Commit 8fdc756d authored by Ian Lynagh's avatar Ian Lynagh
Browse files

Corrections for warnings in the user guide

parent dbbc561d
......@@ -878,6 +878,20 @@ ghc -c Foo.hs</screen>
function or type is used. Entities can be marked as
deprecated using a pragma, see <xref
linkend="deprecated-pragma"/>.</para>
<para>This option is on by default.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-fwarn-dodgy-imports</option>:</term>
<listitem>
<indexterm><primary><option>-fwarn-dodgy-imports</option></primary>
</indexterm>
<para>Causes a warning to be emitted when a a datatype
<literal>T</literal> is imported
with all constructors, i.e. <literal>T(..)</literal>, but has been
exported abstractly, i.e. <literal>T</literal>.</para>
</listitem>
</varlistentry>
......@@ -954,7 +968,7 @@ ghc -c Foo.hs</screen>
g [] = 2
</programlisting>
<para>This option isn't enabled be default because it can be
<para>This option isn't enabled by default because it can be
a bit noisy, and it doesn't always indicate a bug in the
program. However, it's generally considered good practice
to cover all the cases in your functions.</para>
......@@ -982,7 +996,7 @@ f :: Foo -> Foo
f foo = foo { x = 6 }
</programlisting>
<para>This option isn't enabled be default because it can be
<para>This option isn't enabled by default because it can be
very noisy, and it often doesn't indicate a bug in the
program.</para>
</listitem>
......@@ -1055,12 +1069,8 @@ f foo = foo { x = 6 }
inner-scope value has the same name as an outer-scope value,
i.e. the inner value shadows the outer one. This can catch
typographical errors that turn into hard-to-find bugs, e.g.,
in the inadvertent cyclic definition <literal>let x = ... x
... in</literal>.</para>
<para>Consequently, this option
<emphasis>will</emphasis> complain about cyclic recursive
definitions.</para>
in the inadvertent capture of what would be a recursive call in
<literal>f = ... let f = id in ... f ...</literal>.</para>
</listitem>
</varlistentry>
......@@ -1094,7 +1104,7 @@ f foo = foo { x = 6 }
</term>
<listitem>
<para>By default, the compiler will warn you if a set of
patterns are overlapping, i.e.,</para>
patterns are overlapping, e.g.,</para>
<programlisting>
f :: String -&#62; Int
......@@ -1119,7 +1129,7 @@ f "2" = 2
patterns that can fail, eg. <literal>\(x:xs)->...</literal>.
Normally, these aren't treated as incomplete patterns by
<option>-fwarn-incomplete-patterns</option>.</para>
<para>``Lambda-bound patterns'' includes all places where there is a single pattern,
<para>&ldquo;Lambda-bound patterns&rdquo; includes all places where there is a single pattern,
including list comprehensions and do-notation. In these cases, a pattern-match
failure is quite legitimate, and triggers filtering (list comprehensions) or
the monad <literal>fail</literal> operation (monads). For example:
......@@ -1129,10 +1139,6 @@ f "2" = 2
</programlisting>
Switching on <option>-fwarn-simple-patterns</option> will elicit warnings about
these probably-innocent cases, which is why the flag is off by default. </para>
<para> The <literal>deriving( Read )</literal> mechanism produces monadic code with
pattern matches, so you will also get misleading warnings about the compiler-generated
code. (This is arguably a Bad Thing, but it's awkward to fix.)</para>
</listitem>
</varlistentry>
......@@ -1157,7 +1163,7 @@ f "2" = 2
the Haskell defaulting mechanism for numeric types kicks
in. This is useful information when converting code from a
context that assumed one default into one with another,
e.g., the `default default' for Haskell 1.4 caused the
e.g., the &lsquo;default default&rsquo; for Haskell 1.4 caused the
otherwise unconstrained value <constant>1</constant> to be
given the type <literal>Int</literal>, whereas Haskell 98
defaults it to <literal>Integer</literal>. This may lead to
......
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