Github user achristianson commented on the issue:
https://github.com/apache/nifi-minifi-cpp/pull/328
@phrocker
Try deleting the following generated files & trying again:
/extensions/expression-language/Parser.*
/extensions/expression-language/Scanner.cpp
/extensions/expression-language/location.hh
/extensions/expression-language/position.hh
/extensions/expression-language/stack.hh---
