Fixes #3853 Stack overflow analyzing generators Fix union comparison and merging of generators.
Fixes #3853 Stack overflow analyzing generators
Fix union comparison and merging of generators.

int19h/PTVS,int19h/PTVS,huguesv/PTVS,int19h/PTVS,zooba/PTVS,huguesv/PTVS,zooba/PTVS,int19h/PTVS,zooba/PTVS,Microsoft/PTVS,Microsoft/PTVS,zooba/PTVS,Microsoft/PTVS,Microsoft/PTVS,huguesv/PTVS,Microsoft/PTVS,zooba/PTVS,int19h/PTVS,int19h/PTVS,zooba/PTVS,huguesv/PTVS,huguesv/PTVS,Microsoft/PTVS,huguesv/PTVS