Backend crash when inlined method contains try

[smarter]

object Test {
  inline def crash() = {
    try {
      println("hi")
    }
  }

  def main(args: Array[String]): Unit = {
    crash()
  }
}

Unexpected tree in genLoad: EmptyTree/class dotty.tools.dotc.ast.Trees$Thicket at: <no position>
java.lang.RuntimeException: Unexpected tree in genLoad: EmptyTree/class dotty.tools.dotc.ast.Trees$Thicket at: <no position>
        at dotty.tools.backend.jvm.DottyBackendInterface.abort(DottyBackendInterface.scala:381)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:431)
        at scala.tools.nsc.backend.jvm.BCodeSyncAndTry$SyncAndTryBuilder.emitFinalizer(BCodeSyncAndTry.scala:376)
        at scala.tools.nsc.backend.jvm.BCodeSyncAndTry$SyncAndTryBuilder.genLoadTry(BCodeSyncAndTry.scala:293)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:307)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.emitNormalMethodBody$1(BCodeSkelBuilder.scala:607)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genDefDef(BCodeSkelBuilder.scala:641)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:510)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:512)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genPlainClass(BCodeSkelBuilder.scala:119)
        at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:201)
        at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:154)
        at dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:357)
        at dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:323)
        at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:56)
        at dotty.tools.dotc.core.Phases$Phase$$anonfun$runOn$1.apply(Phases.scala:283)
        at dotty.tools.dotc.core.Phases$Phase$$anonfun$runOn$1.apply(Phases.scala:281)
        at scala.collection.immutable.List.map(List.scala:273)
        at dotty.tools.dotc.core.Phases$Phase$class.runOn(Phases.scala:281)
        at dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:40)
        at dotty.tools.dotc.Run$$anonfun$compileUnits$1$$anonfun$apply$mcV$sp$1.apply(Run.scala:76)
        at dotty.tools.dotc.Run$$anonfun$compileUnits$1$$anonfun$apply$mcV$sp$1.apply(Run.scala:73)
        at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
        at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:186)
        at dotty.tools.dotc.Run$$anonfun$compileUnits$1.apply$mcV$sp(Run.scala:73)
        at dotty.tools.dotc.Run$$anonfun$compileUnits$1.apply(Run.scala:67)
        at dotty.tools.dotc.Run$$anonfun$compileUnits$1.apply(Run.scala:67)
        at dotty.tools.dotc.util.Stats$.monitorHeartBeat(Stats.scala:76)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:67)
        at dotty.tools.dotc.Run.compileSources(Run.scala:64)
        at dotty.tools.dotc.Run.compile(Run.scala:48)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:26)
        at dotty.tools.dotc.Driver.process(Driver.scala:124)
        at dotty.tools.dotc.Driver.process(Driver.scala:93)
        at dotty.tools.dotc.Driver.process(Driver.scala:105)
        at dotty.tools.dotc.Driver.main(Driver.scala:132)
        at dotty.tools.dotc.Main.main(Main.scala)

[DarkDimius]

It's not due to backend.
We should augment Ycheck to ensure that there are no Thickets\EmptyTrees.

[smarter]

We should augment Ycheck to ensure that there are no Thickets\EmptyTrees.

Are you sure? There are many cases where EmptyTree reaches backend, for example here's the tree for an empty class at genBCode (all the Thicket(List()) are just EmptyTree):

PackageDef(Ident(<empty>), List(
  TypeDef(Test, 
    Template(
      DefDef(<init>, List(), List(List()), TypeTree(), 
        Block(List(
          Apply(Select(Super(This(Ident(Test)), Ident()), <init>), List())
        ), Literal(()))
      )
    , List(TypeTree()), ValDef(_, Thicket(List()), Thicket(List())), List())
  )
))

[smarter]

Here's the tree of my original example that crashes:

PackageDef(Ident(<empty>), List(
  TypeDef(Test$, 
    Template(
      DefDef(<init>, List(), List(List()), TypeTree(), 
        Block(List(
          Apply(Select(Super(This(Ident(Test$)), Ident()), <init>), List())
        ), Literal(()))
      )
    , List(TypeTree()), ValDef(_, Thicket(List()), Thicket(List())), List(
      DefDef(crash, List(), List(List()), TypeTree(), 
        Try(Apply(Ident(println), List(Literal("hi"))), List(), Thicket(List()))
      )
    ,
      DefDef(main, List(), List(List(ValDef(args, TypeTree(), Thicket(List()))))
        , 
      TypeTree(), 
        Try(Apply(Ident(println), List(Literal("hi"))), List(), Thicket(List()))
      )
    ))
  )
,ValDef(Test, TypeTree(), Apply(Select(New(TypeTree()), <init>), List()))))

I can't see any difference between crash (which compiles fine by itself) and main (which causes the crash)

[DarkDimius]

@smarter, I've meant the method bodies. The Backend ignores the high-level tree structure of packages and classes and uses types instead.

[smarter]

Found the issue, will make a PR soon.