presto-main/src/main/java/io/prestosql/sql/planner/NullabilityAnalyzer.java/NullabilityAnalyzer/mayReturnNullOnNonNullInput
class NullabilityAnalyzer:    public static boolean mayReturnNullOnNonNullInput(Expression expression)
    {
        requireNonNull(expression, "expression is null");

        AtomicBoolean result = new AtomicBoolean(false);
        new Visitor().process(expression, result);
        return result.get();
    }