presto-parser/src/main/java/io/prestosql/sql/tree/DefaultTraversalVisitor.java/DefaultTraversalVisitor/visitCoalesceExpression
class DefaultTraversalVisitor:    @Override
    protected R visitCoalesceExpression(CoalesceExpression node, C context)
    {
        for (Expression operand : node.getOperands()) {
            process(operand, context);
        }

        return null;
    }