'protected[package]' no much of a protection after all

On 26/07/2011 08:29, Gerolf Seitz wrote:
> As far as I understand, a trait declared as "protected[mypackage] trait MyTrait" should
> only be accessible from inside the "mypackage" package.
> However, this is not at all the case. The code in this gist [0] compiles and runs fine.
>
> Is there a misunderstanding on my part or is it a bug/regression?

Looks like a regression.

My test version of your code:

# T1.scala
package c.d

protected[d] trait MyTrait
{
def doFoo() { println("Foo") }
}

# T2.scala

package a.b

import c.d.MyTrait

class MyClass extends MyTrait
{
def doBar() { doFoo(); println("Bar") }
}

object X
{
def main(args: Array[String])
{
val mc = new MyClass
mc.doBar()
}
}

D:\Temp\Scala
> C:\Java\scala-2.8.1.final\bin\scalac.bat T1.scala

D:\Temp\Scala
> C:\Java\scala-2.8.1.final\bin\scalac.bat T2.scala
T2.scala:5: error: trait MyTrait cannot be accessed in package c.d
class MyClass extends MyTrait
^
T2.scala:7: error: not found: value doFoo
def doBar() { doFoo(); println("Bar") }
^
two errors found

D:\Temp\Scala
> C:\Java\scala-2.9.0.final\bin\scalac.bat T1.scala

D:\Temp\Scala
> C:\Java\scala-2.9.0.final\bin\scalac.bat T2.scala

D:\Temp\Scala
> C:\Java\scala-2.9.0.final\bin\scala.bat a.b.X
Foo
Bar

I took a code snippet from the online Programming in Scala [1] to activate the protection,
ie. to get a compilation error:

package bobsrockets
{
package navigation
{
private[navigation] class Navigator
{
protected[navigation] def useStarChart() {}
class LegOfJourney
{
private[Navigator] val distance = 100
}
private[this] var speed = 200
}
}
package launch
{
import navigation._
object Vehicle
{
private[launch] val guide = new Navigator
def vroom() = guide.useStarChart
}
}
}

D:\Temp\Scala
> C:\Java\scala-2.8.1.final\bin\scalac.bat T3.scala
T3.scala:20: error: class Navigator cannot be accessed in package bobsrockets.navigation
private[launch] val guide = new Navigator
^
one error found

D:\Temp\Scala
> C:\Java\scala-2.9.0.final\bin\scalac.bat T3.scala
error: scala.MatchError: (of class
scala.tools.nsc.typechecker.Infer$Inferencer$AccessError)
at scala.tools.nsc.ast.Trees$Transformer.transform(Trees.scala:754)
at
scala.tools.nsc.transform.TypingTransformers$TypingTransformer.transform(TypingTransformers.scala:53)
at
scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:243)
at scala.tools.nsc.ast.Trees$Transformer.transform(Trees.scala:831)
[...] (long stack trace)

Note that I first thought this snippet was compiled because if I do fsc T3.scala, I get no
errors...

Maybe this problem is already in the bug tracker, I will try and see if I can locate it
(the bug tracker, then the bug...).

[1] http://www.artima.com/pins1ed/packages-and-imports.html "Public members" (no anchors,
alas)

"protected def this has general access"
https://issues.scala-lang.org/browse/SI-4128

Comment from Paul Phillips: "Protected protected constructors. They have been essentially
public since r19547, which was for SI-1836 but loosened the noose too much."

This bug is marked as fixed (and doesn't apply to the same kind of syntactic objects), but
perhaps there are some other creeping bugs...

Also found "compiler crash with protected class access"
https://issues.scala-lang.org/browse/SI-612

but it is closed a long time ago (but it shows there is a precedence on my crash...)

I see no other related issue (at least in the open ones), so I might open one, unless you
want to do it yourself, Gerolf.

Side note: if I change protected[d] to private[d], I get the compiler to throw an error...
(as it should)
If I interpret correctly the pins1ed book, protected[x] and private[x] are the same thing,
no? ("All qualifiers can also be applied to protected, with the same meaning as private."
or do I misinterpret this sentence?)

On 26/07/2011 13:28, Philippe Lhoste wrote:
> I see no other related issue (at least in the open ones), so I might open one, unless you
> want to do it yourself, Gerolf.

Following a private answer, I created SI-4845
https://issues.scala-lang.org/browse/SI-4845