https://gist.github.com/laco0416/4c408a6f4d67b483033f の調査

Java8Sample.java

package jp.javelindev.snippets;

public class Java8Sample {

    public static void main(String[] args) {
        Laco laco = new Laco();
        SampleClass sample = new SampleClass();

        sample.func(laco); //ClassCastException SomeClassはLacoにキャストできません
    }

}

class SomeClass {
    
}

class Laco extends SomeClass {

}

class SuperClass<T extends SomeClass> {

    public void func(T item) {

    }
}

class SampleClass extends SuperClass<Laco> {

    @Override
    public void func(Laco item) {
        System.out.println("func is executed.");
    }
}