I was trying to build some of your projects (SwiftGtk, SwiftHelloGtkBuilder) and they all fail with the latest Swift:

Swift version 4.0 (swift-4.0-RELEASE)
Target: x86_64-unknown-linux-gnu

Running Ubuntu 16.04 64 bits:

Linux 4.10.0-35-generic #39~16.04.1-Ubuntu SMP Wed Sep 13 09:02:42 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

The error can be reproduced just by cloning any of the repos, cd'ing into them, and then running the enclosed build.sh. I have installed all the library requirements. The error message is in the file attached: error.txt

The compilations of all the aforementioned projects stop when the gir2swift project is building, this is why I post this bug here.