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scabug opened this issue Jan 7, 2013 · 3 comments
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scalac compiles without error access to static protected (not visible) field #6934

scabug opened this issue Jan 7, 2013 · 3 comments
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@hrhino
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access java interop regression
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2.12.4

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@scabug
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scabug commented Jan 7, 2013 •
edited by retronym
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Scala 2.10.0 compiles without reporting an error the following classes:

// test/JavaClass.java
package test;

public class JavaClass {

  protected static int STATIC_PROTECTED_FIELD= 4;

}
// test2/ScalaMain.scala
package test2

object ScalaMain {

  def main(args: Array[String]) {
    val a = test.JavaClass.STATIC_PROTECTED_FIELD
  }

}

But it fails during execution:

$ scalac -version
Scala compiler version 2.10.0 -- Copyright 2002-2012, LAMP/EPFL
$ scalac test*/*
$ javac test/*
$ scala test2.ScalaMain
java.lang.IllegalAccessError: tried to access field test.JavaClass.STATIC_PROTECTED_FIELD from class test2.ScalaMain$
	at test2.ScalaMain$.main(ScalaMain.scala:6)
	at test2.ScalaMain.main(ScalaMain.scala)
	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.util.ScalaClassLoader$$anonfun$run$1.apply(ScalaClassLoader.scala:71)
	at scala.tools.nsc.util.ScalaClassLoader$class.asContext(ScalaClassLoader.scala:31)
	at scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.asContext(ScalaClassLoader.scala:139)
	at scala.tools.nsc.util.ScalaClassLoader$class.run(ScalaClassLoader.scala:71)
	at scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.run(ScalaClassLoader.scala:139)
	at scala.tools.nsc.CommonRunner$class.run(ObjectRunner.scala:28)
	at scala.tools.nsc.ObjectRunner$.run(ObjectRunner.scala:45)
	at scala.tools.nsc.CommonRunner$class.runAndCatch(ObjectRunner.scala:35)
	at scala.tools.nsc.ObjectRunner$.runAndCatch(ObjectRunner.scala:45)
	at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:74)
	at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:96)
	at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:105)
	at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

Compilation correctly fails when using Scala 2.9.2

$ ~/opt/scala-2.9.2/bin/scalac -version
Scala compiler version 2.9.2 -- Copyright 2002-2011, LAMP/EPFL
$ ~/opt/scala-2.9.2/bin/scalac test*/*
test2/ScalaMain.scala:6: error: variable STATIC_PROTECTED_FIELD in object JavaClass cannot be accessed in object test.JavaClass
 Access to protected variable STATIC_PROTECTED_FIELD not permitted because
 enclosing class object ScalaMain in package test2 is not a subclass of 
 object JavaClass in package test where target is defined
    val a = test.JavaClass.STATIC_PROTECTED_FIELD
                           ^
one error found

Compilation also correctly fails on 2.10.0 for non-static protected fields.
@scabug
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scabug commented Jan 7, 2013

Imported From: https://issues.scala-lang.org/browse/SI-6934?orig=1
Reporter: @skyluc
Affected Versions: 2.10.0, 2.11.0-M7
See #1806

@scabug
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scabug commented Jan 7, 2013

@retronym said:
Most probably introduced with the fix for #1806: scala/scala@1ebbe02

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scabug commented Jan 7, 2013

@retronym said:
Assigning to Paul to gauge whether there is a way to accomodate #1806 while disallowing this.

@scabug scabug added this to the Backlog milestone Apr 7, 2017
hrhino added a commit to hrhino/scala that referenced this issue Sep 5, 2017
@hrhino
Classes can access protected static members of their Java superclas…
fd63444 
…ses.

This more-or-less reverts the fix added in 1ebbe02. Instead
of wantonly treating `protected static` Java members like they're
public, it suffices to modify `isSubClassOrCompanion` to consider
a class a "subclass or companion" of the companions of its parent
classes, provided the parent is a Java-defined class.

It's a bit wacky, but comparing the Java and Scala definitions of
`protected` access:

SLS 5.2.8:
    Protected members of a class can be accessed from within

    - the template of the defining class,
    - all templates that have the defining class as a base class,
    - the companion module of any of those classes.

JLS 6.6.1:
    A member (class, interface, field, or method) of a reference type
    ... is accessible only if the type is accessible and the member
    or constructor is declared to permit access:

    ...
    - if the member or constructor is declared protected, then access
      is permitted only when one of the following is true:

      - Access to the member or constructor occurs from within the
        package containing the class in which the protected member
        or constructor is declared.
      - Access is correct as described in §6.6.2.

JLS 6.6.2.1:
    Let C be the class in which a protected member is declared.
    Access is permitted only within the body of a subclass S of C.

The important differences are that Java protected members are
indeed accessible from the package that they're declared in (this
behavior is implemented by `accessBoundary`, and that `static`
methods are treated the same as instance methods for purposes of
access control. Therefore, I feel comfortable adding the third
case to `isSubClassOrCompanion`, thus taking the Java access
control model when dealing with Java-defined types.

Fixes scala/bug#6934, review by adriaanm and (of course) whoever
feels like swinging by and saying hi.
@hrhino hrhino self-assigned this Sep 5, 2017
hrhino added a commit to hrhino/scala that referenced this issue Sep 5, 2017
@hrhino
Classes can access protected static members of their Java superclas…
01c3bbb 
…ses.

This more-or-less reverts the fix added in 1ebbe02. Instead
of wantonly treating `protected static` Java members like they're
public, it suffices to modify `isSubClassOrCompanion` to consider
a class a "subclass or companion" of the companions of its parent
classes, provided the parent is a Java-defined class.

It's a bit wacky, but comparing the Java and Scala definitions of
`protected` access:

SLS 5.2.8:
    Protected members of a class can be accessed from within

    - the template of the defining class,
    - all templates that have the defining class as a base class,
    - the companion module of any of those classes.

JLS 6.6.1:
    A member (class, interface, field, or method) of a reference type
    ... is accessible only if the type is accessible and the member
    or constructor is declared to permit access:

    ...
    - if the member or constructor is declared protected, then access
      is permitted only when one of the following is true:

      - Access to the member or constructor occurs from within the
        package containing the class in which the protected member
        or constructor is declared.
      - Access is correct as described in §6.6.2.

JLS 6.6.2.1:
    Let C be the class in which a protected member is declared.
    Access is permitted only within the body of a subclass S of C.

The important differences are that Java protected members are
indeed accessible from the package that they're declared in (this
behavior is implemented by `accessBoundary`, and that `static`
methods are treated the same as instance methods for purposes of
access control. Therefore, I feel comfortable adding the third
case to `isSubClassOrCompanion`, thus taking the Java access
control model when dealing with Java-defined types.

I also scouted a grammar tweak, which makes this have a few more
files in the diff than would be expected.

Fixes scala/bug#6934, review by adriaanm and (of course) whoever
feels like swinging by and saying hi.
@hrhino hrhino mentioned this issue Sep 5, 2017
Merged
@hrhino hrhino modified the milestones: 2.12.4, Backlog Sep 5, 2017
@SquidDev SquidDev mentioned this issue Dec 14, 2017
Closed
@stefanobaghino stefanobaghino mentioned this issue Jan 20, 2018
Closed
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