Sometimes, I've found the need to incrementally clean projects to get rid of all error problems, but not with the latest commit c37bff349b on Sep 7.
Start cleaning individual projects first with projects in core, with those having "xtext" in their name first, followed by those having shortest names.
It seems that Eclipse inexplicably determines incorrect build orders.
This happens sometimes just within cleaning my own projects.
Clean/build of com.multitude.bless.codegeneration clears all the bogus error messages in my own plugins.