The recent addition of -XUnliftedNewtypes means that user-defined newtypes (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0098-unlifted-newtypes.rst) can indeed be unlifted and unboxed. There is also a proposal for more general unlifted data (https://github.com/ghc-proposals/ghc-proposals/pull/265).

If the wiki is out of date, do you think you could update it?

Thanks!

Richard

On Jan 20, 2020, at 9:45 AM, Csaba Hruska <csaba.hruska@gmail.com> wrote:

Hello,

According to GHC Wiki it seems that only primitive types can be unlifted.

Is this true in general? (i.e. no user type can be unlifted)

<image.png>
Does the Stg to Cmm codegen support compilation for a variable of user defined ADT as unlifted?

i.e. some analysis proved that it is always a constructor and never a thunk.

Thanks,

Csaba

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