Unfortunately, reify
is not flexible enough for your use case, but there's good news. In macro paradise (and most likely in 2.11.0) we have a better tool to construct trees, called quasiquotes: http://docs.scala-lang.org/overviews/macros/quasiquotes.html.
scala> def makeList_impl(c: Context)(clazz: c.Expr[Class[_]]): c.Expr[Any] = {
| import c.universe._
| val ConstantType(Constant(tpe: Type)) = clazz.tree.tpe
| c.Expr[Any](q"List[$tpe]()")
| }
makeList_impl: (c: scala.reflect.macros.Context)(clazz: c.Expr[Class[_]])c.Expr[Any]
scala> def makeList(clazz: Class[_]): Any = macro makeList_impl
defined term macro makeList: (clazz: Class[_])Any
scala> makeList(classOf[Int])
res2: List[Int] = List()
scala> makeList(classOf[String])
res3: List[String] = List()
Quasiquotes are even available in 2.10.x with a minor tweak to the build process (http://docs.scala-lang.org/overviews/macros/paradise.html#macro_paradise_for_210x), so you might want to give them a try.