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StackOverflow in importers when a symbol has an existential info #8833

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scabug opened this issue Sep 2, 2014 · 5 comments
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StackOverflow in importers when a symbol has an existential info #8833

scabug opened this issue Sep 2, 2014 · 5 comments
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@xeno-by
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@scabug
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scabug commented Sep 2, 2014 

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

case class C[T](i: T)

object Test extends App {
  calculate(C(2))
  def calculate(c: C[_]): Unit = {
    val tree = q"${reify(c).tree}.i"
    cm.mkToolBox().eval(tree)
  }
}
...
	at scala.reflect.internal.Symbols$Symbol.orElse(Symbols.scala:2498)
	at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:193)
	at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
	at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:166)
	at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
	at scala.reflect.internal.Importers$StandardImporter$$anonfun$recreateType$6.apply(Importers.scala:253)
	at scala.reflect.internal.Importers$StandardImporter$$anonfun$recreateType$6.apply(Importers.scala:253)
	at scala.collection.immutable.List.map(List.scala:272)
	at scala.reflect.internal.Importers$StandardImporter.recreateType(Importers.scala:253)
	at scala.reflect.internal.Importers$StandardImporter.importType(Importers.scala:284)
	at scala.reflect.internal.Importers$StandardImporter.recreateSymbol(Importers.scala:107)
	at scala.reflect.internal.Importers$StandardImporter.scala$reflect$internal$Importers$StandardImporter$$cachedRecreateSymbol$1(Importers.scala:145)
	at scala.reflect.internal.Importers$StandardImporter$$anonfun$recreateOrRelink$1$1.apply(Importers.scala:194)
	at scala.reflect.internal.Importers$StandardImporter$$anonfun$recreateOrRelink$1$1.apply(Importers.scala:193)
	at scala.reflect.internal.Symbols$Symbol.orElse(Symbols.scala:2498)
	at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:193)
	at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
	at scala.reflect.internal.Importers$StandardImporter.recreateOrRelink$1(Importers.scala:166)
	at scala.reflect.internal.Importers$StandardImporter.importSymbol(Importers.scala:210)
	at scala.reflect.internal.Importers$StandardImporter$$anonfun$recreateType$6.apply(Importers.scala:253)
...
@scabug
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scabug commented Sep 2, 2014

Imported From: https://issues.scala-lang.org/browse/SI-8833?orig=1
Reporter: @xeno-by
Affected Versions: 2.10.4, 2.11.2

@scabug
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scabug commented Sep 2, 2014

@xeno-by said:
http://stackoverflow.com/questions/25569776/ast-unquoting-using-quasiquotes-and-tree-returned-from-reify

@scabug
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scabug commented Sep 2, 2014

@xeno-by said:
The problem is caused by the existential skolem used in the info of the FreeTermSymbol that represents the captured parameter c. This skolem has the free term as its owner, and that leads to a SO. Importing the free term recurs into importing the info, which recurs into importing all parts of the type, which recurs into importing the skolem, which recurs into importing its owner, etc ad infinitum.

@scabug
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scabug commented Sep 2, 2014

@xeno-by said (edited on Sep 2, 2014 9:06:13 AM UTC):
The workaround is to dissociate the skolem from the free term, e.g. by creating the info for the free term manually like this.

2.10.x:

-val tree = q"${reify(c).tree}"
+val csym = build.newFreeTerm("c", c)
+build.setTypeSignature(csym, typeOf[C[_]])
+val tree = q"$csym.i"

2.11.x:

-val tree = q"${reify(c).tree}"
+val csym = internal.reificationSupport.newFreeTerm("c", c)
+internal.reificationSupport.setInfo(csym, typeOf[C[_]])
+val tree = q"$csym.i"

@SethTisue
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closing all quasiquotes tickets; see #10755

@SethTisue SethTisue mentioned this issue Mar 1, 2018
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