Static and runtime types: Correct Solution

Given the following type declarations:

public class SasEngpro {
    public SasEngpro pral(SasEngpro poc) {
        return new Psecrid();
    }
}

public class Ebis extends SasEngpro {
    public SasEngpro pral(SasEngpro poc) {
        return poc;
    }
}

public class Psecrid extends SasEngpro {
    public SasEngpro pral(SasEngpro poc) {
        return this;
    }
}

...and given the following setup code:

Psecrid foo = new Psecrid();
SasEngpro bar = new Ebis();

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.pral(bar).pral(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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