fatal error: malformed or corrupted AST file - Xcode

Question

I get this error when building my app in the latest version of Xcode:

fatal error: malformed or corrupted AST file: \'Unable to load module \"/Users

Answer 1

tried to re-install XCode which didnt resolve the issue, also created a new local user account & get the same error so in the end I gave up & restored to a time machine backup from a few days before... seems to be ok again... for now!