Binding
class BindingException(val unresolved: String, val available: List<String>, val hint: String? = null) : RuntimeException(source)
A declared name that does not resolve against the element it was given to.
hint carries the reason when the plain "no such name" reading would be wrong — most often a LeverRef that resolves perfectly well, just not here. E.3 requires the message to name the unresolved item and list what was available; when the two elements share an alias, that pair alone reads as a contradiction ("staff is unavailable; available: staff"), so the hint is what makes the message actionable rather than baffling.