Generic instances for GHC AST

[Ryan Scott]

> If the unboxed types are a problem for the automatic Generic derivation, a
> manual instance could be written instead.

As of recently [1], -XDeriveGeneric should be capable of handing
unboxed types, so that removes one major technical limitation. I'm not
sure which unboxed types GHC's API uses off of the top of my head, but
if you need something other than Addr#, Char#, Double#, Int#, or
Word#, it wouldn't be too difficult to add support for them.


Ryan S.
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[1] https://git.haskell.org/ghc.git/commit/6cde981a8788b225819be28659caddc35b77972d