Create a header file named "sample.h" with the following contents:

===============================
#pragma once

class A{
public:
	int tratatatata;
};

#include "sample.h" //<--parser complains about recursive include directive
===============================

Result:
C++ code assistance complains about recursive include directive, although it does not make any harm because of #pragma once. Using #ifndef guards instead of #pragma once does not make any difference.
The problem is that in a large and complex project similar stuff makes parser stuck, it enters some kind of infinite loop and never completes the parsing of the project.

This would be useful for example if you have two classes depending on each other and you want to define their functions as inline:

==================================
file A.h:

#pragma once
class B;

class A{
public:
    int a;

    inline void func(const B& b);
}

#include "B.h"

inline void A::func(const B& b){
    b.b = 10;
}



=======================================
file B.h

#pragma once
class A;

class B{
public:
    int b;

    inline void func(const A& a);
}

#include "A.h"

inline void B::func(const A& a){
    a.a = 10;
}