ConstantFolding should not short-circuit on right value

[glchapman]

FWIW, Constant folding has this for LogicalAnd and LogicalOr:

            if (op.Kind == BoundBinaryOperatorKind.LogicalAnd)
            {
                if (leftConstant != null && !(bool)leftConstant.Value ||
                    rightConstant != null && !(bool)rightConstant.Value)
                {
                    return new BoundConstant(false);
                }
            }

            if (op.Kind == BoundBinaryOperatorKind.LogicalOr)
            {
                if (leftConstant != null && (bool)leftConstant.Value ||
                    rightConstant != null && (bool)rightConstant.Value)
                {
                    return new BoundConstant(true);
                }
            }

The short-circuiting on non-null rightConstant is incorrect. It gives the correct value for the overall binary op expression, but the left hand side still has to be evaluated in case it has side effects. Here's an example of an incorrect evaluation in msi:

» function foo(): bool {print("foo") return false}

» foo() && false

False

Note that "foo" is not printed.

[ltrzesniewski]

That's a duplicate of #125 🙂

[glchapman]

Sorry -- I searched for "ConstantFolding" but not "constant folding" so I didn't find 125.