Tried to avoid a specific literal type widening with an implicit class:
implicit class keepAsListOfInt(val listOfInt: List[Int]) extends AnyVal { def :+(long: Long): List[Int] = listOfInt :+ long.toInt } // Won't compile - already widened to List[AnyVal] val listOfInt: List[Int] = List(1) :+ 2L But since the compiler has already widened the expression List(1) :+ 2L to List[AnyVal] the implicit conversion is never called. Can I somehow enforce the conversion implicitly?
UPDATE - Thanks to sachav's reply and Alexey's valid concerns, the following code seems to do the job:
import scala.language.implicitConversions implicit def listAnyValToListInt(l: List[AnyVal]): List[Int] = l.map { case n: Int => n case n: Long if n < Int.MinValue => throw new IllegalArgumentException("Can't cast too small Long to Int: " + n) case n: Long if n > Int.MaxValue => throw new IllegalArgumentException("Can't cast too big Long to Int: " + n) case n: Long => n.toInt case v => throw new IllegalArgumentException("Invalid value: " + v) } val valid: List[Int] = List(1) :+ 2 val invalid: List[Int] = List(1) :+ 30000000000L // fails at runtime It would still be nice though if there was a compile-time solution.
