Constructor not accepting list of derived class as argument [duplicate]

I have tried using both base class and interface and in both instances I am told a constructor that takes my arguments does not exist. I have two classes that are related to each other and I want to instantiate a different class with either one. Here's what my set up looks like:

The base class

public class MyClassBase implements MyClassBaseIF {
    public MyClassBase(){
        //stuff
    }
}

The child class

public class MyClassChild extends MyClassBase implements MyClassBaseIF {
    public MyClassChild() {
        //stuff
    }
}

The interface

public interface MyClassBaseIF {
    public void doStuff() {
        //stuff
    }
}

I want to instantiate a new class that takes a list of either the base class or the child as a constructor argument. I've tried doing it via interface and simply via inheritance, it does not matter to me which to implement as long as one works but I get the same error with both

public class BigImportantClass {
    public BigImportantClass(List<MyClassBaseIF> stuff) {
        List<MyClassBaseIF> a = stuff;
    }
}

or

public class BigImportantClass {
    public BigImportantClass(List<MyClassBase> stuff) {
        List<MyClassBase> a = stuff;
    }
}

if I create a list of List<MyClassChild> x = functionThatReturnsTheList() no matter which construction option I use for new BigImportantClass(x) I still get

The constructor BigImportantClass(List< MyClassChild >) is undefined

Is my issue rooted in the fact that I'm dealing with a list of base/child/interface or is there something more fundamentally wrong I'm doing?

This is how I ended up implementing a solution

public class BigImportantClass {
    public BigImportantClass(List<? extends MyClassBaseIF> stuff) {
        List<MyClassBaseIF> a = new ArrayList<>();
        a.addAll(stuff);
    }
}

This lets me still do sorting and adding to a list that I'm doing elsewhere.