That GsonBuilder example is also screaming for an extension function like so: inline fun <reified T> GsonBuilder.registerTypeAdapter(adapter: Any) = this.reg

That GsonBuilder example is also screaming for an extension function like so: inline fun <reified T> GsonBuilder.registerTypeAdapter(adapter: Any) = this.registerTypeAdapter(T::class.java, adapter) Bam, now it'd be: val gson = GsonBuilder().registerTypeAdapter<LocalDate>(LocalDateAdapter()).create()