Create a new swift Cocoa App in Xcode 10 with an accented character in the app name, i.e. "Belzebù".
Then the app fails at launch with these runtime errors:
"Belzebù[22477:5859551] Unknown class _TtC8Belzebù11AppDelegate in Interface Builder file at path..."
"Belzebù[22477:5859551] Failed to connect (window) outlet from (NSObject) to (NSWindow): missing setter or instance variable"
Reverting to the legacy build system solves the issue.
P.S. I do not know if it is correct to report this bug here.