Completed CombinedMessage redesigning and constraining on concatenation

compatibility-validator/build.gradle.kts

@@ -7,6 +7,11 @@ plugins {
 
 description = "Binary and source compatibility validator for mirai-core and mirai-core-qqandroid"
 
+repositories {
+    mavenCentral()
+    jcenter()
+}
+
 kotlin {
     sourceSets {
         all {
@@ -17,7 +22,19 @@ kotlin {
         main {
             dependencies {
                 api(kotlin("stdlib"))
-                api(project(":mirai-core-qqandroid"))
+                runtimeOnly(project(":mirai-core-qqandroid"))
+                compileOnly("net.mamoe:mirai-core-qqandroid-jvm:0.33.0")
+                api(kotlinx("coroutines-core", Versions.Kotlin.coroutines))
+            }
+        }
+
+        test {
+            dependencies {
+                api(kotlin("stdlib"))
+                api(kotlin("test"))
+                api(kotlin("test-junit"))
+                runtimeOnly(project(":mirai-core-qqandroid"))
+                compileOnly("net.mamoe:mirai-core-qqandroid-jvm:0.33.0")
                 api(kotlinx("coroutines-core", Versions.Kotlin.coroutines))
             }
         }

compatibility-validator/src/main/kotlin/compatibility/testKotlinCompatibility.kt

+/*
+ * 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 compatibility
+
+fun main() {
+
+}
\ No newline at end of file

compatibility-validator/src/test/kotlin/compatibility/CombinedMessageTest.kt

+package compatibility
+
+import net.mamoe.mirai.message.data.*
+import net.mamoe.mirai.utils.MiraiInternalAPI
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+@OptIn(MiraiInternalAPI::class)
+internal class CombinedMessageTest {
+
+
+    @Test
+    fun testAsSequence() {
+        var message: Message = "Hello ".toMessage()
+        message += "World"
+
+        assertEquals(
+            "Hello World",
+            (message as CombinedMessage).asSequence().joinToString(separator = "")
+        )
+    }
+
+    @Test
+    fun testAsSequence2() {
+        var message: Message = "Hello ".toMessage()
+        message += listOf(
+            PlainText("W"),
+            PlainText("o"),
+            PlainText("r") + PlainText("ld")
+        ).asMessageChain()
+
+        assertEquals(
+            "Hello World",
+            (message as CombinedMessage).asSequence().joinToString(separator = "")
+        )
+    }
+}
+
+fun <T> Iterator<T>.joinToString(
+    separator: CharSequence = ", ",
+    prefix: CharSequence = "",
+    postfix: CharSequence = "",
+    limit: Int = -1,
+    truncated: CharSequence = "...",
+    transform: ((T) -> CharSequence)? = null
+): String {
+    return joinTo(StringBuilder(), separator, prefix, postfix, limit, truncated, transform).toString()
+}
+
+fun <T, A : Appendable> Iterator<T>.joinTo(
+    buffer: A,
+    separator: CharSequence = ", ",
+    prefix: CharSequence = "",
+    postfix: CharSequence = "",
+    limit: Int = -1,
+    truncated: CharSequence = "...",
+    transform: ((T) -> CharSequence)? = null
+): A {
+    buffer.append(prefix)
+    var count = 0
+    for (element in this) {
+        if (++count > 1) buffer.append(separator)
+        if (limit < 0 || count <= limit) {
+            buffer.appendElement(element, transform)
+        } else break
+    }
+    if (limit in 0 until count) buffer.append(truncated)
+    buffer.append(postfix)
+    return buffer
+}
+
+internal fun <T> Appendable.appendElement(element: T, transform: ((T) -> CharSequence)?) {
+    when {
+        transform != null -> append(transform(element))
+        element is CharSequence? -> append(element)
+        element is Char -> append(element)
+        else -> append(element.toString())
+    }
+}
\ No newline at end of file

compatibility-validator/src/test/kotlin/compatibility/TestKotlinCompatibility.kt

+/*
+ * 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 compatibility
+
+import net.mamoe.mirai.message.data.Message
+import net.mamoe.mirai.message.data.PlainText
+import org.junit.Test
+
+
+internal class TestKotlinCompatibility {
+
+    @Test
+    fun testMessageChain() {
+        val x = PlainText("te") + PlainText("st")
+
+        println(Message::class.java.declaredMethods.joinToString("\n"))
+        println()
+        println(x::class.java.declaredMethods.joinToString("\n"))
+    }
+}
\ No newline at end of file

mirai-core-qqandroid/src/commonMain/kotlin/net/mamoe/mirai/qqandroid/QQAndroidBot.common.kt

@@ -56,6 +56,7 @@ import kotlin.coroutines.CoroutineContext
 import kotlin.jvm.JvmSynthetic
 import kotlin.math.absoluteValue
 import kotlin.random.Random
+import net.mamoe.mirai.qqandroid.network.protocol.data.jce.FriendInfo as JceFriendInfo
 
 @OptIn(ExperimentalContracts::class)
 internal fun Bot.asQQAndroidBot(): QQAndroidBot {
@@ -98,8 +99,9 @@ internal abstract class QQAndroidBotBase constructor(
 
     override val friends: ContactList<QQ> = ContactList(LockFreeLinkedList())
 
-    override lateinit var nick: String
-        internal set
+    override val nick: String get() = selfInfo.nick
+
+    internal lateinit var selfInfo: JceFriendInfo
 
     override val selfQQ: QQ by lazy {
         @OptIn(LowLevelAPI::class)

mirai-core-qqandroid/src/commonMain/kotlin/net/mamoe/mirai/qqandroid/contact/QQImpl.kt

@@ -51,7 +51,7 @@ import kotlin.jvm.JvmSynthetic
 internal inline class FriendInfoImpl(
     private val jceFriendInfo: net.mamoe.mirai.qqandroid.network.protocol.data.jce.FriendInfo
 ) : FriendInfo {
-    override val nick: String get() = jceFriendInfo.nick ?: ""
+    override val nick: String get() = jceFriendInfo.nick
     override val uin: Long get() = jceFriendInfo.friendUin
 }
 

mirai-core-qqandroid/src/commonMain/kotlin/net/mamoe/mirai/qqandroid/network/QQAndroidBotNetworkHandler.kt

@@ -223,8 +223,8 @@ internal class QQAndroidBotNetworkHandler(bot: QQAndroidBot) : BotNetworkHandler
                         }
 
                         // self info
-                        data.selfInfo?.apply {
-                            bot.nick = nick ?: ""
+                        data.selfInfo?.run {
+                            bot.selfInfo = this
 //                            bot.remark = remark ?: ""
 //                            bot.sex = sex
                         }

mirai-core-qqandroid/src/commonMain/kotlin/net/mamoe/mirai/qqandroid/network/protocol/data/jce/FriendList.kt

@@ -109,7 +109,7 @@ internal class FriendInfo(
     @JceId(11) val sqqOnLineStateV2: Byte? = null,
     @JceId(12) val sShowName: String? = "",
     @JceId(13) val isRemark: Byte? = null,
-    @JceId(14) val nick: String? = "",
+    @JceId(14) val nick: String = "",
     @JceId(15) val specialFlag: Byte? = null,
     @JceId(16) val vecIMGroupID: ByteArray? = null,
     @JceId(17) val vecMSFGroupID: ByteArray? = null,

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/Bot.kt

@@ -87,6 +87,7 @@ expect abstract class Bot() : CoroutineScope, LowLevelBotAPIAccessor {
     /**
      * 昵称
      */
+    @SinceMirai("0.33.1")
     abstract val nick: String
 
     /**

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/event/subscribeMessages.kt

@@ -24,7 +24,7 @@ import net.mamoe.mirai.message.ContactMessage
 import net.mamoe.mirai.message.FriendMessage
 import net.mamoe.mirai.message.GroupMessage
 import net.mamoe.mirai.message.data.Message
-import net.mamoe.mirai.message.data.first
+import net.mamoe.mirai.message.data.firstIsInstance
 import net.mamoe.mirai.utils.SinceMirai
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.InvocationKind
@@ -700,7 +700,7 @@ open class MessageSubscribersBuilder<M : ContactMessage, out Ret, R : RR, RR>(
     @MessageDsl
     @SinceMirai("0.30.0")
     inline fun <reified N : Message> has(noinline onEvent: @MessageDsl suspend M.(N) -> R): Ret =
-        content({ message.any { it is N } }, { onEvent.invoke(this, message.first()) })
+        content({ message.any { it is N } }, { onEvent.invoke(this, message.firstIsInstance()) })
 
     /**
      * 如果 [mapper] 返回值非空, 就执行 [onEvent]

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

@@ -357,8 +357,8 @@ suspend inline fun <reified M : Message> ContactMessage.nextMessageContaining(
 ): M {
     return subscribingGet<ContactMessage, ContactMessage>(timeoutMillis) {
         takeIf { this.isContextIdenticalWith(this@nextMessageContaining) }
-            .takeIf { this.message.any<M>() }
-    }.message.first()
+            .takeIf { this.message.anyIsInstance<M>() }
+    }.message.firstIsInstance()
 }
 
 @JvmSynthetic
@@ -370,8 +370,8 @@ inline fun <reified M : Message> ContactMessage.nextMessageContainingAsync(
         @Suppress("RemoveExplicitTypeArguments")
         subscribingGet<ContactMessage, ContactMessage>(timeoutMillis) {
             takeIf { this.isContextIdenticalWith(this@nextMessageContainingAsync) }
-                .takeIf { this.message.any<M>() }
-        }.message.first<M>()
+                .takeIf { this.message.anyIsInstance<M>() }
+        }.message.firstIsInstance<M>()
     }
 }
 
@@ -391,8 +391,8 @@ suspend inline fun <reified M : Message> ContactMessage.nextMessageContainingOrN
 ): M? {
     return subscribingGetOrNull<ContactMessage, ContactMessage>(timeoutMillis) {
         takeIf { this.isContextIdenticalWith(this@nextMessageContainingOrNull) }
-            .takeIf { this.message.any<M>() }
-    }?.message?.first()
+            .takeIf { this.message.anyIsInstance<M>() }
+    }?.message?.firstIsInstance()
 }
 
 @JvmSynthetic
@@ -403,8 +403,8 @@ inline fun <reified M : Message> ContactMessage.nextMessageContainingOrNullAsync
     return this.bot.async(coroutineContext) {
         subscribingGetOrNull<ContactMessage, ContactMessage>(timeoutMillis) {
             takeIf { this.isContextIdenticalWith(this@nextMessageContainingOrNullAsync) }
-                .takeIf { this.message.any<M>() }
-        }?.message?.first<M>()
+                .takeIf { this.message.anyIsInstance<M>() }
+        }?.message?.firstIsInstance<M>()
     }
 }
 

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

@@ -17,6 +17,7 @@ package net.mamoe.mirai.message.data
 import net.mamoe.mirai.LowLevelAPI
 import net.mamoe.mirai.contact.Member
 import net.mamoe.mirai.contact.nameCardOrNick
+import net.mamoe.mirai.utils.MiraiInternalAPI
 import kotlin.jvm.JvmMultifileClass
 import kotlin.jvm.JvmName
 import kotlin.jvm.JvmStatic
@@ -56,6 +57,7 @@ private constructor(val target: Long, val display: String) :
     }
 
     // 自动为消息补充 " "
+    @OptIn(MiraiInternalAPI::class)
     @Suppress("INAPPLICABLE_JVM_NAME")
     @Deprecated("for binary compatibility", level = DeprecationLevel.HIDDEN)
     @JvmName("followedBy")
@@ -67,7 +69,7 @@ private constructor(val target: Long, val display: String) :
         return followedByInternalForBinaryCompatibility(PlainText(" ") + tail)
     }
 
-    override fun followedBy(tail: Message): Message {
+    override fun followedBy(tail: Message): MessageChain {
         if (tail is PlainText && tail.stringValue.startsWith(' ')) {
             return super.followedBy(tail)
         }

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

@@ -12,6 +12,7 @@
 
 package net.mamoe.mirai.message.data
 
+import net.mamoe.mirai.utils.MiraiInternalAPI
 import net.mamoe.mirai.utils.SinceMirai
 import kotlin.jvm.JvmMultifileClass
 import kotlin.jvm.JvmName
@@ -42,6 +43,7 @@ object AtAll :
     override fun contentToString(): String = display
 
     // 自动为消息补充 " "
+    @OptIn(MiraiInternalAPI::class)
     @Deprecated("for binary compatibility", level = DeprecationLevel.HIDDEN)
     @Suppress("INAPPLICABLE_JVM_NAME")
     @JvmName("followedBy")
@@ -53,7 +55,7 @@ object AtAll :
         return followedByInternalForBinaryCompatibility(PlainText(" ") + tail)
     }
 
-    override fun followedBy(tail: Message): Message {
+    override fun followedBy(tail: Message): MessageChain {
         if (tail is PlainText && tail.stringValue.startsWith(' ')) {
             return super.followedBy(tail)
         }

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

@@ -14,11 +14,13 @@ package net.mamoe.mirai.message.data
 
 import net.mamoe.mirai.utils.MiraiExperimentalAPI
 import net.mamoe.mirai.utils.MiraiInternalAPI
+import net.mamoe.mirai.utils.PlannedRemoval
 import kotlin.jvm.JvmMultifileClass
 import kotlin.jvm.JvmName
+import kotlin.jvm.JvmSynthetic
 
 /**
- * 链接的两个消息.
+ * 快速链接的两个消息 (避免构造新的 list).
  *
  * 不要直接构造 [CombinedMessage], 使用 [Message.plus]
  * 要连接多个 [Message], 使用 [buildMessageChain]
@@ -27,64 +29,68 @@ import kotlin.jvm.JvmName
  *
  * Left-biased list
  */
+@MiraiInternalAPI("this API is going to be internal")
 class CombinedMessage
-@Deprecated(message = "use Message.plus", level = DeprecationLevel.ERROR)
-@MiraiInternalAPI("CombinedMessage 构造器可能会在将来被改动") constructor(
-    @MiraiExperimentalAPI("CombinedMessage.left 可能会在将来被改动")
-    val left: SingleMessage,
-    @MiraiExperimentalAPI("CombinedMessage.tail 可能会在将来被改动")
-    val tail: SingleMessage
-) : Iterable<SingleMessage>, Message {
-
-    /*
-    // 不要把它用作 local function, 会编译错误
-    @OptIn(MiraiExperimentalAPI::class)
-    private suspend fun SequenceScope<Message>.yieldCombinedOrElements(message: Message) {
-        when (message) {
-            is CombinedMessage -> {
-                // fast path, 避免创建新的 iterator, 也不会挂起协程
-                yieldCombinedOrElements(message.left)
-                yieldCombinedOrElements(message.tail)
-            }
-            is Iterable<*> -> {
-                // 更好的性能, 因为协程不会挂起.
-                // 这可能会导致爆栈 (十万个元素), 但作为消息序列足够了.
-                message.forEach {
-                    yieldCombinedOrElements(
-                        it as? Message ?: error(
-                            "A Message implementing Iterable must implement Iterable<Message>, " +
-                                    "whereas got ${it!!::class.simpleName}"
-                        )
-                    )
-                }
-            }
-            else -> {
-                check(message is SingleMessage) {
-                    "unsupported Message type. " +
-                            "A Message must be a CombinedMessage, a Iterable<Message> or a SingleMessage"
-                }
-                yield(message)
-            }
-        }
-    }
-    */
-
+internal constructor(
+    internal val left: Message, // 必须已经完成 constrain single
+    internal val tail: Message
+) : Message, MessageChain {
     @OptIn(MiraiExperimentalAPI::class)
     fun asSequence(): Sequence<SingleMessage> = sequence {
-        yield(left)
-        yield(tail)
+        yieldCombinedOrElementsFlatten(this@CombinedMessage)
     }
 
     override fun iterator(): Iterator<SingleMessage> {
         return asSequence().iterator()
     }
 
+    @PlannedRemoval("1.0.0")
+    @Deprecated(
+        "有歧义, 自行使用 contentToString() 比较",
+        ReplaceWith("this.contentToString() == other"),
+        DeprecationLevel.HIDDEN
+    )
+    override fun contains(sub: String): Boolean {
+        return contentToString().contains(sub)
+    }
+
+    override val size: Int = when {
+        left === EmptyMessageChain && tail !== EmptyMessageChain -> 1
+        left === EmptyMessageChain && tail === EmptyMessageChain -> 0
+        left !== EmptyMessageChain && tail === EmptyMessageChain -> 1
+        left !== EmptyMessageChain && tail !== EmptyMessageChain -> 2
+        else -> error("stub")
+    }
+
     @OptIn(MiraiExperimentalAPI::class)
     override fun toString(): String {
         return tail.toString() + left.toString()
     }
 
     override fun contentToString(): String {
-        return toString()
+        return left.contentToString() + tail.contentToString()
+    }
+}
+
+@JvmSynthetic
+// 不要把它用作 local function, 会编译错误
+@OptIn(MiraiExperimentalAPI::class, MiraiInternalAPI::class)
+private suspend fun SequenceScope<SingleMessage>.yieldCombinedOrElementsFlatten(message: Message) {
+    when (message) {
+        is CombinedMessage -> {
+            // fast path, 避免创建新的 iterator, 也不会挂起协程
+            yieldCombinedOrElementsFlatten(message.left)
+            yieldCombinedOrElementsFlatten(message.tail)
+        }
+        is MessageChain -> {
+            yieldAll(message)
+        }
+        else -> {
+            check(message is SingleMessage) {
+                "unsupported Message type: ${message::class}" +
+                        "A Message must be a CombinedMessage, a Iterable<Message> or a SingleMessage"
+            }
+            yield(message)
+        }
     }
-}
+}
\ No newline at end of file

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

@@ -30,7 +30,6 @@ class PlainText(val stringValue: String) :
     @Suppress("unused")
     constructor(charSequence: CharSequence) : this(charSequence.toString())
 
-    override operator fun contains(sub: String): Boolean = sub in stringValue
     override fun toString(): String = stringValue
     override fun contentToString(): String = stringValue
 

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/BotConfiguration.kt

@@ -97,30 +97,6 @@ open class BotConfiguration {
     fun fileBasedDeviceInfo(filename: String = "device.json") {
         deviceInfo = getFileBasedDeviceInfoSupplier(filename)
     }
-
-
-    @PlannedRemoval("0.34.0")
-    @Deprecated(
-        "use fileBasedDeviceInfo(filepath", level = DeprecationLevel.ERROR,
-        replaceWith = ReplaceWith("fileBasedDeviceInfo")
-    )
-    operator fun FileBasedDeviceInfo.unaryPlus() {
-        fileBasedDeviceInfo(this.filepath)
-    }
-}
-
-/**
- * 使用文件系统存储设备信息.
- */
-@PlannedRemoval("0.34.0")
-@Deprecated(
-    "use fileBasedDeviceInfo(filepath", level = DeprecationLevel.ERROR
-)
-inline class FileBasedDeviceInfo(val filepath: String) {
-    /**
-     * 使用 "device.json" 存储设备信息
-     */
-    companion object ByDeviceDotJson
 }
 
 @OptIn(ExperimentalMultiplatform::class)

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

 package net.mamoe.mirai.message.data
 
+import net.mamoe.mirai.utils.MiraiInternalAPI
 import kotlin.test.Test
 import kotlin.test.assertEquals
-import kotlin.time.ExperimentalTime
-import kotlin.time.measureTime
 
+@OptIn(MiraiInternalAPI::class)
 internal class CombinedMessageTest {
 
+
     @Test
     fun testAsSequence() {
         var message: Message = "Hello ".toMessage()
@@ -32,84 +33,6 @@ internal class CombinedMessageTest {
             (message as CombinedMessage).asSequence().joinToString(separator = "")
         )
     }
-
-    private val toAdd = "1".toMessage()
-
-    @OptIn(ExperimentalTime::class)
-    @Test
-    fun speedTest() = repeat(100) {
-        var count = 1L
-
-        repeat(Int.MAX_VALUE) {
-            count++
-        }
-
-        var combineMessage: Message = toAdd
-
-        println(
-            "init combine ok " + measureTime {
-                repeat(1000) {
-                    combineMessage += toAdd
-                }
-            }.inMilliseconds
-        )
-
-        val list = mutableListOf<Message>()
-        println(
-            "init messageChain ok " + measureTime {
-                repeat(1000) {
-                    list += toAdd
-                }
-            }.inMilliseconds
-        )
-
-        measureTime {
-            list.joinToString(separator = "")
-        }.let { time ->
-            println("list foreach: ${time.inMilliseconds} ms")
-        }
-
-        measureTime {
-            (combineMessage as CombinedMessage).iterator().joinToString(separator = "")
-        }.let { time ->
-            println("combined iterate: ${time.inMilliseconds} ms")
-        }
-
-        measureTime {
-            (combineMessage as CombinedMessage).asSequence().joinToString(separator = "")
-        }.let { time ->
-            println("combined sequence: ${time.inMilliseconds} ms")
-        }
-
-        repeat(5) {
-            println()
-        }
-    }
-
-    @OptIn(ExperimentalTime::class)
-    @Test
-    fun testFastIteration() {
-        println("start!")
-        println("start!")
-        println("start!")
-        println("start!")
-
-        var combineMessage: Message = toAdd
-
-        println(
-            "init combine ok " + measureTime {
-                repeat(1000) {
-                    combineMessage += toAdd
-                }
-            }.inMilliseconds
-        )
-
-        measureTime {
-            (combineMessage as CombinedMessage).iterator().joinToString(separator = "")
-        }.let { time ->
-            println("combine: ${time.inMilliseconds} ms")
-        }
-    }
 }
 
 fun <T> Iterator<T>.joinToString(
@@ -140,7 +63,7 @@ fun <T, A : Appendable> Iterator<T>.joinTo(
             buffer.appendElement(element, transform)
         } else break
     }
-    if (limit >= 0 && count > limit) buffer.append(truncated)
+    if (limit in 0 until count) buffer.append(truncated)
     buffer.append(postfix)
     return buffer
 }

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

@@ -10,9 +10,11 @@
 package net.mamoe.mirai.message.data
 
 import net.mamoe.mirai.utils.MiraiExperimentalAPI
+import net.mamoe.mirai.utils.MiraiInternalAPI
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertSame
+import kotlin.test.assertTrue
 
 
 @OptIn(MiraiExperimentalAPI::class)
@@ -25,7 +27,7 @@ internal class TestConstrainSingleMessage : ConstrainSingle<TestConstrainSingleM
     override fun toString(): String = "<TestConstrainSingleMessage#${super.hashCode()}>"
 
     override fun contentToString(): String {
-        TODO("Not yet implemented")
+        return ""
     }
 
     override val key: Message.Key<TestConstrainSingleMessage>
@@ -46,16 +48,75 @@ internal class TestConstrainSingleMessage : ConstrainSingle<TestConstrainSingleM
     }
 }
 
+@OptIn(MiraiExperimentalAPI::class)
 internal class ConstrainSingleTest {
 
-    @OptIn(MiraiExperimentalAPI::class)
+    @OptIn(MiraiInternalAPI::class)
+    @Test
+    fun testCombine() {
+        val result = PlainText("te") + PlainText("st")
+        assertTrue(result is CombinedMessage)
+        assertEquals("te", result.left.contentToString())
+        assertEquals("st", result.tail.contentToString())
+        assertEquals(2, result.size)
+        assertEquals("test", result.contentToString())
+    }
+
+    @Test
+    fun testSinglePlusChain() {
+        val result = PlainText("te") + buildMessageChain {
+            add(TestConstrainSingleMessage())
+            add("st")
+        }
+        assertTrue(result is MessageChainImplByCollection)
+        assertEquals(3, result.size)
+        assertEquals(result.contentToString(), "test")
+    }
+
+    @Test
+    fun testSinglePlusChainConstrain() {
+        val chain = buildMessageChain {
+            add(TestConstrainSingleMessage())
+            add("st")
+        }
+        val result = TestConstrainSingleMessage() + chain
+        assertSame(chain, result)
+        assertEquals(2, result.size)
+        assertEquals(result.contentToString(), "st")
+        assertTrue { result.first() is TestConstrainSingleMessage }
+    }
+
+    @Test
+    fun testSinglePlusSingle() {
+        val new = TestConstrainSingleMessage()
+        val combined = (TestConstrainSingleMessage() + new)
+
+        assertTrue(combined is SingleMessageChainImpl)
+        assertSame(new, combined.delegate)
+    }
+
     @Test
-    fun testConstrainSingleInPlus() {
+    fun testChainPlusSingle() {
         val new = TestConstrainSingleMessage()
-        val combined = (TestConstrainSingleMessage() + new) as CombinedMessage
 
-        assertEquals(combined.left, EmptyMessageChain)
-        assertSame(combined.tail, new)
+        val result = buildMessageChain {
+            add(" ")
+            add(Face(Face.hao))
+            add(TestConstrainSingleMessage())
+            add(
+                PlainText("ss")
+                        + " "
+            )
+        } + buildMessageChain {
+            add(PlainText("p "))
+            add(new)
+            add(PlainText("test"))
+        }
+
+        assertEquals(7, result.size)
+        assertEquals(" [表情]ss p test", result.contentToString())
+        result as MessageChainImplByCollection
+        assertSame(new, result.delegate.toTypedArray()[2])
     }
 
     @Test // net.mamoe.mirai/message/data/MessageChain.kt:441