Class declaration in same scope as using declaration compiles in GCC but not MSVS

Question

Is the following program well-formed according to the c++ standard?

namespace X { class A; }

namespace Y { using X::A; class A {}; }

int main() {}
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Answer 1

Not too sure but you can try something like this :

namespace X { class A; }

namespace Y 
{
  class X::A {}; 
}

int main() 
{
  return 0;
}