assertion failed: bad parameter reference this.A at tryCatchPatterns

[julienrf]

When compiling the following code:

https://github.com/msteindorfer/collection-strawman/blob/681ca06be902c6f901fd74a1aaa7d2c87fb2d9a5/collections/src/main/scala/strawman/collection/immutable/ChampHashSet.scala#L564-L578

We get the following error:

java.lang.AssertionError: assertion failed: bad parameter reference this.A at tryCatchPatterns
the parameter is type A in class SetKeyIterator but the prefix strawman.collection.immutable.SetKeyIterator(this)
does not define any corresponding arguments.
	at dotty.DottyPredef$.assertFail(DottyPredef.scala:39)
	at dotty.tools.dotc.core.Types$NamedType.argDenot(Types.scala:1747)
	at dotty.tools.dotc.core.Types$NamedType.fromDesignator$1(Types.scala:1675)
	at dotty.tools.dotc.core.Types$NamedType.computeDenot(Types.scala:1696)
	at dotty.tools.dotc.core.Types$NamedType.denotAt(Types.scala:1647)
	at dotty.tools.dotc.core.Types$NamedType.denot(Types.scala:1636)
	at dotty.tools.dotc.core.Types$NamedType.info(Types.scala:1630)
	at dotty.tools.dotc.core.TypeComparer.secondTry(TypeComparer.scala:282)
	at dotty.tools.dotc.core.TypeComparer.firstTry(TypeComparer.scala:277)
	at dotty.tools.dotc.core.TypeComparer.op$7(TypeComparer.scala:118)
	at dotty.tools.dotc.core.TypeComparer.op$1(TypeComparer.scala:32)
	at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:109)
	at dotty.tools.dotc.core.ConstraintHandling.isSubTypeWhenFrozen(ConstraintHandling.scala:161)
	at dotty.tools.dotc.core.Types$Type.op$17(Types.scala:771)
	at dotty.tools.dotc.core.Types$Type.frozen_$less$colon$less(Types.scala:770)
	at dotty.tools.dotc.core.Types$Type.overrides(Types.scala:807)
	at dotty.tools.dotc.typer.RefChecks$.compatibleTypes$4(RefChecks.scala:272)
	at dotty.tools.dotc.typer.RefChecks$.checkOverride$1(RefChecks.scala:380)
	at dotty.tools.dotc.typer.RefChecks$.dotty$tools$dotc$typer$RefChecks$$$checkAllOverrides(RefChecks.scala:401)
	at dotty.tools.dotc.typer.RefChecks.transformTemplate(RefChecks.scala:846)
	at dotty.tools.dotc.transform.MegaPhase.goTemplate(MegaPhase.scala:906)

See the full stack-trace here https://travis-ci.org/scala/collection-strawman/builds/330072462#L1269

[allanrenucci]

I believe it is a duplicate of #3775. @julienrf Can you try rewriting def next as def next() and let me know if this fixes the issue.

[julienrf]

Indeed @allanrenucci, writing next() solved our issue, thanks!