is it possible to define reified generic types in ...

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[janvladimirmostert]

is it possible to define reified generic types in an interface or will i have to pass in the type as a second parameter?

simple example that i'm playing around with:

interface JsonProvider {
	fun <T> fromJson(input: String): T
	fun <T> fromJsonList(input: String): List<T>
}

Gson for example now requires the class type to be passed in:

class Blah : JsonProvider {

	val gson = com.google.gson.Gson()

	override fun <T> fromJson(input: String): T {
		return gson.fromJson(input, T::class.java)
	}

unless that T is reified and fromJson / fromJsonList are inlined, IntelliJ complains and reifying that T inside the interface doesn't seem to be supported.

[diesieben07]

reified only works for inline and inline functions cannot be open (which version should the compiler inline at the call site?). Since every interface method is open, interface methods cannot reasonably use reified.
You should accept a Class<T> in the interface method and then use an inline extension function which has a reified parameter and delegates to the actual interface method.

[Ruckus]

interface JsonProvider {
    fun <T> fromJson(input: String, type: Class<T>)
}

inline fun <reified T> JsonProvider.fromJson(input: String) = fromJson(input, T::class.java)

[janvladimirmostert]

Thanks @diesieben07 and @Ruckus, that makes perfect sense.