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Array created using ClassTag[Array[Nothing]] cannot hold Array[Nothing] created by new #9754

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scabug opened this issue Apr 14, 2016 · 3 comments
Open

Array created using ClassTag[Array[Nothing]] cannot hold Array[Nothing] created by new #9754

scabug opened this issue Apr 14, 2016 · 3 comments
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@scabug
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scabug commented Apr 14, 2016

The following program

import scala.reflect.ClassTag

object Program {
  def test[T: ClassTag](x: T) = {
    val arr = new Array[T](1)
    println(arr.getClass)
    println(x.getClass)
    arr(0) = x
  }

  def main(args: Array[String]): Unit = {
    test(new Array[Nothing](0))
  }

}

throws the exception java.lang.ArrayStoreException:

[error] (run-main-8) java.lang.ArrayStoreException: [Ljava.lang.Object;
java.lang.ArrayStoreException: [Ljava.lang.Object;
	at scala.runtime.ScalaRunTime$.array_update(ScalaRunTime.scala:89)
	at Program$.test(Program.scala:8)
	at Program$.main(Program.scala:12)
	at Program.main(Program.scala)
	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:497)

The output of the program

class [[Lscala.runtime.Nothing$;
class [Ljava.lang.Object;

explains the problem. The array arr created using ClassTag has element type Array[scala.runtime.Nothing$] but array created by new has type Array[java.lang.Object].

Same exception is thrown with Null. For other types it works fine.
@scabug
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scabug commented Apr 14, 2016

Imported From: https://issues.scala-lang.org/browse/SI-9754?orig=1
Reporter: Radek Micek (radekm)
See #5353, #7543

@scabug
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scabug commented Sep 29, 2016

@SethTisue said:
is this already covered by SI-5353 and/or SI-7543?

@scabug scabug added the quickfix label Apr 7, 2017
@scabug scabug added this to the Backlog milestone Apr 7, 2017
@SethTisue
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Scala 3 ticket in the Array[Nothing] space: scala/scala3#9586

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