fixes ensugars signature
fixes ensugars signature

If a tree inherited both SymTree and NameTree, that led to problems

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