Classes can access protected static members of their Java superclasses

[hrhino]

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.

[lrytz]

Nice!

Curious: where is it implemented that Scalac allows an access to a java-defined protected member in a non-subclass in the same package (basically your test-case that says "double-checking that we can still do this")?

[hrhino]

That's just because both JavaParsers and ClassfileParser treat protected in Java as protected[containingPackage].

[lrytz]

Thanks!

[lrytz]

LGTM, I'll let it sit in the queue so @adriaanm can take a look.

[adriaanm]

Excellent, thanks!

[retronym]

Does this PR fix scala/bug#9272 ?

[hrhino]

I don't think so:

hhoughton:tmp hhoughton$ scala-launch 2.12.4-bin-c2a5883 -cp android-4.1.1.4.jar
Welcome to Scala 2.12.4-bin-c2a5883 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_121).
Type in expressions for evaluation. Or try :help.

scala> import android._, content._, provider._, ContactsContract._
import android._
import content._
import provider._
import ContactsContract._

scala> :paste
// Entering paste mode (ctrl-D to finish)

val ops: java.util.ArrayList[ContentProviderOperation] = new java.util.ArrayList[ContentProviderOperation]
    ops.add(ContentProviderOperation.newInsert(RawContacts.CONTENT_URI)
            .withValue(RawContacts.ACCOUNT_TYPE, AccountType)
            .withValue(RawContacts.ACCOUNT_NAME, AccountName).build)

// Exiting paste mode, now interpreting.

<pastie>:27: error: value ACCOUNT_TYPE is not a member of object android.provider.ContactsContract.RawContacts
            .withValue(RawContacts.ACCOUNT_TYPE, AccountType)
                                   ^
<pastie>:27: error: not found: value AccountType
            .withValue(RawContacts.ACCOUNT_TYPE, AccountType)
                                                 ^
<pastie>:28: error: value ACCOUNT_NAME is not a member of object android.provider.ContactsContract.RawContacts
            .withValue(RawContacts.ACCOUNT_NAME, AccountName).build)
                                   ^
<pastie>:28: error: not found: value AccountName
            .withValue(RawContacts.ACCOUNT_NAME, AccountName).build)
                                                 ^

scala>

I'm surprised that this works in Java, but it does.

hhoughton:tmp hhoughton$ cat Ax.java Sax.java Wax.java
// Ax.java
package a;

public class Ax {
  protected static interface Max {
    static int Bax = 1;
  }
}

// Sax.java
package a;

public class Sax implements Ax.Max {}


// Wax.java
package b;

import a.*;

public class Wax {
  int hax = Sax.Bax;
}


hhoughton:tmp hhoughton$ javac Ax.java Sax.java Wax.java
hhoughton:tmp hhoughton$ echo $?
0

(but of course:)

hhoughton:tmp hhoughton$ scala-launch 2.12.4-bin-c2a5883 -cp .
Welcome to Scala 2.12.4-bin-c2a5883 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_121).
Type in expressions for evaluation. Or try :help.

scala> val flax = Sax.Bax
<console>:11: error: value Bax is not a member of object Sax
       val flax = Sax.Bax
                      ^