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import scala.reflect.runtime.universe._
import scala.reflect.runtime.{universe => ru}
import scala.reflect.macros.blackbox.Context
import scala.language.experimental.macros
case class Utils[C <: Context]( c:C ) {
import c.universe._
import c.{Tree=>_}
object removeDoubleReify extends c.universe.Transformer {
def apply( tree:Tree ) = transform(tree)
override def transform(tree: Tree): Tree = {
super.transform {
tree match {
case Apply(TypeApply(Select(_this, termname), _), reification::Nil )
if termname.toString == "factory" => c.unreifyTree(reification)
case Apply(Select(_this, termname), reification::Nil )
if termname.toString == "factory" => c.unreifyTree(reification)
case _ => tree
}
}
}
}
}
object QueryableMacros{
def _helper[C <: Context,S:c.WeakTypeTag]( c:C )( name:String, projection:c.Expr[_] ) = {
import c.universe._
import internal._
val element_type = implicitly[c.WeakTypeTag[S]].tpe
val foo = c.Expr[ru.Expr[Queryable[S]]](
c.reifyTree( gen.mkRuntimeUniverseRef, EmptyTree, c.typecheck(
Utils[c.type](c).removeDoubleReify(
Apply(Select(c.prefix.tree, TermName( name )), List( projection.tree ))
).asInstanceOf[Tree]
)))
c.universe.reify{ Queryable.factory[S]( foo.splice )}
}
def map[T:c.WeakTypeTag, S:c.WeakTypeTag]
(c: Context)
(projection: c.Expr[T => S]): c.Expr[Queryable[S]] = _helper[c.type,S]( c )( "_map", projection )
}
class Queryable[T]{
def _map[S]( projection: T => S ) : Queryable[S] = ???
def map[S]( projection: T => S ) : Queryable[S] = macro QueryableMacros.map[T,S]
}
object Queryable{
def factory[S]( projection:ru.Expr[Queryable[S]] ) : Queryable[S] = null
}
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