Trait can redefine the final methods from a class AnyRef

[maseev]

Doing this:

scala> trait Fun {
         override def notify(): Unit = {
         }
       } 
// defined trait Fun
scala> class MyClass extends Fun 
// defined class MyClass
scala> new MyClass 

kills the REPL with this:

Exception in thread "main" java.lang.VerifyError: class rs$line$1$Fun overrides final method notify.()V
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:642)
        at dotty.tools.repl.AbstractFileClassLoader.findClass(AbstractFileClassLoader.scala:28)
        at dotty.tools.repl.AbstractFileClassLoader.loadClass(AbstractFileClassLoader.scala:32)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:642)
        at dotty.tools.repl.AbstractFileClassLoader.findClass(AbstractFileClassLoader.scala:28)
        at dotty.tools.repl.AbstractFileClassLoader.loadClass(AbstractFileClassLoader.scala:32)
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
        at java.lang.Class.getDeclaredMethods(Class.java:1975)
        at dotty.tools.repl.Rendering.valueOf(Rendering.scala:56)
        at dotty.tools.repl.Rendering.renderVal(Rendering.scala:79)
        at dotty.tools.repl.ReplDriver.displayMembers$3$$anonfun$3(ReplDriver.scala:269)
        at scala.collection.TraversableLike.$anonfun$map$1(TraversableLike.scala:234)
        at scala.collection.mutable.ResizableArray.foreach(ResizableArray.scala:59)
        at scala.collection.mutable.ResizableArray.foreach$(ResizableArray.scala:52)
        at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
        at scala.collection.TraversableLike.map(TraversableLike.scala:234)
        at scala.collection.TraversableLike.map$(TraversableLike.scala:227)
        at scala.collection.AbstractTraversable.map(Traversable.scala:104)
        at dotty.tools.repl.ReplDriver.displayMembers$7(ReplDriver.scala:269)
        at dotty.tools.repl.ReplDriver.displayDefinitions$$anonfun$3$$anonfun$2(ReplDriver.scala:296)
        at scala.Option.map(Option.scala:146)
        at dotty.tools.repl.ReplDriver.displayDefinitions$$anonfun$1(ReplDriver.scala:296)
        at dotty.tools.dotc.core.Periods.atPhase(Periods.scala:26)
        at dotty.tools.dotc.core.Phases.atPhase(Phases.scala:36)
        at dotty.tools.repl.ReplDriver.displayDefinitions(ReplDriver.scala:301)
        at dotty.tools.repl.ReplDriver.compile$$anonfun$2(ReplDriver.scala:226)
        at scala.util.Either.fold(Either.scala:188)
        at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:227)
        at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:190)
        at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:143)
        at dotty.tools.repl.Main$.main(Main.scala:6)
        at dotty.tools.repl.Main.main(Main.scala)

I guess the compiler should check this case somewhere here, but apparently, it does not.

[allanrenucci]

scala/scala@88ed763 should be ported to our fork of scala at https://github.com/lampepfl/scala/tree/dotty-library

[smarter]

Nice catch! :)

scala/scala@88ed763 should be ported to our fork of scala at https://github.com/lampepfl/scala/tree/dotty-library

That shouldn't matter for this particular issue since we run dotty with the scala-library from 2.12.