Prevent nulls by requiring override of PlanVisitor.visitPlan
`PlanVisitor` is a generic class and does not know the type of context
`C`, so should not assume `null` is a good value to return by default.
*/
package com.facebook.presto.sql.planner.plan;
-public class PlanVisitor<C, R>
+public abstract class PlanVisitor<C, R>
{
- protected R visitPlan(PlanNode node, C context)
- {
- return null;
- }
+ protected abstract R visitPlan(PlanNode node, C context);
public R visitRemoteSource(RemoteSourceNode node, C context)
{
