Updated to Kotlin 2.1.0

build.gradle.kts

@@ -1,10 +1,12 @@
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+
 buildscript {
     repositories {
         mavenCentral()
     }
 
     dependencies {
-        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:1.9.21")
+        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:2.1.0")
     }
 }
 
@@ -13,7 +15,7 @@ plugins {
     id("com.gradleup.shadow") version "8.3.5"
     id("maven-publish")
     id("java")
-    kotlin("jvm") version "1.9.21"
+    kotlin("jvm") version "2.1.0"
 }
 
 dependencies {
@@ -108,12 +110,12 @@ allprojects {
 
     dependencies {
         // Kotlin
-        implementation(kotlin("stdlib", version = "1.9.21"))
+        implementation(kotlin("stdlib", version = "2.1.0"))
         implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")
 
         // Included in spigot jar, no need to move to implementation
         compileOnly("org.jetbrains:annotations:23.0.0")
-        compileOnly("com.google.guava:guava:31.1-jre")
+        compileOnly("com.google.guava:guava:32.0.0-jre")
 
         // Test
         testImplementation("org.junit.jupiter:junit-jupiter-api:5.9.2")
@@ -157,8 +159,8 @@ allprojects {
         }
 
         compileKotlin {
-            kotlinOptions {
-                jvmTarget = "17"
+            compilerOptions {
+                jvmTarget.set(JvmTarget.JVM_17)
             }
         }
 

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/events/EcoEventManager.kt

@@ -80,9 +80,11 @@ class EcoEventManager(private val plugin: EcoPlugin) : EventManager {
     }
 
     override fun registerPacketListener(listener: PacketListener) {
-        listeners[listener.priority] += RegisteredPacketListener(
-            plugin,
-            listener
+        listeners[listener.priority].add(
+            RegisteredPacketListener(
+                plugin,
+                listener
+            )
         )
     }
 }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/slot/EcoSlotBuilder.kt

@@ -23,7 +23,7 @@ class EcoSlotBuilder(private val provider: SlotProvider) : SlotBuilder {
     private var notCaptiveFor: (Player) -> Boolean = { _ -> false}
 
     override fun onClick(type: ClickType, action: SlotHandler): SlotBuilder {
-        handlers[type] += action
+        handlers[type].add(action)
         return this
     }
 

eco-core/core-nms/common/src/main/kotlin/com/willfp/eco/internal/spigot/proxy/common/ai/entity/RangedBowAttackGoalFactory.kt

@@ -10,7 +10,7 @@ import net.minecraft.world.entity.monster.RangedAttackMob
 
 object RangedBowAttackGoalFactory : EntityGoalFactory<EntityGoalRangedBowAttack> {
     override fun create(apiGoal: EntityGoalRangedBowAttack, entity: PathfinderMob): Goal? {
-        (if (entity !is Monster) return null)
+        if (entity !is Monster) return null
         if (entity !is RangedAttackMob) return null
 
         return RangedBowAttackGoal(

eco-core/core-nms/common/src/main/kotlin/com/willfp/eco/internal/spigot/proxy/common/ai/entity/RangedCrossbowAttackGoalFactory.kt

@@ -11,7 +11,7 @@ import net.minecraft.world.entity.monster.RangedAttackMob
 
 object RangedCrossbowAttackGoalFactory : EntityGoalFactory<EntityGoalRangedCrossbowAttack> {
     override fun create(apiGoal: EntityGoalRangedCrossbowAttack, entity: PathfinderMob): Goal? {
-        (if (entity !is Monster) return null)
+        if (entity !is Monster) return null
         if (entity !is RangedAttackMob) return null
         if (entity !is CrossbowAttackMob) return null
 

gradle.properties

@@ -1,2 +1 @@
 version = 6.74.4
-kotlin.incremental.useClasspathSnapshot=false