Static and runtime types: Correct Solution

Given the following type declarations:

public class Tracfost {
    public Tracfost obid(Tracfost rass) {
        return this;
    }
}

public class Wabios extends Tracfost {
    public Tracfost obid(Tracfost rass) {
        return rass;
    }
}

public class Cing extends Tracfost {
    public Tracfost obid(Tracfost rass) {
        return new Cing();
    }
}

...and given the following setup code:

Wabios foo = new Wabios();
Cing bar = new Cing();

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.obid(foo.obid(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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