It's not a bug but it's not user friendly

[forax at univ-mlv.fr]

> De: "mandy chung" <mandy.chung at oracle.com>
> À: "Remi Forax" <forax at univ-mlv.fr>, "core-libs-dev"
> <core-libs-dev at openjdk.java.net>
> Envoyé: Lundi 14 Décembre 2020 22:41:23
> Objet: Re: It's not a bug but it's not user friendly

> I think [ https://bugs.openjdk.java.net/browse/JDK-8199149 |
> https://bugs.openjdk.java.net/browse/JDK-8199149 ] is the relevant RFE.

> Mandy
Yes, thanks. 

Rémi 

> On 12/12/20 8:07 AM, Remi Forax wrote:

>> A student of mine send me a code that can be reduced to this code

>> ---
>> import java.lang.invoke.MethodHandles;
>> import java.lang.invoke.VarHandle;

>> public class ThereIsABugButWhere {
>>   private static final VarHandle TEXT;
>>   static {
>>     try {
>>      TEXT = MethodHandles.lookup().findVarHandle(ThereIsABugButWhere.class, "text",
>>       String.class);
>>     } catch (NoSuchFieldException | IllegalAccessException e) {
>>       throw new AssertionError(e);
>>     }
>>   }

>>   private final String text;

>>   ThereIsABugButWhere() {
>>     text = "FOO";
>>   }

>>   public void update(String s) {
>>     TEXT.compareAndSet(this, "FOO", s);
>>   }

>>   public static void main(String[] args) {
>>     new ThereIsABugButWhere().update("BAR");
>>   }
>> }

>> ---
>> If you execute it, you get
>> Exception in thread "main" java.lang.UnsupportedOperationException
>> 	at java.base/java.lang.invoke.VarForm.getMemberName(VarForm.java:99)
>>	at
>> 	java.base/java.lang.invoke.VarHandleGuards.guard_LLL_Z(VarHandleGuards.java:77)
>> 	at ThereIsABugButWhere.update(ThereIsABugButWhere.java:22)
>> 	at ThereIsABugButWhere.main(ThereIsABugButWhere.java:26)

>> It takes me 20 mins to find the issue ...
>> I think we can improve the error message or even better report the issue at the
>> right location :)

>> regards,
>> Rémi