Create 8.8.1 release notes

Summary:
I have some pending commits which will debut in GHC 8.8.1,
but we don't yet have release notes for this. This adds them, and
deletes the stale 8.4.1 and 8.4.2 release notes.

Test Plan: Read it

Reviewers: bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D5025

3 files changed, 20 insertions, 466 deletions

diff --git a/docs/users_guide/8.4.2-notes.rst b/8.8.1-notes.rst
index e579e83c7c..f77c50eb02 100644
--- a/docs/users_guide/8.4.2-notes.rst
+++ b/8.8.1-notes.rst
@@ -1,59 +1,50 @@
-.. _release-8-4-2:
+.. _release-8-8-1:
 
-Release notes for version 8.4.2
+Release notes for version 8.8.1
 ===============================
 
-TODO
+The significant changes to the various parts of the compiler are listed in the
+following sections. There have also been numerous bug fixes and performance
+improvements over the 8.6.1 release.
+
 
 Highlights
 ----------
 
-The highlights, since the 8.4.1 release, are:
+The highlights, since the 8.6.1 release, are:
 
-- TODO
+- Many, many bug fixes.
 
 
 Full details
 ------------
 
-
 Language
-~~~~~~~~
+~~~~~~~
 
-- Fix a regression in which derived ``Read`` instances for record data types
-  with field names ending with ``#`` (by way of :ghc-flag:`-XMagicHash`) would
-  no longer parse valid output.
 
 Compiler
-~~~~~~~~
+~~~~~~~
 
 
 Runtime system
-~~~~~~~~~~~~~~
+~~~~~~~~~~~~~
 
 
 Template Haskell
-~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~
 
 
 ``ghc`` library
-~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~
 
 
 ``base`` library
-~~~~~~~~~~~~~~~~
-
-- Add the ``readFieldHash`` function to ``GHC.Read`` which behaves like
-  ``readField``, but for a field that ends with a ``#`` symbol.
-
-``integer-gmp`` library
-~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~
 
-- Define ``powModSecInteger``, a "secure" version of ``powModInteger`` using
-  the ``mpz_powm_sec`` function.
 
 Build system
-~~~~~~~~~~~~
+~~~~~~~~~~~
 
 
 Included libraries
@@ -77,7 +68,9 @@ for further change information.
     compiler/ghc.cabal:                      The compiler itself
     libraries/ghci/ghci.cabal:               The REPL interface
     libraries/ghc-boot/ghc-boot.cabal:       Internal compiler library
+    libraries/ghc-boot-th/ghc-boot-th.cabal: Internal compiler library
     libraries/ghc-compact/ghc-compact.cabal: Core library
+    libraries/ghc-heap/ghc-heap.cabal:       GHC heap-walking library
     libraries/ghc-prim/ghc-prim.cabal:       Core library
     libraries/haskeline/haskeline.cabal:     Dependency of ``ghci`` executable
     libraries/hpc/hpc.cabal:                 Dependency of ``hpc`` executable
@@ -85,7 +78,9 @@ for further change information.
     libraries/mtl/mtl.cabal:                 Dependency of ``Cabal`` library
     libraries/parsec/parsec.cabal:           Dependency of ``Cabal`` library
     libraries/process/process.cabal:         Dependency of ``ghc`` library
+    libraries/stm/stm.cabal:                 Dependency of ``haskeline`` library
     libraries/template-haskell/template-haskell.cabal:     Core library
+    libraries/terminfo/terminfo.cabal:       Dependency of ``haskeline`` library
     libraries/text/text.cabal:               Dependency of ``Cabal`` library
     libraries/time/time.cabal:               Dependency of ``ghc`` library
     libraries/transformers/transformers.cabal: Dependency of ``ghc`` library
diff --git a/docs/users_guide/8.4.1-notes.rst b/docs/users_guide/8.4.1-notes.rst
deleted file mode 100644
index 305f9629c0..0000000000
--- a/docs/users_guide/8.4.1-notes.rst
+++ /dev/null
@@ -1,441 +0,0 @@
-.. _release-8-4-1:
-
-Release notes for version 8.4.1
-===============================
-
-The significant changes to the various parts of the compiler are listed in the
-following sections. There have also been numerous bug fixes and performance
-improvements over the 8.2.1 release.
-
-
-Highlights
-----------
-
-The highlights, since the 8.2.1 release, are:
-
-- GHC is now capable of deriving more instances
-
-- More refinement of the :ghc-flag:`-XTypeInType` story and improvements in type
-  error messages.
-
-- Further improvements in code generation
-
-- Many, many bug fixes.
-
-
-Full details
-------------
-
-Language
-~~~~~~~~
-
-- Data families have been generalised a bit: a data family declaration can now
-  end with a kind variable ``k`` instead of ``Type``. Additionally, data/newtype
-  instance no longer need to list all the patterns of the family if they don't
-  wish to; this is quite like how regular datatypes with a kind signature can omit
-  some type variables.
-
-- There are now fewer restrictions regarding whether kind variables can appear
-  on the right-hand sides of type and data family instances. Before, there was
-  a strict requirements that all kind variables on the RHS had to be explicitly
-  bound by type patterns on the LHS. Now, kind variables can be *implicitly*
-  bound, which allows constructions like these: ::
-
-    data family Nat :: k -> k -> *
-    -- k is implicitly bound by an invisible kind pattern
-    newtype instance Nat :: (k -> *) -> (k -> *) -> * where
-      Nat :: (forall xx. f xx -> g xx) -> Nat f g
-
-    class Funct f where
-      type Codomain f :: *
-    instance Funct ('KProxy :: KProxy o) where
-      -- o is implicitly bound by the kind signature
-      -- of the LHS type pattern ('KProxy)
-      type Codomain 'KProxy = NatTr (Proxy :: o -> *)
-
-- Implicitly bidirectional pattern synonyms no longer allow bang patterns
-  (``!``) or irrefutable patterns (``~``) on the right-hand side. Previously,
-  this was allowed, although the bang patterns and irrefutable patterns would
-  be silently ignored when used in an expression context. This is now a proper
-  error, and explicitly bidirectional pattern synonyms should be used in their
-  stead. That is, instead of using this (which is an error): ::
-
-      pattern StrictJust a = Just !a
-
-  Use this: ::
-
-      pattern StrictJust a <- Just !a where
-        StrictJust !a = Just a
-
-- GADTs with kind-polymorphic type arguments now require :ghc-flag:`-XTypeInType`.
-  For instance, consider the following, ::
-
-      data G :: k -> * where
-        GInt   :: G Int
-        GMaybe :: G Maybe
-
-  In previous releases this would compile with :ghc-flag:`-XPolyKinds` alone due
-  to bug :ghc-ticket:`13391`. As of GHC 8.4, however, this requires
-  :ghc-flag:`-XTypeInType`. Note that since GADT kind signatures aren't generalized,
-  this will also require that you provide a :ref:`CUSK
-  <complete-kind-signatures>` by explicitly quantifying over the kind argument,
-  ``k``, ::
-
-      data G :: forall k. k -> * where
-        GInt   :: G Int
-        GMaybe :: G Maybe
-
-- The order in which type variables are quantified in GADT constructor type
-  signatures has changed. Before, if you had ``MkT`` as below: ::
-
-      data T a where
-        MkT :: forall b a. b -> T a
-
-  Then the type of ``MkT`` would (counterintuitively) be
-  ``forall a b. b -> T a``! Now, GHC quantifies the type variables in the
-  order that the users writes them, so the type of ``MkT`` is now
-  ``forall b a. b -> T a`` (this matters for :ghc-flag:`-XTypeApplications`).
-
-- The new :ghc-flag:`-XEmptyDataDeriving` extension allows deriving ``Eq``,
-  ``Ord``, ``Read``, and ``Show`` instances directly for empty data types, as
-  in ``data Empty deriving Eq``. (Previously, this would require the use of
-  :ghc-flag:`-XStandaloneDeriving` to accomplish.)
-
-  One can also now derive ``Data`` instances directly for empty data types (as
-  in ``data Empty deriving Data``) without needing to use
-  :ghc-flag:`-XStandaloneDeriving`. However, since already requires a GHC
-  extension (:ghc-flag:`-XDeriveDataTypeable`), one does not need to enable
-  :ghc-flag:`-XEmptyDataDeriving` to do so. This also goes for other classes
-  which require extensions to derive, such as :ghc-flag:`-XDeriveFunctor`.
-
-- Hexadecimal floating point literals (e.g. ``0x0.1p4``), enabled with
-  :ghc-flag:`-XHexFloatLiterals`.  See
-  :ref:`Hexadecimal floating point literals <hex-float-literals>`
-  for the full details.
-
-Compiler
-~~~~~~~~
-
-- LLVM code generator (e.g. :ghc-flag:`-fllvm`) compatible with LLVM releases in
-  the |llvm-version| series.
-
-- Add warning flag :ghc-flag:`-Wmissing-export-lists` which causes the type
-  checker to warn when a module does not include an explicit export list.
-
-- The ``configure`` script now no longer accepts ``--with-TOOL`` flags (e.g.
-  ``--with-nm``, ``--with-ld``, etc.). Instead, these are taken from environment
-  variables, as is typical in ``autoconf`` scripts. For instance,
-  ``./configure --with-nm=/usr/local/bin/nm`` turns into
-  ``./configure NM=/usr/local/bin/nm``.
-
-- Derived ``Functor``, ``Foldable``, and ``Traversable`` instances are now
-  optimized when their last type parameters have phantom roles.
-  Specifically, ::
-
-    fmap _ = coerce
-    traverse _ x = pure (coerce x)
-    foldMap _ _ = mempty
-
-  These definitions of ``foldMap`` and ``traverse`` are lazier than the ones we
-  would otherwise derive, as they may produce results without inspecting their
-  arguments at all.
-
-  See also :ref:`deriving-functor`, :ref:`deriving-foldable`, and
-  :ref:`deriving-traversable`.
-
-- Derived instances for empty data types are now substantially different
-  than before. Here is an overview of what has changed. These examples will
-  use a running example of ``data Empty a`` to describe what happens when an
-  instance is derived for ``Empty``:
-
-  - Derived ``Eq`` and ``Ord`` instances would previously emit code that used
-    ``error``: ::
-
-      instance Eq (Empty a) where
-        (==) = error "Void =="
-
-      instance Ord (Empty a) where
-        compare = error "Void compare"
-
-    Now, they emit code that uses maximally defined, lazier semantics: ::
-
-      instance Eq (Empty a) where
-        _ == _ = True
-
-      instance Ord (Empty a) where
-        compare _ _ = EQ
-
-  - Derived ``Read`` instances would previous emit code that used
-    ``parens``: ::
-
-      instance Read (Empty a) where
-        readPrec = parens pfail
-
-    But ``parens`` forces parts of the parsed string that it doesn't need to.
-    Now, the derived instance will not use ``parens`` (that it, parsing
-    ``Empty`` will always fail, without reading *any* input): ::
-
-      instance Read (Empty a) where
-        readPrec = pfail
-
-  - Derived ``Show`` instances would previously emit code that used
-    ``error``: ::
-
-      instance Show (Empty a) where
-        showsPrec = error "Void showsPrec"
-
-    Now, they emit code that inspects the argument. That is, if the argument
-    diverges, then showing it will also diverge: ::
-
-      instance Show (Empty a) where
-        showsPrec _ x = case x of {}
-
-  - Derived ``Functor``, ``Foldable``, ``Traversable``, ``Generic``,
-    ``Generic1``, ``Lift``, and ``Data`` instances previously emitted code that
-    used ``error``: ::
-
-      instance Functor Empty where
-        fmap = error "Void fmap"
-
-      instance Foldable Empty where
-        foldMap = error "Void foldMap"
-
-      instance Traversable Empty where
-        traverse = error "Void traverse"
-
-      instance Generic (Empty a) where
-        from = M1 (error "No generic representation for empty datatype Empty")
-        to (M1 _) = error "No values for empty datatype Empty"
-      -- Similarly for Generic1
-
-      instance Lift (Empty a) where
-        lift _ = error "Can't lift value of empty datatype Empty"
-
-      instance Data a => Data (Empty a) where
-        gfoldl _ _ _ = error "Void gfoldl"
-        toConstr _ = error "Void toConstr"
-        ...
-
-    Now, derived ``Functor``, ``Traversable, ``Generic``, ``Generic1``,
-    ``Lift``, and ``Data`` instances emit code which inspects their
-    arguments: ::
-
-      instance Functor Empty where
-        fmap _ x = case x of {}
-
-      instance Traversable Empty where
-        traverse _ x = pure (case x of {})
-
-      instance Generic (Empty a) where
-        from x = M1 (case x of {})
-        to (M1 x) = case x of {}
-
-      -- Similarly for Generic1
-
-      instance Lift (Empty a) where
-        lift x = pure (case x of {})
-
-      instance Data a => Data (Empty a) where
-        gfoldl _ x = case x of {}
-        toConstr x = case x of {}
-        ...
-
-    Derived ``Foldable`` instances now are maximally lazy: ::
-
-      instance Foldable Empty where
-        foldMap _ _ = mempty
-
-- Derived ``Foldable`` instances now derive custom definitions for ``null``
-  instead of using the default one. This leads to asymptotically better
-  performance for recursive types not shaped like cons-lists, and allows ``null``
-  to terminate for more (but not all) infinitely large structures.
-
-- :ghc-flag:`-fsplit-sections` is now supported on x86_64 Windows and is on by default.
-  See :ghc-ticket:`12913`.
-
-- Configure on Windows now supports the ``--enable-distro-toolchain``
-  ``configure`` flag, which can be used to build a GHC using compilers on your
-  ``PATH`` instead of using the bundled bindist. See :ghc-ticket:`13792`
-
-- GHC now enables :ghc-flag:`-fllvm-pass-vectors-in-regs` by default. This means
-  that GHC will now use native vector registers to pass vector arguments across
-  function calls.
-
-- The optional ``instance`` keyword is now usable in type family instance
-  declarations. See :ghc-ticket:`13747`
-
-- Lots of other bugs. See `Trac <https://ghc.haskell.org/trac/ghc/query?status=closed&milestone=8.4.1&col=id&col=summary&col=status&col=type&col=priority&col=milestone&col=component&order=priority>`_
-  for a complete list.
-
-- New flags :ghc-flag:`-fignore-optim-changes` and
-  :ghc-flag:`-fignore-hpc-changes` allow GHC to reuse previously compiled
-  modules even if they were compiled with different optimisation or HPC
-  flags. These options are enabled by default by :ghc-flag:`--interactive`.
-  See :ghc-ticket:`13604`
-
-Runtime system
-~~~~~~~~~~~~~~
-
-- Function ``hs_add_root()`` was removed. It was a no-op since GHC-7.2.1
-  where module initialisation stopped requiring a call to ``hs_add_root()``.
-
-- Proper import library support added to GHC which can handle all of the libraries produced
-  by ``dlltool``. The limitation of them needing to be named with the suffix
-  ``.dll.a`` is also removed. See :ghc-ticket:`13606`, :ghc-ticket:`12499`,
-  :ghc-ticket:`12498`
-
-- The GHCi runtime linker on Windows now supports the ``big-obj`` file format.
-
-- The runtime system's :ref:`native stack backtrace <backtrace-signal>` support
-  on POSIX platforms is now triggered by ``SIGQUIT`` instead of ``SIGUSR2`` as
-  it was in previous releases. This change is to bring GHC's behavior into
-  compliance with the model set by the most Java virtual machine
-  implementations.
-
-- The GHC runtime on Windows now uses Continue handlers instead of Vectorized
-  handlers to trap exceptions. This change gives other exception handlers a chance
-  to handle the exception before the runtime does. Furthermore The RTS flag
-  :rts-flag:`--install-seh-handlers=<yes|no>` Can be used on Wndows to
-  completely disable the runtime's handling of exceptions. See
-  :ghc-ticket:`13911`, :ghc-ticket:`12110`.
-
-- The GHC runtime on Windows can now generate crash dumps on unhandled exceptions
-  using the RTS flag :rts-flag:`--generate-crash-dumps`.
-
-- The GHCi runtime linker now avoid calling GCC to find libraries as much as possible by caching
-  the list of search directories of GCC and querying the file system directly. This results in
-  much better performance, especially on Windows.
-
-- The GHC runtime on Windows can now generate stack traces on unhandled exceptions.
-  When running in GHCi more information is displayed about the symbols if available.
-  This behavior can be controlled with the RTS flag `--generate-stack-traces=<yes|no>`.
-
-Template Haskell
-~~~~~~~~~~~~~~~~
-
-- Template Haskell now reifies data types with GADT syntax accurately.
-  Previously, TH used heuristics to determine whether a data type
-  should be reified using GADT syntax, which could lead to incorrect results,
-  such as ``data T1 a = (a ~ Int) => MkT1`` being reified as a GADT and
-  ``data T2 a where MkT2 :: Show a => T2 a`` *not* being reified as a GADT.
-
-  In addition, reified GADT constructors now more accurately track the order in
-  which users write type variables. Before, if you reified ``MkT`` as below: ::
-
-      data T a where
-        MkT :: forall b a. b -> T a
-
-  Then the reified type signature of ``MkT`` would have been headed by
-  ``ForallC [PlainTV a, PlainTV b]``. Now, reifying ``MkT`` will give a type
-  headed by ``ForallC [PlainTV b, PlainTV a]``, as one would expect.
-
-
-- ``Language.Haskell.TH.FamFlavour``, which was deprecated in GHC 8.2,
-  has been removed.
-
-``ghc`` library
-~~~~~~~~~~~~~~~
-
-- hsSyn Abstract Syntax Tree (AST) is now extensible via the mechanism described in `Trees that Grow <http://www.jucs.org/jucs_23_1/trees_that_grow/jucs_23_01_0042_0062_najd.pdf>`_
-
-  The main change for users of the GHC API is that the AST is no longer indexed
-  by the type used as the identifier, but by a specific index type, ::
-
-      type GhcPs   = GhcPass 'Parsed      -- Old 'RdrName' type param
-      type GhcRn   = GhcPass 'Renamed     -- Old 'Name' type param
-      type GhcTc   = GhcPass 'Typechecked -- Old 'Id' type para,
-      type GhcTcId = GhcTc                -- Old 'TcId' type param
-
-  The simplest way to support the current GHC as well as earlier ones is to define ::
-
-      #if MIN_VERSION_ghc(8,3,0)
-      type ParseI     = GhcPs
-      type RenameI    = GhcRn
-      type TypecheckI = GhcTc
-      #else
-      type ParseI     = RdrName
-      type RenameI    = Name
-      type TypecheckI = Var
-      #endif
-
-  and then replace all hardcoded index types accordingly. For polymorphic types,
-  the constraint ::
-
-      #if MIN_VERSION_ghc(8,3,0)
-      -- |bundle up the constraints required for a trees that grow pass
-      type IsPass pass = (DataId pass, OutputableBndrId pass, SourceTextX pass)
-      else
-      type IsPass pass = (DataId pass, OutputableBndrId pass)
-      #endif
-
-  can be used.
-
-``base`` library
-~~~~~~~~~~~~~~~~
-
-- Blank strings can now be used as values for environment variables using the
-  ``System.Environment.Blank`` module. See :ghc-ticket:`12494`
-
-- ``Data.Type.Equality.==`` is now a closed type family. It works for all kinds
-  out of the box. Any modules that previously declared instances of this family
-  will need to remove them. Whereas the previous definition was somewhat ad
-  hoc, the behavior is now completely uniform. As a result, some applications
-  that used to reduce no longer do, and conversely. Most notably, ``(==)`` no
-  longer treats the ``*``, ``j -> k``, or ``()`` kinds specially; equality is
-  tested structurally in all cases.
-
-Build system
-~~~~~~~~~~~~
-
-- ``dll-split`` has been removed and replaced with an automatic partitioning utility ``gen-dll``.
-  This utility can transparently split and compile any DLLs that require this. Note that the ``rts`` and
-  ``base`` can not be split at this point because of the mutual recursion between ``base`` and ``rts``.
-  There is currently no explicit dependency between the two in the build system and such there is no way
-  to notify ``base`` that the ``rts`` has been split, or vice versa.
-  (see :ghc-ticket:`5987`).
-
-
-Included libraries
-------------------
-
-The package database provided with this distribution also contains a number of
-packages other than GHC itself. See the changelogs provided with these packages
-for further change information.
-
-.. ghc-package-list::
-
-    libraries/array/array.cabal:             Dependency of ``ghc`` library
-    libraries/base/base.cabal:               Core library
-    libraries/binary/binary.cabal:           Dependency of ``ghc`` library
-    libraries/bytestring/bytestring.cabal:   Deppendency of ``ghc`` library
-    libraries/Cabal/Cabal/Cabal.cabal:       Dependency of ``ghc-pkg`` utility
-    libraries/containers/containers.cabal:   Dependency of ``ghc`` library
-    libraries/deepseq/deepseq.cabal:         Dependency of ``ghc`` library
-    libraries/directory/directory.cabal:     Dependency of ``ghc`` library
-    libraries/filepath/filepath.cabal:       Dependency of ``ghc`` library
-    compiler/ghc.cabal:                      The compiler itself
-    libraries/ghci/ghci.cabal:               The REPL interface
-    libraries/ghc-boot/ghc-boot.cabal:       Internal compiler library
-    libraries/ghc-compact/ghc-compact.cabal: Core library
-    libraries/ghc-prim/ghc-prim.cabal:       Core library
-    libraries/haskeline/haskeline.cabal:     Dependency of ``ghci`` executable
-    libraries/hpc/hpc.cabal:                 Dependency of ``hpc`` executable
-    libraries/integer-gmp/integer-gmp.cabal: Core library
-    libraries/mtl/mtl.cabal:                 Dependency of ``Cabal`` library
-    libraries/parsec/parsec.cabal:           Dependency of ``Cabal`` library
-    libraries/process/process.cabal:         Dependency of ``ghc`` library
-    libraries/template-haskell/template-haskell.cabal:     Core library
-    libraries/text/text.cabal:               Dependency of ``Cabal`` library
-    libraries/time/time.cabal:               Dependency of ``ghc`` library
-    libraries/transformers/transformers.cabal: Dependency of ``ghc`` library
-    libraries/unix/unix.cabal:               Dependency of ``ghc`` library
-    libraries/Win32/Win32.cabal:             Dependency of ``ghc`` library
-    libraries/xhtml/xhtml.cabal:             Dependency of ``haddock`` executable
-
-Win32
-~~~~~
-
-.. attention::
-
-    This release is a backwards incompatible release which corrects the type of
-    certain APIs. See issue `#24 <https://github.com/haskell/win32/issues/24>`_.
diff --git a/docs/users_guide/index.rst b/docs/users_guide/index.rst
index 7f42dca802..c20aec7e56 100644
--- a/docs/users_guide/index.rst
+++ b/docs/users_guide/index.rst
@@ -12,8 +12,8 @@ Contents:
 
    license
    intro
-   8.4.2-notes
    8.6.1-notes
+   8.8.1-notes
    ghci
    runghc
    usage