Early Java pickling applies Scala visibility to Java

[szeiger]

Early Java pickling (using -Ypickle-java) applies the wrong (Scala) visibility when typing Java sources. Given P.scala:

package com.example.test

private[test] class P

and U.java

package com.example.test2;

import com.example.test.P;

public class U {
    private P p;
}

$ ~/scala/scala-2.13.10/bin/scalac -Ypickle-java -Ypickle-write p-pickle.jar -d p.jar P.scala U.java
U.java:6: error: not found: type P
    private P p;
            ^
1 error

The Scala package-private (or private-within) visibility is erased in the bytecode, making the class public for Java. This normally allows U.java to be compiled with Zinc in a mixed project. The extra Java typing introduced by -Ypickle-java breaks this. I encountered this originally in 2.12.15 and it is reproducible in 2.12.17 and 2.13.10.

[lrytz]

This is unrelated to -Ypickle-java per se. The difference is that -Ypickle-java forces all declarations in Java sources, and trying to do so results in the accessibility error. This gives the same error without additional compiler flags:

P.scala

package com.example.test
private[test] class P
class K {
  def t = (new com.example.test2.U).p
}

U.java

package com.example.test2;
import com.example.test.P;
public class U {
    public P p;
}

The inconsistency with respect to separate compilation counts as a bug, I guess. On the other hand it's easy to work around (adjust the visibility of the Scala class) since both you are in control of both source files.