https://github.com/scala/bug/issues/11542

A.java

import java.util.Arrays;

public class A {
  public class B {
    public class C1 {
      public C1(int a1) {}
    }

    public class C2 {
      public C2(String a1) {}
    }

    public class C3 {
      public C3(int[] a1) {}
    }

    public class C4 {
      public C4(scala.Option<Integer> a1) {}
    }

    public class C5 {
      public C5(scala.collection.immutable.List<Integer> a1) {}
    }

    public class C6 {
      public C6(scala.Option<String> a1) {}
    }
  }
}

class Main {
  static void f(Class<?> c) {
    System.out.println(Arrays.toString(c.getConstructors()[0].getGenericParameterTypes()));
  }

  public static void main(String[] args) {
    f(A.B.C1.class); // [class A$B, int]
    f(A.B.C2.class); // [class A$B, class java.lang.String]
    f(A.B.C3.class); // [class A$B, class [I]
    f(A.B.C4.class); // [scala.Option<java.lang.Integer>]
    f(A.B.C5.class); // [scala.collection.immutable.List<java.lang.Integer>]
    f(A.B.C6.class); // [scala.Option<java.lang.String>]
  }
}