CODEWITHSUNDEEP
androidandroid-studiokotlinandroid-studio-3.0
Stanley Ko
Stanley Ko

Reputation: 3497

Kotlin generic type, Type inference failed

Kotlin reference document said this example is valid.

https://kotlinlang.org/docs/reference/generics.html#upper-bounds

fun <T> cloneWhenGreater(list: List<T>, threshold: T): List<T>
    where T : Comparable<T>,
          T : Cloneable {
  return list.filter { it > threshold }.map { it.clone() }
}

But in Android studio 3.0, it shows thin red line under it.clone(). And error message is:

Type inference failed. Expected type mismatch.
Required: List<T>
Found: List<Any>

Why this example cannot be compiled?

Upvotes: 0

Views: 699

Answers (1)

s1m0nw1
s1m0nw1

Reputation: 82047

The problem is the use of clone(), which is protected as the compiler complains. The problem's already been discussed here: https://discuss.kotlinlang.org/t/is-the-documentation-correct/2925

Upvotes: 1

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