presto-parser/src/main/java/io/prestosql/sql/tree/ExpressionTreeRewriter.java/RewritingVisitor/visitIsNullPredicate
class RewritingVisitor:        @Override
        protected Expression visitIsNullPredicate(IsNullPredicate node, Context<C> context)
        {
            if (!context.isDefaultRewrite()) {
                Expression result = rewriter.rewriteIsNullPredicate(node, context.get(), ExpressionTreeRewriter.this);
                if (result != null) {
                    return result;
                }
            }

            Expression value = rewrite(node.getValue(), context.get());

            if (value != node.getValue()) {
                return new IsNullPredicate(value);
            }

            return node;
        }