I have a theory, but I don't know how to test it. We have a fairly large iOS project of about 200 Swift files and 240 obj-C files (and an equal amount of header files). We're still on Swift 1.2, which means that quite regularly, the entire project gets rebuilt.

I've noticed that each .swift file takes about 4-6 seconds to compile; in other projects this is at most 2.

Now, I've noticed that in the build output, warnings generated in header files get repeated for every .swift file, which makes me believe the swift compiler will re-parse all headers included in the bridging header. Since we have ~160 import statements in the bridging header, this kinda adds up.

So, basic questions:

* Does the size of our bridging header impact build times?
* Is there any way to optimize this, so it parses the headers only once?
* Does Swift 2 have this same issue?
* Any other tricks to optimize this? Besides rewriting everything in Swift, that's kinda too labor-intensive a project for us to undertake at this time.