initialization of static member of template class

Consider the following:

template<class T>
struct A
{
  struct B
  {} static const b;
};

// case 1
template<class T>
typename A<T>::B const A<T>::b;

// case 2
template<class T>
typename A<T>::B const A<T>::b{};

int main()
{
  A<int> a;
  a.b;
  return 0;
}

case1:

gcc 5.2 passes
msvc 2015 update 1 passes
clang 3.7 error:

default initialization of an object of const type 'const typename A<int>::B' without a user-provided default constructor

case2:

gcc 5.2 passes
clang 3.7 passes:
msvc 2015 update 1 error:

error C2143: syntax error: missing ';' before '<end Parse>'

Which compiler is right / wrong in each case?