Improve ContactList

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

@@ -2,9 +2,7 @@
 
 package net.mamoe.mirai.contact
 
-import net.mamoe.mirai.utils.LockFreeLinkedList
-import net.mamoe.mirai.utils.MiraiInternalAPI
-import net.mamoe.mirai.utils.joinToString
+import net.mamoe.mirai.utils.*
 
 
 /**
@@ -52,3 +50,35 @@ inline fun <C : Contact> LockFreeLinkedList<C>.filteringGetOrNull(filter: (C) ->
     return null
 }
 
+
+/**
+ * Collect all the elements into a [MutableList] then cast it as a [List]
+ */
+fun <E : Contact> ContactList<E>.toList(): List<E> = toMutableList()
+
+/**
+ * Collect all the elements into a [MutableList].
+ */
+@UseExperimental(MiraiInternalAPI::class)
+fun <E : Contact> ContactList<E>.toMutableList(): MutableList<E> = this.delegate.toMutableList()
+
+/**
+ * Collect all the elements into a [MutableSet] then cast it as a [Set]
+ */
+fun <E : Contact> ContactList<E>.toSet(): Set<E> = toMutableSet()
+
+/**
+ * Collect all the elements into a [MutableSet].
+ */
+@UseExperimental(MiraiInternalAPI::class)
+fun <E : Contact> ContactList<E>.toMutableSet(): MutableSet<E> = this.delegate.toMutableSet()
+
+/**
+ * Builds a [Sequence] containing all the elements in [this] in the same order.
+ *
+ * Note that the sequence is dynamic, that is, elements are yielded atomically only when it is required
+ */
+@UseExperimental(MiraiInternalAPI::class)
+fun <E : Contact> ContactList<E>.asSequence(): Sequence<E> {
+    return this.delegate.asSequence()
+}
\ No newline at end of file