What’s the rationale for v2.19.2 to have entire stan lang’s grammars
directory cloned? In v2.18.x these src’s are from StanHeaders and rstan just have to #include
them. Which path does rstan 2.19.2 actually use in compilation, its own grammars
or StanHeaders’?
The StanHeaders ones are copied from 2.19 into rstan and then used. This was necessary to avoid using the ones that came with 2.18.1.10, which were modified to work with rstan 2.18 to restore backward compatibility. For 2.20, hopefully we won’t have to do (as) much.