This needs to go into the style guide and style checker if it is something we want to encourage going forward.
I don’t agree that this belongs in the style guide.
This follows the general rule that headers that use something need to include the file that something is defined in. I wouldn’t make a style rule for each thing.
Why is it OK to use std::unique_ptr without including <memory>? Because <memory> is included in "config.h" perhaps?
I agree with Darin. This doesn't belong in the style guide. But this just an opinion. :)