What can we improve in JSR292 for Java 9?

[Jochen Theodorou]

Am 08.03.2015 18:39, schrieb Peter Levart:
>
>
> On 03/08/2015 01:38 PM, Jochen Theodorou wrote:
>> Am 08.03.2015 12:16, schrieb Remi Forax:
>> [...]
>>> You need to restrict the set of method handles that are allowed to be
>>> installed inside a CallSite corresponding to such kind of invokedynamic.
>>> Something like: you can do any transformations you want on the arguments
>>> but not on the receiver (no drop, no permute, no filter) and then you
>>> need to call unconditionally a method handle created using findSpecial
>>> on the super class.
>>
>> unconditionally, like no guard?
>
> @Jochen:
>
> There can be GWT, but it can only select one of target/fallback that are
> both from the restricted set of MHs.
[...]
> So Jochen, can you point me to an algorithm used for MultiMethods
> dispatch in Groovy and I'll try to prepare a proof-of-concept that uses it?

You can use the Java dispatch rules, only that you take runtime types 
for receiver and arguments, instead of the static ones. I suggest you 
also ignore vargs (life is complicated enough). Groovy does some more 
conversions and other fancy stuff, but I think the above is already 
complicated enough, especially because you have to solve the problem of 
a fallback that has to cause a new method selection. If you can solve 
that problem, then I see use for super-init-calls with that style.

So far we have to install a "dispatcher" handle through the static 
callsite bootstrapper, because of the lack of runtimetype information. 
Which then will do the actual method selection of course. That means the 
first handle we install is not the target and the first invocation of 
the real target method is done from inside my runtime in the dynamic 
bootstrapper, since I cannot simply fallback to the static case anymore. 
It is the same for any case in which the guards for checking the runtime 
types fail. A PIC should have similar problems.

bye Jochen

-- 
Jochen "blackdrag" Theodorou - Groovy Project Tech Lead
blog: http://blackdragsview.blogspot.com/
german groovy discussion newsgroup: de.comp.lang.misc
For Groovy programming sources visit http://groovy-lang.org