The following code compiles with no warning but does not work as intended.

inline def isXAssignableToY[X <: Matchable, Y]: Boolean = {
    inline erasedValue[X] match {
        case _: Y => true
        case _ => false
    }
}

def isSerializable[A <: Matchable]: Boolean = isXAssignableToY[A, Serializable]

def isSuperOfString[B]: Boolean = isXAssignableToY[String, B]

@main def test19058(): Unit = {
    val a = isXAssignableToY[String, Serializable]
    println(a) // prints true as intended

    val b = isSerializable[String]
    println(b) // prints false, not as intended

    val c = isSuperOfString[Serializable]
    println(c) // prints false, not as intended
}

The methods isSerializable and isSuperOfString don’t do what is intended because they pass an abstract type parameter to isXAssignableToY.

How can I constraint the isXAssignableToY method usage such that the compiler complains when the type arguments are abstract type parameters?

This question is related to this other question: Misleading unreachable warning when a type pattern match that is the result of a inline expansion is involved?