Referring to a Scala 2 trait which has a companion object leads to a crash when a method with the same name also exists

[DieBauer]

Minimized code

Using the Finagle library I get a crash on a specific construct.
This works in dotty 0.24.0 (and Scala 2.13) but crashes in all recent versions.

Since it's occuring with a 3rd party library, I find it hard to create minimized code.
But it's a bad story for backward compatibility.

I have a Scastie including the sbt dependency: https://scastie.scala-lang.org/LylIH9JBTv6k0a655eG7aw

import com.twitter.finagle.Stack
import com.twitter.finagle.liveness.FailureAccrualFactory

class A {
   val t = Stack.Param[FailureAccrualFactory.Param](FailureAccrualFactory.Param(???))
}

Output (click arrow to expand)

scala.MatchError: NoType (of class dotty.tools.dotc.core.Types$NoType$)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.sourceOfSelf$1(SymDenotations.scala:1000)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.sourceModule(SymDenotations.scala:1002)
	at dotty.tools.dotc.core.TypeErasure.dotty$tools$dotc$core$TypeErasure$$apply(TypeErasure.scala:502)
	at dotty.tools.dotc.core.TypeErasure.eraseInfo(TypeErasure.scala:550)
	at dotty.tools.dotc.core.TypeErasure$.transformInfo(TypeErasure.scala:202)
	at dotty.tools.dotc.transform.Erasure.transform(Erasure.scala:82)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:803)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
	at dotty.tools.dotc.core.Symbols$Symbol.recomputeDenot(Symbols.scala:119)
	at dotty.tools.dotc.core.Symbols$Symbol.computeDenot(Symbols.scala:113)
	at dotty.tools.dotc.core.Symbols$Symbol.denot(Symbols.scala:106)
	at dotty.tools.dotc.core.Symbols$.toDenot(Symbols.scala:487)
	at dotty.tools.dotc.core.SymDenotations$ClassDenotation.registeredCompanion(SymDenotations.scala:2143)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.copySymDenotation(SymDenotations.scala:1477)
	at dotty.tools.dotc.transform.Flatten.transformSym(Flatten.scala:35)
	at dotty.tools.dotc.core.DenotTransformers$SymTransformer.transform(DenotTransformers.scala:70)
	at dotty.tools.dotc.core.DenotTransformers$SymTransformer.transform$(DenotTransformers.scala:65)
	at dotty.tools.dotc.transform.Flatten.transform(Flatten.scala:14)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:803)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:823)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:823)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
	at dotty.tools.dotc.core.Symbols$Symbol.recomputeDenot(Symbols.scala:119)
	at dotty.tools.dotc.core.Symbols$Symbol.computeDenot(Symbols.scala:113)
	at dotty.tools.dotc.core.Symbols$Symbol.denot(Symbols.scala:106)
	at dotty.tools.dotc.core.Symbols$.toDenot(Symbols.scala:487)
	at dotty.tools.dotc.transform.GenericSignatures$.fullNameInSig$1(GenericSignatures.scala:116)
	at dotty.tools.dotc.transform.GenericSignatures$.classSig$2(GenericSignatures.scala:165)
	at dotty.tools.dotc.transform.GenericSignatures$.jsig$1(GenericSignatures.scala:227)
	at dotty.tools.dotc.transform.GenericSignatures$.boxedSig$1(GenericSignatures.scala:66)
	at dotty.tools.dotc.transform.GenericSignatures$.argSig$1(GenericSignatures.scala:139)
	at dotty.tools.dotc.transform.GenericSignatures$.classSig$1$$anonfun$1(GenericSignatures.scala:171)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.dotc.transform.GenericSignatures$.classSig$2(GenericSignatures.scala:171)
	at dotty.tools.dotc.transform.GenericSignatures$.jsig$1(GenericSignatures.scala:227)
	at dotty.tools.dotc.transform.GenericSignatures$.methodResultSig$1(GenericSignatures.scala:104)
	at dotty.tools.dotc.transform.GenericSignatures$.jsig$1(GenericSignatures.scala:265)
	at dotty.tools.dotc.transform.GenericSignatures$.javaSig0(GenericSignatures.scala:299)
	at dotty.tools.dotc.transform.GenericSignatures$.javaSig(GenericSignatures.scala:38)
	at dotty.tools.backend.jvm.BCodeHelpers.dotty$tools$backend$jvm$BCodeHelpers$$getGenericSignatureHelper(BCodeHelpers.scala:863)
	at dotty.tools.backend.jvm.BCodeHelpers.dotty$tools$backend$jvm$BCodeHelpers$$getStaticForwarderGenericSignature(BCodeHelpers.scala:927)
	at dotty.tools.backend.jvm.BCodeHelpers$BCForwardersGen.addForwarder(BCodeHelpers.scala:522)
	at dotty.tools.backend.jvm.BCodeHelpers$BCForwardersGen.addForwarders$$anonfun$2(BCodeHelpers.scala:593)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.backend.jvm.BCodeHelpers$BCForwardersGen.addForwarders(BCodeHelpers.scala:595)
	at dotty.tools.backend.jvm.BCodeHelpers$BCForwardersGen.addForwarders$(BCodeHelpers.scala:499)
	at dotty.tools.backend.jvm.BCodeHelpers$JCommonBuilder.addForwarders(BCodeHelpers.scala:653)
	at dotty.tools.backend.jvm.BCodeHelpers$JMirrorBuilder.genMirrorClass(BCodeHelpers.scala:701)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:218)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:192)
	at dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:531)
	at dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:497)
	at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:58)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:296)
	at scala.collection.immutable.List.map(List.scala:246)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:297)
	at dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:62)
	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:195)
	at dotty.tools.dotc.Main.process(Main.scala)
	at xsbt.CachedCompilerImpl.run(CachedCompilerImpl.java:69)
	at xsbt.CompilerInterface.run(CompilerInterface.java:41)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:248)
	at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:122)
	at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:95)
	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:91)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
	at sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:186)
	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:82)
	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3$adapted(MixedAnalyzingCompiler.scala:77)
	at sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:215)
	at sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:77)
	at sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:146)
	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:343)
	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:343)
	at sbt.internal.inc.Incremental$.doCompile(Incremental.scala:120)
	at sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:100)
	at sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:180)
	at sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:98)
	at sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:102)
	at sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:155)
	at sbt.internal.inc.Incremental$.compile(Incremental.scala:92)
	at sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:75)
	at sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:348)
	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:301)
	at sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:168)
	at sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:248)
	at sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:74)
	at sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1765)
	at sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1738)
	at scala.Function1.$anonfun$compose$1(Function1.scala:49)
	at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
	at sbt.std.Transform$$anon$4.work(Transform.scala:67)
	at sbt.Execute.$anonfun$submit$2(Execute.scala:281)
	at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:19)
	at sbt.Execute.work(Execute.scala:290)
	at sbt.Execute.$anonfun$submit$1(Execute.scala:281)
	at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
	at sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

[griggt]

An even simpler example with the same error:

import com.twitter.finagle.liveness.FailureAccrualFactory

trait A {
  def p: FailureAccrualFactory.Param
}

Compilation fails on 0.26.0 and newer.

[b-studios]

The source of FailureAccrualFactory.Param can be found here:

https://github.com/twitter/finagle/blob/d2e7485782faeada129d43d7511167c31811df81/finagle-core/src/main/scala/com/twitter/finagle/liveness/FailureAccrualFactory.scala#L78-L80

[griggt]

Don't know if it's relevant but the companion object for FailureAccrualFactory.Param has a private[finagle] access modifier. By contrast, NackAdmissionFilter and BackupRequestFilter have the same sort of pattern with their Param trait but with a public companion object, and they don't have an issue, e.g.

import com.twitter.finagle.filter._
import com.twitter.finagle.client._

trait A {
  def p: NackAdmissionFilter.Param
  def q: BackupRequestFilter.Param
}

compiles successfully.

https://github.com/twitter/finagle/blob/34167989a6dc964e24e20212516fba89fa58bb23/finagle-core/src/main/scala/com/twitter/finagle/client/BackupRequestFilter.scala#L72-L82

https://github.com/twitter/finagle/blob/34167989a6dc964e24e20212516fba89fa58bb23/finagle-core/src/main/scala/com/twitter/finagle/filter/NackAdmissionFilter.scala#L61-L80

[griggt]

Upon further inspection, I believe the issue may be caused by public "factory" methods defined with the same name as the trait/companion:

https://github.com/twitter/finagle/blob/d2e7485782faeada129d43d7511167c31811df81/finagle-core/src/main/scala/com/twitter/finagle/liveness/FailureAccrualFactory.scala#L129

[DieBauer]

@griggt I indeed tried to reproduce this way, but when defining this class in dotty, the error doesn't occur. So maybe it's in the scala 2 - dotty interop.

[griggt]

Standalone reproducer:

//src/dotty-issues/i9916/standalone/lib$ cat build.sbt
scalaVersion := "2.13.3"
name := "i9916-lib"
organization := "io.grigg"
version := "1.0"

//src/dotty-issues/i9916/standalone/lib$ cat src/main/scala/Lib.scala 
package i9916

object Lib {
  trait P
  private object P
  def P(x: Int): P = ???
}

//src/dotty-issues/i9916/standalone/lib$ sbt publishLocal

//src/dotty-issues/i9916/standalone/test$ cat build.sbt
scalaVersion := "0.28.0-bin-20200928-09eaed7-NIGHTLY"
name := "i9916-test"
version := "0.1"
libraryDependencies += ("io.grigg" %% "i9916-lib" % "1.0").withDottyCompat(scalaVersion.value)

//src/dotty-issues/i9916/standalone/test$ cat src/main/scala/Test.scala 
import i9916.Lib

trait X {
  def p: Lib.P
}

//src/dotty-issues/i9916/standalone/test$ sbt compile 

Compiler output -- click to expand

[info] Compiling 1 Scala source to /src/dotty-issues/i9916/standalone/test/target/scala-0.28/classes ...
Error while emitting Test.scala
[info] exception occurred while compiling /src/dotty-issues/i9916/standalone/test/src/main/scala/Test.scala
scala.MatchError: NoType (of class dotty.tools.dotc.core.Types$NoType$) while compiling /src/dotty-issues/i9916/standalone/test/src/main/scala/Test.scala
[error] ## Exception when compiling 1 sources to /src/dotty-issues/i9916/standalone/test/target/scala-0.28/classes
[error] scala.MatchError: NoType (of class dotty.tools.dotc.core.Types$NoType$)
[error] dotty.tools.dotc.core.SymDenotations$SymDenotation.sourceOfSelf$1(SymDenotations.scala:1007)
[error] dotty.tools.dotc.core.SymDenotations$SymDenotation.sourceModule(SymDenotations.scala:1009)
[error] dotty.tools.dotc.core.TypeErasure.dotty$tools$dotc$core$TypeErasure$$apply(TypeErasure.scala:504)
[error] dotty.tools.dotc.core.TypeErasure.eraseInfo(TypeErasure.scala:552)
[error] dotty.tools.dotc.core.TypeErasure$.transformInfo(TypeErasure.scala:202)
[error] dotty.tools.dotc.transform.Erasure.transform(Erasure.scala:82)
[error] dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:803)
[error] dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
[error] dotty.tools.dotc.core.Symbols$Symbol.recomputeDenot(Symbols.scala:119)
[error] dotty.tools.dotc.core.Symbols$Symbol.computeDenot(Symbols.scala:113)
[error] dotty.tools.dotc.core.Symbols$Symbol.denot(Symbols.scala:106)
[error] dotty.tools.dotc.core.Symbols$.toDenot(Symbols.scala:487)
[error] dotty.tools.dotc.core.SymDenotations$ClassDenotation.registeredCompanion(SymDenotations.scala:2146)
[error] dotty.tools.dotc.core.SymDenotations$SymDenotation.copySymDenotation(SymDenotations.scala:1484)
[error] dotty.tools.dotc.transform.Flatten.transformSym(Flatten.scala:35)
[error] dotty.tools.dotc.core.DenotTransformers$SymTransformer.transform(DenotTransformers.scala:70)
[error] dotty.tools.dotc.core.DenotTransformers$SymTransformer.transform$(DenotTransformers.scala:65)
[error] dotty.tools.dotc.transform.Flatten.transform(Flatten.scala:14)
[error] dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:803)
[error] dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
[error] dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:823)
[error] dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
[error] dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:823)
[error] dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
[error] dotty.tools.dotc.core.Types$NamedType.computeDenot(Types.scala:2056)
[error] dotty.tools.dotc.core.Types$NamedType.denot(Types.scala:2019)
[error] dotty.tools.dotc.core.Types$NamedType.info(Types.scala:2007)
[error] dotty.tools.backend.jvm.BCodeHelpers.dotty$tools$backend$jvm$BCodeHelpers$$typeToTypeKind(BCodeHelpers.scala:819)
[error] dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.toTypeKind(BCodeHelpers.scala:299)
[error] dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.toTypeKind$(BCodeHelpers.scala:210)
[error] dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.toTypeKind(BCodeSkelBuilder.scala:62)
[error] dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.asmMethodType(BCodeHelpers.scala:283)
[error] dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.asmMethodType$(BCodeHelpers.scala:210)
[error] dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.asmMethodType(BCodeSkelBuilder.scala:62)
[error] dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genDefDef(BCodeSkelBuilder.scala:673)
[error] dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:591)
[error] dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen$$anonfun$1(BCodeSkelBuilder.scala:597)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:597)
[error] dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genPlainClass(BCodeSkelBuilder.scala:223)
[error] dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:229)
[error] dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:194)
[error] dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:533)
[error] dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:499)
[error] dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:60)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:296)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:297)
[error] dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:64)
[error] dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:185)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$5(Run.scala:195)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:203)
[error] dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:63)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:210)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:147)
[error] dotty.tools.dotc.Run.compile(Run.scala:129)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
[error] dotty.tools.dotc.Driver.process(Driver.scala:195)
[error] dotty.tools.dotc.Main.process(Main.scala)
[error] xsbt.CachedCompilerImpl.run(CachedCompilerImpl.java:69)
[error] xsbt.CompilerInterface.run(CompilerInterface.java:41)
[error] java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] java.base/java.lang.reflect.Method.invoke(Method.java:566)
[error] sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:248)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:122)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:95)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:91)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:186)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:82)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3$adapted(MixedAnalyzingCompiler.scala:77)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:215)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:77)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:146)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:343)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:343)
[error] sbt.internal.inc.Incremental$.doCompile(Incremental.scala:120)
[error] sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:100)
[error] sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:180)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:98)
[error] sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:102)
[error] sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:155)
[error] sbt.internal.inc.Incremental$.compile(Incremental.scala:92)
[error] sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:75)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:348)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:301)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:168)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:248)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:74)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1765)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1738)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:67)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:281)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:19)
[error] sbt.Execute.work(Execute.scala:290)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:281)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
[error] java.base/java.lang.Thread.run(Thread.java:834)
[error]            
[error] scala.MatchError: NoType (of class dotty.tools.dotc.core.Types$NoType$)
[error] 	at dotty.tools.dotc.core.SymDenotations$SymDenotation.sourceOfSelf$1(SymDenotations.scala:1007)
[error] 	at dotty.tools.dotc.core.SymDenotations$SymDenotation.sourceModule(SymDenotations.scala:1009)
[error] 	at dotty.tools.dotc.core.TypeErasure.dotty$tools$dotc$core$TypeErasure$$apply(TypeErasure.scala:504)
[error] 	at dotty.tools.dotc.core.TypeErasure.eraseInfo(TypeErasure.scala:552)
[error] 	at dotty.tools.dotc.core.TypeErasure$.transformInfo(TypeErasure.scala:202)
[error] 	at dotty.tools.dotc.transform.Erasure.transform(Erasure.scala:82)
[error] 	at dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:803)
[error] 	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
[error] 	at dotty.tools.dotc.core.Symbols$Symbol.recomputeDenot(Symbols.scala:119)
[error] 	at dotty.tools.dotc.core.Symbols$Symbol.computeDenot(Symbols.scala:113)
[error] 	at dotty.tools.dotc.core.Symbols$Symbol.denot(Symbols.scala:106)
[error] 	at dotty.tools.dotc.core.Symbols$.toDenot(Symbols.scala:487)
[error] 	at dotty.tools.dotc.core.SymDenotations$ClassDenotation.registeredCompanion(SymDenotations.scala:2146)
[error] 	at dotty.tools.dotc.core.SymDenotations$SymDenotation.copySymDenotation(SymDenotations.scala:1484)
[error] 	at dotty.tools.dotc.transform.Flatten.transformSym(Flatten.scala:35)
[error] 	at dotty.tools.dotc.core.DenotTransformers$SymTransformer.transform(DenotTransformers.scala:70)
[error] 	at dotty.tools.dotc.core.DenotTransformers$SymTransformer.transform$(DenotTransformers.scala:65)
[error] 	at dotty.tools.dotc.transform.Flatten.transform(Flatten.scala:14)
[error] 	at dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:803)
[error] 	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
[error] 	at dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:823)
[error] 	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
[error] 	at dotty.tools.dotc.core.Denotations$SingleDenotation.goForward$1(Denotations.scala:823)
[error] 	at dotty.tools.dotc.core.Denotations$SingleDenotation.current(Denotations.scala:852)
[error] 	at dotty.tools.dotc.core.Types$NamedType.computeDenot(Types.scala:2056)
[error] 	at dotty.tools.dotc.core.Types$NamedType.denot(Types.scala:2019)
[error] 	at dotty.tools.dotc.core.Types$NamedType.info(Types.scala:2007)
[error] 	at dotty.tools.backend.jvm.BCodeHelpers.dotty$tools$backend$jvm$BCodeHelpers$$typeToTypeKind(BCodeHelpers.scala:819)
[error] 	at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.toTypeKind(BCodeHelpers.scala:299)
[error] 	at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.toTypeKind$(BCodeHelpers.scala:210)
[error] 	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.toTypeKind(BCodeSkelBuilder.scala:62)
[error] 	at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.asmMethodType(BCodeHelpers.scala:283)
[error] 	at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.asmMethodType$(BCodeHelpers.scala:210)
[error] 	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.asmMethodType(BCodeSkelBuilder.scala:62)
[error] 	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genDefDef(BCodeSkelBuilder.scala:673)
[error] 	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:591)
[error] 	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen$$anonfun$1(BCodeSkelBuilder.scala:597)
[error] 	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] 	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] 	at scala.collection.immutable.List.foreach(List.scala:333)
[error] 	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:597)
[error] 	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genPlainClass(BCodeSkelBuilder.scala:223)
[error] 	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:229)
[error] 	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:194)
[error] 	at dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:533)
[error] 	at dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:499)
[error] 	at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:60)
[error] 	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:296)
[error] 	at scala.collection.immutable.List.map(List.scala:246)
[error] 	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:297)
[error] 	at dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:64)
[error] 	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:185)
[error] 	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] 	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] 	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] 	at dotty.tools.dotc.Run.runPhases$5(Run.scala:195)
[error] 	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:203)
[error] 	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error] 	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:63)
[error] 	at dotty.tools.dotc.Run.compileUnits(Run.scala:210)
[error] 	at dotty.tools.dotc.Run.compileSources(Run.scala:147)
[error] 	at dotty.tools.dotc.Run.compile(Run.scala:129)
[error] 	at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
[error] 	at dotty.tools.dotc.Driver.process(Driver.scala:195)
[error] 	at dotty.tools.dotc.Main.process(Main.scala)
[error] 	at xsbt.CachedCompilerImpl.run(CachedCompilerImpl.java:69)
[error] 	at xsbt.CompilerInterface.run(CompilerInterface.java:41)
[error] 	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
[error] 	at sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:248)
[error] 	at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:122)
[error] 	at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:95)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:91)
[error] 	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:186)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:82)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3$adapted(MixedAnalyzingCompiler.scala:77)
[error] 	at sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:215)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:77)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:146)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:343)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:343)
[error] 	at sbt.internal.inc.Incremental$.doCompile(Incremental.scala:120)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:100)
[error] 	at sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:180)
[error] 	at sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:98)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:102)
[error] 	at sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:155)
[error] 	at sbt.internal.inc.Incremental$.compile(Incremental.scala:92)
[error] 	at sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:75)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:348)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:301)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:168)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:248)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:74)
[error] 	at sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1765)
[error] 	at sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1738)
[error] 	at scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] 	at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] 	at sbt.std.Transform$$anon$4.work(Transform.scala:67)
[error] 	at sbt.Execute.$anonfun$submit$2(Execute.scala:281)
[error] 	at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:19)
[error] 	at sbt.Execute.work(Execute.scala:290)
[error] 	at sbt.Execute.$anonfun$submit$1(Execute.scala:281)
[error] 	at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error] 	at sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error] 	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] 	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
[error] 	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] 	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
[error] 	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
[error] 	at java.base/java.lang.Thread.run(Thread.java:834)
[error] (Compile / compileIncremental) scala.MatchError: NoType (of class dotty.tools.dotc.core.Types$NoType$)

[griggt]

@DieBauer Yes, the issue only arises when the library is compiled with Scala 2.

[griggt]

The regression appears to have been introduced by e88c5b7 in #8652.

[DieBauer]

BTW the private part of object doesn't matter:

object Lib {
  trait P
  object P
  def P(x: Int): P = ???
}

also fails when compiled with scala 2.13 and used in dotty.

[griggt]

Just curious, does the Dotty testing framework support regression tests for this sort of issue, i.e. where the test depends on some code compiled by Scala 2.x?