[Codename Milan] MSVC rejects correct code with variadic templates by Ivan Sorokin

Hi Bengt,    
    
The syntax for parameter packs with function pointers can take a little getting used to, but the original example is actually legal (as is your own). Consider both examples expanded with types T1, T2, and T3:    
    
template <typename ...T>    
void f(void (* ...a)(T)) {}    
    
turns into    
    
void f(void (*a_1)(T1), void (*a_2)(T2), void (*a_3)(T3));    
    
template<typename... T>    
void f(void (*a)(T...)) {}    
    
turns into    
    
void f(void (*a)(T1, T2, T3));    
    
Another way to think about this is: a function pointer type itself contains several types, a return type and parameters. The entire function pointer type can be expanded as a parameter pack (the first example), or sub-elements of the function pointer types can be expanded (in your example, the parameters). All of these expansions can be further combined into more complicated expansions, which made testing this feature very "interesting".    
    
Jamie Eckman    
Visual C++ Team

I can't see that the example code should compile, the T should have ... after it inside the declaration. It is hard to understand what the intention of the declaration was, so I can't really show how it should be written. An example showng f which takes a function of "any" parameters is:

template<typename... T> f(void (*a)(T...)) {}

This could be what was intended...

Hi: this issue has been fixed. The fix should show up in the next release of Visual C++.

Thanks
Jonathan Caves
Visual C++ Compiler Team

Thanks for your feedback.

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