## next (edit as necessary)

- `magicDict` has been renamed to `withDict` and is now defined in
  `GHC.Magic.Dict` instead of `GHC.Prim`. `withDict` now has the type:

  ```
  withDict :: forall {rr :: RuntimeRep} st dt (r :: TYPE rr). st -> (dt => r) -> r
  ```

  Unlike `magicDict`, `withDict` can be used without defining an
  intermediate data type. For example, the `withTypeable` function from the
  `Data.Typeable` module can now be defined as:

  ```
  withTypeable :: forall k (a :: k) rep (r :: TYPE rep). ()
               => TypeRep a -> (Typeable a => r) -> r
  withTypeable rep k = withDict @(TypeRep a) @(Typeable a) rep k
  ```

  Note that the explicit type applications are required, as the call to
  `withDict` would be ambiguous otherwise.

- Primitive types and functions which handle boxed values are now levity-polymorphic,
  meaning that they now also work with unlifted boxed values (i.e. values whose type
  has kind `TYPE (BoxedRep Unlifted)`).

  The following type constructors are now levity-polymorphic:

    - `Array#`, `SmallArray#`, `Weak#`, `StablePtr#`, `StableName#`,

    - `MutableArray#`, `SmallMutableArray#`, `MutVar#`,
      `TVar#`, `MVar#`, `IOPort#`.

  For example, `Array#` used to have kind:

  ```
  Type -> UnliftedType
  ```

  but it now has kind:

  ```
  forall {l :: Levity}. TYPE (BoxedRep l) -> UnliftedType
  ```

  Similarly, `MutVar#` used to have kind:

  ```
  Type -> Type -> UnliftedType
  ```

  but it now has kind:

  ```
  forall {l :: Levity}. Type -> TYPE (BoxedRep l) -> UnliftedType
  ```

  This means that in `Array# a`, `MutableArray# s a`, `MutVar# s a`, ...,
  the element type `a`, must always be boxed, but it can now either be lifted
  or unlifted.
  In particular, arrays and mutable variables can now be used to store
  other arrays and mutable variables.

  All functions which use these updated primitive types are also levity-polymorphic:

    - all array operations (reading/writing/copying/...), for both arrays and small arrays,
      mutable and immutable:

      - `newArray#`, `readArray#`, `writeArray#`, `sizeofArray#`, `sizeofMutableArray#`, `indexArray#`,
        `unsafeFreezeArray#`, `unsafeThawArray#`, `copyArray#`, `copyMutableArray#`, `cloneArray#`,
        `cloneMutableArray#`, `freezeArray#`, `thawArray#`, `casArray#`,

      - `newSmallArray#`, `shrinkSmallMutableArray#`, `readSmallArray#`, `writeSmallArray#`, `sizeofSmallArray#`,
        `getSizeofSmallMutableArray#`, `indexSmallArray#`, `unsafeFreezeSmallArray#`,
        `unsafeThawSmallArray#`, `copySmallArray#`, `copySmallMutableArray#`, `cloneSmallArray#`,
        `cloneSmallMutableArray#`, `freezeSmallArray#`, `thawSmallArray#`, `casSmallArray#`,

    - `newMutVar#`, `readMutVar#`, `writeMutVar#`,`casMutVar#`,

    - operations on `MVar#` and `TVar#`:

      - `newTVar#`, `readTVar#`, `readTVarIO#`, `writeTVar#`,

      - `newMVar#`, `takeMVar#`, `tryTakeMVar#`, `putMVar#`,
        `tryPutMVar#`, `readMVar#`, `tryReadMVar#`,

    - `STM` operations `atomically#`, `retry#`, `catchRetry#` and `catchSTM#`.

    - `newIOPort#`, `readIOPort#`, `writeIOPort#`,

    - `mkWeak#`, `mkWeakNoFinalizer#`, `addCFinalizerToWeak#`, `deRefWeak#`, `finalizeWeak#`,

    - `makeStablePtr#`, `deRefStablePtr#`, `eqStablePtr#`, `makeStableName#`, `stableNameToInt#`,

  For example, the full type of `newMutVar#` is now:

  ```
  newMutVar#
    :: forall {l :: Levity} s (a :: TYPE (BoxedRep l)).
       a -> State# s -> (# State# s, MVar# s a #)
  ```

  and the full type of `writeSmallArray#` is:

  ```
  writeSmallArray#
    :: forall {l :: Levity} s (a :: TYPE ('BoxedRep l)).
       SmallMutableArray# s a -> Int# -> a -> State# s -> State# s
  ```

- `ArrayArray#` and `MutableArrayArray#` have been moved from `GHC.Prim` to `GHC.Exts`.
  They are deprecated, because their functionality is now subsumed by `Array#`
  and `MutableArray#`.

- `mkWeak#`, `mkWeakNoFinalizer#`, `touch#` and `keepAlive#` are now
  levity-polymorphic instead of representation-polymorphic. For instance:

  ```
  mkWeakNoFinalizer#
    :: forall {l :: Levity} {k :: Levity}
              (a :: TYPE ('BoxedRep l))
              (b :: TYPE ('BoxedRep k)).
       a -> b -> State# RealWorld -> (# State# RealWorld, Weak# b #)
  ```

  That is, the type signature now quantifies over the `Levity` of `a`
  instead of its `RuntimeRep`. In addition, this variable is now inferred,
  instead of specified, meaning that it is no longer eligible for visible type application.
  Note that `b` is now also levity-polymorphic, due to the change outlined in the
  previous point.

- Primitive functions for throwing and catching exceptions are now more polymorphic
  than before. For example, `catch#` now has type:

  ```
  catch#
    :: forall {r :: RuntimeRep} {l :: Levity}
              (a :: TYPE r)
              (b :: TYPE ('BoxedRep l)).
        ( State# RealWorld -> (# State# RealWorld, a #) )
    -> ( b -> State# RealWorld -> (# State# RealWorld, a #) )
    -> State# RealWorld -> (# State# RealWorld, a #)
  ```

  The following functions are concerned:

    - `catch#`,

    - `raise#`, `raiseIO#`,

    - `maskAsyncExceptions#`, `maskUninterruptible#`, `unmaskAsyncExceptions#`.

  Note in particular that `raise#` is now both representation-polymorphic
  (with an inferred `RuntimeRep` argument) and levity-polymorphic, with type:

  ```
  raise# :: forall {l :: Levity} {r :: RuntimeRep}
                   (a :: TYPE (BoxedRep l))
                   (b :: TYPE r).
            a -> b
  ```

- ``fork#`` and ``forkOn#`` are now representation-polymorphic. For example, ``fork#``
  now has type: ::

      fork# :: forall {r :: RuntimeRep} (a :: TYPE r).
               (State# RealWorld -> (# State# RealWorld, a #))
            -> (State# RealWorld -> (# State# RealWorld, a #))

- `reallyUnsafePtrEquality#` has been made more general, as it is now
   both levity-polymorphic and heterogeneous:

  ```
  reallyUnsafePtrEquality#
    :: forall {l :: Levity} {k :: Levity}
              (a :: TYPE (BoxedRep l))
              (b :: TYPE (BoxedRep k))
    . a -> b -> Int#
  ```

   This means that `reallyUnsafePtrEquality#` can be used on primitive arrays
   such as `Array#` and `ByteArray#`. It can also be used on values of
   different types, without needing to call `unsafeCoerce#`.

- The following functions have been moved from `GHC.Prim` to `GHC.Exts`:
  - `sameMutableArray#`, `sameSmallMutableArray#`, `sameMutableByteArray#`
     and `sameMutableArrayArray#`,
  - `sameMutVar#`, `sameTVar#` and`sameMVar#`,
  - `sameIOPort#`,
  - `eqStableName#`.

- The following functions have been added to `GHC.Exts`:

  ```
  sameArray# :: Array# a -> Array# a -> Int#
  sameSmallArray# :: SmallArray# a -> SmallArray# a -> Int#
  sameByteArray# :: ByteArray# -> ByteArray# -> Int#
  sameArrayArray# :: ArrayArray# -> ArrayArray# -> Int#
  ```

## 0.8.0 (edit as necessary)

- Change array access primops to use type with size maxing the element size:

   - `index{Int,Word}<N>Array# :: ByteArray# -> Int# -> {Int,Word}<N>#`
   - `indexWord8ArrayAs{Int,Word}<N># :: ByteArray# -> Int# -> {Int,Word}<N>#`
   - `read{Int,Word}<N>Array# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, {Int,Word}<N># #)`
   - `write{Int,Word}<N>Array# :: MutableByteArray# s -> Int# -> {Int,Word}<N># -> State# s -> State# s`
   - `readWord8ArrayAs{Int,Word}<N># :: MutableByteArray# s -> Int# -> State# s -> (# State# s, {Int,Word}<N># #)`
   - `writeWord8ArrayAs{Int,Word}<N># :: MutableByteArray# s -> Int# -> {Int,Word}<N># -> State# s -> State# s`

  This was already the for the 64-bit access primops, but not the smaller ones.

- Rename some numeric prim type conversion primops:

   - `extend{Int,Word}<N>#` -> `extend<N>To{Int,Word}#`
   - `narrow{Int,Word}<N>#` -> `intTo{Int,Word}<N>#`

- Add primops for atomic compare and swap for sizes other that wordsize:

   	casInt8Array# :: MutableByteArray# s -> Int# -> Int8# -> Int8# -> State# s -> (# State# s, Int8# #)
	casInt16Array# :: MutableByteArray# s -> Int# -> Int16# -> Int16# -> State# s -> (# State# s, Int16# #)
	casInt32Array# :: MutableByteArray# s -> Int# -> Int32# -> Int32# -> State# s -> (# State# s, Int32# #)
	casInt64Array# :: MutableByteArray# s -> Int# -> Int64# -> Int64# -> State# s -> (# State# s, Int64# #)
	atomicCasWord8Addr# :: Addr# -> Word8# -> Word8# -> State# s -> (# State# s, Word8# #)
	atomicCasWord16Addr# :: Addr# -> Word16# -> Word16# -> State# s -> (# State# s, Word16# #)
	atomicCasWord32Addr# :: Addr# -> Word32# -> Word32# -> State# s -> (# State# s, Word32# #)
	atomicCasWord64Addr# :: Addr# -> WORD64 -> WORD64 -> State# s -> (# State# s, WORD64 #)

## 0.7.0 (edit as necessary)

- Shipped with GHC 9.0.1

- Add known-key `cstringLength#` to `GHC.CString`. This is just the
  C function `strlen`, but a built-in rewrite rule allows GHC to
  compute the result at compile time when the argument is known.

- In order to support unicode better the following functions in `GHC.CString`
  gained UTF8 counterparts:

        unpackAppendCStringUtf8# :: Addr# -> [Char] -> [Char]
        unpackFoldrCStringUtf8# :: Addr# -> (Char -> a -> a) -> a -> a

- unpackFoldrCString* variants can now inline in phase [0].

  If the folding function is known this allows for unboxing of the
  Char argument resulting in much faster code.

- Renamed the singleton tuple `GHC.Tuple.Unit` to `GHC.Tuple.Solo`.

- Add primops for atomic exchange:

        atomicExchangeAddrAddr# :: Addr# -> Addr# -> State# s -> (# State# s, Addr# #)
        atomicExchangeWordAddr# :: Addr# -> Word# -> State# s -> (# State# s, Word# #)

- Add primops for atomic compare and swap at a given Addr#:

        atomicCasAddrAddr# :: Addr# -> Addr# -> Addr# -> State# s -> (# State# s, Addr# #)
        atomicCasWordAddr# :: Addr# -> Word# -> Word# -> State# s -> (# State# s, Word# #)

- Add an explicit fixity for `(~)` and `(~~)`:

        infix 4 ~, ~~

- Introduce `keepAlive#` to replace `touch#` in controlling object lifetime without
  the soundness issues of the latter (see
  [#17760](https://gitlab.haskell.org/ghc/ghc/-/issues/17760)).

## 0.6.1 (edit as necessary)

- Shipped with GHC 8.10.1

- Add primop for shrinking `SmallMutableArray#`
  to `GHC.Prim`:

        shrinkSmallMutableArray# :: SmallMutableArray# s a -> Int# -> State# s -> State# s

  Note that `resizeSmallMutableArray#` is not included as
  as primitive. It has been implemented in library space in
  `GHC.Exts`. See the release notes of `base`.

- Added to `GHC.Prim`:

        closureSize# :: a -> Int#

- Added to `GHC.Prim`:

        bitReverse# :: Word# -> Word#
        bitReverse8# :: Word# -> Word#
        bitReverse16# :: Word# -> Word#
        bitReverse32# :: Word# -> Word#
        bitReverse64# :: Word# -> Word#

  `bitReverse#` is a primop that, for a `Word` of 8, 16, 32 or 64 bits,
  reverses the order of its bits e.g. `0b110001` becomes `0b100011`.
  These primitives use optimized machine instructions when available.

- Add Int# multiplication primop:

      timesInt2# :: Int# -> Int# -> (# Int#, Int#, Int# #)

   `timesInt2#` computes the multiplication of its two parameters and returns a
   triple (isHighNeeded,high,low) where high and low are respectively the high
   and low bits of the double-word result. isHighNeeded is a cheap way to test
   if the high word is a sign-extension of the low word (isHighNeeded = 0#) or
   not (isHighNeeded = 1#).

## 0.6.0

- Shipped with GHC 8.8.1

- Added to `GHC.Prim`:

        traceBinaryEvent# :: Addr# -> Int# -> State# s -> State# s

## 0.5.3

- Shipped with GHC 8.6.1

- Added to `GHC.Prim`:

        addWordC# :: Word# -> Word# -> (# Word#, Int# #)

- `unpackClosure#` can now unpack any valid Haskell closure.
  Previously it returned empty pointer and non-pointer arrays
  for thunks.

- Add unaligned bytearray access primops (#4442)

         readWord8ArrayAsChar# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Char# #)
         readWord8ArrayAsAddr# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Addr# #)
         readWord8ArrayAsFloat# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Float# #)
         readWord8ArrayAsDouble# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Double# #)
         readWord8ArrayAsStablePtr# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, StablePtr# #)
         readWord8ArrayAsInt16# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Int16# #)
         readWord8ArrayAsInt32# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Int32# #)
         readWord8ArrayAsInt64# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Int64# #)
         readWord8ArrayAsInt# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Int# #)

         readWord8ArrayAsWord16# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Word16# #)
         readWord8ArrayAsWord32# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Word32# #)
         readWord8ArrayAsWord64# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Word64# #)
         readWord8ArrayAsWord# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Word# #)

         writeWord8ArrayAsChar# :: MutableByteArray# s -> Int# -> Char# -> State# s -> State# s
         writeWord8ArrayAsAddr# :: MutableByteArray# s -> Int# -> Addr# -> State# s -> State# s
         writeWord8ArrayAsFloat# :: MutableByteArray# s -> Int# -> Float# -> State# s -> State# s
         writeWord8ArrayAsDouble# :: MutableByteArray# s -> Int# -> Double# -> State# s -> State# s
         writeWord8ArrayAsStablePtr# :: MutableByteArray# s -> Int# -> StablePtr# -> State# s -> State# s

         writeWord8ArrayAsInt16# :: MutableByteArray# s -> Int# -> Int16# -> State# s -> State# s
         writeWord8ArrayAsInt32# :: MutableByteArray# s -> Int# -> Int32# -> State# s -> State# s
         writeWord8ArrayAsInt64# :: MutableByteArray# s -> Int# -> Int64# -> State# s -> State# s
         writeWord8ArrayAsInt# :: MutableByteArray# s -> Int# -> Int# -> State# s -> State# s

         writeWord8ArrayAsWord16# :: MutableByteArray# s -> Int# -> Word16# -> State# s -> State# s
         writeWord8ArrayAsWord32# :: MutableByteArray# s -> Int# -> Word32# -> State# s -> State# s
         writeWord8ArrayAsWord64# :: MutableByteArray# s -> Int# -> Word64# -> State# s -> State# s
         writeWord8ArrayAsWord# :: MutableByteArray# s -> Int# -> Word# -> State# s -> State# s

## 0.5.2.0

- Shipped with GHC 8.4.1

- Added to `GHC.Prim`:

        compareByteArrays# :: ByteArray# -> Int# -> ByteArray# -> Int# -> Int# -> Int#

- Don't allocate a thunk for each unpacked UTF-8 character in `unpackCStringUtf8#`

## 0.5.1.1 *November 2017*

- Shipped with GHC 8.2.2

- Changed strictness properties of `catchRetry#` (#14171)

## 0.5.1.0 *July 2017*

- Shipped with GHC 8.2.1

- Added to `GHC.Prim`:

        fabsDouble# :: Double# -> Double#
        fabsFloat# :: Float# -> Float#
        isByteArrayPinned# :: ByteArray# -> Int#
        isMutableByteArrayPinned# :: MutableByteArray# s -> Int#
        anyToAddr# :: a -> State# (RealWorld) -> (# State# (RealWorld),Addr# #)

- New primitives for compact regions in `GHC.Prim`:

        Compact#
        compactNew#
        compactResize#
        compactContains#
        compactContainsAny#
        compactGetFirstBlock#
        compactGetNextBlock#
        compactAllocateBlock#
        compactFixupPointers#
        compactAdd#
        compactAddWithSharing#
        compactSize#

- Generalised `noDuplicate#` from

        noDuplicate# :: State# (RealWorld) -> State# (RealWorld)

    to

        noDuplicate# :: State# s -> State# s


## 0.5.0.0

- Shipped with GHC 8.0.1

- `GHC.Classes`: new `class IP (a :: Symbol) b | a -> b`

- `GHC.Prim`: changed type signatures from

        check# :: (State# RealWorld -> (# State# RealWorld, a #)) -> State# RealWorld -> (# State# RealWorld, () #)
        finalizeWeak# :: Weak# a -> State# RealWorld -> (# State# RealWorld, Int#, State# RealWorld -> (# State# RealWorld, () #) #)
        mkWeak# :: a -> b -> c -> State# RealWorld -> (# State# RealWorld, Weak# b #)

    to

        check# :: (State# RealWorld -> (# State# RealWorld, a #)) -> State# RealWorld -> State# RealWorld
        finalizeWeak# :: Weak# a -> State# RealWorld -> (# State# RealWorld, Int#, State# RealWorld -> (# State# RealWorld, b #) #)
        mkWeak# :: a -> b -> (State# RealWorld -> (# State# RealWorld, c #)) -> State# RealWorld -> (# State# RealWorld, Weak# b #)

- Removed from `GHC.Prim`:

        parAt# :: b -> a -> Int# -> Int# -> Int# -> Int# -> c -> Int#
        parAtAbs# :: a -> Int# -> Int# -> Int# -> Int# -> Int# -> b -> Int#
        parAtForNow# :: b -> a -> Int# -> Int# -> Int# -> Int# -> c -> Int#
        parAtRel# :: a -> Int# -> Int# -> Int# -> Int# -> Int# -> b -> Int#
        parGlobal# :: a -> Int# -> Int# -> Int# -> Int# -> b -> Int#
        parLocal# :: a -> Int# -> Int# -> Int# -> Int# -> b -> Int#

- Added to `GHC.Prim`:

        getSizeofMutableByteArray# :: MutableByteArray# d -> State# d -> (# State# d, Int# #)
        subWordC# :: Word# -> Word# -> (# Word#, Int# #)
        runRW# :: (State# RealWorld -> (# State# RealWorld, o #)) -> (# State# RealWorld, o #)

- Added to `GHC.Types`:

        data Module = Module TrName TrName
        data Nat
        data Symbol
        data TrName = TrNameS Addr# | TrNameD [Char]
        data TyCon = TyCon Word# Word# Module TrName