path: root/docs/users_guide/7.10.1-notes.xml

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<sect1 id="release-7-10-1">
  <title>Release notes for version 7.10.1</title>

  <para>
      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 7.8 branch.
  </para>

  <sect2>
    <title>Highlights</title>

    <para>
        The highlights, since the 7.8 branch, are:
    </para>

    <itemizedlist>
        <listitem>
            <para>
                TODO FIXME
           </para>
       </listitem>
   </itemizedlist>
  </sect2>

  <sect2>
    <title>Full details</title>
    <sect3>
        <title>Language</title>
        <itemizedlist>
            <listitem>
                <para>
                    Added support for <link linkend="binary-literals">binary integer literals</link>
               </para>
           </listitem>
            <listitem>
                <para>
                    Simplified rules for implicit quantification. In previous versions of GHC,
                    it was possible to use the <literal>=></literal> arrow
                    to quantify over type variables in <literal>data</literal> and
                    <literal>type</literal> declarations without a
                    <literal>forall</literal> quantifier. For example,
                    <literal>data Fun = Fun (Ord a => a -> b)</literal> was identical to
                    <literal>data Fun = Fun (forall a b. Ord a => a -> b)</literal>, while
                    <literal>data Fun = Fun (a -> b)</literal> caused a not-in-scope error.
                    This implicit quantification is now deprecated, and variables
                    in higher-rank constructors should be quantified with <literal>forall</literal>
                    regardless of whether a class context is present or not.
                    GHC 7.10 raises a warning (controlled by
                    <option>-fwarn-context-quantification</option>, enabled by default)
                    and GHC 7.12 will raise an error. See <link linkend="univ">examples</link>
                    in GHC documentation.
                </para>
                <para>
                    The change also applies to Template Haskell splices such as
                    <literal>[t|Ord a => a|]</literal>, which should be written as
                    <literal>[t|forall a. Ord a => a|]</literal>.
                </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>Compiler</title>
        <itemizedlist>
            <listitem>
                <para>
                    GHC now checks that all the language extensions required for
                    the inferred type signatures are explicitly enabled. This
                    means that if any of the type signatures inferred in your
                    program requires some language extension you will need to
                    enable it. The motivation is that adding a missing type
                    signature inferred by GHC should yield a program that
                    typechecks. Previously this was not the case.
                </para>
                <para>
                    This is a breaking change. Code that used to compile in the
                    past might fail with an error message requiring some
                    particular language extension (most likely
                    <option>-XTypeFamilies</option>, <option>-XGADTs</option> or
                    <option>-XFlexibleContexts</option>).
                </para>
                <para>
                    <option>-fwarn-tabs</option> warning flag is turned on by
                    default with this release of GHC. It can be suppressed
                    either by using <literal>GHC_OPTIONS</literal> pragma or by
                    specifying <option>-fno-warn-tabs</option> flag.
                </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>GHCi</title>
        <itemizedlist>
            <listitem>
                <para>
                    TODO FIXME
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>Template Haskell</title>
        <itemizedlist>
            <listitem>
                <para>
                    Added support for generating LINE pragma declarations
                    (<xref linkend="line-pragma"/>).
               </para>

               <para>
                    The type <literal>Pred</literal> (which stores a type
                    constraint) is now a synonym for <literal>Type</literal>,
                    in order to work with the <literal>ConstraintKinds</literal>
                    extension. This is a breaking change and may require
                    some rewriting of Template Haskell code.
               </para>

               <para>
                 <literal>reifyInstances</literal> now treats unbound type
                 variables as univerally quantified, allowing lookup of, say,
                 the instance for <literal>Eq [a]</literal>.
               </para>

               <para>
                 More kind annotations appear in reified types, in order to
                 disambiguate types that would otherwise be ambiguous in the
                 presence of <literal>PolyKinds</literal>. In particular, all
                 reified <literal>TyVarBndr</literal>s are now
                 <literal>KindedTV</literal>s. (This does not affect Template
                 Haskell quotations, just calls to <literal>reify</literal>.)
               </para>

               <para>
                 Various features unsupported in quotations were previously
                 silently ignored. These now cause errors.
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>Runtime system</title>
        <itemizedlist>
            <listitem>
                <para>
                    TODO FIXME
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>Build system</title>
        <itemizedlist>
            <listitem>
                <para>
                    <literal>ghc-pkg</literal> now respects <option>--user</option>
                    and <option>--global</option> when modifying packages (e.g.
                    changing exposed/trust flag or unregistering).  Previously,
                    <literal>ghc-pkg</literal> would ignore these flags and modify
                    whichever package it found first on the database stack.  To
                    recover the old behavior, simply omit these flags.
               </para>
           </listitem>
            <listitem>
                <para>
                    <literal>ghc-pkg</literal> accepts a <option>--user-package-db</option>
                    flag which allows a user to override the location of the user package
                    database.  Unlike databases specified using <option>--package-db</option>,
                    a user package database configured this way respects
                    the <option>--user</option> flag.
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>Package system</title>
        <itemizedlist>
            <listitem>
                <para>
                    TODO: cover module renaming, thinning, re-export etc
               </para>
            </listitem>
            <listitem>
                <para>
                    ghc-pkg (and ghc) have dropped support for single-file style
                    package databases. Since version 6.12, ghc-pkg has defaulted
                    to a new database format (using a directory of files, one per
                    package plus a binary cache).
               </para>
               <para>
                    This change will not affect programs and scripts that use
                    <literal>ghc-pkg init</literal> to create package databases.
               </para>
               <para>
                    This will affect scripts that create package databases
                    using tricks like
<programlisting>
echo "[]" > package.conf
</programlisting>
                    Such scripts will need to be modified to use
                    <literal>ghc-pkg init</literal>, and to delete databases
                    by directory removal, rather than simple file delete.
               </para>
           </listitem>
       </itemizedlist>
    </sect3>
  </sect2>

  <sect2>
    <title>Libraries</title>

    <sect3>
        <title>array</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 0.5.0.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>base</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 4.7.0.0)
               </para>
           </listitem>
            <listitem>
                <para>
                    GHC has had its internal Unicode database for
                    parsing updated to the Unicode 7.0 standard.
                </para>
           </listitem>
            <listitem>
                <para>
                    Attempting to access a portion of the result of
                    <literal>System.IO.hGetContents</literal> that was not yet
                    read when the handle was closed now throws an exception.
                    Previously, a lazy read from a closed handle would simply
                    end the result string, leading to silent or delayed
                    failures.
                </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>bin-package-db</title>
        <itemizedlist>
            <listitem>
                <para>
                    This is an internal package, and should not be used.
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>binary</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 0.7.1.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>bytestring</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 0.10.4.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>Cabal</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.18.1.3)
              </para>
          </listitem>
      </itemizedlist>
    </sect3>

    <sect3>
        <title>containers</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 0.5.4.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>deepseq</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.3.0.2)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>directory</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.2.0.2)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>filepath</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.3.0.2)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>ghc</title>
        <itemizedlist>
            <listitem>
                <para>
                    Many internal functions in GHC related to package IDs have been
                    renamed to refer to package keys, e.g. <literal>PackageId</literal>
                    is now <literal>PackageKey</literal>, the wired-in names
                    such as <literal>primPackageId</literal> are now
                    <literal>primPackageKey</literal>, etc.  This reflects a distinction
                    that we are now making: a package ID is, as before, the user-visible
                    ID from Cabal <literal>foo-1.0</literal>; a package key is now
                    a compiler-internal entity used for generating linking symbols, and
                    may not correspond at all to the package ID.  In
                    particular, there may be multiple package keys per
                    package ID.
               </para>
           </listitem>
            <listitem>
                <para>
                    The ghc library no longer depends on the Cabal library. This means
                    that users of the ghc library are no longer forced to use the same
                    version of Cabal as ghc did. It also means that Cabal is freed up
                    to be able to depend on packages that ghc does not want to depend
                    on (which for example may enable improvements to Cabal's parsing
                    infrastructure).
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>ghc-prim</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 0.3.1.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>haskell98</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 2.0.0.3)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>haskell2010</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.1.1.1)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>hoopl</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 3.10.0.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>hpc</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 0.6.0.1)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>integer-gmp</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 0.5.1.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>old-locale</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.0.0.6)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>old-time</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.1.0.2)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>process</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.2.0.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>template-haskell</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 2.9.0.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>time</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 1.4.1)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>unix</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 2.7.0.0)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>

    <sect3>
        <title>Win32</title>
        <itemizedlist>
            <listitem>
                <para>
                    Version number XXXXX (was 2.3.0.1)
               </para>
           </listitem>
       </itemizedlist>
    </sect3>
  </sect2>

  <sect2>
    <title>Known bugs</title>
    <itemizedlist>
        <listitem>
            <para>
                TODO FIXME
           </para>
       </listitem>
   </itemizedlist>
  </sect2>
</sect1>