Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Scala reflection doesn't understand Java enumerations #6374

Closed
scabug opened this issue Sep 14, 2012 · 4 comments
Closed

Scala reflection doesn't understand Java enumerations #6374

scabug opened this issue Sep 14, 2012 · 4 comments
Assignees
@xeno-by
Labels
has PR reflection
Milestone
2.10.0-M7

Comments

@scabug
Copy link

scabug commented Sep 14, 2012 

enum SimpleEnumeration {
  FOO,
  BAR
}
import scala.reflect.runtime.universe._

object Test extends App {
  println(typeOf[SimpleEnumeration].declarations)
}
scala.reflect.internal.Symbols$CyclicReference: illegal cyclic reference involving type E
	at scala.reflect.internal.Symbols$Symbol$$anonfun$info$3.apply(Symbols.scala:1188)
	at scala.reflect.internal.Symbols$Symbol$$anonfun$info$3.apply(Symbols.scala:1186)
	at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
	at scala.reflect.internal.Symbols$Symbol.lock(Symbols.scala:468)
	at scala.reflect.internal.Symbols$Symbol.info(Symbols.scala:1186)
	at scala.reflect.internal.Types$$anonfun$40.apply(Types.scala:4316)
	at scala.reflect.internal.Types$$anonfun$40.apply(Types.scala:4315)
	at scala.reflect.internal.util.Collections$class.mapWithIndex(Collections.scala:122)
	at scala.reflect.internal.SymbolTable.mapWithIndex(SymbolTable.scala:12)
	at scala.reflect.internal.Types$class.typeParamsToExistentials(Types.scala:4315)
	at scala.reflect.internal.SymbolTable.typeParamsToExistentials(SymbolTable.scala:12)
	at scala.reflect.internal.Types$class.typeParamsToExistentials(Types.scala:4321)
	at scala.reflect.internal.SymbolTable.typeParamsToExistentials(SymbolTable.scala:12)
	at scala.reflect.internal.Types$$anon$11.apply(Types.scala:4352)
	at scala.reflect.runtime.JavaMirrors$JavaMirror.typeToScala(JavaMirrors.scala:1004)
	at scala.reflect.runtime.JavaMirrors$JavaMirror.typeToScala(JavaMirrors.scala:1007)
	at scala.reflect.runtime.JavaMirrors$JavaMirror$TypeParamCompleter$$anonfun$complete$1.apply(JavaMirrors.scala:567)
	at scala.reflect.runtime.JavaMirrors$JavaMirror$TypeParamCompleter$$anonfun$complete$1.apply(JavaMirrors.scala:567)
	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
	at scala.collection.immutable.List.foreach(List.scala:309)
	at scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
	at scala.collection.AbstractTraversable.map(Traversable.scala:105)
	at scala.reflect.runtime.JavaMirrors$JavaMirror$TypeParamCompleter.complete(JavaMirrors.scala:567)
	at scala.reflect.internal.Symbols$Symbol.info(Symbols.scala:1198)
	at scala.reflect.internal.Types$$anonfun$40.apply(Types.scala:4316)
	at scala.reflect.internal.Types$$anonfun$40.apply(Types.scala:4315)
	at scala.reflect.internal.util.Collections$class.mapWithIndex(Collections.scala:122)
	at scala.reflect.internal.SymbolTable.mapWithIndex(SymbolTable.scala:12)
	at scala.reflect.internal.Types$class.typeParamsToExistentials(Types.scala:4315)
	at scala.reflect.internal.SymbolTable.typeParamsToExistentials(SymbolTable.scala:12)
	at scala.reflect.internal.Types$class.typeParamsToExistentials(Types.scala:4321)
	at scala.reflect.internal.SymbolTable.typeParamsToExistentials(SymbolTable.scala:12)
	at scala.reflect.internal.Types$$anon$11.apply(Types.scala:4352)
	at scala.reflect.runtime.JavaMirrors$JavaMirror.typeToScala(JavaMirrors.scala:1004)
	at scala.reflect.runtime.JavaMirrors$JavaMirror.typeToScala(JavaMirrors.scala:1007)
	at scala.reflect.runtime.JavaMirrors$JavaMirror$FromJavaClassCompleter.completeRest(JavaMirrors.scala:653)
	at scala.reflect.runtime.JavaMirrors$JavaMirror$FromJavaClassCompleter.complete(JavaMirrors.scala:644)
	at scala.reflect.internal.Symbols$Symbol.info(Symbols.scala:1198)
	at scala.reflect.internal.Types$TypeRef.decls(Types.scala:2421)
	at scala.reflect.internal.Types$TypeApiImpl.declarations(Types.scala:298)
	at scala.reflect.internal.Types$TypeApiImpl.declarations(Types.scala:295)
	at Test$delayedInit$body.apply(Test.scala:4)
	at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
	at scala.App$$anonfun$main$1.apply(App.scala:61)
	at scala.App$$anonfun$main$1.apply(App.scala:61)
	at scala.collection.immutable.List.foreach(List.scala:309)
	at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:32)
	at scala.collection.mutable.ListBuffer.foreach(ListBuffer.scala:45)
	at scala.App$class.main(App.scala:61)
	at Test$.main(Test.scala:3)
	at Test.main(Test.scala)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at scala.tools.nsc.util.ScalaClassLoader$$anonfun$run$1.apply(ScalaClassLoader.scala:71)
	at scala.tools.nsc.util.ScalaClassLoader$class.asContext(ScalaClassLoader.scala:31)
	at scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.asContext(ScalaClassLoader.scala:139)
	at scala.tools.nsc.util.ScalaClassLoader$class.run(ScalaClassLoader.scala:71)
	at scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.run(ScalaClassLoader.scala:139)
	at scala.tools.nsc.CommonRunner$class.run(ObjectRunner.scala:28)
	at scala.tools.nsc.ObjectRunner$.run(ObjectRunner.scala:45)
	at scala.tools.nsc.CommonRunner$class.runAndCatch(ObjectRunner.scala:35)
	at scala.tools.nsc.ObjectRunner$.runAndCatch(ObjectRunner.scala:45)
	at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:74)
	at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:96)
	at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:105)
	at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
@scabug
Copy link
Author

scabug commented Sep 14, 2012

Imported From: https://issues.scala-lang.org/browse/SI-6374?orig=1
Reporter: @xeno-by
Affected Versions: 2.10.0
Other Milestones: 2.10.0

@scabug
Copy link
Author

scabug commented Sep 14, 2012

@xeno-by said (edited on Sep 17, 2012 12:05:00 PM UTC):
Here's the deal:

  1. SimpleEnumeration is being completed. Completion triggers typeToScala(superclazz), which is Enum
    =======
  2. typeToScala(Enum) recurs into typeToScala(Enum)
  3. typeToScala(Enum) = rawToExistential(typeRef(clazz.owner.thisType, clazz, List()))
  4. rawToExistential = existentialAbstraction(mapOver(typeParamsToExistentials(sym)), typeRef(apply(pre), sym, mapOver(typeParamsToExistentials(sym)) map (_.tpe)))
  5. typeParamsToExistentials = clazz.newExistential(newTypeName("?"+i), clazz.pos) setInfo tparam.info.bounds
  6. tparam.info = TypeParamCompleter.complete
  7. TypeParamCompleter.complete = sym setInfo TypeBounds.upper(glb(jtvar.getBounds.toList map typeToScala map objToAny))
  8. Since Enum is defined as Enum<E extends Enum>, jtvar.getBounds map typeToScala recurs back into Step 2, with the argument being not Enum, but Enum, which eventually leads to a cyclic reference

I can't immediately see how to evade the error. Could anyone chime in?

@scabug
Copy link
Author

scabug commented Sep 17, 2012

@xeno-by said:
scala/scala#1324

@scabug
Copy link
Author

scabug commented Sep 19, 2012

@gkossakowski said:
Closed in scala/scala#1324

@scabug scabug closed this as completed Sep 19, 2012
@scabug scabug added this to the 2.10.0-M7 milestone Apr 7, 2017
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees

@xeno-by xeno-by

Labels
has PR reflection
Projects
None yet
Milestone
2.10.0-M7
Development

No branches or pull requests
2 participants
@xeno-by @scabug