Static and runtime types: Correct Solution

Given the following type declarations:

public class Gusu {
    public Gusu nason(Gusu co) {
        return co;
    }
}

public class Wedmir extends Gusu {
    public Gusu nason(Gusu co) {
        return this;
    }
}

public class Olfa extends Gusu {
    public Gusu nason(Gusu co) {
        return new Wedmir();
    }
}

...and given the following setup code:

Olfa foo = new Olfa();
Wedmir bar = new Wedmir();

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.nason(foo.nason(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

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