RC4 candidate for the first 2.8.0 beta

Just some quick explanation why we pushed out a 4th candidate so
quickly after the 3rd. There were two critical changes that did not
make it into the third candidate.

One change affects type erasure to make it faster and improve
interoperability with Java. Unfortunately that's a change which breaks
binary compatibility with old code. So it would have been very tricky
to schedlue it for inclusion later when we want to keep binary
compatibility as much as is feasible.

The other change re-tightens a type checking rule for null that was
accidentally dropped in the move from 2.7 to 2.8. Variables of
abstract types may be assigned `null' only if the type has `Null' as
lower bound. So the following is illegal:

def f[T]() { val x: T = null }

You have to write

def f[T >: Null]() { val x: T = null }

instead. In my experience such a tightening of the rules has to be
done as quickly as possible, before there's lots of code that relies
on the loop hole.

If all goes well with the RC4 we plan to release a public beta before
the holidays.

Cheers

Hey Martin,

On Sat, 2009-12-19 at 11:29 +0100, martin odersky wrote:
> One change affects type erasure to make it faster and improve
> interoperability with Java. Unfortunately that's a change which breaks
> binary compatibility with old code. So it would have been very tricky
> to schedlue it for inclusion later when we want to keep binary
> compatibility as much as is feasible.

Is this ticket #1377?

https://lampsvn.epfl.ch/trac/scala/ticket/1377

If so, can it be closed then?

Best,
Ismael

On Sat, Dec 19, 2009 at 5:21 PM, Ismael Juma wrote:
> Hey Martin,
>
> On Sat, 2009-12-19 at 11:29 +0100, martin odersky wrote:
>> One change affects type erasure to make it faster and improve
>> interoperability with Java. Unfortunately that's a change which breaks
>> binary compatibility with old code. So it would have been very tricky
>> to schedlue it for inclusion later when we want to keep binary
>> compatibility as much as is feasible.
>
> Is this ticket #1377?
>
> https://lampsvn.epfl.ch/trac/scala/ticket/1377
>
> If so, can it be closed then?
>
It does indeed look like it. I closed the ticket.

Cheers

Lift built against RC3, but with RC4 we get this error:
java.lang.reflect.InvocationTargetException 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 org.scala_tools.maven.executions.MainHelper.runMain(MainHelper.java:151) at org.scala_tools.maven.executions.MainWithArgsInFile.main(MainWithArgsInFile.java:26)Caused by: java.lang.AssertionError: assertion failed: type error: can't convert from REFERENCE(net.liftweb.util.StringHelpers) to REFERENCE(net.liftweb.util.BasicTypesHelpers) in unit BasicTypesHelpers.scala at scala.tools.nsc.backend.icode.GenICode$ICodePhase.adapt(GenICode.scala:943) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.scala$tools$nsc$backend$icode$GenICode$ICodePhase$$genLoad(GenICode.scala:927) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.genLoadLabelArguments(GenICode.scala:990) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.scala$tools$nsc$backend$icode$GenICode$ICodePhase$$genLoad(GenICode.scala:710) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.genLoadIf(GenICode.scala:363) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.scala$tools$nsc$backend$icode$GenICode$ICodePhase$$genLoad(GenICode.scala:511) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.genLoadIf(GenICode.scala:363) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.scala$tools$nsc$backend$icode$GenICode$ICodePhase$$genLoad(GenICode.scala:511) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.scala$tools$nsc$backend$icode$GenICode$ICodePhase$$genLoad(GenICode.scala:484) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.scala$tools$nsc$backend$icode$GenICode$ICodePhase$$genLoad(GenICode.scala:850) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:130) at scala.tools.nsc.backend.icode.GenICode$ICodePhase$$anonfun$gen$1.apply(GenICode.scala:87) at scala.tools.nsc.backend.icode.GenICode$ICodePhase$$anonfun$gen$1.apply(GenICode.scala:87) at scala.collection.LinearSeqLike$class.foreach(LinearSeqLike.scala:97) at scala.collection.immutable.List.foreach(List.scala:46) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:87) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:152) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:106) at scala.tools.nsc.backend.icode.GenICode$ICodePhase$$anonfun$gen$1.apply(GenICode.scala:87) at scala.tools.nsc.backend.icode.GenICode$ICodePhase$$anonfun$gen$1.apply(GenICode.scala:87) at scala.collection.LinearSeqLike$class.foreach(LinearSeqLike.scala:97) at scala.collection.immutable.List.foreach(List.scala:46) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:87) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:97) at scala.tools.nsc.backend.icode.GenICode$ICodePhase$$anonfun$gen$1.apply(GenICode.scala:87) at scala.tools.nsc.backend.icode.GenICode$ICodePhase$$anonfun$gen$1.apply(GenICode.scala:87) at scala.collection.LinearSeqLike$class.foreach(LinearSeqLike.scala:97) at scala.collection.immutable.List.foreach(List.scala:46) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:87) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:97) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.gen(GenICode.scala:83) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.apply(GenICode.scala:79) at scala.tools.nsc.Global$GlobalPhase$$anonfun$applyPhase$1.apply(Global.scala:281) at scala.tools.nsc.Global$GlobalPhase$$anonfun$applyPhase$1.apply(Global.scala:281) at scala.tools.nsc.reporters.Reporter.withSource(Reporter.scala:48) at scala.tools.nsc.Global$GlobalPhase.applyPhase(Global.scala:281) at scala.tools.nsc.Global$GlobalPhase$$anonfun$run$1.apply(Global.scala:259) at scala.tools.nsc.Global$GlobalPhase$$anonfun$run$1.apply(Global.scala:259) at scala.collection.Iterator$class.foreach(Iterator.scala:582) at scala.collection.mutable.ListBuffer$$anon$1.foreach(ListBuffer.scala:285) at scala.tools.nsc.Global$GlobalPhase.run(Global.scala:259) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.run(GenICode.scala:72) at scala.tools.nsc.Global$Run.compileSources(Global.scala:749) at scala.tools.nsc.Global$Run.compile(Global.scala:839) at scala.tools.nsc.Main$.process(Main.scala:109) at scala.tools.nsc.Main$.main(Main.scala:123) at scala.tools.nsc.Main.main(Main.scala) ... 6 more
Heiko
My job: weiglewilczek.com
My blog: heikoseeberger.name
Follow me: twitter.com/hseeberger
OSGi on Scala: scalamodules.org
Lift, the simply functional web framework: liftweb.net

Thanks for letting us know. This looks like something stirred up by
the change in erasure. We'll investigate Monday what it is.

Cheers

On Sun, Dec 20, 2009 at 12:39 PM, martin odersky wrote:
> Thanks for letting us know. This looks like something stirred up by
> the change in erasure. We'll investigate Monday what it is.
>
> Cheers
>
>  -- Martin
>
I could reproduce the fault and think I found the underlying problem:
There was a problem with the erasure of self types and it looks like
this problem was unmasked by my previous, unrelated change to erasure.
I'll think about a fix now.

Cheers