Enable beta K2 compiler

buildSrc/src/main/kotlin/toolkit-kotlin-conventions.gradle.kts

@@ -55,7 +55,7 @@ tasks.withType<KotlinCompile>().all {
     kotlinOptions {
         jvmTarget = javaVersion.majorVersion
         apiVersion = project.kotlinTarget().get()
-        languageVersion = project.kotlinTarget().get()
+        languageVersion = "2.0"
         freeCompilerArgs = listOf("-Xjvm-default=all")
     }
 }

plugins/amazonq/chat/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/gettingstarted/QGettingStartedContent.kt

@@ -67,7 +67,8 @@
                     AmazonQToolWindow.getStarted(project)
                 }
             }
-            null
+
+            JBCefJSQuery.Response(null)
         }
         receiveMessageQuery.addHandler(handler)
     }

plugins/amazonq/chat/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/webview/BrowserConnector.kt

@@ -73,7 +73,8 @@
     private fun addMessageHook(browser: Browser) = callbackFlow {
         val handler = Function<String, Response> {
             trySend(it)
-            null
+
+            Response(null)
         }
 
         browser.receiveMessageQuery.addHandler(handler)

plugins/amazonq/chat/jetbrains-community/src/software/aws/toolkits/jetbrains/services/cwc/controller/chat/messenger/ChatPromptHandler.kt

@@ -54,7 +54,8 @@
                     return@onCompletion
                 } // for any other exception, let the `catch` operator handle it.
                 else if (error != null) {
-                    throw error
+                    // smartcast is failing on 2.0: Type mismatch: inferred type is '@R|kotlin/ParameterName|(name = String(cause))  kotlin/Throwable?' but 'kotlin/Throwable' was expected
+                    throw error as Throwable
                 }
 
                 // Send the gathered suggestions in a final answer-part message