Main.cpp:6:9: error: constructor cannot have a return type
    int main_demo(int a) {
    ~~~ ^~~~~~~~~
Main.cpp:11:9: error: constructor cannot have a return type
    int main_demo(int a ,int b) {
    ~~~ ^~~~~~~~~
Main.cpp:18:5: error: must use 'class' tag to refer to type 'main_demo' in this scope
    main_demo object;
    ^
    class 
Main.cpp:17:5: note: class 'main_demo' is hidden by a non-type declaration of 'main_demo' here
int main_demo() {
    ^
Main.cpp:19:12: error: cannot refer to type member 'main_demo' in 'main_demo' with '.'
    object.main_demo(5);
           ^
Main.cpp:4:7: note: member 'main_demo' declared here
class main_demo {
      ^
Main.cpp:20:12: error: cannot refer to type member 'main_demo' in 'main_demo' with '.'
    object.main_demo(5,10);
           ^
Main.cpp:4:7: note: member 'main_demo' declared here
class main_demo {
      ^
5 errors generated.