Making objects for existing java classes crashes the compiler

[hobwekiva]

minimized code

package java
package lang
object String

Stack trace

dotty.tools.dotc.core.Denotations$StaleSymbol: stale symbol; class String#1417 in module class lang, defined in Period(1..2, run = 1), is referred to in run Period(1..1, run = 2) while compiling testing/Test.scala
Exception in thread "main" dotty.tools.dotc.core.Denotations$StaleSymbol: stale symbol; class String#1417 in module class lang, defined in Period(1..2, run = 1), is referred to in run Period(1..1, run = 2)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.staleSymbolError(Denotations.scala:1060)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.bringForward(Denotations.scala:870)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:918)
	at dotty.tools.dotc.core.Symbols$Symbol.recomputeDenot(Symbols.scala:486)
	at dotty.tools.dotc.core.Symbols$Symbol.computeDenot(Symbols.scala:481)
	at dotty.tools.dotc.core.Symbols$Symbol.denot(Symbols.scala:475)
	at dotty.tools.dotc.core.Symbols$ClassSymbol.classDenot(Symbols.scala:810)
	at dotty.tools.dotc.core.Symbols$.toClassDenot(Symbols.scala:850)
	at dotty.tools.dotc.core.Definitions.StringModule(Definitions.scala:509)
	at dotty.tools.dotc.core.Definitions.String_valueOf_Object(Definitions.scala:511)
	at dotty.tools.backend.jvm.DottyBackendInterface.<init>(DottyBackendInterface.scala:148)
	at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:51)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:315)
	at scala.collection.immutable.List.map(List.scala:219)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:316)
	at dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:55)
	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:161)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$5(Run.scala:171)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:179)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:65)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:186)
	at dotty.tools.dotc.Run.compileSources(Run.scala:123)
	at dotty.tools.dotc.Run.compile(Run.scala:106)
	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)

package java
package lang
object Integer

Stack trace

Error while emitting Test.scala
exception occurred while compiling testing/Test.scala
java.lang.AssertionError: assertion failed: Bad superClass for class Integer: val <none> while compiling testing/Test.scala
Exception in thread "main" java.lang.AssertionError: assertion failed: Bad superClass for class Integer: val <none>
	at dotty.DottyPredef$.assertFail(DottyPredef.scala:17)
	at dotty.tools.backend.jvm.BTypesFromSymbols.setClassInfo(BTypesFromSymbols.scala:66)
	at dotty.tools.backend.jvm.BTypesFromSymbols.classBTypeFromSymbol$$anonfun$4(BTypesFromSymbols.scala:60)
	at scala.collection.mutable.HashMap.getOrElse(HashMap.scala:416)
	at dotty.tools.backend.jvm.BTypesFromSymbols.classBTypeFromSymbol(BTypesFromSymbols.scala:61)
	at dotty.tools.backend.jvm.CoreBTypes.BOXED_INT(CoreBTypes.scala:59)
	at dotty.tools.backend.jvm.CoreBTypes.boxedClassOfPrimitive(CoreBTypes.scala:74)
	at dotty.tools.backend.jvm.CoreBTypes.boxedClasses(CoreBTypes.scala:80)
	at dotty.tools.backend.jvm.CoreBTypesProxy.boxedClasses(CoreBTypes.scala:223)
	at dotty.tools.backend.jvm.BTypes$BType.isBoxed(BTypes.scala:93)
	at dotty.tools.backend.jvm.BTypes$ClassBType.isBoxed(BTypes.scala:579)
	at dotty.tools.backend.jvm.BTypes$BType.conformsTo(BTypes.scala:121)
	at dotty.tools.backend.jvm.BTypes$ClassBType.conformsTo(BTypes.scala:579)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.adapt(BCodeBodyBuilder.scala:931)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:437)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.emitNormalMethodBody$1(BCodeSkelBuilder.scala:597)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genDefDef(BCodeSkelBuilder.scala:630)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:501)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen$$anonfun$1(BCodeSkelBuilder.scala:503)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:503)
	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genPlainClass(BCodeSkelBuilder.scala:109)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:217)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:184)
	at dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:514)
	at dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:480)
	at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:51)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:315)
	at scala.collection.immutable.List.map(List.scala:219)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:316)
	at dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:55)
	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:161)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$5(Run.scala:171)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:179)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:65)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:186)
	at dotty.tools.dotc.Run.compileSources(Run.scala:123)
	at dotty.tools.dotc.Run.compile(Run.scala:106)
	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)

[odersky]

Not sure we should even try to fix this

[sjrd]

Supporting this will be necessary to be able to compile the JDK implementations of Scala.js and Native with Dotty.

[griggt]

The String example compiles since f8dbf7c in #9099.