+optSrcSpanFileName :: SrcSpan -> Maybe FastString
+optSrcSpanFileName (SrcSpanOneLine { srcSpanFile = nm }) = Just nm
+optSrcSpanFileName (SrcSpanMultiLine { srcSpanFile = nm }) = Just nm
+optSrcSpanFileName (SrcSpanPoint { srcSpanFile = nm}) = Just nm
+optSrcSpanFileName _ = Nothing
+