</varlistentry>
<varlistentry>
+ <term><option>-fwarn-identities</option>:</term>
+ <listitem>
+ <indexterm><primary><option>-fwarn-identities</option></primary></indexterm>
+ <para>Causes the compiler to emit a warning when a Prelude numeric
+ conversion converts a type T to the same type T; such calls
+ are probably no-ops and can be omitted. The functions checked for
+ are: <literal>toInteger</literal>,
+ <literal>toRational</literal>,
+ <literal>fromIntegral</literal>,
+ and <literal>realToFrac</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
<term><option>-fwarn-implicit-prelude</option>:</term>
<listitem>
<indexterm><primary><option>-fwarn-implicit-prelude</option></primary></indexterm>
<indexterm><primary>incomplete patterns, warning</primary></indexterm>
<indexterm><primary>patterns, incomplete</primary></indexterm>
- <para>Similarly for incomplete patterns, the function
- <function>g</function> below will fail when applied to
+ <para>Similarly for incomplete patterns, the functions
+ <function>g</function> and <function>h</function> below will fail when applied to
non-empty lists, so the compiler will emit a warning about
this when <option>-fwarn-incomplete-patterns</option> is
enabled.</para>
<programlisting>
g [] = 2
+h = \[] -> 2
</programlisting>
<para>This option isn't enabled by default because it can be
<filename>.hcr</filename>. The Core format is described in <ulink url="../../core.pdf">
<citetitle>An External Representation for the GHC Core Language</citetitle></ulink>,
and sample tools
- for manipulating Core files (in Haskell) are in the GHC source distribution
- directory under <literal>utils/ext-core</literal>.
- Note that the format of <literal>.hcr</literal>
+ for manipulating Core files (in Haskell) are available in the
+ <ulink url="http://hackage.haskell.org/package/extcore">extcore package on Hackage</ulink>. Note that the format of <literal>.hcr</literal>
files is <emphasis>different</emphasis> from the Core output format that GHC generates
for debugging purposes (<xref linkend="options-debugging"/>), though the two formats appear somewhat similar.</para>