pprClassPred clas tys = ppr_type_app TopPrec (getName clas) tys
pprTheta :: ThetaType -> SDoc
-pprTheta theta = parens (sep (punctuate comma (map pprPred theta)))
+pprTheta [pred] = pprPred pred
+pprTheta theta = parens (sep (punctuate comma (map pprPred theta)))
pprThetaArrow :: ThetaType -> SDoc
pprThetaArrow [] = empty