Compiler Error C2884

'name' : introduced by using-declaration conflicts with local function 'function'

You tried to define a function more than once. The first definition was a local definition, and the second was made from a namespace with a using declaration.

namespace A {
   void z(int);
}

void f() {
   void z(int);
   using A::z; // error C2884, z is already defined
}