P30 - Attempt to find routes through an implicit relation

Most problems are detected when Inform translates the source text, but this is one of the exceptions, a "run-time problem" which emerges only during play.

Finding the best route through a relation, or counting the number of steps from one thing to another in the sense of a given relation, is not allowed for relations which are hard-wired into the spatial structure used by Inform (things such as containment or support), or for relations defined explicitly by conditions. It's only allowed for relations created in your own source text and which you can set and unset at will.