known-packages-plus

(in-package "ACL2")

(define known-packages+
  (state)
  :returns (pkg-names string-listp)
  :parents (std/system)
  :short "Enhanced variant of @(tsee known-packages)."
  :long (topstring-p "This returns the same result as @(tsee known-packages),
    but it includes a run-time check (which should always succeed) on the result
    that allows us to prove the return type theorem
    without strengthening the guard on @('state').")
  (b* ((result (known-packages state)))
    (if (string-listp result)
      result
      (raise "Internal error: ~
              the list of keys ~x0 of the alist of known packages ~
              is not a true list of strings."
        result))))