Type inference after erasure uses package private type over public one leading to java.lang.IllegalAccessError at runtime

[chungonn]

Below is a minimal code fragment to reproduce the problem. It works from Scala 3.0 to Scala 3.2.0 and it breaks with Scala 3.2.1 and Scala.3.2.2-RC1

With Scala 3.2.1, when the method jweEncrypt is invoked, it throws a java.lang.IllegalAccessError. With all versions prior to Scala 3.2.1, the method is able to be executed.

Java Version

Java 17

Compiler version

Scala 3.2.1, Scala 3.2.2-RC1

Minimized code

Change the scala3Version to 3.2.0 then run the test suite to see the expected output.

build.sbt

val scala3Version = "3.2.1"

lazy val root = project
  .in(file("."))
  .settings(
    name := "Test",
    version := "0.1.0-SNAPSHOT",

    scalaVersion := scala3Version,

    libraryDependencies ++= Seq(
      "com.nimbusds" % "nimbus-jose-jwt" % "9.25.6",
      "org.scalameta" %% "munit" % "0.7.29" % Test
    )
  )

MySuite.scala

class MySuite extends munit.FunSuite {

  def jweEncrypter(publicJwk: JWK): Try[JWEEncrypter] = Try {
    publicJwk match
      case rsa: RSAKey => new RSAEncrypter(rsa)
      case ec: ECKey => new ECDHEncrypter(ec)
      case _ => throw new RuntimeException(s"Unsupported jwk ${publicJwk}")
  }

  test("JWS signing and verify using private cert pem file") {
    val jwkTry = jweEncrypter(null)
    println(s"jwkTry = ${jwkTry}")
  }
}

Output

Testing started at 3:22 pm ...

Process finished with exit code 255

java.lang.IllegalAccessError: failed to access class com.nimbusds.jose.crypto.impl.BaseJWEProvider from class MySuite (com.nimbusds.jose.crypto.impl.BaseJWEProvider and MySuite are in unnamed module of loader 'app')

	at MySuite.jweEncrypter(MySuite.scala:14)
	at MySuite.$init$$$anonfun$1(MySuite.scala:17)

Expectation

Testing started at 3:26 pm ...
jwkTry = Failure(java.lang.RuntimeException: Unsupported jwk null)

Process finished with exit code 0

[chungonn]

I have a simple test project for the above code, I can upload it if required.

[WojciechMazur]

Thank you for this report, I've managed to reproduce it locally. It seems to be a regression introduced since 3.2.0. I'll try to provide dependency free minimization soon

[WojciechMazur]

Reproducer

// Encrypter.java
package repro;
public interface Encrypter{}

// BaseProvider.java
package repro.impl;

import repro.*;
abstract class BaseProvider{}

// Case1Provider.java
package repro.impl;

public abstract class Case1Provider extends BaseProvider {}

// Case1.java
package repro;

import repro.impl.*;

public class Case1 extends Case1Provider implements Encrypter {
  public Case1(){}
}

// Case2Provider.java
package repro.impl;

public abstract class Case2Provider extends BaseProvider {}

// Case2.java
package repro;

import repro.impl.*;

public class Case2 extends Case2Provider implements Encrypter {
  public Case2(){}
}

// test.scala
import repro.*
import scala.util.Try

def get(arg: Any): Try[Encrypter] = Try {
  val x: Any = 1
  arg match
    case 1 => new Case1()
    case 2 => new Case2()
    case _ => throw new RuntimeException(s"Unsupported got $arg")
}

@main def Test = 
    val result = get(null)

[WojciechMazur]

One notable difference between 3.2.0 and 3.2.1 is the type infereded for anonymous function of method get after erasure phase.
In bytecode of 3.2.1 we have signature:

  private final repro.impl.BaseProvider get$$anonfun$1(java.lang.Object);

in 3.2.0 it was :

  private final repro.Encrypter get$$anonfun$1(java.lang.Object);

In case if both classes Case1 and Case2 would not inherit from a common public ancestor then signature of get$$anonfun$1 would be inferred to java package private final repro.impl.BaseProvider and though would always lead to IllegalAccessException in runtime.

At the time of typer phase anonfun in inferred to be (repro.impl.BaseProvider & repro.Encrypter

[WojciechMazur]

Bisect points to 824496b

[odersky]

I don't think 824496b introduced that problem but maybe it was hidden by some obscure type inference difference before.