Value class parameterized by subtype of primitive type crashes compiler

[scabug]

Attempting to run this code in the Repl:

implicit class Foo[T <: Long](val a : T) extends AnyVal {
    def bar = a + 1
}

Results in:

ReplGlobal.abort: Erasure should have added an unboxing operation to prevent this cast. Tree: $this.$asInstanceOf[Long]()
error:
  Erasure should have added an unboxing operation to prevent this cast. Tree: $this.$asInstanceOf[Long]()
     while compiling: <console>
        during phase: jvm
     library version: version 2.12.1
    compiler version: version 2.12.1
  reconstructed args: -deprecation -feature

  last tree to typer: TypeTree(class Long)
       tree position: line 11 of <console>
            tree tpe: Long
              symbol: (final abstract) class Long in package scala
   symbol definition: final abstract class Long extends  (a ClassSymbol)
      symbol package: scala
       symbol owners: class Long
           call site: constructor $read$Foo in package $line3

<Cannot read source file>
scala.reflect.internal.FatalError: 
  Erasure should have added an unboxing operation to prevent this cast. Tree: $this.$asInstanceOf[Long]()
     while compiling: <console>
        during phase: jvm
     library version: version 2.12.1
    compiler version: version 2.12.1
  reconstructed args: -deprecation -feature

  last tree to typer: TypeTree(class Long)
       tree position: line 11 of <console>
            tree tpe: Long
              symbol: (final abstract) class Long in package scala
   symbol definition: final abstract class Long extends  (a ClassSymbol)
      symbol package: scala
       symbol owners: class Long
           call site: constructor $read$$iw$$iw$Foo in package $line3

<Cannot read source file>
        at scala.reflect.internal.Reporting.abort(Reporting.scala:61)
        at scala.reflect.internal.Reporting.abort$(Reporting.scala:57)
        at scala.tools.nsc.interpreter.IMain$$anon$1.scala$tools$nsc$interpreter$ReplGlobal$$super$abort(IMain.scala:242)
        at scala.tools.nsc.interpreter.ReplGlobal.abort(ReplGlobal.scala:23)
        at scala.tools.nsc.interpreter.ReplGlobal.abort$(ReplGlobal.scala:21)
        at scala.tools.nsc.interpreter.IMain$$anon$1.abort(IMain.scala:242)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genTypeApply$1(BCodeBodyBuilder.scala:539)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genApply(BCodeBodyBuilder.scala:552)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:298)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genArithmeticOp(BCodeBodyBuilder.scala:129)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genPrimitiveOp(BCodeBodyBuilder.scala:218)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genApply(BCodeBodyBuilder.scala:653)
        at scala.tools.nsc.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:298)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.emitNormalMethodBody$1(BCodeSkelBuilder.scala:603)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genDefDef(BCodeSkelBuilder.scala:635)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:509)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.$anonfun$gen$7(BCodeSkelBuilder.scala:511)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:511)
        at scala.tools.nsc.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genPlainClass(BCodeSkelBuilder.scala:113)
        at scala.tools.nsc.backend.jvm.GenBCode$BCodePhase$Worker1.visit(GenBCode.scala:190)
        at scala.tools.nsc.backend.jvm.GenBCode$BCodePhase$Worker1.$anonfun$run$1(GenBCode.scala:139)
        at scala.tools.nsc.backend.jvm.GenBCode$BCodePhase$Worker1.run(GenBCode.scala:139)
        at scala.tools.nsc.backend.jvm.GenBCode$BCodePhase.buildAndSendToDisk(GenBCode.scala:381)
        at scala.tools.nsc.backend.jvm.GenBCode$BCodePhase.run(GenBCode.scala:350)
        at scala.tools.nsc.Global$Run.compileUnitsInternal(Global.scala:1418)
        at scala.tools.nsc.Global$Run.compileUnits(Global.scala:1403)
        at scala.tools.nsc.Global$Run.compileSources(Global.scala:1398)
        at scala.tools.nsc.interpreter.IMain.compileSourcesKeepingRun(IMain.scala:430)
        at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.compileAndSaveRun(IMain.scala:801)
        at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.compile(IMain.scala:759)
        at scala.tools.nsc.interpreter.IMain$Request.compile$lzycompute(IMain.scala:948)
        at scala.tools.nsc.interpreter.IMain$Request.compile(IMain.scala:943)
        at scala.tools.nsc.interpreter.IMain.compile(IMain.scala:599)
        at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:588)
        at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:560)
        at scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:825)
        at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:684)
        at scala.tools.nsc.interpreter.ILoop.processLine(ILoop.scala:402)
        at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:423)
        at scala.tools.nsc.interpreter.ILoop.$anonfun$process$1(ILoop.scala:993)
        at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:892)
        at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:75)
        at scala.tools.nsc.MainGenericRunner.run$1(MainGenericRunner.scala:88)
        at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:99)
        at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:104)
        at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
error: Error while emitting <console>

  Erasure should have added an unboxing operation to prevent this cast. Tree: $this.$asInstanceOf[Long]()
     while compiling: <console>
        during phase: jvm
     library version: version 2.12.1
    compiler version: version 2.12.1
  reconstructed args: -deprecation -feature

  last tree to typer: TypeTree(class Long)
       tree position: line 11 of <console>
            tree tpe: Long
              symbol: (final abstract) class Long in package scala
   symbol definition: final abstract class Long extends  (a ClassSymbol)
      symbol package: scala
       symbol owners: class Long
           call site: constructor $read$Foo in package $line3

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-10221?orig=1 Reporter: Matt Snelling (mzsnelling) Affected Versions: 2.12.1

[dwijnand]

https://github.com/scala/bug/issues/12008 duplicates this, but it adds a reason for using a type parameter: including Singleton:

    class V[I <: Int with Singleton](val i: I) extends AnyVal

    val i = new V[1](1)
    def accept[I <: Int with Singleton](i: V[I]): I = i.i