Static and runtime types: Correct Solution

Given the following type declarations:

public class Irsos {
    public Irsos zissno(Irsos em) {
        return em;
    }
}

public class Stermsciet extends Irsos {
    public Irsos zissno(Irsos em) {
        return this;
    }
}

public class Ledur extends Irsos {
    public Irsos zissno(Irsos em) {
        return new Ledur();
    }
}

...and given the following setup code:

Irsos foo = new Ledur();
Irsos bar = new Stermsciet();

Part 1

Draw an AST for the following expression, labeling the static type (a.k.a. compile-time type) of each node in the tree:

foo.zissno(bar).zissno(bar)

(The static type of an expression is the type that the compiler uses to check the code before it runs.)

Solution

Part 2

Draw an AST for the same expression, this time labeling the runtime type of each node in the tree.

(The runtime type of an expression is the type of the actual value that appears when the code runs.)

Solution

Related puzzles: