RFR: 8210742: Compound var declaration splitting seems broken

[Maurizio Cimadamore]

I understand.

One thing that I don't 100% get is what is the set of requirements we 
need to preserve; in this case we have a parser error, meaning that the 
input source file is wrong according to the grammar; javac ends up 
creating a variable tree node anyway, and then this node gets eventually 
type-checked, and what we are talking about here is that, when this 
type-checking happens (on this tree that is the result of a javac error 
recovery step), we are observing a type checking difference from 10 to 11.

Now, it seems like NB would like to have 'var' be applied in all 
branches of the compound assignment, and have all types be inferred.

But, as you said, for a variable type such as 'var x[]' we can't do 
much, so we will report an error and we will, I think, create an AST of 
type 'var[]' which will be left untouched, I believe, by type-checking.

So, I guess what I'm really asking for is some explanation of what the 
desired behavior should be, and why - so that we can make sure that, 
moving forward, we create the right kind of synthetic recovery trees in 
all cases.

(of course none of this is an issue for javac which will shut down 
immediately after discovering a parser error w/o even attempting 
attribution).

Maurizio

On 15/11/2018 15:22, srinivas wrote:
>
> Hi Maurizio,
>
> Thanks for the review.
>
> Yes - Initially I thought of making this code common to all branches.
>
> Below are the reasons for not doing that.
>
> 1) the reported issue from NB team is for simple 'var x' types but not 
> for arrays.
>
> 2) I don't have enough data to preserve the type for arrays or not and 
> I want to avoid breaking any assumption related to arrays error cases
>
> both from NB team and javac tests.
>
> Please let me know if I should include array case as well and refactor 
> the fix.
>
> Regards,
>
> Srinivas
>
>
>
> On 15/11/18 5:13 PM, Maurizio Cimadamore wrote:
>>
>> Hi,
>> I think what you are doing is ok, but I have some comments:
>>
>> 1) it seems like this code:
>>
>>
>> startPos = TreeInfo.getStartPos(mods);
>> if (startPos == Position.NOPOS)
>>    startPos = TreeInfo.getStartPos(type);
>>
>> should probably be lifted outside the 'if' - e.g. should apply to all 
>> cases after the check for "isRestrictedLocalVarTypeName"
>>
>> 2) A similar argument applies, kind of, to setting type to 'null'. 
>> With your patch we do that in 2/3 branches; the branch that is left 
>> out is when you have a var declaration like this:
>>
>> var foo[] = ...
>>
>> In this case the parser will still attempt to create a var tree with 
>> 'var' as its type. If we are worried about how the AST would look in 
>> erroneous cases, then I think this is a problem too.
>>
>> Cheers
>> Maurizio
>>
>> On 15/11/2018 10:31, srinivas wrote:
>>> Hi,
>>>
>>> Please review http://cr.openjdk.java.net/~sdama/8210742/webrev.00/
>>>
>>> for https://bugs.openjdk.java.net/browse/JDK-8210742.
>>>
>>> Regards,
>>>
>>> Srinivas
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