In Monte, this object is proven by the compiler/interpreter to be transitively immutable:

  object popsicle as DeepFrozen:
    to getFlavor() :Str:
      # Obviously immutable.
      return "lime"

    to getObservedColor(eye):
      # The eye might not be immutable, but that's still okay.
      # All that's required is that this object not secretly stash the eye.
      return eye.observeCMYK(38, 0, 78, 1)

You radically underestimate the intelligence of your fellow humans.