From 7015f0f4e95a2ce2db9abdc2b347e7b6ad3c5737 Mon Sep 17 00:00:00 2001
From: Him188 <Him188@mamoe.net>
Date: Mon, 6 Apr 2020 20:01:19 +0800
Subject: [PATCH] Fix `MessageChainBuilder.addAndCheckConstrainSingle`

---
 .../kotlin/net.mamoe.mirai/message/data/builder.kt       | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/builder.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/builder.kt
index 179d1c1e5..bd540c4e1 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/builder.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/builder.kt
@@ -63,8 +63,13 @@ class MessageChainBuilder private constructor(
             }
             val key = element.key
 
-            container[container.indexOfFirst(firstConstrainSingleIndex) { it is ConstrainSingle<*> && it.key == key }] =
-                element
+            val index = container.indexOfFirst(firstConstrainSingleIndex) { it is ConstrainSingle<*> && it.key == key }
+            if (index != -1) {
+                container[index] = element
+            } else {
+                add(element)
+            }
+
             return true
         } else {
             return container.add(element)