C++ enum keyword in function parameters

Question

What is the point of using the enum keyword in the function parameter? It seems to do the same thing without it.

enum myEnum{
  A, B, C
};

void x(myEnum e){}

void y(enum myEnum e){}

Is there a difference between the two?

Answer 1

In this function declaration

void x(myEnum e){}

the enumeration myEnum shall be already declared and not hidden.

In this function declaration

void y(enum myEnum e){}

there is used the so-called elaborated type name. If in the scope there is declared for example a variable with the name myEnum like

int myEnum;

then using this function declaration

void y(enum myEnum e){}

allows to refer to the enumeration with the name myEnum that without the keyword enum would be hidden by the declaration of the variable.

Here is a demonstrative program.

#include <iostream>

enum myEnum{
  A, B, C
};

void x(myEnum e){}

int myEnum; 

//  compiler error
//void y(myEnum e){} 

void y(enum myEnum e){}

int main() {
    // your code goes here
    return 0;
}

As it is seen the commented function declaration will not compile if to uncomment it.