Macro-based heterogeneous list constructor.

hlist-constructor.scala

import scala.language.experimental.macros
import scala.reflect.macros.Context
import shapeless._

object hlist {
  def apply(xs: Any*) = macro apply_impl

  def apply_impl(c: Context)(xs: c.Expr[Any]*) = {
    import c.universe._

    xs.map(_.tree) match {
      case Seq(Typed(_, Ident(tpnme.WILDCARD_STAR))) => 
        c.abort(c.enclosingPosition, "Can't use _* type ascription here!")

      case _ => xs.foldRight[c.Expr[HList]](reify(HNil)) {
        case (x, acc) => reify(x.splice :: acc.splice)
      }
    }
  }
}

// Now `hlist(1, "a", 'a)` will have inferred type `Int :: String :: Symbol :: HNil`.