Deriving from abstract class/method without implementation does not fail to compile

[Christopher Currie]

Given the following files:

// Base.java

public class Base {

  public boolean foo() { return true; }

}

// Abstract.java

public abstract class Abstract extends Base {

  public abstract boolean foo(); // force re-implementation in derived classes

}

// DerivedJava.java

public class DerivedJava extends Abstract {}

// DerivedScala.scala

class DerivedScala extends Abstract

// Main.scala

object Main extends App {

  new DerivedScala().foo()

}

WIth these present, javac will fail to compile DerivedJava, complaining that foo needs to be defined. However, scalac will not fail to compile DerivedScala.scala, and when Main.scala is compiled and run, it crashes with AbstractMethodError (shown here from the REPL):

scala> class Derived extends Abstract

defined class Derived

scala> new Derived().foo()

java.lang.AbstractMethodError: Derived.foo()Z

        at .<init>(<console>:9)

        at .<clinit>(<console>)

        at .<init>(<console>:11)

        at .<clinit>(<console>)

        at $print(<console>)

        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

        at java.lang.reflect.Method.invoke(Method.java:597)

        at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:704)

        at scala.tools.nsc.interpreter.IMain$Request$$anonfun$14.apply(IMain.scala:920)

        at scala.tools.nsc.interpreter.Line$$anonfun$1.apply$mcV$sp(Line.scala:43)

        at scala.tools.nsc.io.package$$anon$2.run(package.scala:25)

        at java.lang.Thread.run(Thread.java:680)

Is there a bug for this? I spend some time looking for one in JIRA but could not track one down.

Thanks,

Christopher

[Jason Zaugg]

On Mon, Jul 2, 2012 at 7:34 AM, Christopher Currie
<chris...@currie.com> wrote:
> Is there a bug for this? I spend some time looking for one in JIRA but could
> not track one down.

I don't think so; please lodge one. It's not quite the same as the
recently fixed SI-4989.

-jason

[Christopher Currie]

Done, created as https://issues.scala-lang.org/browse/SI-6013