suspend fun main() {
	val x = getItems1()
	val y = getItems2()
}

suspend fun getItems1() = httpClient.get<PayloadContainer<Items>>("<https://api.warframe.market/v1/items>").payload

suspend fun getItems2() = httpClient.getUnwrapped<Items>("<https://api.warframe.market/v1/items>")

suspend inline fun <reified PayloadType> HttpClient.getUnwrapped(url: String) =
	get<PayloadContainer<PayloadType>>(url).payload

//for some reason this API wraps all it's payloads in another payload so we need to unwrap 1 layer

data class PayloadContainer<PayloadType>(val payload: PayloadType)

getItems1()

works perfectly fine,

getItems2()

gives me the following error:

class java.util.LinkedHashMap cannot be cast to class payload.Items (java.util.LinkedHashMap is in module java.base of loader 'bootstrap'; payload.Items is in unnamed module of loader 'app')

can someone explain the problem? It seems to have to do with type erasure, but shouldn't

reified

prevent that ?

get<PayloadContainer<PayloadType>>(url).payload

It looks like you are trying to replicate the functionality in Ktor - which allows you to pass a type parameter to the (already reified) HttpClient.get function specifying the destination class of the deserialisation. I can't explain why it's not working but the specific technique they use is here: https://github.com/ktorio/ktor/blob/master/ktor-client/ktor-client-core/jvm/src/io/ktor/client/call/TypeInfoJvm.kt You might have better chances asking in the ktor channel