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.)
