Add tests for MessageChain delegations

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

@@ -17,10 +17,7 @@ import net.mamoe.mirai.JavaFriendlyAPI
 import net.mamoe.mirai.message.MessageEvent
 import net.mamoe.mirai.utils.PlannedRemoval
 import kotlin.js.JsName
-import kotlin.jvm.JvmMultifileClass
-import kotlin.jvm.JvmName
-import kotlin.jvm.JvmOverloads
-import kotlin.jvm.JvmSynthetic
+import kotlin.jvm.*
 import kotlin.reflect.KProperty
 
 /**
@@ -222,7 +219,8 @@ inline operator fun <reified T : Message> MessageChain.getValue(thisRef: Any?, p
  * 可空的委托
  * @see orNull
  */
-inline class OrNullDelegate<out R : Message?>(private val value: Any?) {
+@Suppress("NON_PUBLIC_PRIMARY_CONSTRUCTOR_OF_INLINE_CLASS")
+inline class OrNullDelegate<out R> @PublishedApi internal constructor(@JvmField @PublishedApi internal val value: Any?) {
     @Suppress("UNCHECKED_CAST")
     operator fun getValue(thisRef: Any?, property: KProperty<*>): R = value as R
 }
@@ -257,10 +255,9 @@ inline fun <reified T : Message> MessageChain.orNull(): OrNullDelegate<T?> =
  */
 @Suppress("RemoveExplicitTypeArguments")
 @JvmSynthetic
-inline fun <reified T : Message?> MessageChain.orElse(
-    lazyDefault: () -> T
-): OrNullDelegate<T> =
-    OrNullDelegate<T>(this.firstIsInstanceOrNull<T>() ?: lazyDefault())
+inline fun <reified T : R, R : Message?> MessageChain.orElse(
+    lazyDefault: () -> R
+): OrNullDelegate<R> = OrNullDelegate<R>(this.firstIsInstanceOrNull<T>() ?: lazyDefault())
 
 // endregion delegate
 

mirai-core/src/commonTest/kotlin/net/mamoe/mirai/message.data/TestMessageChainDelegate.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.message.data
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+internal class TestMessageChainDelegate {
+    private val message = messageChainOf(AtAll, PlainText("test"))
+
+    @Test
+    fun testGetValue() {
+        @Suppress("UNUSED_VARIABLE")
+        val atAll: AtAll by message
+        val plain: PlainText by message
+        assertEquals(plain.content, "test")
+    }
+
+    @Test
+    fun testOrNull() {
+        @Suppress("UNUSED_VARIABLE")
+        val atAll: AtAll? by message.orNull()
+        val plain: PlainText? by message.orNull()
+        assertEquals(plain!!.content, "test")
+    }
+
+    @Test
+    fun testOrElse() {
+        val message = messageChainOf()
+
+        @Suppress("UNUSED_VARIABLE")
+        val plain: PlainText? by message.orElse { PlainText("test") }
+        assertEquals(plain!!.content, "test")
+    }
+
+}