What's this using usage on a class name

[marhuum]

what is using for a class name scoping the name too ?
as read one's code

class T  {

public:
virtual int m();

//..
}

struct M : public T {

  using T::T;             // <- ?
  int m() override 
  
  //..
}

[Peter87]

You are inheriting the constructors from T.

https://en.cppreference.com/w/cpp/language/using_declaration#Inheriting_constructors