gcc and clang implicitly instantiate template arguments during operator overload resolution

Question

Consider this code:

struct A; // incomplete type

template
struct D { T d; };

template 
struct B { int * p = nullptr; };

int          


        

Answer 1

Well, I think in Visual Studio 2013 code should look like(without = nullptr):

  struct A; // incomplete type

  template
  struct D { T d; };

  template 
  struct B { int * p; };

  int void_main() {
    B> u, v;
    u = v;          //  compiles
    u.operator=(v); // compiles
    return 0;
    }

In this case it should compile well just because incomplete types can be used for specific template class specialization usage.

As for the run-time error - the variable v used without initialization - it's correct - struct B does not have any constructor => B::p is not initialized and could contain garbage.