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

[Mandy Chung]

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

Mandy

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