* * the error causes, thus considering all error nodes equal to each other but not to any other node.
 */
fun DeclarativeDocument.structurallyEqualsAsData(other: DeclarativeDocument): Boolean {
    fun ValueNode.structurallyEquals(other: ValueNode): Boolean = when (this) {
        is LiteralValueNode -> other is LiteralValueNode &&
            value == other.value

            parsed, new SourceIdentifier("test")
        )
        def expectedDocument = LanguageTreeToDomKt.toDocument(languageTree)
        DataStructuralEqualityKt.structurallyEqualsAsData(doc, expectedDocument)
    }