gistfile1.scala

package examples

object SJ extends App {

  trait Getter[T] {
    def get(s: String): Option[T]
  }

  def get[T: Getter](s: String, default: T): T =
    implicitly[Getter[T]].get(s).getOrElse(default)

  // another way to write 'get'
  def get2[T](s: String, default: T)(implicit g: Getter[T]): T =
    g.get(s).getOrElse(default)

  implicit val getInt = new Getter[Int] {
    def get(s: String): Option[Int] =
      try {
        Some(s.toInt)
      } catch {
        case _: NumberFormatException => None
      }
  }

  implicit val getString = new Getter[String] {
    def get(s: String): Option[String] = Option(s)
  }

  println(get("123", 456))
  println(get("foo", 456))
  println(get("foo", "bar"))
  println(get(null, "baz"))

}

Imagine get() is defined without the default, i.e.:

def get[[T: Getter]](s: String): T = ...

Now assume we have 2 case classes as follows:

case class A(a: String)
case class B(a: Int)

It looks like the types of the case class values aren't considered during type inference. In particular, the compiler complains of ambiguous implicit types with the following:

A(get("someString"))
B(get("someInt"))

Any ideas? Thanks!