- * Return a function which combines a part of the filename with a scope, for use in logging.
- * @param {string} filename
+ * @callback ScopeFn
+ * @param {String} scope
+ * @returns {String}
+ */
+/**
+ * Return a function which prefixes a provided scope with the most-
+ * relevant part of the filename, for use in logging.
+ * @param {String} filename
+ * @returns {ScopeFn}