7.12.1-notes.rst 9.87 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
.. _release-7-12-1:

Release notes for version 7.12.1
================================

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 7.10 branch.

Highlights
----------

The highlights, since the 7.10 branch, are:

-  TODO FIXME

Full details
------------

Language
~~~~~~~~

-  TODO FIXME.

-  The parser now supports Haddock comments on GADT data constructors.
   For example,

   ::

                             data Expr a where
                               -- | Just a normal sum
                               Sum :: Int -> Int -> Expr Int

-  Implicit parameters of the new ghc-prim type ``GHC.Types.CallStack``
   are treated specially, and automatically solved for the current
   source location. For example

   ::

                             f = print (?stk :: CallStack)

   will print the singleton stack containing the occurrence of ``?stk``.
   If there is another ``CallStack`` implicit in-scope, the new location
   will be appended to the existing stack, e.g.

   ::

                             f :: (?stk :: CallStack) => IO ()
                             f = print (?stk :: CallStack)

   will print the occurrence of ``?stk`` and the call-site of ``f``. The
   name of the implicit parameter does not matter.

   See the release notes for ghc-prim for a description of the
   ``CallStack`` type.

-  To conform to the common case, the default role assigned to
   parameters of datatypes declared in ``hs-boot`` files is
   ``representational``. However, if the constructor(s) for the datatype
   are given, it makes sense to do normal role inference. This is now
   implemented, effectively making the default role for non-abstract
   datatypes in ``hs-boot`` files to be ``phantom``, like it is in
   regular Haskell code.

-  Wildcards can be used in the type arguments of type/data family
   instance declarations to indicate that the name of a type variable
   doesn't matter. They will be replaced with new unique type variables.
   See :ref:`data-instance-declarations` for more details.

-  GHC now allows to declare type families as injective. Injectivity
   information can then be used by the typechecker. See
   :ref:`injective-ty-fams` for details.

-  Due to a :ghc-ticket:`security issue <10826>`, Safe Haskell now forbids
   annotations in programs marked as ``-XSafe``.

77
78
79
-  Generic instances can be derived for data types whose constructors have
   arguments with certain unlifted types. See :ref:`generic-programming` for
   more details.
80

81
82
83
-  The ``-XDeriveAnyClass`` extension now fills in associated type family
   default instances when deriving a class that contains them.

84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
Compiler
~~~~~~~~

-  Added the option ``-dth-dec-file``. This dumps out a .th.hs file of
   all Template Haskell declarations in a corresponding .hs file. The
   idea is that application developers can check this into their
   repository so that they can grep for identifiers used elsewhere that
   were defined in Template Haskell. This is similar to using
   ``-ddump-to-file`` with ``-ddump-splices`` but it always generates a
   file instead of being coupled to ``-ddump-to-file`` and only outputs
   code that does not exist in the .hs file and a comment for the splice
   location in the original file.

-  Added the option ``-fprint-expanded-types``. When enabled, GHC also
   prints type-synonym-expanded types in type errors.

-  Added the option ``-fcpr-anal``. When enabled, the demand analyser
   performs CPR analysis. It is implied by ``-O``. Consequently,
   ``-fcpr-off`` is now removed, run with ``-fno-cpr-anal`` to get the
   old ``-fcpr-off`` behaviour.

GHCi
~~~~

-  ``Main`` with an explicit module header but without ``main`` is now
   an error (#7765).

111
-  The ``:back`` and ``:forward`` commands now take an optional count
112
113
114
   allowing the user to move forward or backward in history several
   steps at a time.

115
-  Added commands ``:load!`` and ``:reload!``, effectively setting
116
117
118
   "-fdefer-type-errors" before loading a module and unsetting it after
   loading if it has not been set before (#8353).

119
120
-  ``ghci -e`` now behaves like ``ghc -e`` (#9360).

121
122
123
124
125
126
127
128
129
130
131
132
Template Haskell
~~~~~~~~~~~~~~~~

-  The ``TemplateHaskell`` now no longer automatically errors when used
   with a stage 1 compiler (i.e. GHC without interpreter support); in
   particular, plain Haskell quotes (not quasi-quotes) can now be
   compiled without erroring. Splices and quasi-quotes continue to only
   be supported by a stage 2 compiler.

-  Partial type signatures can now be used in splices, see
   :ref:`pts-where`.

133
134
135
136
-  ``Template Haskell`` now fully supports typed holes and quoting unbound
   variables.  This means it is now possible to use pattern splices nested
   inside quotation brackets.

137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
-  ``Template Haskell`` now supports the use of ``UInfixT`` in types to
   resolve infix operator fixities, in the same vein as ``UInfixP`` and
   ``UInfixE`` in patterns and expressions. ``ParensT`` and ``InfixT``
   have also been introduced, serving the same functions as their
   pattern and expression counterparts.

-  Primitive chars (e.g., ``[| 'a'# |]``) and primitive strings (e.g.,
   ``[| "abc"# |]``) can now be quoted with Template Haskell. The
   ``Lit`` data type also has a new constructor, ``CharPrimL``, for
   primitive char literals.

-  ``addTopDecls`` now accepts annotation pragmas.

-  Internally, the implementation of quasi-quotes has been unified with
   that of normal Template Haskell splices. Under the previous
   implementation, top-level declaration quasi-quotes did not cause a
   break in the declaration groups, unlike splices of the form
   ``$(...)``. This behavior has been preserved under the new
   implementation, and is now recognized and documented in
   :ref:`th-syntax`.

-  The ``Lift`` class is now derivable via the ``-XDeriveLift`` extension. See
   :ref:`deriving-lift` for more information.


Runtime system
~~~~~~~~~~~~~~

-  TODO FIXME.

Build system
~~~~~~~~~~~~

-  TODO FIXME.

Package system
~~~~~~~~~~~~~~

-  TODO FIXME.

Libraries
---------

array
~~~~~

-  Version number XXXXX (was 0.5.0.0)

base
~~~~

-  Version number XXXXX (was 4.7.0.0)

-  A new module ``GHC.SrcLoc`` was added, exporting a new type
   ``SrcLoc``. A ``SrcLoc`` contains package, module, and file names, as
   well as start and end positions.

-  A new type ``CallStack`` was added for use with the new implicit
   callstack parameters. A ``CallStack`` is a ``[(String, SrcLoc)]``,
   sorted by most-recent call.

-  A new function, ``interruptible``, was added to ``GHC.IO`` allowing
   an ``IO`` action to be run such that it can be interrupted by an
   asynchronous exception, even if exceptions are masked (except if
   masked with ``interruptibleMask``).

   This was introduced to fix the behavior of ``allowInterrupt``, which
   would previously incorrectly allow exceptions in uninterruptible
   regions (see :ghc-ticket:`9516`).

-  Per-thread allocation counters (``setAllocationCounter`` and
   ``getAllocationCounter``) and limits (``enableAllocationLimit``,
   ``disableAllocationLimit`` are now available from ``System.Mem``. Previously
   this functionality was only available from ``GHC.Conc``.


binary
~~~~~~

-  Version number XXXXX (was 0.7.1.0)

bytestring
~~~~~~~~~~

-  Version number XXXXX (was 0.10.4.0)

Cabal
~~~~~

-  Version number XXXXX (was 1.18.1.3)

containers
~~~~~~~~~~

-  Version number XXXXX (was 0.5.4.0)

deepseq
~~~~~~~

-  Version number XXXXX (was 1.3.0.2)

directory
~~~~~~~~~

-  Version number XXXXX (was 1.2.0.2)

filepath
~~~~~~~~

-  Version number XXXXX (was 1.3.0.2)

ghc
~~~

-  TODO FIXME.

-  The ``HsBang`` type has been removed in favour of ``HsSrcBang`` and
   ``HsImplBang``. Data constructors now always carry around their
   strictness annotations as the user wrote them, whether from an
   imported module or not.

258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
-  Moved `startsVarSym`, `startsVarId`, `startsConSym`, `startsConId`,
   `startsVarSymASCII`, and `isVarSymChar` from `Lexeme` to the `GHC.Lemexe`
   module of the `ghc-boot` library.

ghc-boot
~~~~~~~~

-  This is an internal package. Use with caution.

-  This package was renamed from `bin-package-db` to reflect its new purpose
   of containing intra-GHC functionality that needs to be shared across
   multiple GHC boot libraries.

-  Added `GHC.Lexeme`, which contains functions for determining if a
   character can be the first letter of a variable or data constructor in
   Haskell, as defined by GHC. (These functions were moved from `Lexeme`
   in `ghc`.)

276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
ghc-prim
~~~~~~~~

-  Version number XXXXX (was 0.3.1.0)

haskell98
~~~~~~~~~

-  Version number XXXXX (was 2.0.0.3)

haskell2010
~~~~~~~~~~~

-  Version number XXXXX (was 1.1.1.1)

hoopl
~~~~~

-  Version number XXXXX (was 3.10.0.0)

hpc
~~~

-  Version number XXXXX (was 0.6.0.1)

integer-gmp
~~~~~~~~~~~

-  Version number XXXXX (was 0.5.1.0)

old-locale
~~~~~~~~~~

-  Version number XXXXX (was 1.0.0.6)

old-time
~~~~~~~~

-  Version number XXXXX (was 1.1.0.2)

process
~~~~~~~

-  Version number XXXXX (was 1.2.0.0)

template-haskell
~~~~~~~~~~~~~~~~

-  Version number XXXXX (was 2.9.0.0)

-  The ``Lift`` type class for lifting values into Template Haskell
   splices now has a default signature ``lift :: Data a => a -> Q Exp``,
   which means that you do not have to provide an explicit
   implementation of ``lift`` for types which have a ``Data`` instance.
   To manually use this default implementation, you can use the
   ``liftData`` function which is now exported from
   ``Language.Haskell.TH.Syntax``.

-  ``Info``'s constructors no longer have ``Fixity`` fields. A
   ``qReifyFixity`` function was added to the ``Quasi`` type class (as
   well as the ``reifyFixity`` function, specialized for ``Q``) to allow
   lookup of fixity information for any given ``Name``.

time
~~~~

-  Version number XXXXX (was 1.4.1)

unix
~~~~

-  Version number XXXXX (was 2.7.0.0)

Win32
~~~~~

-  Version number XXXXX (was 2.3.0.1)

Known bugs
----------

-  TODO FIXME