Crashes when defining a polymorphic function with by name parameters: `assertion failed: Not a valid PolyFunction refinement`

[Atry]

Compiler version

3.5.1

Minimized code

def k: [A] => (=> A) => [B] => (=> B) => A = { [A] => a => [B] => b =>
  lazy val lazyA = a
  lazyA
}

Output (click arrow to expand)

[info] compiling 1 Scala source to /home/nixos/m-combinator.scala/target/scala-3.5.1/classes ...
[info] 
[info]   exception occurred while typechecking /home/nixos/m-combinator.scala/M.scala
[info] 
[info]   An unhandled exception was thrown in the compiler.
[info]   Please file a crash report here:
[info]   https://github.com/scala/scala3/issues/new/choose
[info]   For non-enriched exceptions, compile with -Xno-enrich-error-messages.
[info] 
[info]      while compiling: /home/nixos/m-combinator.scala/M.scala
[info]         during phase: typer
[info]                 mode: Mode(ImplicitsEnabled)
[info]      library version: version 2.13.14
[info]     compiler version: version 3.5.1
[info]             settings: -classpath /home/nixos/m-combinator.scala/target/scala-3.5.1/classes:/home/nixos/.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.5.1/scala3-library_3-3.5.1.jar:/home/nixos/.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.14/scala-library-2.13.14.jar -d /home/nixos/m-combinator.scala/target/scala-3.5.1/classes
[error] ## Exception when compiling 1 sources to /home/nixos/m-combinator.scala/target/scala-3.5.1/classes
[error] java.lang.AssertionError: assertion failed: Not a valid PolyFunction refinement: PolyType(List(B), List(TypeBounds(TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Nothing),TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Any))), MethodType(List(b), List(ExprType(TypeParamRef(B))), TypeRef(NoPrefix,type A)))
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
[error] dotty.tools.dotc.core.Definitions$PolyFunctionOf$.apply(Definitions.scala:1205)
[error] dotty.tools.dotc.core.Types$Type.toFunctionType(Types.scala:1978)
[error] dotty.tools.dotc.typer.TypeAssigner.assignType(TypeAssigner.scala:425)
[error] dotty.tools.dotc.typer.TypeAssigner.assignType$(TypeAssigner.scala:16)
[error] dotty.tools.dotc.typer.Typer.assignType(Typer.scala:145)
[error] dotty.tools.dotc.typer.Typer.typedClosure(Typer.scala:1973)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3426)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3499)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3691)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1406)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3422)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3499)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.typedPolyFunctionValue(Typer.scala:1923)
[error] dotty.tools.dotc.typer.Typer.typedPolyFunction(Typer.scala:1891)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3425)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3499)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3691)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1406)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3422)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3499)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3691)
[error] dotty.tools.dotc.typer.Typer.$anonfun$64(Typer.scala:2838)
[error] dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
[error] dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2838)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3396)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3498)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3602)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3648)
[error] dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1399)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1403)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3422)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3499)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.typedPolyFunctionValue(Typer.scala:1923)
[error] dotty.tools.dotc.typer.Typer.typedPolyFunction(Typer.scala:1891)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3425)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3499)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3691)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1406)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3422)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3499)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3691)
[error] dotty.tools.dotc.typer.Typer.$anonfun$64(Typer.scala:2838)
[error] dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
[error] dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2838)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3396)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3498)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3602)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3648)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:3096)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3402)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3406)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3498)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3602)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3648)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:3229)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3448)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3499)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3576)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3580)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3691)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:47)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:503)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:53)
[error] dotty.tools.dotc.typer.TyperPhase.$anonfun$4(TyperPhase.scala:99)
[error] scala.collection.Iterator$$anon$6.hasNext(Iterator.scala:479)
[error] scala.collection.Iterator$$anon$9.hasNext(Iterator.scala:583)
[error] scala.collection.immutable.List.prependedAll(List.scala:152)
[error] scala.collection.immutable.List$.from(List.scala:685)
[error] scala.collection.immutable.List$.from(List.scala:682)
[error] scala.collection.IterableOps$WithFilter.map(Iterable.scala:900)
[error] dotty.tools.dotc.typer.TyperPhase.runOn(TyperPhase.scala:98)
[error] dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:343)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$1(Run.scala:336)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:384)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:396)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:396)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:282)
[error] dotty.tools.dotc.Run.compile(Run.scala:267)
[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$7(MixedAnalyzingCompiler.scala:194)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:249)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:184)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:164)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:164)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:212)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$3(Incremental.scala:178)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$3$adapted(Incremental.scala:176)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:454)
[error] sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:117)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:265)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:409)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:496)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:396)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:170)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:488)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:425)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2427)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2377)
[error] sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:41)
[error] sbt.internal.io.Retry$.apply(Retry.scala:47)
[error] sbt.internal.io.Retry$.apply(Retry.scala:29)
[error] sbt.internal.io.Retry$.apply(Retry.scala:24)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:41)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2375)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$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] stack trace is suppressed; run last Compile / compileIncremental for the full output
[error] (Compile / compileIncremental) java.lang.AssertionError: assertion failed: Not a valid PolyFunction refinement: PolyType(List(B), List(TypeBounds(TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Nothing),TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Any))), MethodType(List(b), List(ExprType(TypeParamRef(B))), TypeRef(NoPrefix,type A)))
[error] Total time: 0 s, completed Sep 26, 2024, 5:27:02 PM

[Gedochao]

Do note that it doesn't crash in LTS, returning a valid (?) error (with Scala 3.3.4 and 3.3.5-RC1-bin-20240925-9eb858b-NIGHTLY):

-- Error: /Users/pchabelski/IdeaProjects/scala-cli-tests-2/untitled/compiler-repro/repro.scala:1:54 
1 |def k: [A] => (=> A) => [B] => (=> B) => A = { [A] => a => [B] => b =>
  |                                                      ^
  |                 cannot infer type; expected type <?> is not fully defined
1 error found
Compilation failed

crashes on 3.4.0+