Crash by combining match types, intersection types and structural types

[Katrix]

Compiler version

3.1.0

Minimized code

class DiscordRecord(fields: Map[String, Any]) extends Selectable {
  def selectDynamic(name: String): Any = fields(name)
}

type IdentifyScope = DiscordRecord {
  val username: String
}

type IncludeIf[Stated <: String, Requirement <: String, IfMatch] = Seq[Stated] match {
  case Seq[Requirement] => IfMatch
  case _ => Any
}

type RawUser[Scopes <: String] = DiscordRecord & IncludeIf[Scopes, "identify", IdentifyScope]

val obj: RawUser["identify"] = ???
obj.username

Removing the intersection type in RawUser fixes the problem. It's not needed in this case, but using an intersection type with something not redundant also crashes. The crash only happens when it would otherwise compile (I think). Changing obj.username to obj.foo does not compile sucessfully without a crash. Similarly, changing RawUser["identify"] to RawUser["foo"] also does not compile sucessfully without a crash.

Output (click arrow to expand)

Details

exception while typing this.obj.username of class class dotty.tools.dotc.ast.Trees$Select # -1
exception while typing @scala.annotation.internal.SourceFile("src/main/scala/testing/testing.scala")
  class
 testing() extends Object() {
  class DiscordRecord(fields: scala.collection.immutable.Map[String, Any])
     extends
   Object(), Selectable {
    private val fields: scala.collection.immutable.Map[String, Any]
    def selectDynamic(name: String): Any = DiscordRecord.this.fields.apply(name)
    private val $outer: testing.testing
    final def testing$testing$DiscordRecord$$$outer: testing.testing =
      DiscordRecord.this.$outer
  }
  type IdentifyScope = testing.this.DiscordRecord{username: String}
  type IncludeIf =

      ([Stated <: String, Requirement <: String, IfMatch] =>>
        scala.collection.immutable.Seq[Stated] match {
          case scala.collection.immutable.Seq[Requirement] => IfMatch
          case _ => Any
        }
      )
     @_
  type RawUser =

      [Scopes <: String] =>> testing.this.DiscordRecord &
        testing.this.IncludeIf[Scopes, ("identify" : String),
          testing.this.IdentifyScope
        ]

  def obj: testing.this.RawUser[("identify" : String)] = ???
  this.obj.username
} of class class dotty.tools.dotc.ast.Trees$TypeDef # -1
exception while typing package testing {
  @scala.annotation.internal.SourceFile("src/main/scala/testing/testing.scala")
    class
   testing() extends Object() {
    class DiscordRecord(fields: scala.collection.immutable.Map[String, Any])
       extends
     Object(), Selectable {
      private val fields: scala.collection.immutable.Map[String, Any]
      def selectDynamic(name: String): Any =
        DiscordRecord.this.fields.apply(name)
      private val $outer: testing.testing
      final def testing$testing$DiscordRecord$$$outer: testing.testing =
        DiscordRecord.this.$outer
    }
    type IdentifyScope = testing.this.DiscordRecord{username: String}
    type IncludeIf =

        ([Stated <: String, Requirement <: String, IfMatch] =>>
          scala.collection.immutable.Seq[Stated] match {
            case scala.collection.immutable.Seq[Requirement] => IfMatch
            case _ => Any
          }
        )
       @_
    type RawUser =

        [Scopes <: String] =>> testing.this.DiscordRecord &
          testing.this.IncludeIf[Scopes, ("identify" : String),
            testing.this.IdentifyScope
          ]

    def obj: testing.this.RawUser[("identify" : String)] = ???
    this.obj.username
  }
} of class class dotty.tools.dotc.ast.Trees$PackageDef # -1
[info] exception occurred while compiling D:\DevProjects\Incubating\AckCordNext\src\main\scala\testing\testing.scala
java.lang.AssertionError: assertion failed:  <none> while compiling D:\DevProjects\Incubating\AckCordNext\src\main\scala\testing\testing.scala
[error] ## Exception when compiling 15 sources to D:\DevProjects\Incubating\AckCordNext\target\scala-3.1.0\classes
[error] java.lang.AssertionError: assertion failed:  <none>
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedSelect(Erasure.scala:721)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2725)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2817)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2936)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2959)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1053)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2409)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1043)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$2(Typer.scala:2743)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2747)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2817)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2909)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2959)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1053)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2532)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2788)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2818)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2883)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:2887)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3003)
[error] dotty.tools.dotc.transform.Erasure.run(Erasure.scala:132)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:308)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:309)
[error] dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:261)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$5(Run.scala:272)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:280)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:68)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:289)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:222)
[error] dotty.tools.dotc.Run.compile(Run.scala:206)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:39)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:88)
[error] dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:192)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:247)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:182)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:210)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:175)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:173)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:459)
[error] sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:263)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:414)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:501)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:401)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:167)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:482)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:420)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2357)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2314)
[error] sbt.internal.io.Retry$.apply(Retry.scala:46)
[error] sbt.internal.io.Retry$.apply(Retry.scala:28)
[error] sbt.internal.io.Retry$.apply(Retry.scala:23)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:31)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2310)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:68)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:282)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:23)
[error] sbt.Execute.work(Execute.scala:291)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:282)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:64)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] java.lang.Thread.run(Thread.java:748)

[odersky]

Compiling with -Ycheck:all gives

exception occurred while compiling i13889.scala
java.lang.AssertionError: assertion failed: Denotation some String#4963 of selection <<obj#7657:RawUser#2840[("identify" : String)]>.username:String#4963> with type (obj#7657.username : String#4963) does not have a symbol while compiling i13889.scala
Exception in thread "main" java.lang.AssertionError: assertion failed: Denotation some String#4963 of selection <<obj#7657:RawUser#2840[("identify" : String)]>.username:String#4963> with type (obj#7657.username : String#4963) does not have a symbol

for the last line: obj.userName.