C++ using 'this' keyword in member initialization list - c++

Question

I was writing an Integer struct
struct Integer
{
int value;
Integer(int value_) : value(_value){ }
};
This works fine but instead I wanted to use value name for the parameter too and this causes a name clash. That's why I tried to use this keyword like below
struct Integer
{
int value;
Integer(int value) : this->value(value){ }
};
But I got an error and I don't seem to understand the problem here. I would be very happy to learn. Thanks for your answers.

Answer 1

This works fine but instead I wanted to use value name for the parameter too and this causes a name clash.
No it doesn't.
Integer(int value) : value(value){ }
This is just fine (if a little confusing to some).
It is simply not permitted in the language grammar to write this-> there, probably because it would make no sense to specify any other object: the this-> is implicitly done for you.

Answer 2

The standard way is to write
struct Integer
{
int value;
Integer(int value) : value(value){ }
};
In the initializer list : value(value), the first value refers to the member (because that's what a member initializer initializes), while the second value refers to the constructor argument (because that's an expression, and the name in an expression is looked up by the ordinary rules).

Answer 3

As other answers already mentioned, it is not defined in the C++grammer / syntax.
See it here.
And there is no need to specify this. To disambiguate class vs. member you don't use this, you use the scope resoultion operator.
See this (strange) example:
#include <iostream>
class A{
public:
A(int a){
std::cout << "A("<< a << ")\n";
}
A(){
std::cout << "A()\n";
}
};
class B : public A
{
public:
int A;
B(int a) : A::A(42), A(a)
{}
};
int main()
{
B b = 12;
std::cout << b.A;
return 0;
}
And of course this already exists:
#include <iostream>
class B;
class A{
public:
A(int a){
std::cout << "A("<< a << ")\n";
}
A(){
std::cout << "A()\n";
}
A(B& b);
};
class B : public A
{
public:
int A;
B(int a) : A::A(*this), A(a)
{}
};
inline A::A(B& b){
std::cout << "A(B&)\n";
}
int main()
{
B b = 12;
std::cout << b.A;
return 0;
}