CODEWITHSUNDEEP
scalareflectionscala-2.10scala-quasiquotes
yjshen
yjshen

Reputation: 6693

AST unquoting using quasiquotes and tree returned from reify

I was trying to use Toolbox and quasiquote together to do code generation tasks, and faced with StackOverflowError while using AST of object returned from reify(x).tree, my code is as follows:

abstract class A[T] {def i: T}
class B(val i: Int) extends A[Int]
object A {

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

    val javaSeparator = "$"
    val curId = new java.util.concurrent.atomic.AtomicInteger()

    protected def freshName(prefix: String): TermName = {
        newTermName(s"$prefix$javaSeparator${curId.getAndIncrement}")
 }

 def main(args: Array[String]) {
    val b = new B(2)
    calculate(b)
 }

 def calculate(a: A[_]): Unit = {

    val toolBox = runtimeMirror(getClass.getClassLoader).mkToolBox()
    val i = freshName("i")
    val aTree = reify(a).tree

    val tree = q"""
       val $i = $aTree.i
      println($i)
   """

   toolBox.eval(tree)
  }
}

when I remove type parameter of class A or use def calculate(a: B), the toolBox.eval success and work as expected, i.e. print 2 in console.

I don't quite understand why this happens, can someone explain why class definition with type parameters fails the evaluation?

Upvotes: 1

Views: 537

Answers (1)

Eugene Burmako
Eugene Burmako

Reputation: 13048

This is https://issues.scala-lang.org/browse/SI-8833. Until the bug is fixed, you can use a workaround outlined in the comments in JIRA. I've only provided a workaround for 2.11.x, and if you need one for 2.10.x, please leave a comment.

Upvotes: 1

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