+ | otherwise
+ = pprSorry "Vectorise.Builtins.indexBuiltin"
+ (vcat [ text ""
+ , text "DPH builtin function '" <> text fn <> text "' of size '" <> ppr i <> text "' is not yet implemented."
+ , text "This function does not appear in your source program, but it is needed"
+ , text "to compile your code in the backend. This is a known, current limitation"
+ , text "of DPH. If you want it to to work you should send mail to cvs-ghc@haskell.org"
+ , text "and ask what you can do to help (it might involve some GHC hacking)."])
+