diff options
Diffstat (limited to 'docs/users_guide/9.4.1-notes.rst')
| -rw-r--r-- | docs/users_guide/9.4.1-notes.rst | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/docs/users_guide/9.4.1-notes.rst b/docs/users_guide/9.4.1-notes.rst index 91d866d982..cea17cac60 100644 --- a/docs/users_guide/9.4.1-notes.rst +++ b/docs/users_guide/9.4.1-notes.rst @@ -63,6 +63,9 @@ Compiler - New :ghc-flag:`-Wredundant-strictness-flags` that checks for strictness flags (``!``) applied to unlifted types, which are always strict. +- New :ghc-flag:`-Wforall-identifier` (enabled by default) that warns against + using the name ``forall`` as an identifer on the term level. + - New :ghc-flag:`-fprof-late` that adds automatic CCS annotations to all top level functions *after* core optimisation have been run. @@ -189,13 +192,19 @@ Compiler ``base`` library ~~~~~~~~~~~~~~~~ -- ``GHC.Exts.magicDict`` has been renamed to ``withDict`` and given a more - specific type: :: +- There's a new special function ``withDict`` in ``GHC.Exts``: :: 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 + where ``dt`` must be a class containing exactly one method, whose type + must be ``st``. + + This function converts ``st`` to a type class dictionary. + It removes the need for ``unsafeCoerce`` in implementation of reflection + libraries. It should be used with care, because it can introduce + incoherent instances. + + For example, the ``withTypeable`` function from the ``Data.Typeable`` module can now be defined as: :: withTypeable :: forall k (a :: k) rep (r :: TYPE rep). () @@ -205,6 +214,9 @@ Compiler Note that the explicit type applications are required, as the call to ``withDict`` would be ambiguous otherwise. + This replaces the old ``GHC.Exts.magicDict``, which required + an intermediate data type and was less reliable. + ``ghc-prim`` library ~~~~~~~~~~~~~~~~~~~~ @@ -255,7 +267,7 @@ Compiler ``unsafeThawSmallArray#``, ``copySmallArray#``, ``copySmallMutableArray#``, ``cloneSmallArray#``, ``cloneSmallMutableArray#``, ``freezeSmallArray#``, ``thawSmallArray#``, ``casSmallArray#``, - - ``newMutVar#``,``readMutVar#``,``writeMutV#``,``casMutVar#``, + - ``newMutVar#``, ``readMutVar#``, ``writeMutVar#``, ``casMutVar#``, - operations on ``MVar#`` and ``TVar#``: @@ -284,7 +296,7 @@ Compiler :: 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``. +- ``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#``. |