encountering an odd error trying out porting an ex...

# ktor

[Peter]

encountering an odd error trying out porting an existing working application (1.6.8) to ktor 2.0.1:

[Peter]

java.lang.UnsupportedOperationException: This class is an internal synthetic class generated by the Kotlin compiler, such as an anonymous class for a lambda, a SAM wrapper, a callable reference, etc. It's not a Kotlin class or interface, so the reflection library has no idea what declarations it has. Please use Java reflection to inspect this class: class com.xxx.SessionManagementKt$swapUserSession$1$1
 	at kotlin.reflect.jvm.internal.KClassImpl.reportUnresolvedClass(KClassImpl.kt:316)
 	at kotlin.reflect.jvm.internal.KClassImpl.access$reportUnresolvedClass(KClassImpl.kt:44)
...
 	at kotlin.jvm.internal.CallableReference.getTypeParameters(CallableReference.java:156)
	at kotlin.reflect.jvm.internal.ReflectionFactoryImpl.typeParameter(ReflectionFactoryImpl.java:134)
 	at kotlin.jvm.internal.Reflection.typeParameter(Reflection.java:174)
 	at com.xxx.SessionManagement$swapUserSession$1$1.invokeSuspend(SessionManagement.kt:162)
 	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
 	at arrow.continuations.generic.SuspendMonadContinuation.resumeWith(SuspendingComputation.kt:54)
 	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:46)
 	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
 	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:164)
 	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:469)
 	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:503)
 	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986)
 	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
 	at io.ktor.server.netty.EventLoopGroupProxy$Companion.create$lambda-1$lambda-0(NettyApplicationEngine.kt:260)

[Peter]

it appears to be happening inside a route:

fun <A, B, C>Route.swapUserSession(...) {
    authenticate("auth-basic") {
        post("/internal/session") {
            ...
            doThing() 
        }
    } 
}

suspend fun <A, B, C>doThing(): Bla<A>

[Peter]

using kotlin 1.6.21

[Peter]

the suspend fun is a top level function and has generic parameters, so does the function that creates the route

[Peter]

i'm not sure why reflection is (now?) involved here

[Peter]

the invocation to doThing() actually succeeds and returns a value

[Peter]

@Aleksei Tirman [JB] any idea by any chance?

[Aleksei Tirman [JB]]

Sorry for the long delay with a replay. Unfortunately, I cannot reproduce it with the following code:

fun main() {
    embeddedServer(Netty, port = 3333) {
        install(Authentication) {
            basic("auth-basic") {
                validate {
                    UserIdPrincipal("123")
                }
            }
        }
        routing {
            swapUserSession<Int, Int, Int>()
        }
    }.start(wait = true)
}

fun <A, B, C> Route.swapUserSession() {
    authenticate("auth-basic") {
        post("/") {
            //...
            doThing<A,B,C>()
        }
    }
}

suspend fun <A, B, C>doThing(): Bla<A> {
    return Bla<Int>() as Bla<A>
}

class Bla<T> {

}