Unable to find class in inherited scope

[thesamet]

Compiler version

Using Scala 3.0.0, I am unable to compile Java code that is generated by protoc (protobuf compiler). The following is a minimized version of the generated code to demonstrate the issue.

Minimized code

// src/main/java/mytest/Ex.java
package mytest;

public final class Ex {
  private Ex() {}

  public static final class Foo extends MyInterface {
    private Foo() {
    }

    @SuppressWarnings({"unused"})
    protected java.lang.Object newInstance(
        UnusedPrivateParameter unused) {
      return new Foo();
    }
  }
}

// src/main/java/mytest/MyInterface.java
package mytest;

public class MyInterface {
    public static final class UnusedPrivateParameter {};
}

The Scala code doesn't matter, but it needs to exist:

// src/main/scala/Main.scala
package foo

object Main {}

Output

sbt:ppp> compile
[info] compiling 1 Scala source and 2 Java sources to /tmp/ppp/target/scala-3.0.0/classes ...
[error] -- [E006] Not Found Error: /tmp/ppp/src/main/java/mytest/Ex.java:12:8 ----------
[error] 12 |        UnusedPrivateParameter unused) {
[error]    |        ^^^^^^^^^^^^^^^^^^^^^^
[error]    |        Not found: type UnusedPrivateParameter
[error] one error found
[error] one error found
[error] (Compile / compileIncremental) Compilation failed
[error] Total time: 3 s, completed May 22, 2021, 10:36:18 AM

Expectation

Should compile with no errors.

Workaround

Adding compileOrder := CompileOrder.JavaThenScala results in successful compilation.

[som-snytt]

Scala 2 works, presumably due to fixes to looking up Java-defined members in Java sources.

The previous behavior was that statics belong to companions in the Scala language model and are not inherited.

[dylemma]

(don't mind me, I typo'd the number of the issue I was trying to reference with that PR)

[odersky]

It would be good to know when and how this was fixed in Scala 2. The normal behavior is that UnusedPrivateMember is not visible, so there must be a hack to make it visible for Java compiled code.

[som-snytt]

Perhaps

scala/scala#7671

with terms

is:pr author:retronym is:closed java lookup

[odersky]

@som-snytt That looks like the probaby fix, yes. Maybe we can get a volunteer to forward port it?

[smarter]

Closing as a duplicate of #6138 then

[som-snytt]

OK I see someone is already looking into the other ticket. Oh wait, that was 2019. OSS is hard.