Closed
Description
Compiler version
From 3.0.0 to 3.3.1.
Minimized code
This code compiles fine, but fails at runtime with a ClassCastException. Note that it contains no @uncheckedVariance annotations or forced down-casting:
class Box[+A](value: A) {
private var cached: A = value
def get: A = cached
def put[AA >: A](value: AA): Unit = {
val box: Box[AA] = this
box.cached = value
}
}
trait Animal
object Dog extends Animal
object Cat extends Animal
val dogBox: Box[Dog.type] = new Box(Dog)
dogBox.put(Cat)
val dog: Dog.type = dogBox.getNote: I actually noticed this in the lampepfl/gears repository (see sample).
Expectation
The compiler should issue an error like:
Covariant type A occurs in contravariant position in type A of value cached