RuntimeException: Unexpected New(..) reached GenBCode when using @alpha on constructor

[panacekcz]

Using @alpha on a constructor doesn't make sense (at least for the jvm backend), so should be either forbidden or ignored.

minimized code

class A(i:Int){
  @scala.annotation.alpha("E") def this() = this(3)
}
object O{
  def main(args: Array[String]) = {
    new A()
  }
}

Stack trace

Unexpected New(A/TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class A)) reached GenBCode.
  Call was genLoad(New(TypeTree[TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class A)]),LA;)
Error while emitting alpha-init.scala
exception occurred while compiling alpha-init.scala
java.lang.RuntimeException: Unexpected New(A/TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class A)) reached GenBCode.
  Call was genLoad(New(TypeTree[TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class A)]),LA;) while compiling alpha-init.scala
Exception in thread "main" java.lang.RuntimeException: Unexpected New(A/TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class A)) reached GenBCode.
  Call was genLoad(New(TypeTree[TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class A)]),LA;)
	at dotty.tools.backend.jvm.DottyBackendInterface.abort(DottyBackendInterface.scala:394)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:315)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:264)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoadQualifier(BCodeBodyBuilder.scala:1010)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genNormalMethodCall$1(BCodeBodyBuilder.scala:782)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genApply(BCodeBodyBuilder.scala:814)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:339)
	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:409)
	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)