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's a block duration of validity. E.g If you define a namespace alias as below, the namespace alias abc would be invalid outside {...} block.

 {  
    namespace abc = xyz;
    abc::test t;  //valid 
 }
  abc::test t;  //invalid