How to collapse source sets in a java library

api__build.gradle__java-library-version

plugins {
    id "java-library"
}

sourceSets {
    base {
    }
}

dependencies {
    api sourceSets.base.output
}

api__build.gradle__java-version

plugins {
    id "java"
}

sourceSets {
    base {
    }
    main {
        output.dir(sourceSets.base.output)
    }
}

dependencies {
    compileOnly sourceSets.base.output
}

api__src__base__java__local__api__base__AnEnum.java

package local.api.base;

public enum AnEnum {}

api__src__main__java__local__api__main__AnInterface.java

package local.api.main;

import local.api.base.AnEnum;

public interface AnInterface {
  AnEnum anEnum();
}

dist__build.gradle

plugins {
    id "java-library-distribution"
}

dependencies {
    implementation project(":impl")
}

impl__build.gradle

plugins {
    id "java-library"
}

dependencies {
    api project(":api")
}

impl__src__main__java__local__impl__main__AClass.java

package local.impl.main;

import local.api.base.AnEnum;
import local.api.main.AnInterface;

public class AClass implements AnInterface {
  @Override
  public AnEnum anEnum() {
    return null;
  }
}