- rhs = mkGenericRhs sel_id clas_tyvar tycon
-
- -- The tycon is only used in the generic case, and in that
- -- case we require that the instance decl is for a single-parameter
- -- type class with type variable arguments:
- -- instance (...) => C (T a b)
- clas_tyvar = ASSERT (not (null (classTyVars clas))) head (classTyVars clas)
- Just tycon = maybe_tycon
- maybe_tycon = case inst_tys of
- [ty] -> case tcSplitTyConApp_maybe ty of
- Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon
- _ -> Nothing
- _ -> Nothing
-