The question isn't whether or not feature A can be implemented in language X, it is whether or not it has to be implemented as a local or global transformation. This is what the paper cited above defines as expressibility: adding a feature that requires a global transformation increases expressibility.
I made no claims about whether or not more or less expressibility is a good thing or how it relates to productivity. Nothing in my responses has anything to do with whether or not functional or imperative styles are better in terms of productivity or maintainability. In fact, by the definition in the paper, adding imperative features to a functional language increases expressibility. Also, adding goto to a language increases expressibility, so it is not a metric that is solely related to maintainability and productivity.
I am not arguing that Xtend is a bad idea at all, in fact I think it's a great idea. The whole reason people like languages with powerful macro systems is that they can implement features that Xtend gives to Java in the language itself, rather than having to wait for a new language implementation.
Closures are code+data and objects are also code+data, so adding closures to a language with an object system does not increase expressibility.
The main difference is that with closures you write the code and the data part (the environment) is captured implicitly, whereas with objects, both the code and data are explicit. This makes it possible to convert a closure into an object, and an object into a closure, without having to change the whole program.
It is a little more difficult to go from closures to objects because you have to find the free variables and make them explicit, but it still isn't a global transformation. If you want to see how to implement objects with closures, check out SICP.
You misunderstand what a local syntax transformation is. A syntax transformation is just a function that takes syntax as input and returns syntax as output. The function can be arbitrarily complex, even "inferring" things from the input syntax.
The key point is whether the transform is local or global. An example of a global transform is turning a program into continuation-passing style because it must change every function definition and function call in the program.
The transforms that Xtend is doing appear to be local. Converting closures to anonymous inner classes is a local transformation. Their "type inference" isn't real whole-program type inference, it just saves keystrokes within certain expressions. The fact that they can show you the underlying Java code that each new feature turns into indicates that the transforms are local.
Also, these types of transformations really are trivial in languages with full-featured macro systems (like most LISP dialects).
This is not a meaningless comparison; it points out one of the main deficiencies of java: lack of first-class functions. The closest you can come is using anonymous inner classes, which is kind of kludgy.
This is sad because this is one of the only technologies my mom is comfortable with using. She uses this service on almost a daily basis. When I called her and told her about this story, she asked if there was some way to call them up and complain about it. I know Google is notorious for not having very good customer service, but does anyone know if there is a number she could call?
Intellij has a few features that I would have a hard time living without. Code inspection is probably the number one feature that is pretty amazing. You can configure it to check everything from warning about null pointers to unused variables to questionable practices (like an assignment in a conditional). When you have a green light, you can be reasonably sure that the code is clean from most basic problems. The autocomplete is the best I've seen in any IDE, and it allows matches on CamelCase by just typing the capital letters and brings up choices based on type inference. The version control integration is also pretty amazing; I think they could sell the change management and merging portion as a stand alone tool that would do really well on its own. Overall, IntelliJ lets me get into a flow with programming by making a lot of the warts of Java melt away. Sometimes it feels like it's almost writing the code for you and you are just giving it some direction. I know that some of these features have been implemented in Eclipse, but the way they all integrate so seamlessly makes IntelliJ a fun environment to code in. I miss these features in other languages that don't have an advanced IDE.
I made no claims about whether or not more or less expressibility is a good thing or how it relates to productivity. Nothing in my responses has anything to do with whether or not functional or imperative styles are better in terms of productivity or maintainability. In fact, by the definition in the paper, adding imperative features to a functional language increases expressibility. Also, adding goto to a language increases expressibility, so it is not a metric that is solely related to maintainability and productivity.
I am not arguing that Xtend is a bad idea at all, in fact I think it's a great idea. The whole reason people like languages with powerful macro systems is that they can implement features that Xtend gives to Java in the language itself, rather than having to wait for a new language implementation.