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Singleton type leaks from transparent inline method with double opaque types #26785

Open
Open
Singleton type leaks from transparent inline method with double opaque types#26785
Assignees
jchyb
Labels
area:inlinearea:opaque-typesitype:bugitype:crashregressionThis worked in a previous version but doesn't anymore

Description

@maxbanister
maxbanister
opened on Aug 12, 2026

Compiler version

3.8.3

https://scastie.scala-lang.org/nwKctBj1TzuIF5hQOx9gjg

Minimized code

enum HList[+T]:
	case HNil extends HList[Nothing]
	case HCons[T0, E <: T0, L <: HList[T0]](h: E, t: L) extends HList[T0]

import HList.*

object Append:
	//                    v This variance causes typer to crash
	opaque type Append[T, +E <: T, L <: HList[T]] <: HList[T] = HList[T]
	def append[T, E <: T](lst: HList[T], elem: E): Append[T, E, lst.type] = ???
	transparent inline def apply[T, E <: T](lst: HList[T], elem: E): Append[T, E, lst.type] =
		append[T, E](lst, elem)

object Rev:
	opaque type Rev[T, L <: HList[T]] <: HList[T] = HList[T]
	def rev[T](lst: HList[T]): Rev[T, lst.type] = ???
	transparent inline def apply[T](lst: HList[T]): Rev[T, lst.type] =
		inline lst match
			case HNil => HNil
			case HCons(h, t) =>
				// This is the problematic line
				Append(Rev.rev(t), h)

object TestMain:
	import Rev.Rev
	def failure[T, L <: HList[T]](lst: L): Nothing =
		lst match
			case base: HNil.type => ???
			case ind @ HCons(h, t) =>
				// Failure originates here
				val g = Rev(ind)
		???

Output (click arrow to expand)

Details 
[error] ## Exception when compiling 3 sources to /home/max/IdeaProjects/typeshit/target/scala-3.8.3/classes
[error] java.lang.AssertionError: assertion failed: leak: (t : L$2) in {
[error]   val $scrutinee1: (ind : HList.HCons[T0$2, E$2, L$2] & L) = ind
[error]   val $proxy2: E$2 = $scrutinee1.h
[error]   val h: E$2 = $proxy2
[error]   val $proxy3: L$2 = $scrutinee1.t
[error]   val t: L$2 = $proxy3
[error]   {
[error]     val $proxy4: Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]} =
[error]       Append.$asInstanceOf[
[error]         Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]}]
[error]     val Append$_this:
[error]       ($proxy4 : Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]})
[error]        = $proxy4
[error]     val lst$proxy1: Rev.Rev[T0$2, (t : L$2)] = Rev.rev[T0$2](t)
[error]     Append$_this.append[T0$2, E$2](lst$proxy1, h)
[error]   }.$asInstanceOf[
[error]     Append.Append[T0$2, E$2, (?1 : Rev.Rev[T0$2, (t : L$2)])] &
[error]       Append.Append[T0$2, E$2, (lst$proxy1 : Rev.Rev[T0$2, (t : L$2)])]
[error]   ]:Append.Append[T0$2, E$2, (lst$proxy1 : Rev.Rev[T0$2, (t : L$2)])]
[error] }
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:10)
[error] dotty.tools.dotc.typer.Typer.ensureNoLocalRefs(Typer.scala:1604)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1560)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3811)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] dotty.tools.dotc.inlines.Inliner$InlineTyper.typedUnadapted(Inliner.scala:1070)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] dotty.tools.dotc.inlines.Inliner$InlineTyper.reduceInlineMatchExpr$1(Inliner.scala:1040)
[error] dotty.tools.dotc.inlines.Inliner$InlineTyper.typedMatchFinish(Inliner.scala:1054)
[error] dotty.tools.dotc.typer.Typer.typedMatch(Typer.scala:2227)
[error] dotty.tools.dotc.inlines.Inliner$InlineTyper.typedMatch(Inliner.scala:977)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3818)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] dotty.tools.dotc.inlines.Inliner$InlineTyper.typedUnadapted(Inliner.scala:1070)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.inlines.Inliner.inlined(Inliner.scala:797)
[error] dotty.tools.dotc.inlines.Inlines$InlineCall.expand(Inlines.scala:585)
[error] dotty.tools.dotc.inlines.Inlines$.inlineCall(Inlines.scala:188)
[error] dotty.tools.dotc.typer.Typer.adaptNoArgsOther$1(Typer.scala:4789)
[error] dotty.tools.dotc.typer.Typer.adaptNoArgs$1(Typer.scala:4897)
[error] dotty.tools.dotc.typer.Typer.adapt1(Typer.scala:5166)
[error] dotty.tools.dotc.typer.Typer.adapt(Typer.scala:4366)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] dotty.tools.dotc.typer.Namer.typedAheadExpr$$anonfun$1(Namer.scala:1831)
[error] dotty.tools.dotc.typer.Namer.typedAhead(Namer.scala:1821)
[error] dotty.tools.dotc.typer.Namer.typedAheadExpr(Namer.scala:1831)
[error] dotty.tools.dotc.typer.Namer.typedAheadRhs$1$$anonfun$1(Namer.scala:2218)
[error] dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
[error] dotty.tools.dotc.typer.Namer.typedAheadRhs$1(Namer.scala:2218)
[error] dotty.tools.dotc.typer.Namer.rhsType$1(Namer.scala:2226)
[error] dotty.tools.dotc.typer.Namer.cookedRhsType$1(Namer.scala:2256)
[error] dotty.tools.dotc.typer.Namer.lhsType$1(Namer.scala:2257)
[error] dotty.tools.dotc.typer.Namer.inferredResultType(Namer.scala:2269)
[error] dotty.tools.dotc.typer.Namer.inferredType$1(Namer.scala:1874)
[error] dotty.tools.dotc.typer.Namer.valOrDefDefSig(Namer.scala:1880)
[error] dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:839)
[error] dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:1013)
[error] dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:876)
[error] dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:176)
[error] dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:190)
[error] dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:192)
[error] dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:404)
[error] dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:3750)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3775)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3896)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:4011)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:4058)
[error] dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1537)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1541)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3811)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] dotty.tools.dotc.typer.Typer.caseRest$1(Typer.scala:2380)
[error] dotty.tools.dotc.typer.Typer.typedCase(Typer.scala:2400)
[error] dotty.tools.dotc.typer.Typer.typedCases$$anonfun$1(Typer.scala:2323)
[error] dotty.tools.dotc.core.Decorators$.loop$1(Decorators.scala:99)
[error] dotty.tools.dotc.core.Decorators$.mapconserve(Decorators.scala:115)
[error] dotty.tools.dotc.typer.Typer.typedCases(Typer.scala:2321)
[error] dotty.tools.dotc.typer.Typer.$anonfun$41(Typer.scala:2304)
[error] dotty.tools.dotc.typer.Applications.harmonic(Applications.scala:2861)
[error] dotty.tools.dotc.typer.Applications.harmonic$(Applications.scala:490)
[error] dotty.tools.dotc.typer.Typer.harmonic(Typer.scala:163)
[error] dotty.tools.dotc.typer.Typer.typedMatchFinish(Typer.scala:2304)
[error] dotty.tools.dotc.typer.Typer.typedMatch(Typer.scala:2227)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3818)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:4038)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:4058)
[error] dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1537)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1541)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3811)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] dotty.tools.dotc.typer.Typer.$anonfun$69(Typer.scala:3141)
[error] dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
[error] dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:3141)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3785)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3896)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:4011)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:4058)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:3449)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3791)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3795)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3896)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:4011)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:4058)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:3584)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3837)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:47)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:533)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:53)
[error] dotty.tools.dotc.typer.TyperPhase.$anonfun$4(TyperPhase.scala:99)
[error] scala.collection.Iterator$$anon$6.hasNext(Iterator.scala:495)
[error] scala.collection.Iterator$$anon$9.hasNext(Iterator.scala:597)
[error] scala.collection.immutable.List.prependedAll(List.scala:159)
[error] scala.collection.immutable.List$.from(List.scala:681)
[error] scala.collection.immutable.List$.from(List.scala:681)
[error] scala.collection.IterableOps$WithFilter.map(Iterable.scala:906)
[error] dotty.tools.dotc.typer.TyperPhase.runOn(TyperPhase.scala:98)
[error] dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:380)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1324)
[error] dotty.tools.dotc.Run.runPhases$1(Run.scala:373)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$2(Run.scala:420)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$adapted$1(Run.scala:420)
[error] scala.Function0.apply$mcV$sp(Function0.scala:42)
[error] dotty.tools.dotc.Run.showProgress(Run.scala:482)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:420)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:432)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:432)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:319)
[error] dotty.tools.dotc.Run.compile(Run.scala:304)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:141)
[error] dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:196)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:252)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:186)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:166)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:241)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:166)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:214)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:542)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:542)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$3(Incremental.scala:182)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$3$adapted(Incremental.scala:180)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:458)
[error] sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:264)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:413)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:500)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:400)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:208)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:542)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:496)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:433)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2343)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2293)
[error] sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:41)
[error] sbt.internal.io.Retry$.sbt$internal$io$Retry$$impl(Retry.scala:114)
[error] sbt.internal.io.Retry$.io(Retry.scala:102)
[error] sbt.internal.io.Retry$.io(Retry.scala:78)
[error] sbt.internal.io.Retry$.io(Retry.scala:67)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:41)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2291)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:63)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:69)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:283)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:24)
[error] sbt.Execute.work(Execute.scala:292)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:283)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:65)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
[error] java.base/java.lang.Thread.run(Thread.java:1583)
[error]            
[error] java.lang.AssertionError: assertion failed: leak: (t : L$2) in {
[error]   val $scrutinee1: (ind : HList.HCons[T0$2, E$2, L$2] & L) = ind
[error]   val $proxy2: E$2 = $scrutinee1.h
[error]   val h: E$2 = $proxy2
[error]   val $proxy3: L$2 = $scrutinee1.t
[error]   val t: L$2 = $proxy3
[error]   {
[error]     val $proxy4: Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]} =
[error]       Append.$asInstanceOf[
[error]         Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]}]
[error]     val Append$_this:
[error]       ($proxy4 : Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]})
[error]        = $proxy4
[error]     val lst$proxy1: Rev.Rev[T0$2, (t : L$2)] = Rev.rev[T0$2](t)
[error]     Append$_this.append[T0$2, E$2](lst$proxy1, h)
[error]   }.$asInstanceOf[
[error]     Append.Append[T0$2, E$2, (?1 : Rev.Rev[T0$2, (t : L$2)])] &
[error]       Append.Append[T0$2, E$2, (lst$proxy1 : Rev.Rev[T0$2, (t : L$2)])]
[error]   ]:Append.Append[T0$2, E$2, (lst$proxy1 : Rev.Rev[T0$2, (t : L$2)])]
[error] }
[error] 	at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:10)
[error] 	at dotty.tools.dotc.typer.Typer.ensureNoLocalRefs(Typer.scala:1604)
[error] 	at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1560)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3811)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] 	at dotty.tools.dotc.inlines.Inliner$InlineTyper.typedUnadapted(Inliner.scala:1070)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] 	at dotty.tools.dotc.inlines.Inliner$InlineTyper.reduceInlineMatchExpr$1(Inliner.scala:1040)
[error] 	at dotty.tools.dotc.inlines.Inliner$InlineTyper.typedMatchFinish(Inliner.scala:1054)
[error] 	at dotty.tools.dotc.typer.Typer.typedMatch(Typer.scala:2227)
[error] 	at dotty.tools.dotc.inlines.Inliner$InlineTyper.typedMatch(Inliner.scala:977)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3818)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] 	at dotty.tools.dotc.inlines.Inliner$InlineTyper.typedUnadapted(Inliner.scala:1070)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.inlines.Inliner.inlined(Inliner.scala:797)
[error] 	at dotty.tools.dotc.inlines.Inlines$InlineCall.expand(Inlines.scala:585)
[error] 	at dotty.tools.dotc.inlines.Inlines$.inlineCall(Inlines.scala:188)
[error] 	at dotty.tools.dotc.typer.Typer.adaptNoArgsOther$1(Typer.scala:4789)
[error] 	at dotty.tools.dotc.typer.Typer.adaptNoArgs$1(Typer.scala:4897)
[error] 	at dotty.tools.dotc.typer.Typer.adapt1(Typer.scala:5166)
[error] 	at dotty.tools.dotc.typer.Typer.adapt(Typer.scala:4366)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] 	at dotty.tools.dotc.typer.Namer.typedAheadExpr$$anonfun$1(Namer.scala:1831)
[error] 	at dotty.tools.dotc.typer.Namer.typedAhead(Namer.scala:1821)
[error] 	at dotty.tools.dotc.typer.Namer.typedAheadExpr(Namer.scala:1831)
[error] 	at dotty.tools.dotc.typer.Namer.typedAheadRhs$1$$anonfun$1(Namer.scala:2218)
[error] 	at dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
[error] 	at dotty.tools.dotc.typer.Namer.typedAheadRhs$1(Namer.scala:2218)
[error] 	at dotty.tools.dotc.typer.Namer.rhsType$1(Namer.scala:2226)
[error] 	at dotty.tools.dotc.typer.Namer.cookedRhsType$1(Namer.scala:2256)
[error] 	at dotty.tools.dotc.typer.Namer.lhsType$1(Namer.scala:2257)
[error] 	at dotty.tools.dotc.typer.Namer.inferredResultType(Namer.scala:2269)
[error] 	at dotty.tools.dotc.typer.Namer.inferredType$1(Namer.scala:1874)
[error] 	at dotty.tools.dotc.typer.Namer.valOrDefDefSig(Namer.scala:1880)
[error] 	at dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:839)
[error] 	at dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:1013)
[error] 	at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:876)
[error] 	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:176)
[error] 	at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:190)
[error] 	at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:192)
[error] 	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:404)
[error] 	at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:3750)
[error] 	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3775)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3896)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:4011)
[error] 	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:4058)
[error] 	at dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1537)
[error] 	at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1541)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3811)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] 	at dotty.tools.dotc.typer.Typer.caseRest$1(Typer.scala:2380)
[error] 	at dotty.tools.dotc.typer.Typer.typedCase(Typer.scala:2400)
[error] 	at dotty.tools.dotc.typer.Typer.typedCases$$anonfun$1(Typer.scala:2323)
[error] 	at dotty.tools.dotc.core.Decorators$.loop$1(Decorators.scala:99)
[error] 	at dotty.tools.dotc.core.Decorators$.mapconserve(Decorators.scala:115)
[error] 	at dotty.tools.dotc.typer.Typer.typedCases(Typer.scala:2321)
[error] 	at dotty.tools.dotc.typer.Typer.$anonfun$41(Typer.scala:2304)
[error] 	at dotty.tools.dotc.typer.Applications.harmonic(Applications.scala:2861)
[error] 	at dotty.tools.dotc.typer.Applications.harmonic$(Applications.scala:490)
[error] 	at dotty.tools.dotc.typer.Typer.harmonic(Typer.scala:163)
[error] 	at dotty.tools.dotc.typer.Typer.typedMatchFinish(Typer.scala:2304)
[error] 	at dotty.tools.dotc.typer.Typer.typedMatch(Typer.scala:2227)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3818)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:4038)
[error] 	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:4058)
[error] 	at dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1537)
[error] 	at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1541)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3811)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] 	at dotty.tools.dotc.typer.Typer.$anonfun$69(Typer.scala:3141)
[error] 	at dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
[error] 	at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:3141)
[error] 	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3785)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3896)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:4011)
[error] 	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:4058)
[error] 	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:3449)
[error] 	at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3791)
[error] 	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3795)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3896)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:4011)
[error] 	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:4058)
[error] 	at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:3584)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3837)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3897)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3984)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3989)
[error] 	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:4101)
[error] 	at dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:47)
[error] 	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] 	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] 	at dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:533)
[error] 	at dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:53)
[error] 	at dotty.tools.dotc.typer.TyperPhase.$anonfun$4(TyperPhase.scala:99)
[error] 	at scala.collection.Iterator$$anon$6.hasNext(Iterator.scala:495)
[error] 	at scala.collection.Iterator$$anon$9.hasNext(Iterator.scala:597)
[error] 	at scala.collection.immutable.List.prependedAll(List.scala:159)
[error] 	at scala.collection.immutable.List$.from(List.scala:681)
[error] 	at scala.collection.immutable.List$.from(List.scala:681)
[error] 	at scala.collection.IterableOps$WithFilter.map(Iterable.scala:906)
[error] 	at dotty.tools.dotc.typer.TyperPhase.runOn(TyperPhase.scala:98)
[error] 	at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:380)
[error] 	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] 	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] 	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1324)
[error] 	at dotty.tools.dotc.Run.runPhases$1(Run.scala:373)
[error] 	at dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$2(Run.scala:420)
[error] 	at dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$adapted$1(Run.scala:420)
[error] 	at scala.Function0.apply$mcV$sp(Function0.scala:42)
[error] 	at dotty.tools.dotc.Run.showProgress(Run.scala:482)
[error] 	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:420)
[error] 	at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:432)
[error] 	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
[error] 	at dotty.tools.dotc.Run.compileUnits(Run.scala:432)
[error] 	at dotty.tools.dotc.Run.compileSources(Run.scala:319)
[error] 	at dotty.tools.dotc.Run.compile(Run.scala:304)
[error] 	at dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
[error] 	at dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:141)
[error] 	at dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] 	at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:196)
[error] 	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:252)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:186)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:166)
[error] 	at sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:241)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:166)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:214)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:542)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:542)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$apply$3(Incremental.scala:182)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$apply$3$adapted(Incremental.scala:180)
[error] 	at sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:458)
[error] 	at sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] 	at sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] 	at sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] 	at sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:264)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:413)
[error] 	at sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:500)
[error] 	at sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:400)
[error] 	at sbt.internal.inc.Incremental$.apply(Incremental.scala:208)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:542)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:496)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:433)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] 	at sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2343)
[error] 	at sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2293)
[error] 	at sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:41)
[error] 	at sbt.internal.io.Retry$.sbt$internal$io$Retry$$impl(Retry.scala:114)
[error] 	at sbt.internal.io.Retry$.io(Retry.scala:102)
[error] 	at sbt.internal.io.Retry$.io(Retry.scala:78)
[error] 	at sbt.internal.io.Retry$.io(Retry.scala:67)
[error] 	at sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:41)
[error] 	at sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2291)
[error] 	at scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] 	at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:63)
[error] 	at sbt.std.Transform$$anon$4.work(Transform.scala:69)
[error] 	at sbt.Execute.$anonfun$submit$2(Execute.scala:283)
[error] 	at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:24)
[error] 	at sbt.Execute.work(Execute.scala:292)
[error] 	at sbt.Execute.$anonfun$submit$1(Execute.scala:283)
[error] 	at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] 	at sbt.CompletionService$$anon$2.call(CompletionService.scala:65)
[error] 	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
[error] 	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
[error] 	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
[error] 	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
[error] 	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
[error] 	at java.base/java.lang.Thread.run(Thread.java:1583)
[error] (Compile / compileIncremental) java.lang.AssertionError: assertion failed: leak: (t : L$2) in {
[error]   val $scrutinee1: (ind : HList.HCons[T0$2, E$2, L$2] & L) = ind
[error]   val $proxy2: E$2 = $scrutinee1.h
[error]   val h: E$2 = $proxy2
[error]   val $proxy3: L$2 = $scrutinee1.t
[error]   val t: L$2 = $proxy3
[error]   {
[error]     val $proxy4: Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]} =
[error]       Append.$asInstanceOf[
[error]         Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]}]
[error]     val Append$_this:
[error]       ($proxy4 : Append.type{type Append[T,+E <: T,L <: HList[T]] = HList[T]})
[error]        = $proxy4
[error]     val lst$proxy1: Rev.Rev[T0$2, (t : L$2)] = Rev.rev[T0$2](t)
[error]     Append$_this.append[T0$2, E$2](lst$proxy1, h)
[error]   }.$asInstanceOf[
[error]     Append.Append[T0$2, E$2, (?1 : Rev.Rev[T0$2, (t : L$2)])] &
[error]       Append.Append[T0$2, E$2, (lst$proxy1 : Rev.Rev[T0$2, (t : L$2)])]
[error]   ]:Append.Append[T0$2, E$2, (lst$proxy1 : Rev.Rev[T0$2, (t : L$2)])]
[error] }

Expectation:
Compilation should throw an error normally without crashing.

The code has been minimized to the best of my ability. I am not totally clear on how this error occurred.

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area:inlinearea:opaque-typesitype:bugitype:crashregressionThis worked in a previous version but doesn't anymore

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