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

[Jan Lahoda]

On 28.8.2018 16:37, Maurizio Cimadamore wrote:
>
>
> On 28/08/18 15:10, Maurizio Cimadamore wrote:
>>
>>
>> On 28/08/18 14:50, Jan Lahoda wrote:
>>> 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"?
>> Well, in my view, the user happened to write a perfectly valid lambda
>> expression where a constant expression was expected. So, if it were
>> me, I'd drop the last error about '->' or ':' expected and just focus
>> on the lambda popping up on an unexpected place.
> In any case, just to be clear - your latest webrev is fine - I think
> we're discussing on very minor error recovery details and I see no need
> to hold back the code because of this. We can file followup issues for
> these kind of bugs, and re-evaluate as we gather more feedback?

Thanks, I'll file a follow-up bug.

Jan

>
> Maurizio
>>
>> Maurizio
>>>
>>> Thanks,
>>>     Jan
>>>
>>>>
>>>> Maurizio
>>
>