Formal model for defender method resolution

[Brian Goetz]

In this example, "default none" was meant to capture what has been 
called reabstraction, but it is really something different and would 
deserve a different name.



On 2/3/2011 12:34 AM, Ali Ebrahimi wrote:
> Hi Brian,
> do you mean "default none" as reabstraction?
>
>
> On Tue, Feb 1, 2011 at 8:11 PM, Brian Goetz<brian.goetz at oracle.com>  wrote:
>
>>> If a bare "default" keyword is not descriptive enough, then maybe the
>> following is more
>>> descriptive:
>>>
>>> interface A {
>>>     void m() default Defaults.m;
>>> }
>>>
>>> interface B {
>>>     void m() default super;
>>> }
>>
>> While we're having a nice syntax bike-shed paint, I'll just point out
>> that it would be nice if the syntax in the default were the same as the
>> syntax in a clarifying override, which is currently:
>>
>>    intf A { void m() default X.a }
>>    intf B { void m() default X.b }
>>    class C implements A, B {
>>      void m() { A.super.m(); }
>>    }
>>
>> I am much more interested in getting a clean semantics of what it
>> *means* to remove a default, and how it might play into default
>> resolution in cases like:
>>
>> intf A { String m() default X.a }
>> intf B { String m() default X.b }
>> intf C extends A { String m() default none }
>> intf D extends A, B, C { }
>>
>> What now?  Do we barf because A and B are contributing conflicting
>> defaults?  If we prune A from consideration (as I believe we should), do
>> we barf because the "none" in C conflicts with the default in B?
>>
>> And, secondarily, whether such a construct (which is analogous to, but
>> distinctly separate from reabstraction) is actually useful enough to
>> overcome the additional complexity?  ("Because its analogous with
>> reabstraction" is way too low a bar.  One can justify any language
>> feature, sensible or not, by that logic.)
>>
>> I'd like to start with the simplest possible design for defenders and
>> then work up from there.  We are clearly nowhere near the simplest
>> possible design yet...
>>
>>
>>
>