private Node resolveFieldDataTypeNode(Symbol fieldDefinition) { 
        fieldDefinition = schemaIndex.getFirstSymbolDefinition(fieldDefinition).get();
        return resolveFieldDataTypeNode(fieldDefinition, new HashSet<>()); 
    }
Try to find the node that holds the dataType element
Also try to not fall into an infinite loop. It could possibly happen if there are cyclic field references somehow
integration/schema-language-server/language-server/src/main/java/ai/vespa/schemals/index/FieldIndex.java