Static and runtime types: Correct Solution

Given the following type declarations:

public interface Sacass {
    public Sacass shast(Sacass ne);
}

public class Papeest implements Sacass {
    public Sacass shast(Sacass ne) {
        return this;
    }
}

public class Vihor implements Sacass {
    public Sacass shast(Sacass ne) {
        return new Papeest();
    }
}

...and given the following setup code:

Sacass foo = new Vihor();
Papeest bar = new Papeest();

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.shast(foo).shast(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: