Bump to v4.0.0.

internal/mapDelete.js

@@ -1,14 +1,23 @@
+import Map from './Map';
+import assocDelete from './assocDelete';
+import hashDelete from './hashDelete';
+import isKeyable from './isKeyable';
+
 /**
- * Removes `key` and its value from the cache.
+ * Removes `key` and its value from the map.
  *
  * @private
  * @name delete
- * @memberOf _.memoize.Cache
+ * @memberOf MapCache
  * @param {string} key The key of the value to remove.
- * @returns {boolean} Returns `true` if the entry was removed successfully, else `false`.
+ * @returns {boolean} Returns `true` if the entry was removed, else `false`.
  */
 function mapDelete(key) {
-  return this.has(key) && delete this.__data__[key];
+  var data = this.__data__;
+  if (isKeyable(key)) {
+    return hashDelete(typeof key == 'string' ? data.string : data.hash, key);
+  }
+  return Map ? data.map['delete'](key) : assocDelete(data.map, key);
 }
 
 export default mapDelete;