badExistential con_name
= hang (ptext SLIT("Data constructor") <+> quotes (ppr con_name) <+>
- ptext SLIT("has existential type variables, or a context, or both"))
+ ptext SLIT("has existential type variables, or a context"))
2 (parens $ ptext SLIT("Use -XExistentialQuantification or -XGADTs to allow this"))
badStupidTheta tc_name