C++ keyword: typename

Usage

• In the template parameter list of a template declaration, typename can be used as an alternative to class to declare type template parameters and template template parameters (since C++17).
• Inside a declaration or a definition of a template, typename can be used to declare that a dependent qualified name is a type.
• Inside a declaration or a definition of a template, (until C++11) typename can be used before a non-dependent qualified type name. It has no effect in this case.
• Inside a requirements for type requirements (since C++20)