Ordering of code in file affects compilation
consider the following module:
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE UnboxedTuples #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeInType #-}
-- | Conversion between unlifted and lifted datatypes
module Packed.Levity
( -- * Types
Rep
, Levity(..)
) where
import Data.Kind (Type)
import GHC.Types (TYPE, RuntimeRep(..), Int(..), Word(..))
import GHC.Exts (Int#, Word#, ByteArray#)
type family Rep (a :: Type) :: RuntimeRep
type instance Rep Int = IntRep
type instance Rep Word = WordRep
type Stuff# = (# Int#, Int# #)
data Stuff = Stuff Int# Int#
type instance Rep Stuff = TupleRep '[ 'IntRep, 'IntRep ]
stuff# :: (# Int#, Int# #) -> Stuff
stuff# (# x, y #) = Stuff x y
unStuff# :: Stuff -> (# Int#, Int# #)
unStuff# (Stuff x y) = (# x, y #)
class Levity (a :: Type) where
type Unlifted a :: TYPE (Rep a)
box :: Unlifted a -> a
unbox :: a -> Unlifted a
instance Levity Int where
type Unlifted Int = Int#
box = I#
unbox (I# i) = i
instance Levity Word where
type Unlifted Word = Word#
box = W#
unbox (W# w) = w
instance Levity Stuff where
type Unlifted Stuff = Stuff#
box = stuff#
unbox = unStuff#
This succeeds to compile.
Now, if we move everything from type family Rep
to unStuff# (
to the bottom of the module, it fails to compile.
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE UnboxedTuples #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeInType #-}
-- | Conversion between unlifted and lifted datatypes
module Packed.Levity
( -- * Types
Rep
, Levity(..)
) where
import Data.Kind (Type)
import GHC.Types (TYPE, RuntimeRep(..), Int(..), Word(..))
import GHC.Exts (Int#, Word#, ByteArray#)
class Levity (a :: Type) where
type Unlifted a :: TYPE (Rep a)
box :: Unlifted a -> a
unbox :: a -> Unlifted a
instance Levity Int where
type Unlifted Int = Int#
box = I#
unbox (I# i) = i
instance Levity Word where
type Unlifted Word = Word#
box = W#
unbox (W# w) = w
instance Levity Stuff where
type Unlifted Stuff = Stuff#
box = stuff#
unbox = unStuff#
type family Rep (a :: Type) :: RuntimeRep
type instance Rep Int = IntRep
type instance Rep Word = WordRep
type Stuff# = (# Int#, Int# #)
data Stuff = Stuff Int# Int#
type instance Rep Stuff = TupleRep '[ 'IntRep, 'IntRep ]
stuff# :: (# Int#, Int# #) -> Stuff
stuff# (# x, y #) = Stuff x y
unStuff# :: Stuff -> (# Int#, Int# #)
unStuff# (Stuff x y) = (# x, y #)
ts.hs:33:25-30: error:
• Expected kind ‘TYPE (Rep Stuff)’,
but ‘Stuff#’ has kind ‘TYPE ('TupleRep '['IntRep, 'IntRep])’
• In the type ‘Stuff#’
In the type instance declaration for ‘Unlifted’
In the instance declaration for ‘Levity Stuff’
|
33 | type Unlifted Stuff = Stuff#
| ^^^^^^
Trac metadata
Trac field | Value |
---|---|
Version | 8.6.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |