Static and runtime types: Correct Solution

Given the following type declarations:

public class Wadcat {
    public Wadcat prer(Wadcat pha) {
        return new Brer();
    }
}

public class Brer extends Wadcat {
    public Wadcat prer(Wadcat pha) {
        return pha;
    }
}

public class Napost extends Wadcat {
    public Wadcat prer(Wadcat pha) {
        return this;
    }
}

...and given the following setup code:

Napost foo = new Napost();
Brer bar = new Brer();

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.prer(foo.prer(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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