what is a good way to approach debugging ```ClassCastExcepti

Question

what is a good way to approach debugging ```ClassCastException kotlin coroutines intrinsics CoroutineSingletons cannot be cast to ``` I am using `suspend fun` as well as Flows but I am not sure where to start with this

wakingrufus · Answer

stacktrace here in case that helps ```Exception in thread main java lang ClassCastException kotlin coroutines intrinsics CoroutineSingletons cannot be cast to io ktor client statement HttpResponse at com github wakingrufus kalibrate example MainKt$main$2$4$1$1$1 invoke Main kt 68 at com github wakingrufus kalibrate example MainKt$main$2$4$1$1$1 invoke Main kt at com github wakingrufus kalibrate scenario Step invoke Step kt 15 at com github wakingrufus kalibrate scenario StepContainer$invoke$1 invokeSuspend Simulation kt 93 at kotlin coroutines jvm internal BaseContinuationImpl resumeWith ContinuationImpl kt 33 at kotlinx coroutines DispatchedTask run DispatchedTask kt 106 at kotlinx coroutines EventLoopImplBase processNextEvent EventLoop common kt 277 at kotlinx coroutines BlockingCoroutine joinBlocking Builders kt 86 at kotlinx coroutines BuildersKt BuildersKt runBlocking Builders kt 61 at kotlinx coroutines BuildersKt runBlocking Unknown Source at kotlinx coroutines BuildersKt BuildersKt runBlocking$default Builders kt at kotlinx coroutines BuildersKt runBlocking$default Unknown Source at com github wakingrufus kalibrate scenario StepContainer invoke Simulation kt 91 at com github wakingrufus kalibrate scenario Simulation runSetup Simulation kt 75 at com github wakingrufus kalibrate scenario Simulation$singletonWorkPattern$1$1$1 invokeSuspend Simulation kt 25 at com github wakingrufus kalibrate scenario Simulation$singletonWorkPattern$1$1$1 invoke Simulation kt at kotlinx coroutines flow SafeFlow collectSafely Builders kt 61 at kotlinx coroutines flow AbstractFlow collect Flow kt 212 at kotlinx coroutines flow FlowKt MergeKt$flattenConcat$$inlined$unsafeFlow$1 collect SafeCollector common kt 114 at kotlinx coroutines flow internal ChannelFlowMerge$collectTo$$inlined$collect$1$lambda$1 invokeSuspend Merge kt 69 at kotlin coroutines jvm internal BaseContinuationImpl resumeWith ContinuationImpl kt 33 at kotlinx coroutines DispatchedTask run DispatchedTask kt 106 at kotlinx coroutines EventLoopImplBase processNextEvent EventLoop common kt 277 at kotlinx coroutines BlockingCoroutine joinBlocking Builders kt 86 at kotlinx coroutines BuildersKt BuildersKt runBlocking Builders kt 61 at kotlinx coroutines BuildersKt runBlocking Unknown Source at kotlinx coroutines BuildersKt BuildersKt runBlocking$default Builders kt at kotlinx coroutines BuildersKt runBlocking$default Unknown Source at com github wakingrufus kalibrate KalibrateDslBuilder invoke KalibrateDsl kt 92 at com github wakingrufus kalibrate KalibrateDslKt$kalibrate$1 invoke KalibrateDsl kt 125 at com github wakingrufus kalibrate KalibrateDslKt$kalibrate$1 invoke KalibrateDsl kt at com xenomachina argparser SystemExitExceptionKt mainBody SystemExitException kt 74 at com xenomachina argparser SystemExitExceptionKt mainBody$default SystemExitException kt 72 at com github wakingrufus kalibrate KalibrateDslKt kalibrate KalibrateDsl kt 124 at com github wakingrufus kalibrate example MainKt main Main kt 16 ```

elizarov · Answer

< C0A974TJ9|ktor>

wakingrufus · Answer

ah ok i can ask there I was thinking that I am probably doing somethign generally wrong with structured concurrency

wakingrufus · Answer

thanks

elizarov · Answer

It looks like ktor specific problem

bartvh · Answer

Did you find a solution I m experiencing the same issue and Google only turns up discussions of old bugs

wakingrufus · Answer

Not yet Going to pick it back up on monday

wakingrufus · Answer

i took the issue to < C0A974TJ9|ktor> and then opened a youtrack bug

wakingrufus · Answer

i got around this by getting rid of my suspend methods and just using flows and then surrounding just the ktor client calls with `runBlocking `

bartvh · Answer

As it happens I also got around it accidentally while refactoring my code in preparation for using Apache HTTP client instead of Ktor sweat smile It probably disappeared because I made some functions non inline letting them return `String` instead of `receive lt reified T gt ` but can t say for sure which change exactly did it Glad it did though since I didn t have to replace the Ktor client entirely in the end

wakingrufus · Answer

interesting i feel like wrapping all my ktor calls with `runBlocking` seems against the spirit I am trying to maximize the throughput in terms of req sec and so I feel like there must be a better way

wakingrufus · Answer

i have an inline function involved as well

wakingrufus · Answer

but i dont think i can get rid of it

wakingrufus · Answer

since the ktor client need the reified generic