CODEWITHSUNDEEP
kotlingenericsoverload-resolution
Lukas Eder
Lukas Eder

Reputation: 220762

kotlin overload resolution ambiguity when generic type is bound to Any

Consider this code:

fun main() {
    class A<T> {
        fun m(t: T): Unit {
            print("T")
        }
        fun m(t: List<T>): Unit {
            print("List<T>")
        }
    }
    
    val a: A<Any> = A()
    val l: List<Any> = listOf()
    a.m(l)
}

The a.m(l) call seems to be ambiguous with the following error:

Overload resolution ambiguity: public final fun m(t: Any): Unit defined in main.A public final fun m(t: List<Any>): Unit defined in main.A

My intuition tells me that the m(t: List<T>) overload should be more specific, but my intuition was already wrong once in the past, when I had a similar case in Java.

I can call the "wrong" overload like this:

a.m(l as Any)

But how can I explicitly call the desired m(t: List<T>) overload? Casting a.m(l as List<Any>) doesn't work.

Upvotes: 5

Views: 914

Answers (1)

Lukas Eder
Lukas Eder

Reputation: 220762

An auxiliary function can help:

fun <T> A<T>.mList(l: List<T>) {
    this.m(l);
}
a.mList(l)

Still curious about an alternative that doesn't involve any indirection like this

Upvotes: 1

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