Static and runtime types: Correct Solution

Given the following type declarations:

public interface Stecuen {
    public Stecuen sinlim(Stecuen ne);
}

public class Drirud implements Stecuen {
    public Stecuen sinlim(Stecuen ne) {
        return ne;
    }
}

public class CesBadu implements Stecuen {
    public Stecuen sinlim(Stecuen ne) {
        return this;
    }
}

...and given the following setup code:

Stecuen foo = new CesBadu();
Stecuen bar = new Drirud();

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.sinlim(foo.sinlim(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: