Selectable with `Fields` crashes with `invalid prefix ContextualMethodType` when `selectDynamic` has implicit context arguments

[soronpo]

Compiler version

v3.6.2-RC1

Minimized code

trait Ctx
class Foo extends Selectable:
  type Fields = (bar: Int, baz: Int)
  def selectDynamic(fieldName: String)(using Ctx): Any = ???

val f = Foo()
val bar = f.bar

Output (click arrow to expand)

[error] java.lang.AssertionError: assertion failed: invalid prefix ContextualMethodType(List(x$2), List(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),trait Ctx)), TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object scala),class Any))
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
[error] dotty.tools.dotc.core.Types$NamedType.<init>(Types.scala:2313)
[error] dotty.tools.dotc.core.Types$TermRef.<init>(Types.scala:2918)
[error] dotty.tools.dotc.core.Types$CachedTermRef.<init>(Types.scala:2999)
[error] dotty.tools.dotc.core.Uniques$NamedTypeUniques.newType$1(Uniques.scala:44)
[error] dotty.tools.dotc.core.Uniques$NamedTypeUniques.enterIfNew(Uniques.scala:46)
[error] dotty.tools.dotc.core.Types$TermRef$.apply(Types.scala:3053)
[error] dotty.tools.dotc.core.Types$TermRef$.apply(Types.scala:3059)
[error] dotty.tools.dotc.ast.tpd$TreeOps$.select$extension(tpd.scala:941)
[error] dotty.tools.dotc.ast.tpd$TreeOps$.cast$extension(tpd.scala:1039)
[error] dotty.tools.dotc.ast.tpd$TreeOps$.cast$extension(tpd.scala:1034)
[error] dotty.tools.dotc.ast.tpd$TreeOps$.ensureConforms$extension(tpd.scala:1048)
[error] dotty.tools.dotc.typer.Typer.trySelectable$1(Typer.scala:876)
[error] dotty.tools.dotc.typer.Typer.typedSelectWithAdapt(Typer.scala:906)
[error] dotty.tools.dotc.typer.Typer.typeSelectOnTerm$1(Typer.scala:993)
[error] dotty.tools.dotc.typer.Typer.typedSelect(Typer.scala:1031)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3468)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3577)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3655)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3770)
[error] dotty.tools.dotc.typer.Namer.typedAheadExpr$$anonfun$1(Namer.scala:1765)
[error] dotty.tools.dotc.typer.Namer.typedAhead(Namer.scala:1755)
[error] dotty.tools.dotc.typer.Namer.typedAheadExpr(Namer.scala:1765)
[error] dotty.tools.dotc.typer.Namer.typedAheadRhs$1$$anonfun$1(Namer.scala:2123)
[error] dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
[error] dotty.tools.dotc.typer.Namer.typedAheadRhs$1(Namer.scala:2123)
[error] dotty.tools.dotc.typer.Namer.rhsType$1(Namer.scala:2131)
[error] dotty.tools.dotc.typer.Namer.cookedRhsType$1(Namer.scala:2150)
[error] dotty.tools.dotc.typer.Namer.lhsType$1(Namer.scala:2151)
[error] dotty.tools.dotc.typer.Namer.inferredResultType(Namer.scala:2162)
[error] dotty.tools.dotc.typer.Namer.inferredType$1(Namer.scala:1808)
[error] dotty.tools.dotc.typer.Namer.valOrDefDefSig(Namer.scala:1814)
[error] dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:823)
[error] dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:990)
[error] dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:859)
[error] dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:175)
[error] dotty.tools.dotc.core.Denotations$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:393)
[error] dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:3440)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3465)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3577)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3655)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3681)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3727)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:3160)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3481)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3485)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3577)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3655)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3681)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3727)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:3293)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3527)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3578)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3655)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3770)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:47)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:507)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:53)
[error] dotty.tools.dotc.typer.TyperPhase.$anonfun$4(TyperPhase.scala:99)
[error] scala.collection.Iterator$$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$7(MixedAnalyzingCompiler.scala:196)
[error] scala.runtime.java8.JFunction0$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$3(Incremental.scala:178)
[error] sbt.internal.inc.Incremental$.$anonfun$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$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:265)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:409)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:496)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:396)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:204)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:542)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:496)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:433)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2419)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2369)
[error] sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:41)
[error] sbt.internal.io.Retry$.apply(Retry.scala:47)
[error] sbt.internal.io.Retry$.apply(Retry.scala:29)
[error] sbt.internal.io.Retry$.apply(Retry.scala:24)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:41)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2367)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$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$2.call(CompletionService.scala:65)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
[error] java.base/java.lang.Thread.run(Thread.java:840)
[error]
[error] stack trace is suppressed; run last lib / Test / compileIncremental for the full output
[error] (lib / Test / compileIncremental) java.lang.AssertionError: assertion failed: invalid prefix ContextualMethodType(List(x$2), List(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),trait Ctx)), TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object scala),class Any))

[Gedochao]

Note: this only started crashing since 3.5.0, although it has not been compiling for earlier versions.

scala-cli compile repro.scala -S 3.4.3

gives

[error] ./repro.scala:4:1
[error] '=>' expected, but 'end of statement' found
[error]   def selectDynamic(fieldName: String)(using Ctx): Any = ???
[error] ^^^
[error] ./repro.scala:7:11
[error] value bar is not a member of Foo
[error] val bar = f.bar
[error]           ^^^^^

So technically, the crash could be considered a regression.

Last good stable version: 3.4.3
First bad stable version: 3.5.0

[soronpo]

This is not a real regression because named tuple syntax did not exist until 3.5 (as experimental). So no bisect is needed. The implementation needs to be fixed to account for the implicit arguments in selectDynamic.

[Gedochao]

This is not a real regression because named tuple syntax did not exist until 3.5 (as experimental).

I know, but a compiler crash was still introduced. Grey zone, I know.

[soronpo]

This is a duplicate of #20512