Unexpected use of "ConditionalExpression" in JLS grammars

[Leon Linhart]

Hi,
Initially, I believed to have found a mistake in the JLS (Java 19 
Edition) that
was introduced with JEP 361. However, while further looking into the 
spec, this
has developed into more of a question than a report.

In several places in the grammar where I'd expect to find 
`ConstantExpression`,
`ConditionalExpression` is used instead. Specifically, in §14.11.1 [1], the
grammar for a `CaseConstant` is defined through a 
`ConditionalExpression`. I'd
tend to think this should at least be a `ConstantExpression` instead as this
would be more in line with the textual description of a case constant:

 > Every case constant must be either a constant expression (§15.29) or 
the name
   of an enum constant (§8.9.1), or a compile-time error occurs.

Although, from a quick reading of the JLS, I'm not sure if 
`ConstantExpression`
covers names of enum constants. However, neither does the current 
definition.
Interestingly, the same production is used for the definition of 
`ElementValue`
for annotations in §9.7.1 [2], which seems similarly out-of-place to me.

My opinion is further reinforced by the fact that the following snippet
compiles despite using a constant expression for a case label that is not a
conditional expression:

     public static final int BASE = 42;

     public void printForBasePlusOne(int i) {
         switch (i) {
             case BASE + 1 -> System.out.println("Test");
             default -> {}
         }
     }

Now, I'm curious about the reasoning behind using `ConditionalExpression` in
these places in the JLS and if this might actually be a mistake. If this 
is not
the right place to ask about this, please point me in the right direction.


Regards
Leon Linhart


[1] 
https://docs.oracle.com/javase/specs/jls/se19/html/jls-14.html#jls-14.11.1
[2] https://docs.oracle.com/javase/specs/jls/se19/html/jls-9.html#jls-9.7.1