some refactoring in self type conversion
some refactoring in self type conversion

Dveim/scalameta,xeno-by/scalameta,DavidDudson/scalameta,scalameta/scalameta,xeno-by/scalameta,olafurpg/scalameta,scalameta/scalameta,olafurpg/scalameta,DavidDudson/scalameta,scalameta/scalameta,MasseGuillaume/scalameta,xeno-by/scalameta,MasseGuillaume/scalameta,scalameta/scalameta,scalameta/scalameta,olafurpg/scalameta,MasseGuillaume/scalameta