Interim JDK 10 RFR of 8187951: Update javax.lang.model.SourceVersion for "var" name

[joe darcy]

Hi Maurizio,

I agree that implementing a more precise version of the 
can-I-use-this-as-a-name check requires more context, such as the 
element kind as you suggest.

My sense is that additional API scope isn't warranted. Within the 
existing set of methods, I think having isName and isKeyword both return 
"false" for var for RELEASE_10 and later would be acceptable.

What to you think?

Thanks,

-Joe


On 9/28/2017 1:35 AM, Maurizio Cimadamore wrote:
>
> Not 100% sure about this. On the one hand, the concept of contextual 
> keyword is, well, associated with a context. So 'open' is a keyword in 
> a module-info file, and 'var' is a keyword when used in a local 
> variable declaration.
>
> But the isName method takes no such context, so it's bound to be lossy.
>
> You tried to reformulate the semantics of isName as something similar 
> to 'is this a valid name for a javax.lang.model.element.Element 
> instance'? I think that _almost_ works - after all elements model:
>
> * variables/fields (VariableElement)
> * methods (ExecutableElement)
> * classes/interfaces/enums/annotations (TypeElement)
> * typevars (TypeParameterElement)
> * modules (ModuleElement)
> * packages (PackageElement)
>
> now, in the last two cases, I'm not sure the implemented logic works 
> well. While 'var' is not a legal name for 
> variables/methods/types/typevars, I think it is a valid name for 
> packages and modules, there's no restriction there.
>
> This unfortunately makes the definition of isName messy, because it 
> doesn't really refer to _all_ elements, but just to a subset of them.
>
> Also, I find this text:
>
> "and {@code "var"} is used for local variable type inference inthe 
> argument version."
>
> I only got a good idea of what you meant by looking at the implementation.
>
> One alternative would be to mark this method as @Deprecated, and add a 
> new method:
>
> public static boolean isName(CharSequence name, *ElementKind kind*, 
> SourceVersion version) { ... }
>
> Where the semantics could be:
>
> is _name_ a valid qualified name for an element of kind _kind_ in 
> version _version_ ?
>
> While not perfect (it still cannot handle module-info keyword, as 
> there's no info on which compilation unit this question refers to), I 
> think it's a step forward in that it lets you discriminate between 
> different kind of elements.
>
> An even more complete variant would be:
>
> public static boolean isName(CharSequence name, *JavaFileObject 
> sourceFile, ElementKind kind*, SourceVersion version) { ... }
>
> Which would let you express in full what you need to express, for both 
> 'var' and module keywords.
>
> Maurizio
>
> On 27/09/17 23:51, joe darcy wrote:
>> Hello,
>>
>> Please review the in-progress work on
>>
>>     8187951: Update javax.lang.model.SourceVersion for "var" name
>> http://cr.openjdk.java.net/~darcy/8187951.0/
>>
>> I'm not 100% certain of the desired semantics here. The handling of 
>> "var" doesn't align with any of the existing syntactic constructs, 
>> including restricted keywords introduced in 9 with modules.
>>
>> The proposal changes gives the "isName" method the semantics of "can 
>> I use this qualified name for a type, field, package, or module."
>>
>> Thanks,
>>
>> -Joe
>>
>

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