overlay mtac2 https://github.com/herbelin/Mtac2 master+adapt-coq-pr18253-no-poly-for-coercion 18253 master+useless-poly-flag-coercion
overlay elpi https://github.com/herbelin/coq-elpi coq-master+adapt-coq-pr18253-no-poly-for-coercion 18253 master+useless-poly-flag-coercion
