Simon is right, you cannot use a type family as an instance head. But why do you need to? Typically, if you're deriving a Data instance that involves type families, the type families would be inside another data type. A real-world example is HsBindLR [1]:
data HsBindLR idL idR
= FunBind {
...
bind_fvs :: PostRn idL NameSet,
...
} | ...
where PostRn is a type family [2]. Now, you can't simply derive Data for HsBindLR, because GHC has no way of knowing what PostRn will evaluate to! But you can use standalone deriving to get what you want:
deriving instance (Data (PostRn idL NameSet), ...) => Data (HsBindLR idL idR)
And in fact, this is what GHC does [3], using a convenient type synonyms for the long, sprawling context you need [4].
So in your example, while you can't directly create a Data instance for NameOrRdrName itself, you can quite easily create Data instances for anything that might use NameOrRdrName. Does that work for your use cases?
Ryan S.
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[1] http://git.haskell.org/ghc.git/blob/bdc555885b8898684549eca70053c9ce0ec7fa39:/compiler/hsSyn/HsBinds.hs#l111
[2] http://git.haskell.org/ghc.git/blob/bdc555885b8898684549eca70053c9ce0ec7fa39:/compiler/hsSyn/PlaceHolder.hs#l47
[3] http://git.haskell.org/ghc.git/blob/bdc555885b8898684549eca70053c9ce0ec7fa39:/compiler/hsSyn/HsBinds.hs#l264
[4] http://git.haskell.org/ghc.git/blob/bdc555885b8898684549eca70053c9ce0ec7fa39:/compiler/hsSyn/PlaceHolder.hs#l102