private
    val elementErrors = IdentityHashMap<LanguageTreeElement, MutableList<ResolutionError>>()

    override fun assignmentResolution(assignment: Assignment): ResolutionTrace.ResolutionOrErrors<AssignmentRecord> =
        assignmentResolutions[assignment]?.let { resolution ->
            check(assignment !in elementErrors)
            Resolution(resolution)
        } ?: elementErrors[assignment]?.let { errors ->