AssertionError on package object match

[sir-wabbit]

Minimized code

Probably directly related to #9289, if not a duplicate. The location of the failure is different but the underlying problem is similar.

// AE-7e0ebe9738cc74e6c98b4b5c59672b4d294bf00e
package object Foo {
  (1: Any) match {
    case Foo => 1
  }
}

Output (click arrow to expand)

exception occurred while compiling test.scala
java.lang.AssertionError: assertion failed: no member Foo . ==, members = Scope{
  final lazy module package object package: Foo.package$
  final module package object package$ extends Object with Serializable {this:
    Foo.package.type
   =>} at (Foo : Foo.type)
  class package: <notype>
} while compiling test.scala
Exception in thread "main" java.lang.AssertionError: assertion failed: no member Foo . ==, members = Scope{
  final lazy module package object package: Foo.package$
  final module package object package$ extends Object with Serializable {this:
    Foo.package.type
   =>} at (Foo : Foo.type)
  class package: <notype>
}
	at dotty.DottyPredef$.assertFail(DottyPredef.scala:17)
	at dotty.tools.dotc.ast.Trees$Instance.applyOverloaded(Trees.scala:1559)
	at dotty.tools.dotc.ast.tpd$TreeOps$.equal$extension(tpd.scala:943)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.emitCondition(PatternMatcher.scala:695)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.emitCondWithPos$1(PatternMatcher.scala:874)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.$anonfun$11(PatternMatcher.scala:877)
	at scala.collection.immutable.List.foldRight(List.scala:352)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.emitWithMashedConditions$1(PatternMatcher.scala:878)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.emit(PatternMatcher.scala:883)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.default$1(PatternMatcher.scala:891)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.maybeEmitSwitch$1(PatternMatcher.scala:897)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.emit(PatternMatcher.scala:901)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.emit(PatternMatcher.scala:885)
	at dotty.tools.dotc.transform.PatternMatcher$Translator.translateMatch(PatternMatcher.scala:996)
	at dotty.tools.dotc.transform.PatternMatcher.transformMatch(PatternMatcher.scala:41)
	at dotty.tools.dotc.transform.MegaPhase.goMatch(MegaPhase.scala:746)
	at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:345)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
	at dotty.tools.dotc.transform.MegaPhase.transformStat$2(MegaPhase.scala:406)
	at dotty.tools.dotc.transform.MegaPhase.$anonfun$1(MegaPhase.scala:409)
	at scala.collection.immutable.List.mapConserve(List.scala:472)
	at dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:409)
	at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:339)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
	at dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:251)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:394)
	at dotty.tools.dotc.transform.MegaPhase.transformStat$2(MegaPhase.scala:404)
	at dotty.tools.dotc.transform.MegaPhase.$anonfun$1(MegaPhase.scala:409)
	at scala.collection.immutable.List.mapConserve(List.scala:472)
	at dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:409)
	at dotty.tools.dotc.transform.MegaPhase.mapPackage$1(MegaPhase.scala:356)
	at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:359)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
	at dotty.tools.dotc.transform.MegaPhase.transformStat$2(MegaPhase.scala:406)
	at dotty.tools.dotc.transform.MegaPhase.$anonfun$1(MegaPhase.scala:409)
	at scala.collection.immutable.List.mapConserve(List.scala:472)
	at dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:409)
	at dotty.tools.dotc.transform.MegaPhase.mapPackage$1(MegaPhase.scala:356)
	at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:359)
	at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
	at dotty.tools.dotc.transform.MegaPhase.transformUnit(MegaPhase.scala:415)
	at dotty.tools.dotc.transform.MegaPhase.run(MegaPhase.scala:427)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:318)
	at scala.collection.immutable.List.map(List.scala:246)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:319)
	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:180)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$5(Run.scala:190)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:198)
	at dotty.runtime.function.JFunction0$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:205)
	at dotty.tools.dotc.Run.compileSources(Run.scala:142)
	at dotty.tools.dotc.Run.compile(Run.scala:124)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
	at dotty.tools.dotc.Driver.process(Driver.scala:194)
	at dotty.tools.dotc.Driver.process(Driver.scala:163)
	at dotty.tools.dotc.Driver.process(Driver.scala:175)
	at dotty.tools.dotc.Driver.main(Driver.scala:202)
	at dotty.tools.dotc.Main.main(Main.scala)

[griggt]

This no longer crashes in 0.28.0-bin-20201014-ca67e4d-NIGHTLY, but the error message could use some improvement:

-- [E007] Type Mismatch Error: i9331.scala:4:9 ---------------------------------
4 |    case Foo => 1
  |         ^^^
  |Found:    Foo.type
  |Required: ?{ == : ? }
  |Note that implicit extension methods cannot be applied because they are ambiguous;
  |both method ArrowAssoc in object Predef and method StringFormat in object Predef provide an extension method `==` on Foo.type

compare Scala 2.13.3:

i9331.scala:4: error: package Foo is not a value
    case Foo => 1