TL;DR; /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Time.swift:127:3: error: unknown attribute '_downgrade_exhaustivity_check' @_downgrade_exhaustivity_check ^ /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/IO.swift:71:21: error: invalid redeclaration of 'init(type:path:oflag:mode:queue:cleanupHandler:)' public convenience init?( ^ I'm going to build Swift rpm package from source on Fedora 26. This error occurs with 3.1 and 3.1.1 releases of swift and its dependencies including swift-llbuild, swift-cmark, swift-lldb, etc. I used this script ( https://github.com/corinnekrych/swift-rpm/blob/master/rpm-from-source.sh) and changed it a bit in order to work in Fedora 26 (it apparently worked on previous versions of Fedora). The latest error(s) I faced is(are): """ /home/ali/rpmbuild/BUILD/build/buildbot_linux/swift-linux-x86_64/bin/swiftc -whole-module-optimization -emit-library -c /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Block.swift /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Data.swift /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Dispatch.swift /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/IO.swift /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Private.swift /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Queue.swift /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Source.swift /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Time.swift /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Wrapper.swift \ -Xcc -fmodule-map-file=/home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/dispatch/module.modulemap -I/home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch -Xcc -fblocks -O -module-name Dispatch -module-link-name dispatch \ -o /home/ali/rpmbuild/BUILD/build/buildbot_linux/libdispatch-linux-x86_64/src/swift/swift_overlay.o -emit-module-path /home/ali/rpmbuild/BUILD/build/buildbot_linux/libdispatch-linux-x86_64/src/swift/Dispatch.swiftmodule /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/Time.swift:127:3: error: unknown attribute '_downgrade_exhaustivity_check' @_downgrade_exhaustivity_check ^ /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/IO.swift:71:21: error: invalid redeclaration of 'init(type:path:oflag:mode:queue:cleanupHandler:)' public convenience init?( ^ /home/ali/rpmbuild/BUILD/swift-corelibs-libdispatch/src/swift/IO.swift:59:21: note: 'init(type:path:oflag:mode:queue:cleanupHandler:)' previously declared here public convenience init( ^ make[2]: *** [Makefile:1004: /home/ali/rpmbuild/BUILD/build/buildbot_linux/libdispatch-linux-x86_64/src/swift/swift_overlay.o] Error 1 make[2]: Leaving directory '/home/ali/rpmbuild/BUILD/build/buildbot_linux/libdispatch-linux-x86_64/src' make[1]: *** [Makefile:545: all] Error 2 make[1]: Leaving directory '/home/ali/rpmbuild/BUILD/build/buildbot_linux/libdispatch-linux-x86_64/src' make: *** [Makefile:453: all-recursive] Error 1 ./utils/build-script: fatal error: command terminated with a non-zero exit status 2, aborting ./utils/build-script: fatal error: command terminated with a non-zero exit status 1, aborting error: Bad exit status from /var/tmp/rpm-tmp.VPka9M (%build) RPM build errors: Bad exit status from /var/tmp/rpm-tmp.VPka9M (%build) """ Please let me know if you need something else. Ali