Type inference of "case class".copy being erased

[arontsang]

case class Foo[T, TCollection <: Iterable[T]](collection: TCollection, name: String)

def doStuff[T, TCollection <: Iterable[T]](foo: Foo[T, TCollection]){
  println(foo.name)
}

val foo = Foo[Int, Seq[Int]](Seq(1, 2), "foo")
doStuff(foo)
val bar = foo.copy(name = "bar")
doStuff(bar)

The code fails to compile on the last line, as T for bar has been erased to Nothing.

[Jasper-M]

If you agree you have to pass the type arguments explicitly when you construct a Foo from scratch, why not when you construct one by copying?

scala> val bar = foo.copy[Int, Seq[Int]](name = "bar")
bar: Foo[Int,Seq[Int]] = Foo(List(1, 2),bar)