RFR: JDK-8192963/JDK-8206986 JEP 325: Switch Expressions (Preview)

[Jan Lahoda]

On 28.8.2018 15:05, Maurizio Cimadamore wrote:
>
>
> On 28/08/18 13:41, Jan Lahoda wrote:
>> It would be nicer if the second error didn't occur, but not sure how
>> to do that. It would be easy to change the classification in this case
>> to lambda, the error would then be:
>> ---
>> SwitchArrowBrokenConstant.java:13: error: : or -> expected
>>             case (a, b) -> {}
>>                              ^
>> ---
>>
>> (Only this single error.) But it seems it might suggest it is OK to
>> continue from here with ':' or '->', while it is not OK. So I incline
>> more to the variant which starts with "')' expected", even if there's
>> a second error that's not very nice.
> If classification is changed to lambda, then can't we add some check in
> the lambda parsing code so that if the 'lambda allowed' mode is not set,
> an error of the kind:
>
> 'lambda not expected here'
>
> is generated?

Yes, that'd be doable I think:
http://cr.openjdk.java.net/~jlahoda/8192963/webrev.classify.as.lambda/

Which would produce:
SwitchArrowBrokenConstant.java:13: error: lambda expression not expected 
here
             case (a, b) -> {}
                         ^
SwitchArrowBrokenConstant.java:13: error: : or -> expected
             case (a, b) -> {}
                              ^

But it is not clear if the user intended to write a lambda expression 
here, or if the intent was to write a "deconstruction pattern"?

Thanks,
     Jan

>
> Maurizio