I think that many people faced problems linked to some missing header file or library and find themselves with the compiler complaining about some undefined symbol or saying that some function has not been defined in the current scope...Furthermore, I think that reading and understanding others source code require at least grasping the used functions and thus the corresponding headers (as you may stumble upon "partial" code...).
I wonder whether reflection (or other features) offers the capability to dynamically introspect the imported headers within the current execution scope for a C++ source file?
(I'm targeting especially C++ interpreters like Cling or Ch, as interpreters do not allow full control over imported headers and many things are done in the background.)