain.