Java 16 pattern matching problem with Switch in Intellij IDEA 2020.3.3 (Expression expected)

Question

As we know Java 16 brings with a new features like Records, sealed interfaces and classes, and also pattern matching.

Today I wanted use them in my training project. However, I ran into a problem, maybe I don't understand something.

So situation looks like in the given code which represents my Intellij Idea project: I have packages: client and order Client class is a sealed interface with three implementation: Regular, Vip and SuperVip:

package com.example.records.domain.client;
public sealed interface Client permits Client.Regular, Client.SuperVip, Client.Vip {
        
            Limit currentLimit();
        
            record Regular() implements Client {
        
                @Override
                public Client.Limit currentLimit() {
                    return Client.Limit.of((short) 10);
                }
            }
        
        
            record Vip() implements Client {
        
                @Override
                public Client.Limit currentLimit() {
                    return Client.Limit.of((short) 20);
                }
            }
        
            record SuperVip() implements Client {
        
                @Override
                public Client.Limit currentLimit() {
                    return Client.Limit.of((short) 100);
                }
            }
        
        
            record Limit(short value) {
                public Limit {
                    if (value < 0) throw new IllegalArgumentException("Values below 0 not allowed!");
                }
        
                static Limit of(short value) {
                    return new Limit(value);
                }
            }
        }

Order class is a simple aggregate knows from DDD: But there is a problem with switch statement:

package com.example.records.domain.order;

import com.example.records.domain.OrderId;
import com.example.records.domain.client.Client;
import com.example.records.domain.client.Client.*;
import com.example.records.shared.Money;
import com.example.records.shared.Result;

import java.util.LinkedList;
import java.util.List;

public class Order() {
    private final OrderId orderId;
    private final Client client;
    private final LinesItems linesItems = LinesItems.empty();

    Order(OrderId orderId, Client client) {
        this.orderId = orderId;
        this.client = client;
    }

    public Result add(LineItem lineItem) {
       return switch (client) {
            case Regular r -> addAnItemIfTheLimitIsNotExceeded(r.);
            case Vip v -> addAnItemIfTheLimitIsNotExceeded(v.);
            case SuperVip sv -> addAnItemIfTheLimitIsNotExceeded(sv.);
        };
    }

    private Result addAnItemIfTheLimitIsNotExceeded(Limit limit) {
        // TODO need impl
        return Result.OK;
    }


    private static class LinesItems {
        private final List<LineItem> lines = new LinkedList<>();

        private LinesItems() {}

        void add(LineItem lineItem) {
            this.lines.add(lineItem);
        }

        Money cost() {
            return lines.stream().map(LineItem::cost).reduce(Money.ZERO, Money::add);
        }

        static LinesItems empty() {
            return new LinesItems();
        }
    }
}

record LineItem(Money cost) {}

Other classes:

package com.example.records.domain;

public record OrderId(String value) {

    public OrderId {
        validate();
    }

    private void validate() {
        if (value == null)
            throw new IllegalArgumentException("Null value not allowed!");
        if (value.isBlank())
            throw new IllegalArgumentException("Blank value not allowed!");
    }
}
package com.example.records.shared;

import java.math.BigDecimal;

public record Money(BigDecimal value) {

    public static final Money ZERO = new Money(new BigDecimal("0.00"));

    public Money add(Money money) {
        return new Money(this.value.add(money.value));
    }
}
package com.example.records.shared;

public sealed interface Result {

    Success OK = new Success();

    record Success() implements Result{}
    record Failure(String message) implements Result {}
}

I'm getting "(Expression expected)" Where did I go wrong? (Experimental features is enabled, I've installed Java 16 open jdk)

Answer 1

Type patterns in instanceof are a final (non-preview) feature in Java 16. However, type patterns in switch are not yet in Java 16; they are expected to arrive soon.

Answer 2

The owner of jeps 394 Gavin Bierman has already submitted a JEP for that feature.

Pattern Matching for switch (Preview)

It has not yet been targeted to a release.

Edit: Just a quick update here. This feature has been proposed to be included in JDK 17. It is the JEP 406 here