Check if type is concrete

gistfile1.txt

  def f[T]: Unit = macro f_impl[T]

  def f_impl[T: c.WeakTypeTag](c: Context): c.Expr[Unit] = {
    import c.universe._

    def isConcreteTypeSymbol(sym: Symbol) =
      sym.isType && !sym.asType.isAbstractType

    def isConcreteType(tpe: Type): Boolean = tpe match {
      case NoPrefix =>
        println("NoPrefix")
        false

      case TypeRef(pre, sym, args) =>
        println(s"TypeRef($pre, $sym, $args)")
        isConcreteType(pre) &&
        isConcreteTypeSymbol(sym) &&
        args.forall(isConcreteType)

      case ExistentialType(quantified, underlying) =>
        println(s"ExistentialType($quantified, $underlying)")
        false

      case _ =>
        println(tpe)
        isConcreteTypeSymbol(tpe.typeSymbol)
    }

    if(!isConcreteType(weakTypeOf[T])) {
      c.error(c.enclosingPosition, "You must provide concrete type.")
    } else {
      c.echo(c.enclosingPosition, "Ok")
    }

    c.literalUnit
  }