Hi! I have discussed this with KDevelop's maintainer.
As Alexis states the code parser will not work with c++ projects if the clang headers are not there. On the other hand if the c++ project is using gcc instead of clang to build the wrong headers would be displayed (even if the headers are meant to track gcc's ones, they are still not the originals). Following the same criterion as for another dependencies: Qt Creator is not *just* a C++ IDE, so anyone wanting to add the relevant headers should either install Recommends by default or proceed to install them by hand. Ideally we should be able to depend upon the same clang/llvm version qtcreator was built with, without having to resort to regular expressions or alike to modify debian/control on each upload. I have not checked if this is doable yet, but will try to do it. I expect the fix to be present in the next Qt Creator version I'll be pushing to unstable, for which I do not have an ETA due to lack of time. Kinds regards, Lisandro.