Scala example source code file (Evals.scala)

This example Scala source code file (Evals.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

context, evals, expr, macro, reflection, runtime, t

The Evals.scala Scala example source code

package scala.reflect.macros
package contexts

import scala.reflect.runtime.{universe => ru}
import scala.tools.reflect.ToolBox

trait Evals {
  self: Context =>

  private lazy val evalMirror = ru.runtimeMirror(universe.analyzer.defaultMacroClassloader)
  private lazy val evalToolBox = evalMirror.mkToolBox()
  private lazy val evalImporter = ru.internal.createImporter(universe).asInstanceOf[ru.Importer { val from: universe.type }]

  def eval[T](expr: Expr[T]): T = {
    expr.tree match {
      case global.Literal(global.Constant(value)) =>
        value.asInstanceOf[T]
      case _ =>
        val imported = evalImporter.importTree(expr.tree)
        evalToolBox.eval(imported).asInstanceOf[T]
    }
  }
}