I tried creating a new blank project and added a couple of classes to it and it works as expected. If I try to use something from one class in the other without a header include I get errors as expected.
So I tried wiping out everything bar the Content, Source and Config folders in my main project, then regenerating the project files. I then rebuilt the project still with no errors!?!?! I blatantly have files using classes from other files with no header includes or nested header includes! What is happening. It is a pretty large project now as I’ve been working on it for a while now.
Maybe this new IWYU foo is causing odd things. I don’t have any includes in my project header, just the Engine.h. Maybe I should get rid of the Engine.h and start including individual Engine header files?