Static and runtime types: Correct Solution

Given the following type declarations:

public class Schali {
    public Schali goacs(Schali psar) {
        return this;
    }
}

public class Miblar extends Schali {
    public Schali goacs(Schali psar) {
        return psar;
    }
}

public class Idtreg extends Schali {
    public Schali goacs(Schali psar) {
        return new Idtreg();
    }
}

...and given the following setup code:

Idtreg foo = new Idtreg();
Schali bar = new Miblar();

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.goacs(bar).goacs(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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