feat(MessageMentions): add repliedUser (#5905)

src/structures/Message.js

@@ -190,7 +190,14 @@ class Message extends Base {
      * All valid mentions that the message contains
      * @type {MessageMentions}
      */
-    this.mentions = new Mentions(this, data.mentions, data.mention_roles, data.mention_everyone, data.mention_channels);
+    this.mentions = new Mentions(
+      this,
+      data.mentions,
+      data.mention_roles,
+      data.mention_everyone,
+      data.mention_channels,
+      data.referenced_message?.author,
+    );
 
     /**
      * ID of the webhook that sent the message, if applicable
@@ -325,6 +332,7 @@ class Message extends Base {
       'mention_roles' in data ? data.mention_roles : this.mentions.roles,
       'mention_everyone' in data ? data.mention_everyone : this.mentions.everyone,
       'mention_channels' in data ? data.mention_channels : this.mentions.crosspostedChannels,
+      'referenced_message' in data ? data.referenced_message.author : this.mentions.repliedUser,
     );
 
     this.flags = new MessageFlags('flags' in data ? data.flags : 0).freeze();

src/structures/MessageMentions.js

@@ -8,7 +8,7 @@ const Util = require('../util/Util');
  * Keeps track of mentions in a {@link Message}.
  */
 class MessageMentions {
-  constructor(message, users, roles, everyone, crosspostedChannels) {
+  constructor(message, users, roles, everyone, crosspostedChannels, repliedUser) {
     /**
      * The client the message is from
      * @type {Client}
@@ -125,6 +125,12 @@ class MessageMentions {
     } else {
       this.crosspostedChannels = new Collection();
     }
+
+    /**
+     * The author of the message that this message is a reply to
+     * @type {?User}
+     */
+    this.repliedUser = repliedUser ? this.client.users.add(repliedUser) : null;
   }
 
   /**