musing on setFromAny

lollift.scala

// goal: define one method which can be given arguments of different types (i.e. without a common supertype)
// lift (diaf) uses setFromAny(arg: Any) and a match, but in doing so loses typesafety. 

case class Foo(i: Int)
case class Bar(v: String)
case class Baz(d: Boolean)

val foo = Foo(1)
val bar = Bar("1")
val baz = Baz(false)

case class QuxArgument[T](value: T)
implicit def fooToQuxArg(x: Foo): QuxArgument[Foo] = QuxArgument(x)
implicit def barToQuxArg(x: Bar): QuxArgument[Bar] = QuxArgument(x)

def qux[T](v: QuxArgument[T]) = v.value match {
  case Foo(x) => println("foo "+x)
  case Bar(x) => println("bar "+x)
  case i => println("wtf "+i)
}

scala> qux(foo)
foo: 1

scala> qux(bar)
bar: 1

scala> qux(baz)
<console>:38: error: type mismatch;
 found   : Baz
 required: QuxArgument[?]
              qux(baz)