//KT-1191 Wrong detection of unused parameters package kt1191 trait FunctionalList { val size: Int val head: T val tail: FunctionalList } fun FunctionalList.plus(element: T) : FunctionalList = object: FunctionalList { override val size: Int get() = 1 + this@plus.size override val tail: FunctionalList get() = this@plus override val head: T get() = element } fun foo(unused: Int) = object { val a : Int get() = unused }