[Haskell-cafe] Generalized Newtype Deriving not allowed in Safe Haskell

[Omari Norman]

When compiling code with Generalized Newtype Deriving and the -fwarn-unsafe
flag, I get

-XGeneralizedNewtypeDeriving is not allowed in Safe Haskell


This happens both in GHC 7.8 and GHC 7.10.


I thought I remembered reading somewhere that GNTD is now part of the safe
language?  The GHC manual used to state that GNTD is not allowed in Safe
Haskell:


https://downloads.haskell.org/~ghc/7.6.3/docs/html/users_guide/safe-haskell.html#safe-language


But this language on GNTD not being part of the safe language was removed
in the 7.8 manual:


https://downloads.haskell.org/~ghc/7.8.2/docs/html/users_guide/safe-haskell.html#safe-language


The GHC release notes don't say anything about this one way or the other.
Thoughts?
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