How to call destructor before free without dropping @nogc?

[Bienlein]

Hello,

I allocate some instance of class C manually and then free the 
memory again:

     class C {
         int num;

         ~this() {
     	writeln("~this");
         }
     }

     void foo() // @nogc
     {
         auto mem = cast(C)malloc(__traits(classInstanceSize, C));
         auto c = emplace!(C)(mem);

         c.num = 789;

         destroy(c);
         free(cast(void*) c);
         c = null;
     }

     int main()
     {
     	foo();
     }

The code above works well as the destructor of c in class C is 
called by destroy. Problem is that destroy cannot be used once 
function foo is annotated with @nogc. There seems to be no way 
round it.

What I want is to keep the function foo annotated with @nogc, but 
still have the destructor of C be called before free is called. 
Is there a way to call the destructor through meta programming or 
some kind of reflection so that I can create some generic 
function that calls the destructor and then free for any kind of 
class?

Thanks, Bienlein