Static and runtime types: Correct Solution

Given the following type declarations:

public class WelCascom {
    public WelCascom plidta(WelCascom beul) {
        return this;
    }
}

public class Glapon extends WelCascom {
    public WelCascom plidta(WelCascom beul) {
        return new Stiacfang();
    }
}

public class Stiacfang extends WelCascom {
    public WelCascom plidta(WelCascom beul) {
        return beul;
    }
}

...and given the following setup code:

WelCascom foo = new Stiacfang();
WelCascom bar = new Glapon();

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.plidta(bar).plidta(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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