If the switch expression is used to use boolean, JDTLS does not report an error

[curtishd]

Swich expressions cannot be passed in boolean, float, double and long primitive types, including their wrapper types. However, JDTLS doesn`t report error here. By the way, My java version is 21.

[rgrunber]

I'm able to reproduce as well. I see the following in the logs :

[Error - 13:11:34] Apr. 29, 2024, 1:11:34 p.m. Exception occurred during problem detection:
----------------------------------- SOURCE BEGIN -------------------------------------
package org.example;

public class App {
    public static void main(String[] args) {
        var casuality = new Casuality();
        var r = casuality.key;
        boolean re = switch (r) {
            case false -> {
                yield true;
            }
            default -> {
                yield false;
            }
        };
        System.out.println(re);
    }
}
----------------------------------- SOURCE END -------------------------------------
boolean constant cannot be casted into int
org.eclipse.jdt.internal.compiler.problem.ShouldNotImplement: boolean constant cannot be casted into int
	at org.eclipse.jdt.internal.compiler.impl.Constant.intValue(Constant.java:1509)
	at org.eclipse.jdt.internal.compiler.ast.CaseStatement$ResolvedCase.<init>(CaseStatement.java:143)
	at org.eclipse.jdt.internal.compiler.ast.CaseStatement.resolveCase(CaseStatement.java:236)
	at org.eclipse.jdt.internal.compiler.ast.SwitchStatement.resolve(SwitchStatement.java:1158)
	at org.eclipse.jdt.internal.compiler.ast.SwitchExpression.resolveType(SwitchExpression.java:418)
	at org.eclipse.jdt.internal.compiler.ast.LocalDeclaration.skipResolveInitializerIfAlreadyCalled2(LocalDeclaration.java:383)
	at org.eclipse.jdt.internal.compiler.ast.LocalDeclaration.resolve(LocalDeclaration.java:402)
	at org.eclipse.jdt.internal.compiler.ast.LocalDeclaration.resolve(LocalDeclaration.java:258)
	at org.eclipse.jdt.internal.compiler.ast.Statement.resolveWithBindings(Statement.java:498)
	at org.eclipse.jdt.internal.compiler.ast.ASTNode.resolveStatements(ASTNode.java:726)
	at org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration.resolveStatements(AbstractMethodDeclaration.java:714)
	at org.eclipse.jdt.internal.compiler.ast.MethodDeclaration.resolveStatements(MethodDeclaration.java:409)
	at org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration.resolve(AbstractMethodDeclaration.java:612)
	at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1517)
	at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1646)
	at org.eclipse.jdt.internal.compiler.ast.CompilationUnitDeclaration.resolve(CompilationUnitDeclaration.java:666)
	at org.eclipse.jdt.internal.compiler.Compiler.resolve(Compiler.java:1068)
	at org.eclipse.jdt.internal.compiler.Compiler.resolve(Compiler.java:1110)
	at org.eclipse.jdt.internal.core.CompilationUnitProblemFinder.process(CompilationUnitProblemFinder.java:280)
	at org.eclipse.jdt.internal.core.CompilationUnitProblemFinder.process(CompilationUnitProblemFinder.java:346)
	at org.eclipse.jdt.internal.core.ReconcileWorkingCopyOperation.makeConsistent(ReconcileWorkingCopyOperation.java:186)
	at org.eclipse.jdt.internal.core.ReconcileWorkingCopyOperation.executeOperation(ReconcileWorkingCopyOperation.java:92)
	at org.eclipse.jdt.internal.core.JavaModelOperation.run(JavaModelOperation.java:740)
	at org.eclipse.jdt.internal.core.JavaModelOperation.runOperation(JavaModelOperation.java:805)
	at org.eclipse.jdt.internal.core.CompilationUnit.reconcile(CompilationUnit.java:1311)
	at org.eclipse.jdt.ls.core.internal.handlers.BaseDocumentLifeCycleHandler.publishDiagnostics(BaseDocumentLifeCycleHandler.java:332)
	at org.eclipse.jdt.ls.core.internal.handlers.BaseDocumentLifeCycleHandler.publishDiagnostics(BaseDocumentLifeCycleHandler.java:295)
	at org.eclipse.jdt.ls.core.internal.handlers.BaseDocumentLifeCycleHandler$PublishDiagnosticJob.run(BaseDocumentLifeCycleHandler.java:777)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

Eclipse does correctly report the error as Cannot switch on a value of type boolean. Only convertible int values, strings or enum variables are permitted so I'm not sure why we're failing on parsing. Update: I must have been using something like Java 17 compliance, but when I set it to 21, I saw the error as well.

[curtishd]

Yes, it's a bit tricky, I've been busy working lately and if someone to pull request, I would appreciate it.

[rgrunber]

I just updated JDT-LS to a newer version of JDT Core after finding eclipse-jdt/eclipse.jdt.core#2382 , which seems very similar (switch expression on a boolean).

Looks like we'll get the fix for free!