\begin{code}
rnSrcDerivDecl :: DerivDecl RdrName -> RnM (DerivDecl Name, FreeVars)
rnSrcDerivDecl (DerivDecl ty)
- = do ty' <- rnLHsType (text "a deriving decl") ty
- let fvs = extractHsTyNames ty'
- return (DerivDecl ty', fvs)
+ = do { standalone_deriv_ok <- doptM Opt_StandaloneDeriving
+ ; unless standalone_deriv_ok (addErr standaloneDerivErr)
+ ; ty' <- rnLHsType (text "a deriving decl") ty
+ ; let fvs = extractHsTyNames ty'
+ ; return (DerivDecl ty', fvs) }
+
+standaloneDerivErr :: SDoc
+standaloneDerivErr
+ = hang (ptext (sLit "Illegal standalone deriving declaration"))
+ 2 (ptext (sLit "Use -XStandaloneDeriving to enable this extension"))
\end{code}
%*********************************************************