AssertionError: duplicate type when exporting conflicting type members

[panacekcz]

minimized code

class A{
  type T = Int // can also be class T
}
class B(x: A, y: A){
  export x._
  export y._
}

Crash output (click arrow to expand)

exception occurred while typechecking export-type-conflict.scala
exception occurred while compiling export-type-conflict.scala
java.lang.AssertionError: assertion failed: duplicate type T#3901; previous was type T#3900 while compiling export-type-conflict.scala
Exception in thread "main" java.lang.AssertionError: assertion failed: duplicate type T#3901; previous was type T#3900
	at dotty.DottyPredef$.assertFail(DottyPredef.scala:17)
	at dotty.tools.dotc.core.Scopes$MutableScope.enter(Scopes.scala:269)
	at dotty.tools.dotc.core.SymDenotations$ClassDenotation.enterNoReplace(SymDenotations.scala:1763)
	at dotty.tools.dotc.core.SymDenotations$ClassDenotation.enter(SymDenotations.scala:1752)
	at dotty.tools.dotc.core.Symbols$Symbol.entered(Symbols.scala:571)
	at dotty.tools.dotc.typer.Namer.processExports$$anonfun$2$$anonfun$1(Namer.scala:1151)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.typer.Namer.dotty$tools$dotc$typer$Namer$ClassCompleter$$_$processExports$$anonfun$1(Namer.scala:1151)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.typer.Namer$ClassCompleter.processExports(Namer.scala:1151)
	at dotty.tools.dotc.typer.Namer$ClassCompleter.completeInCreationContext(Namer.scala:1291)
	at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:840)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:260)
	at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:185)
	at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:187)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:400)
	at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:2118)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2143)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2223)
	at dotty.tools.dotc.typer.Typer.op$1(Typer.scala:2262)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2271)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2274)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2296)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2340)
	at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:1959)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2197)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2224)
	at dotty.tools.dotc.typer.Typer.op$1(Typer.scala:2262)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2271)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2274)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2382)
	at dotty.tools.dotc.typer.FrontEnd.liftedTree1$2(FrontEnd.scala:78)
	at dotty.tools.dotc.typer.FrontEnd.typeCheck$$anonfun$1(FrontEnd.scala:83)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.typer.FrontEnd.monitor(FrontEnd.scala:42)
	at dotty.tools.dotc.typer.FrontEnd.typeCheck(FrontEnd.scala:84)
	at dotty.tools.dotc.typer.FrontEnd.runOn$$anonfun$3(FrontEnd.scala:114)
	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:305)
	at dotty.tools.dotc.typer.FrontEnd.runOn(FrontEnd.scala:114)
	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:167)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$5(Run.scala:177)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:185)
	at dotty.runtime.function.JFunction0$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:192)
	at dotty.tools.dotc.Run.compileSources(Run.scala:129)
	at dotty.tools.dotc.Run.compile(Run.scala:112)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:36)
	at dotty.tools.dotc.Driver.process(Driver.scala:189)
	at dotty.tools.dotc.Driver.process(Driver.scala:158)
	at dotty.tools.dotc.Driver.process(Driver.scala:170)
	at dotty.tools.dotc.Driver.main(Driver.scala:197)
	at dotty.tools.dotc.Main.main(Main.scala)