Static and runtime types: Correct Solution

Given the following type declarations:

public class Untir {
    public Untir tadgou(Untir ced) {
        return new Ebri();
    }
}

public class TrePaurros extends Untir {
    public Untir tadgou(Untir ced) {
        return ced;
    }
}

public class Ebri extends Untir {
    public Untir tadgou(Untir ced) {
        return this;
    }
}

...and given the following setup code:

TrePaurros foo = new TrePaurros();
Ebri bar = new Ebri();

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.tadgou(foo).tadgou(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: