RFR 8144903: JShell: determine incorrectly the type of the expression which is array type of captured type

[ShinyaYoshida]

Hi Maurizio, Thank you.

2015-12-11 6:58 GMT+09:00 Maurizio Cimadamore <
maurizio.cimadamore at oracle.com>:

> Looks good, some comments:
>
> * watch out for the 'useWildcards' variable - you set it to true on the
> first class you see, and you never reset it to false - that could lead to
> spurious behavior - at least in principle (probably not in practice given
> that if a wildcard appears as a toplevel type you never hit visitClassType).
>
I've updated:
http://cr.openjdk.java.net/~shinyafox/kulla/8144903/webrev.04/


> * I think you also use the wildcard lower bound, in case of a toplevel ?
> super T. In that case, T is always better than Object.
>
I don't think so, because this printer is to determine a  suitable variable
type which is assigned the expression of the "type " which is the argument
of this printer.
And a expression of "? super T" is not assignable to T:
F<? super String> f = ...
String s = f.get() // failed to compile

Regards,
shinyafox(Shinya Yoshida)



>
>
> Maurizio
>
>
> On 10/12/15 14:15, ShinyaYoshida wrote:
>
> Hi Maurizio and Robert,
> Thank you for a lot of advice and comments!
>
> Now I agreed.
> It is difficult( or impossible) to determine the completely "right" type
> from bound.
> And when I work hard around that, the work wouldn't bring benefit what is
> worth the working to us.
>
> I'd like propose the fix based on webrev.02:
> http://cr.openjdk.java.net/~shinyafox/kulla/8144903/webrev.03/
>
> In this patch:
> 1. Fix 8144903(this issue)
> 2. Use always wildcard instead of upper bound
> 3. In visitWildcardType, if it is top-level type and it doesn't have
> extends bound, return "Object"
> 4. In TypePrinter, "Object" appears sometimes so I declare 'private static
> final String OBJECT = "Object"' and use it instead of the literal.
> 5. Add & modify some tests
>
> Could you review this?
>
> Best Regards,
> shinyafox(Shinya Yoshida)
>
> 2015-12-10 19:32 GMT+09:00 Maurizio Cimadamore <
> maurizio.cimadamore at oracle.com>:
>
>>
>>
>> On 10/12/15 03:07, Robert Field wrote:
>>
>>    public static Object $2;
>>
>> otherwise the generated code will break.
>>
>> What do you mean by this? How is using Object breaking the generated
>> code? Seems to me you have just widened the type of a variable storing an
>> expression - that ought to work; the only problem here is user
>> expectations: if the user is expecting to pass this to a method accepting a
>> CharSequence he/she will be disappointed. But how big of a problem is this?
>> And, as I pointed out elsewhere, no general solution exists for this.
>>
>> Maurizio
>>
>
>
>