On Saturday 22 May 2010 13:12:40 Peter Dimov wrote:
That's really bad. It effectively means one can't easily tell when one might need the full definition of a type. I ran into this because I wanted to decouple some code defining the body of one function that takes one type from the body of another that takes a different type. In terms of the example, I didn't want changes to A to cause recompilation of functions that take a Wrapper<B>.
I see how that might be a problem, but I don't see a solution. Either way, someone loses. I'd probably remove the typedef typename Tag::type type in this case, as it's the only thing requiring the definition of A.
Unfortunately, in the real code the typedef is needed for some metaprogramming. I will see if I can work around it somehow. Adding the cast to the ?: solves this particular problem but the real code has a good amount of proto- and fusion-generated stuff which assumes conversions with shared_ptr work as if they were bare pointers. It's not obvious where casts are needed or what the casted-to type should be. So it seems I have to choose between making the code compile and keeping separate compilation. Not a choice but it forces one to couple the code more than should be necessary. Isn't a possible solution to amend the standard to require short-circuited overload resolution? Or would that break some other existing examples? The committee is about to finalize the new standard. Is this worth discussing at this late stage? Perhaps I will submit a comment pointing to this thread. Thanks for your help! -Dave