Boolean switch inconsistency between ECJ and javac

[nlisker]

public class Test {

	public static void main(String[] args) {
		new Test().d(true);
	}

	void d(Boolean b) {
		switch (b) {
			case true  -> System.out.println("1");
			case false -> System.out.println("2");
		};
	}
}

In Java 22, this compiles and runs in ECJ, but javac reports

Test.java:11: error: constant label of type boolean is not compatible with switch selector type Boolean
			case true -> System.out.println("1");
			     ^
Test.java:12: error: constant label of type boolean is not compatible with switch selector type Boolean
			case false -> System.out.println("2");
			     ^

However, adding a guard pattern makes it not compile anymore in ECJ:

case true when b.toString().length() == 1 -> System.out.println("1");

Perhaps related to #3558.

[srikanth-sankaran]

See also

#3409

#3128

#3462

[srikanth-sankaran]

@stephan-herrmann - do you want to look at these issues with Bollean switches? If not please assign to me. Thanks.

[srikanth-sankaran]

Behavior change happened at 4.34 M1. Upto 4.33 we reject the code with:

Description Resource Path Location Type
Type mismatch: cannot convert from boolean to Boolean Test.java /pasted_code/src line 9 Java Problem
Type mismatch: cannot convert from boolean to Boolean Test.java /pasted_code/src line 10 Java Problem

[srikanth-sankaran]

Confirmed that this is a regression brought on by BETA_JAVA23 branch being merged onto master via commit f8fb582

[srikanth-sankaran]

JDK23 compiles the code (without any preview flags) - that looks certainly suspect!

And I don't think the problem is particular to booleans.

For example, the following was rejected by JDK22, but accepted by JDK23 (without any preview flags):

public class X {

	public static void main(String[] args) {
		new X().d(10L);
	}

	void d(Long l) {
		switch (l) {
			case 10L  -> System.out.println("1");
			case 20L -> System.out.println("2");
                       default -> System.out.println("Default");
		};
	}
}

@stephan-herrmann - do you agree that JDK23 behavior is incorrect ?