Are you sure that's not supported? That seems like a bug if so.  I'm away from my computer right now so I can't check.  

What ghc version? How are you checking if the unpack is firing? 

Ghc 7.8 should by default be unpacking ALL strict small fields. 

On Sunday, June 15, 2014, Nikita Volkov <nikita.y.volkov@mail.ru> wrote:

Currently the pragma only supports single-constructor types. So in the following example it will simply be ignored:

data A = 
  A1 Char |
  A2 {-# UNPACK #-} !B

data B = 
  B1 Int |
  B2 Bool

However it seems to be easily solvable by changing the type A to something like the following during unpacking:

data A =
  A1 Char |
  A2_1 Int |    -- from B1
  A2_2 Bool     -- from B2

Am I missing something? Why is it not implemented?

​

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