False positive when included header has incorrect includes

[ptomato]

I've found a minimal example for a case where an included header's missing include is reported as an IWYU error in the .cpp file. (In my case, the equivalents of b.h and c.h are library headers, so I get an IWYU error in my code and can't easily change the library headers to have correct includes.)

a.cpp:

#include "c.h"

void a(C c) {
    c.method(42);
}

b.h:

#pragma once
#include <utility>
void b(int&& i);

c.h:

#pragma once
#include "b.h"

struct C {
  template <typename T>
  void method(T&& t) {
    return b(std::forward<T>(t));
  }
};

Command line:

$ include-what-you-use a.cpp 

a.cpp should add these lines:
#include <utility>  // for forward

a.cpp should remove these lines:

The full include-list for a.cpp:
#include <utility>  // for forward
#include "c.h"      // for C
---

Here, c.h should #include <utility> and b.h should not, but IWYU should not suggest anything to be changed in a.cpp.

[kimgr]

I just tried to repro this (sorry about the long delay) -- I suspected it had something to do with other problems around templates and std::move -- but it actually seems to work on mainline. I'm not quite sure what fixed it.

@ptomato Any chance you could take the latest IWYU for a spin with the code that triggered this originally? Thanks.

[ptomato]

Yes, this seems to have been fixed on the latest git commit, I don't get the error anymore with the original code either. Thanks.