Function pointers/delegates default args were stealth removed?

[Walter Bright]

On 8/26/2012 3:26 PM, Manu wrote:
> I just updated to 2.60 and found errors throughout my code where function
> pointers default args no longer work.
> _Every single project_ I've written in D, 5 projects, don't work anymore,
> including my projects at work.
>
> I found this discussion: http://d.puremagic.com/issues/show_bug.cgi?id=3866
> It seems the change was just decided and implemented with basically no
> discussion or argument at all :/
>
> My use cases are dynamic linkage, and cross-language integration.
> I can't manually interact with DLL's containing API's that expect to have
> default arguments if function pointers no longer support them.
> Also when receiving foreign language function pointers, they frequently need to
> have default args too.
>
> I also integrate with many C style API's (rendering engines and the like), which
> involve registration of various callbacks, and lots of those have default args too.
>
> I find this particularly surprising, since I recently motivated implementation
> of new traits which could parse default args from parameter lists, and use that
> to generation function pointers in templates which auto-magically clone
> functions parameter lists verbatim, specifically including the default args...

The trouble is that, as 3866 shows, there is no design anyone could come up with 
that worked in a consistent manner. The only consistent way out was to make 
default arguments a characteristic of the declaration, not of the type.

The trouble for function pointers, is that any default args would need to be 
part of the type, not the declaration.

I know it broke code (for many others, too), and I'm very sorry about that, but 
I don't see another way out.

(Many uses of default arguments can be replaced with overloaded functions.)