ADDITIONAL SYSTEM INFORMATION :
Mac M1
openjdk version "21" 2023-09-19
OpenJDK Runtime Environment (build 21+35-2513)
OpenJDK 64-Bit Server VM (build 21+35-2513, mixed mode, sharing)

A DESCRIPTION OF THE PROBLEM :
I see an infinite loop with with JDK 21 with this pattern match particularly with guarded match.
Able to replicate every single time.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run this code.
----
import java.util.Objects;

public class Replicate {

    record Point(Object a, Object b){}
    public static void main(String[] args) {


        find(new Point(5, null));
        find(new Point(5, 4.5));

    }

    private static void find(Object point){
        switch (point){
            case Point(Integer a, Integer b) -> System.out.println("both ints");
            case Point(Integer a, var b) when tester(b) -> System.out.println("not null");
            case Point(Integer a, var b) -> System.out.println("null");
            case null, default -> System.out.println("Unexpected value: " + point);
        }
    }

    private static boolean tester(Object b){
        System.out.println("received : " + b);
        return Objects.nonNull(b);
    }

}


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The program should print this and terminate.
---
    received: null
    null
    received: 4.5
    not null
ACTUAL -
Prints below infinitely
---
received: null

---------- BEGIN SOURCE ----------
import java.util.Objects;

public class Replicate {

    record Point(Object a, Object b){}
    public static void main(String[] args) {


        find(new Point(5, null));
        find(new Point(5, 4.5));

    }

    private static void find(Object point){
        switch (point){
            case Point(Integer a, Integer b) -> System.out.println("both ints");
            case Point(Integer a, var b) when tester(b) -> System.out.println("not null");
            case Point(Integer a, var b) -> System.out.println("null");
            case null, default -> System.out.println("Unexpected value: " + point);
        }
    }

    private static boolean tester(Object b){
        System.out.println("received : " + b);
        return Objects.nonNull(b);
    }

}

---------- END SOURCE ----------

FREQUENCY : always