What is the scope of a namespace alias in C++?

Question

Does a C++ namespace alias defined inside a function definition have a block, function, file, or other scope (duration of validity)?

Answer 1

It is valid for the duration of the scope in which it is introduced.

Take a look at http://en.cppreference.com/w/cpp/language/namespace_alias, I trust the explanation of cppreference, it's much more standard.