[WiP] Switchexpression

[glelouet]

change : java21 required
Based on master
Implementation of #136

Remaining:

• fix java version. Can't work on 17
• add more tests.

Done:

• add Yield keyword
• add SwitchExpression structure and package
• Switchexpression can have null, default, static, or pattern caes.
• all cases use the yield syntaxic sugar to add to the underlying block. Same for throw.
• null is added at the end, then default. If they are equal, they should be merged (not working since expression .equals is based on ref)
• this is required because switch expressions allow case null, default -> ; so switchexpression allows to add to both null and default, sw._null().andDefault()._throws(…)
• static cases are the usual switch ones case 1, 2 ->
• pattern cases allow a typed var case Integer i and therefore add var-specific addOn, yieldOn, throwOn to create the expression based on the matched variable i+1 or throw new Exception ("received"+i)
• pattern also allows guarding when
• all cases use the yield syntaxic sugar to add to the underlying block.
• when printing (=state) the block, if only contains one yield then its internal expression is used instead

generator example :
https://github.com/glelouet/jcodemodel/blob/switchexpression/jcodemodeltests/src/main/java/com/helger/jcodemodel/tests/switchexpression/SwitchExpressionTestGen.java

result :
https://github.com/glelouet/jcodemodel/blob/switchexpression/jcodemodeltests/src/generated/javatest/com/helger/jcodemodel/tests/switchexpression/BasicSwitch.java

[glelouet]

todo :

1. java21 could not be required. if java.version<21 , then the PatternCases should be exported as if(o instance of Type name){}, all encapsulated in a callable block and yield should return instead ; then the rest of the witch should be converted to an old one (with null test if null case selected). A lot of work though.

2. more tests , especially enums, both referenced and jdefined