Second child of sealed trait in REPL on separate lines crashes

[som-snytt]

Compiler version

HEAD

Minimized code

./bin/scala
Welcome to Scala 3.2.1-RC1-bin-SNAPSHOT-git-baf21dd (18.0.1.1, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.

scala> sealed trait State
// defined trait State

scala> final class On extends State
-- [E112] Syntax Error: ------------------------------------------------------------------------------------------------
1 |final class On extends State
  |            ^
  |            Cannot extend sealed trait State in a different source file
  |
  | longer explanation available when compiling with `-explain`
1 error found

scala> final class Off extends State

Output (click arrow to expand)

Exception in thread "main" java.lang.AssertionError: assertion failed: duplicate child annotation class Off / class On
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.typer.Namer.insertInto$1(Namer.scala:481)
        at dotty.tools.dotc.typer.Namer.addChild(Namer.scala:488)
        at dotty.tools.dotc.typer.Namer$Completer.register$1(Namer.scala:899)
        at dotty.tools.dotc.typer.Namer$Completer.registerIfChild$$anonfun$1(Namer.scala:908)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:333)
        at dotty.tools.dotc.typer.Namer$Completer.registerIfChild(Namer.scala:908)
        at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:811)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:171)
        at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:187)
        at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:189)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:373)
        at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:2822)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2847)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2943)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3009)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3013)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3035)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3085)
        at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2520)
        at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:2869)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2873)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2943)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3009)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3013)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3035)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3085)
        at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2651)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2914)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2944)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3009)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3013)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3129)
        at dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:44)
        at dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$adapted$1(TyperPhase.scala:51)
        at scala.Function0.apply$mcV$sp(Function0.scala:39)
        at dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:417)
        at dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:51)
        at dotty.tools.dotc.typer.TyperPhase.runOn$$anonfun$3(TyperPhase.scala:85)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:333)
        at dotty.tools.dotc.typer.TyperPhase.runOn(TyperPhase.scala:85)
        at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:234)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1328)
        at dotty.tools.dotc.Run.runPhases$1(Run.scala:245)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:253)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:262)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:68)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:262)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:192)
        at dotty.tools.repl.ReplCompiler.runCompilationUnit(ReplCompiler.scala:166)
        at dotty.tools.repl.ReplCompiler.compile(ReplCompiler.scala:177)
        at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:287)
        at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:249)
        at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:168)
        at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:171)
        at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:192)
        at dotty.tools.repl.ReplDriver.runBody$$anonfun$1(ReplDriver.scala:180)
        at dotty.tools.runner.ScalaClassLoader$.asContext(ScalaClassLoader.scala:80)
        at dotty.tools.repl.ReplDriver.runBody(ReplDriver.scala:180)
        at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:171)
        at dotty.tools.repl.ReplDriver.tryRunning(ReplDriver.scala:133)
        at dotty.tools.repl.Main$.main(Main.scala:7)
        at dotty.tools.MainGenericRunner$.run$1(MainGenericRunner.scala:193)
        at dotty.tools.MainGenericRunner$.main(MainGenericRunner.scala:268)
        at dotty.tools.MainGenericRunner.main(MainGenericRunner.scala)

I pasted a sealed trait from the erased defs docs. I thought JLine would take the paste as a unit. Was that just a pipe dream? It used to detect paste by how fast the characters arrived.

Anyway, I don't know what the error message means, but it probably shouldn't do that.