`java.lang.IllegalAccessError: failed to access class` when calling Java API

[RaasAhsan]

Environment

Compiler: 3.0.2, 3.1.0
JVM: tested on AdoptOpenJDK 8, Temurin 11 (compiler and runtime)
OS: tested on darwin x86_64 and darwin arm64

Minimized code

build.sbt

libraryDependencies ++= Seq(
  "software.amazon.smithy" % "smithy-model" % "1.12.0"
)

Main.scala

import software.amazon.smithy.model.shapes._
object Main {
  def main(args: Array[String]): Unit = {
    val string = StringShape.builder.id("com.example#String").build
    val int = IntegerShape.builder.id("com.example#Integer").build
    val foo = StructureShape.builder
      .id("com.example#Foo")
      .addMember("bar", string.getId)
      .addMember("baz", int.getId)
    // commenting out the second addMember 
    // or explicitly typing the expression before it to `StructureShape.Builder` makes it compile
  }
}

Output

Exception in thread main: java.lang.Exception: java.lang.IllegalAccessError: failed to access class software.amazon.smithy.model.shapes.NamedMembersShape$Builder from class Main$ (software.amazon.smithy.model.shapes.NamedMembersShape$Builder and Main$ are in unnamed module of loader 'app')

Expectation

Snippet should terminate without raising an exception. Snippet compiles and terminates successfully on 2.13.5 compiler. This builder pattern is used considerably throughout AWS SDK so likely affects other AWS libraries as well.

[michelou]

@RaasAhsan Please also specify Java version and execution environment.

[RaasAhsan]

Done, let me know if the provided information is sufficient

[som-snytt]

With quick glance at smithy-model, is the difference in inference that addMember is overloaded but id is not?

That is, both return B typearg, but addMember call is typed without expected type? (I don't know if this was a specific improvement in Scala 2.)

[RaasAhsan]

It looks like the specific overload of id being called in the snippet is inherited from AbstractShapeBuilder but it defers to another overload which is overriden by NamedMembersShape.Builder. addMember has 3 overloads which are inherited from NamedMembersShape.Builder.

[odersky]

To address this, we will need a minimization that does not involve third part libraries.

[som-snytt]

The issue is that the parent of the concrete builder is package-private, but javap shows it using that interface in the second call

        50: invokevirtual #87                 // Method software/amazon/smithy/model/shapes/StructureShape$Builder.addMember:(Ljava/lang/String;Lsoftware/amazon/smithy/model/shapes/ShapeId;)Lsoftware/amazon/smithy/model/shapes/NamedMembersShape$Builder;
        53: ldc           #89                 // String baz
        55: aload_2
        56: invokevirtual #90                 // Method software/amazon/smithy/model/shapes/IntegerShape.getId:()Lsoftware/amazon/smithy/model/shapes/ShapeId;
        59: invokevirtual #91                 // Method software/amazon/smithy/model/shapes/NamedMembersShape$Builder.addMember:(Ljava/lang/String;Lsoftware/amazon/smithy/model/shapes/ShapeId;)Lsoftware/amazon/smithy/model/shapes/NamedMembersShape$Builder;
        62: checkcast     #22                 // class software/amazon/smithy/model/shapes/StructureShape$Builder

After erasure, there is a missing cast

[info]           val foo: software.amazon.smithy.model.shapes.StructureShape.Builder =
[info]             software.amazon.smithy.model.shapes.StructureShape.builder().id(
[info]               "com.example#Foo"
[info]             ).asInstanceOf[
[info]               software.amazon.smithy.model.shapes.StructureShape.Builder
[info]             ].addMember("bar", string.getId()).addMember("baz", int.getId()).
[info]               asInstanceOf
[info]             [software.amazon.smithy.model.shapes.StructureShape.Builder]

The reproductive element is that a method (it need not be an overload) is introduced in the package-private subclass, which is used from the client. The interface used to select the method is the private subclass instead of the public child class.

The public superclass is required, or actually not.

package smithlike;

abstract class B0 {
        abstract static class B0Builder<B extends B0Builder<?, ?>, S> {
                public B z() { return (B) this; }
        }
}

package smithlike;

public final class B1 extends B0 {
        public static B1Builder builder() { return new B1Builder(); }

        public static class B1Builder extends B0Builder<B1Builder, String> {
        }
}

package smithclient

import smithlike.*

@main def test() = println {
  B1.builder.z().z()
}

scala 2 also shows only the first cast at erasure, so it must be just a backend issue for the second invocation.

scala.Predef.println(smithlike.B1.builder().z().$asInstanceOf[smithlike.B1.B1Builder]().z())

[eed3si9n]

Here's a PR for this, which backports @lrytz's scala/scala#6023 from Scala 2.x - #21362