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Compiler crash on self-type with final recursive method #9207

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Compiler crash on self-type with final recursive method#9207
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itype:bugitype:crash
@FabioPinheiro

Description

@FabioPinheiro
FabioPinheiro
opened on Jun 19, 2020

Minimized code

class Child
class HelloTest {
  def simpleTest(): Unit = {
    trait Parent {
      this: Child =>
      final def bar: Int = bar
    }
  }
}

Output (click arrow to expand)

https://scastie.scala-lang.org/DYv2XLcbQb2fbvet4U4FdA

Error while emitting rs$line$1
Exception in thread "main" scala.MatchError: AndType(TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),module class rs$line$1$)),class Child),TypeRef(NoPrefix,trait Parent)) (of class dotty.tools.dotc.core.Types$CachedAndType)
	at dotty.tools.backend.jvm.BCodeHelpers.dotty$tools$backend$jvm$BCodeHelpers$$typeToTypeKind(BCodeHelpers.scala:842)
	at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.toTypeKind(BCodeHelpers.scala:291)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.toTypeKind(BCodeSkelBuilder.scala:57)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.symInfoTK(BCodeSkelBuilder.scala:86)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder$locals$.makeLocal(BCodeSkelBuilder.scala:397)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder$locals$.getOrMakeLocal$$anonfun$1(BCodeSkelBuilder.scala:402)
	at scala.collection.mutable.AnyRefMap.getOrElse(AnyRefMap.scala:155)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder$locals$.getOrMakeLocal(BCodeSkelBuilder.scala:402)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:284)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genStat(BCodeBodyBuilder.scala:93)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genBlock$$anonfun$1(BCodeBodyBuilder.scala:921)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genBlock(BCodeBodyBuilder.scala:921)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:420)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.emitNormalMethodBody$1(BCodeSkelBuilder.scala:584)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genDefDef(BCodeSkelBuilder.scala:619)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:498)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen$$anonfun$1(BCodeSkelBuilder.scala:504)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:504)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genPlainClass(BCodeSkelBuilder.scala:136)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:218)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:185)
	at dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:515)
	at dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:481)
	at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:51)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:318)
	at scala.collection.immutable.List.map(List.scala:246)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:319)
	at dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:55)
	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:180)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$5(Run.scala:190)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:198)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:64)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:205)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:147)
	at dotty.tools.repl.ReplCompiler.runCompilationUnit(ReplCompiler.scala:156)
	at dotty.tools.repl.ReplCompiler.compile(ReplCompiler.scala:166)
	at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:231)
	at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:195)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:128)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:131)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:150)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:131)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.repl.Main.main(Main.scala)

This happens on one of the last phases of compilation, during bytecode encoding.
In the case of Scalajs when the recursive method is final the AST have a local variable $this inside of the method bar. This variable is of the type AndType.
So we get a MatchError AndType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class Child),TypeRef(NoPrefix,trait HelloTest$Parent$1)) on https://github.com/lampepfl/dotty/blob/c46ab152b25ed3e8e3574f7a699477666674a42e/compiler/src/dotty/tools/backend/sjs/JSEncoding.scala#L311

...
private <static> trait HelloTest$Parent$1() extends Object {
  final def bar(): Int = 
    {
      var $this: Child & HelloTest$Parent$1 = this
      while <empty> do 
        tailLabel1[Unit]: 
          {
            $this = $this
            return (return[tailLabel1] ()):Int
          }
    }
}
...
scala.MatchError: AndType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class Child),TypeRef(NoPrefix,trait HelloTest$Parent$1)) (of class dotty.tools.dotc.core.Types$CachedAndType) while compiling /home/fabio/dotty/sandbox/scalajs/src/hello.scala
[error] ## Exception when compiling 1 sources to /home/fabio/dotty/sandbox/scalajs/../out/bootstrap/sjsSandbox/scala-0.26/classes
[error] scala.MatchError: AndType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class Child),TypeRef(NoPrefix,trait HelloTest$Parent$1)) (of class dotty.tools.dotc.core.Types$CachedAndType)
[error] dotty.tools.backend.sjs.JSEncoding$.toTypeRefInternal(JSEncoding.scala:333)
[error] dotty.tools.backend.sjs.JSEncoding$.toIRType(JSEncoding.scala:257)
[error] dotty.tools.backend.sjs.JSCodeGen.genStatOrExpr(JSCodeGen.scala:999)
[error] dotty.tools.backend.sjs.JSCodeGen.genStat(JSCodeGen.scala:907)
[error] dotty.tools.backend.sjs.JSCodeGen.genStatOrExpr$$anonfun$8(JSCodeGen.scala:1119)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.backend.sjs.JSCodeGen.genStatOrExpr(JSCodeGen.scala:1119)
[error] dotty.tools.backend.sjs.JSCodeGen.genExpr(JSCodeGen.scala:926)
[error] dotty.tools.backend.sjs.JSCodeGen.genBody$1(JSCodeGen.scala:879)
[error] dotty.tools.backend.sjs.JSCodeGen.genMethodDef(JSCodeGen.scala:884)
[error] dotty.tools.backend.sjs.JSCodeGen.genMethodWithCurrentLocalNameScope$$anonfun$1(JSCodeGen.scala:848)
[error] dotty.tools.backend.sjs.ScopedVar$.withScopedVars(ScopedVar.scala:35)
[error] dotty.tools.backend.sjs.JSCodeGen.genMethodWithCurrentLocalNameScope(JSCodeGen.scala:854)
[error] dotty.tools.backend.sjs.JSCodeGen.genMethod$$anonfun$1(JSCodeGen.scala:747)
[error] dotty.tools.backend.sjs.ScopedVar$.withScopedVars(ScopedVar.scala:35)
[error] dotty.tools.backend.sjs.JSCodeGen.genMethod(JSCodeGen.scala:748)
[error] dotty.tools.backend.sjs.JSCodeGen.genInterface$$anonfun$1(JSCodeGen.scala:441)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.backend.sjs.JSCodeGen.genInterface(JSCodeGen.scala:448)
[error] dotty.tools.backend.sjs.JSCodeGen.genCompilationUnit$$anonfun$3$$anonfun$1(JSCodeGen.scala:169)
[error] dotty.tools.backend.sjs.ScopedVar$.withScopedVars(ScopedVar.scala:35)
[error] dotty.tools.backend.sjs.JSCodeGen.genCompilationUnit$$anonfun$1(JSCodeGen.scala:175)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.backend.sjs.JSCodeGen.genCompilationUnit(JSCodeGen.scala:177)
[error] dotty.tools.backend.sjs.JSCodeGen.run(JSCodeGen.scala:110)
[error] dotty.tools.backend.sjs.GenSJSIR.run(GenSJSIR.scala:15)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:318)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:319)
[error] dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:180)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$5(Run.scala:190)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:198)
[error] dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:64)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:205)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:142)
[error] dotty.tools.dotc.Run.compile(Run.scala:124)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
[error] dotty.tools.dotc.Driver.process(Driver.scala:194)
[error] dotty.tools.dotc.Main.process(Main.scala)
[error] xsbt.CachedCompilerImpl.run(CachedCompilerImpl.java:69)
[error] xsbt.CompilerInterface.run(CompilerInterface.java:41)
[error] java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] java.base/java.lang.reflect.Method.invoke(Method.java:566)
[error] sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:248)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:122)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:95)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:91)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:186)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:82)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3$adapted(MixedAnalyzingCompiler.scala:77)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:215)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:77)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:146)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:343)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:343)
[error] sbt.internal.inc.Incremental$.doCompile(Incremental.scala:120)
[error] sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:100)
[error] sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:180)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:98)
[error] sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:102)
[error] sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:155)
[error] sbt.internal.inc.Incremental$.compile(Incremental.scala:92)
[error] sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:75)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:348)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:301)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:168)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:248)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:74)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1765)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1738)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:67)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:281)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:19)
[error] sbt.Execute.work(Execute.scala:290)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:281)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
[error] java.base/java.lang.Thread.run(Thread.java:834)
[error]            
[error] stack trace is suppressed; run last sjsSandbox / Compile / compileIncremental for the full output
[error] (sjsSandbox / Compile / compileIncremental) scala.MatchError: AndType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class Child),TypeRef(NoPrefix,trait HelloTest$Parent$1)) (of class dotty.tools.dotc.core.Types$CachedAndType)

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