Anonymous class methods don't work

[kazachonak]

The code:

class A

class Test {
  val a = new A {
    def some = "Works"
  } 
  a.some
}

The exception during scalac:

   [scalac] scala.reflect.internal.MissingRequirementError: class scala.runtime.EmptyMethodCache not found.
   [scalac]     at scala.reflect.internal.MissingRequirementError$.signal(MissingRequirementError.scala:16)
   [scalac]     at scala.reflect.internal.MissingRequirementError$.notFound(MissingRequirementError.scala:17)
   [scalac]     at scala.reflect.internal.Definitions$definitions$$anonfun$getModuleOrClass$3.apply(Definitions.scala:697)
   [scalac]     at scala.reflect.internal.Definitions$definitions$$anonfun$getModuleOrClass$3.apply(Definitions.scala:697)
   [scalac]     at scala.reflect.internal.Symbols$Symbol.orElse(Symbols.scala:1773)
   [scalac]     at scala.reflect.internal.Definitions$definitions$.getModuleOrClass(Definitions.scala:696)
   [scalac]     at scala.reflect.internal.Definitions$definitions$.getModuleOrClass(Definitions.scala:705)
   [scalac]     at scala.reflect.internal.Definitions$definitions$.getClass(Definitions.scala:662)
   [scalac]     at scala.reflect.internal.Definitions$definitions$.EmptyMethodCacheClass(Definitions.scala:331)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.mkNewPolyCache$1(CleanUp.scala:246)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.reflectiveMethodCache$1(CleanUp.scala:247)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer$$anonfun$callAsReflective$1$1.cache$1(CleanUp.scala:408)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer$$anonfun$callAsReflective$1$1.lookup$1(CleanUp.scala:409)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer$$anonfun$callAsReflective$1$1.invocation$1(CleanUp.scala:411)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer$$anonfun$callAsReflective$1$1.genDefaultCall$1(CleanUp.scala:419)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer$$anonfun$callAsReflective$1$1.apply(CleanUp.scala:451)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer$$anonfun$callAsReflective$1$1.apply(CleanUp.scala:350)
   [scalac]     at scala.tools.nsc.ast.TreeGen.evalOnce(TreeGen.scala:210)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.callAsReflective$1(CleanUp.scala:350)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.transform(CleanUp.scala:502)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transformStats$1.apply(Trees.scala:1245)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transformStats$1.apply(Trees.scala:1243)
   [scalac]     at scala.collection.immutable.List.loop$1(List.scala:150)
   [scalac]     at scala.collection.immutable.List.mapConserve(List.scala:166)
   [scalac]     at scala.reflect.api.Trees$Transformer.transformStats(Trees.scala:1243)
   [scalac]     at scala.reflect.api.Trees$Transformer.transform(Trees.scala:1157)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.transform(CleanUp.scala:655)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transform$5.apply(Trees.scala:1143)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transform$5.apply(Trees.scala:1141)
   [scalac]     at scala.reflect.api.Trees$Transformer.atOwner(Trees.scala:1252)
   [scalac]     at scala.reflect.api.Trees$Transformer.transform(Trees.scala:1140)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.transform(CleanUp.scala:655)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transformTrees$1.apply(Trees.scala:1227)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transformTrees$1.apply(Trees.scala:1227)
   [scalac]     at scala.collection.immutable.List.loop$1(List.scala:150)
   [scalac]     at scala.collection.immutable.List.mapConserve(List.scala:166)
   [scalac]     at scala.reflect.api.Trees$Transformer.transformTrees(Trees.scala:1227)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.transform(CleanUp.scala:559)
   [scalac]     at scala.reflect.api.Trees$Transformer.transformTemplate(Trees.scala:1229)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transform$2.apply(Trees.scala:1127)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transform$2.apply(Trees.scala:1126)
   [scalac]     at scala.reflect.api.Trees$Transformer.atOwner(Trees.scala:1252)
   [scalac]     at scala.reflect.api.Trees$Transformer.transform(Trees.scala:1125)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.transform(CleanUp.scala:655)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transformStats$1.apply(Trees.scala:1245)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transformStats$1.apply(Trees.scala:1243)
   [scalac]     at scala.collection.immutable.List.loop$1(List.scala:150)
   [scalac]     at scala.collection.immutable.List.mapConserve(List.scala:166)
   [scalac]     at scala.reflect.api.Trees$Transformer.transformStats(Trees.scala:1243)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transform$1.apply(Trees.scala:1121)
   [scalac]     at scala.reflect.api.Trees$Transformer$$anonfun$transform$1.apply(Trees.scala:1121)
   [scalac]     at scala.reflect.api.Trees$Transformer.atOwner(Trees.scala:1252)
   [scalac]     at scala.reflect.api.Trees$Transformer.transform(Trees.scala:1120)
   [scalac]     at scala.tools.nsc.transform.CleanUp$CleanUpTransformer.transform(CleanUp.scala:655)
   [scalac]     at scala.tools.nsc.ast.Trees$Transformer.transformUnit(Trees.scala:204)
   [scalac]     at scala.tools.nsc.transform.Transform$Phase.apply(Transform.scala:30)
   [scalac]     at scala.tools.nsc.Global$GlobalPhase.applyPhase(Global.scala:374)
   [scalac]     at scala.tools.nsc.Global$GlobalPhase$$anonfun$run$1.apply(Global.scala:344)
   [scalac]     at scala.tools.nsc.Global$GlobalPhase$$anonfun$run$1.apply(Global.scala:344)
   [scalac]     at scala.collection.Iterator$class.foreach(Iterator.scala:690)
   [scalac]     at scala.collection.mutable.ListBuffer$$anon$1.foreach(ListBuffer.scala:319)
   [scalac]     at scala.tools.nsc.Global$GlobalPhase.run(Global.scala:344)
   [scalac]     at scala.tools.nsc.Global$Run.compileUnits(Global.scala:1066)
   [scalac]     at scala.tools.nsc.Global$Run.compileSources(Global.scala:1041)
   [scalac]     at scala.tools.nsc.Global$Run.compile(Global.scala:1154)
   [scalac]     at scala.tools.ant.Scalac.executeInternal(Scalac.scala:618)
   [scalac]     at scala.tools.ant.Scalac.execute(Scalac.scala:566)
   [scalac]     at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
   [scalac]     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   [scalac]     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
   [scalac]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   [scalac]     at java.lang.reflect.Method.invoke(Method.java:601)
   [scalac]     at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
   [scalac]     at org.apache.tools.ant.Task.perform(Task.java:348)
   [scalac]     at org.apache.tools.ant.Target.execute(Target.java:390)
   [scalac]     at org.apache.tools.ant.Target.performTasks(Target.java:411)
   [scalac]     at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
   [scalac]     at org.apache.tools.ant.Project.executeTarget(Project.java:1368)
   [scalac]     at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
   [scalac]     at org.eclipse.ant.internal.launching.remote.EclipseDefaultExecutor.executeTargets(EclipseDefaultExecutor.java:32)
   [scalac]     at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
   [scalac]     at org.eclipse.ant.internal.launching.remote.InternalAntRunner.run(InternalAntRunner.java:424)
   [scalac]     at org.eclipse.ant.internal.launching.remote.InternalAntRunner.main(InternalAntRunner.java:138)

I'm using 0.1-M3.
I would like to test on the latest sources, but the build process seems not straightforward.

By the way, thank you for making Scala+GWT possible!

[gkossakowski]

Hi,

The problem here is not with anonymous classes per-se but with structural types that are introduced very often when anonymous classes are involved.

In order to verify if structural types are guilty could you check if following code works?

class A {
  def some: String
}

class Test {
  val a: A = new A {
    def some = "Works"
  }
  a.some
}

[kazachonak]

This works

abstract class A {
 def some: String
}

class Test {
 val a: A = new A {
   def some = "Some"
 }
 a.some
}

Even this works

abstract class A {
 def some: String
}

class Test {
 val a = new A {
   def some = "Some"
   def some2 = "Some2"
 }
 a.some
}

This don't work

abstract class A {
 def some: String
}

class Test {
 val a = new A {
   def some = "Some"
   def some2 = "Some2"
 }
 a.some2
}

[gkossakowski]

Thanks for testing. It's clear that structural types are an issue here and not anonymous classes (although structural types arise often from anonymous classes). There's nothing we can do about structural types without deep changes to GWT.

Therefore, for the time being we should just give people proper error message instead of compiler crash when structural types are involved. I'll change the title and work on better error message.