JEP 276: Dynamic Linking of Language-Defined Object Models

Jochen Theodorou blackdrag at
Sun Oct 18 08:49:10 UTC 2015

On 17.10.2015 13:30, Martijn Verburg wrote:
> This looks very, very promising.  Would it help to get the language
> maintainers of the most popular scripting/dynamic JVM languages involved
> ASAP?  Happy to contact Groovy, Clojure, Scala, JRuby folks (although I
> suspect many of them are on this list).

still easy to miss something like this ;)

But I can give some comments for Groovy on this already. As I understand 
it, this JEP is mostly for calls from Java on objects from other 
languages. I have basically only  main points:

* Invokedynamic (like invokeinterface and invokevirtual) does not like 
calls with null as receiver, quitting the call right away with a NPE. 
But languages may allow for calls on null. That again means some kind of 
dummy receiver is required, if this is supposed to work. Then of course, 
if you want to allow calls on null, every call would have to go through 
the runtime in the end, thus I suspect this will be out of scope for 
this JEP.

* Another part is the lookup of calls itself. To me the JEP is not fully 
clear here. Sure, there is a service for this, but is every call 
checked? That may slow down normal compilation for Java. The JEP speaks 
of methods provided beyond what Java offers - but what about methods 
replacing normal Java methods?

Btw, one part that would make me very happy, is an official API, that 
allows some control of phases of the Java compiler as well as make 
missing classes programatically known to the compiler without requiring 
the java compiler to write those out as well. And that especially 
because I assume that jigsaw will put all the api needed for this into 
hiding by modules.

bye Jochen Theodorou

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