Fix #444: FriendMessageEvent is not a subclass of FriendEvent

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/FriendMessageEvent.kt

@@ -14,11 +14,13 @@ package net.mamoe.mirai.message
 import net.mamoe.mirai.Bot
 import net.mamoe.mirai.contact.Friend
 import net.mamoe.mirai.event.BroadcastControllable
+import net.mamoe.mirai.event.events.FriendEvent
 import net.mamoe.mirai.message.data.MessageChain
 import net.mamoe.mirai.message.data.MessageSource
 import net.mamoe.mirai.message.data.OnlineMessageSource
 import net.mamoe.mirai.message.data.source
 import net.mamoe.mirai.utils.PlannedRemoval
+import net.mamoe.mirai.utils.SinceMirai
 
 /**
  * 机器人收到的好友消息的事件
@@ -29,14 +31,17 @@ public class FriendMessageEvent constructor(
     public override val sender: Friend,
     public override val message: MessageChain,
     public override val time: Int
-) : @PlannedRemoval("1.2.0") FriendMessage(), BroadcastControllable {
+) : @PlannedRemoval("1.2.0") FriendMessage(), BroadcastControllable, @SinceMirai("1.2.0") FriendEvent {
     init {
         val source =
             message[MessageSource] ?: throw IllegalArgumentException("Cannot find MessageSource from message")
         check(source is OnlineMessageSource.Incoming.FromFriend) { "source provided to a FriendMessage must be an instance of OnlineMessageSource.Incoming.FromFriend" }
     }
 
-    public override val bot: Bot get() = sender.bot
+    @SinceMirai("1.2.0")
+    public override val friend: Friend
+        get() = sender
+    public override val bot: Bot get() = super.bot
     public override val subject: Friend get() = sender
     public override val senderName: String get() = sender.nick
     public override val source: OnlineMessageSource.Incoming.FromFriend get() = message.source as OnlineMessageSource.Incoming.FromFriend