This isn't quite a 100% clean sweep of IWYU.
There are some false positives where clang fails.
Additionally there are still a few missed in the frontend side of things
that I didn't get to
Puts the visibility of the main layer, application layers, and
environment in to FEXCore instead of FEX.
These layers aren't specific to FEX/FEXLoader and should live in
FEXCore.
Only the EmptyMapper remains in FEX, which should eventually move over
to FEXConfig since that is the only user.
Instead of having the configuration being loaded and stored in to a
frontend system. First moves the backing store of the configuration in
to FEXCore.
Each layer that is constructed then loads its particular configuration.
After the layers are loaded, then a meta layer is constructed that
merges the layers flat.
This means we will no longer hit the problem where a configuration is
stored in the "main" configuration file, then environment and arguments
passed manage to overwrite it.
The order of the layers going from inner most layer to outer most, with
outermost overwriting previous layer configurations is as follows:
Main < Global application < Local application < Arguments < Environment
One step that needs to be changed in the future is that FEXCore can then
just load its configuration from the layers directly since the data is
in FEXCore now. This will be reserved for a future change so we are less
disruptive.
Ryan Houdek