Decouple package modules with package interfaces

[simendsjo]

On Tuesday, 24 September 2013 at 07:08:24 UTC, Jonathan M Davis 
wrote:
> On Tuesday, September 24, 2013 08:54:42 simendsjo wrote:
>> I just came across a problem where I either has a cyclic
>> dependency, pass around three delegates, implement an interface
>> or somehow hack some communication between two modules.
>> 
>> A simple way would be to add an interface, but interfaces 
>> require
>> implementations to be public. The methods should be package
>> protected though.
>> 
>> It would have been nice if the implementation for an interface
>> wouldn't have to be more visible than the interface itself.
>> 
>> If an interface is "package", it cannot escape that package, so
>> why would the implementation required to be public? The same 
>> goes
>> for "private".
>> 
>> Should I add an enhancement request for this, or does it have
>> problems I'm not seeing?
>
> Only public and protected are virtual. private and package are 
> never virtual.
> This is by design. As such, it is impossible for an interface 
> to be anything
> but public or protected and actually work.
>
> There has been some discussion of making it so that non-virtual 
> is the
> default, in which case, we'd have the virtual keyword, and it 
> would be
> required to make a function virtual (similar to C++). If we 
> ever actually go
> that route, then it may become possible to make package and 
> private functions
> virtual (or it may not - that will depend on what's decided at 
> that point),
> but it's definitely not going to happen if we don't go that 
> route.
>
> So, if you want to use interfaces, you need to be using public 
> or protected to
> implement them. package and private are not an option.
>
> - Jonathan M Davis

Ok, thanks. I'll fix it some other way.