iwyu - 8.18-2 main

"Include what you use" means this: for every symbol (type, function variable,
or macro) that you use in foo.cc, either foo.cc or foo.h should #include a .h
file that exports the declaration of that symbol. The include-what-you-use
tool is a program that can be built with the clang libraries in order to
analyze #includes of source files to find include-what-you-use violations,
and suggest fixes for them.
.
The main goal of include-what-you-use is to remove superfluous #includes.
It does this both by figuring out what #includes are not actually needed for
this file (for both .cc and .h files), and replacing #includes with
forward-declares when possible.