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-- We don't want to see a case match on the result
-- of dataToTag#. We check that by looking for case
-- matches on any literal other than 0# or 1#. We
-- only really expect to see 1# here (and not the tag
-- for OtherOS), but just in case GHC decides to get
-- clever with its knowledge of the possible results
-- of (==#), we also permit 0#.
{-# LANGUAGE MagicHash, BangPatterns #-}
module T14140 where
import GHC.Exts
data OS = Linux | Windows | OSX -- tier 1 desktop OSs
| FreeBSD | OpenBSD | NetBSD -- other free Unix OSs
| DragonFly
| Solaris | AIX | HPUX | IRIX -- ageing Unix OSs
| HaLVM -- bare metal / VMs / hypervisors
| Hurd -- GNU's microkernel
| IOS | Android -- mobile OSs
| Ghcjs
| OtherOS String
-- This is similar to the derived Eq instance. We write it
-- out manually to prevent future deriving changes from
-- changing the test.
instance Eq OS where
OtherOS x == OtherOS y = x == y
(!x) == (!y) = case dataToTag# x ==# dataToTag# y of
1# -> True
_ -> False
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