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        <p class='location'>Trait Encoder</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#associated-types">Associated Types</a><div class="sidebar-links"><a href="#associatedtype.Error">Error</a></div><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.emit_nil">emit_nil</a><a href="#tymethod.emit_usize">emit_usize</a><a href="#tymethod.emit_u64">emit_u64</a><a href="#tymethod.emit_u32">emit_u32</a><a href="#tymethod.emit_u16">emit_u16</a><a href="#tymethod.emit_u8">emit_u8</a><a href="#tymethod.emit_isize">emit_isize</a><a href="#tymethod.emit_i64">emit_i64</a><a href="#tymethod.emit_i32">emit_i32</a><a href="#tymethod.emit_i16">emit_i16</a><a href="#tymethod.emit_i8">emit_i8</a><a href="#tymethod.emit_bool">emit_bool</a><a href="#tymethod.emit_f64">emit_f64</a><a href="#tymethod.emit_f32">emit_f32</a><a href="#tymethod.emit_char">emit_char</a><a href="#tymethod.emit_str">emit_str</a><a href="#tymethod.emit_enum">emit_enum</a><a href="#tymethod.emit_enum_variant">emit_enum_variant</a><a href="#tymethod.emit_enum_variant_arg">emit_enum_variant_arg</a><a href="#tymethod.emit_enum_struct_variant">emit_enum_struct_variant</a><a href="#tymethod.emit_enum_struct_variant_field">emit_enum_struct_variant_field</a><a href="#tymethod.emit_struct">emit_struct</a><a href="#tymethod.emit_struct_field">emit_struct_field</a><a href="#tymethod.emit_tuple">emit_tuple</a><a href="#tymethod.emit_tuple_arg">emit_tuple_arg</a><a href="#tymethod.emit_tuple_struct">emit_tuple_struct</a><a href="#tymethod.emit_tuple_struct_arg">emit_tuple_struct_arg</a><a href="#tymethod.emit_option">emit_option</a><a href="#tymethod.emit_option_none">emit_option_none</a><a href="#tymethod.emit_option_some">emit_option_some</a><a href="#tymethod.emit_seq">emit_seq</a><a href="#tymethod.emit_seq_elt">emit_seq_elt</a><a href="#tymethod.emit_map">emit_map</a><a href="#tymethod.emit_map_elt_key">emit_map_elt_key</a><a href="#tymethod.emit_map_elt_val">emit_map_elt_val</a></div><a class="sidebar-title" href="#implementors">Implementors</a></div><p class='location'><a href='index.html'>rustc_serialize</a></p><script>window.sidebarCurrent = {name: 'Encoder', ty: 'trait', relpath: ''};</script><script defer src="sidebar-items.js"></script></div>
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<h1 class='fqn'><span class='in-band'>Trait <a href='index.html'>rustc_serialize</a>::<wbr><a class="trait" href=''>Encoder</a></span><span class='out-of-band'><span id='render-detail'>
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               </span><a class='srclink' href='../src/rustc_serialize/serialize.rs.html#47-489' title='goto source code'>[src]</a></span></h1>
<pre class='rust trait'>pub trait Encoder {
    type <a href='#associatedtype.Error' class="type">Error</a>;
    fn <a href='#tymethod.emit_nil' class='fnname'>emit_nil</a>(&amp;mut self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_usize' class='fnname'>emit_usize</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_u64' class='fnname'>emit_u64</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u64.html">u64</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_u32' class='fnname'>emit_u32</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u32.html">u32</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_u16' class='fnname'>emit_u16</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u16.html">u16</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_u8' class='fnname'>emit_u8</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_isize' class='fnname'>emit_isize</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.isize.html">isize</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_i64' class='fnname'>emit_i64</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i64.html">i64</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_i32' class='fnname'>emit_i32</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i32.html">i32</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_i16' class='fnname'>emit_i16</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i16.html">i16</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_i8' class='fnname'>emit_i8</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i8.html">i8</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_bool' class='fnname'>emit_bool</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_f64' class='fnname'>emit_f64</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f64.html">f64</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_f32' class='fnname'>emit_f32</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f32.html">f32</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_char' class='fnname'>emit_char</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.char.html">char</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_str' class='fnname'>emit_str</a>(&amp;mut self, v: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_enum' class='fnname'>emit_enum</a>&lt;F&gt;(&amp;mut self, name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_enum_variant' class='fnname'>emit_enum_variant</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;v_name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;v_id: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_enum_variant_arg' class='fnname'>emit_enum_variant_arg</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a_idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_enum_struct_variant' class='fnname'>emit_enum_struct_variant</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;v_name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;v_id: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_enum_struct_variant_field' class='fnname'>emit_enum_struct_variant_field</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f_name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f_idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_struct' class='fnname'>emit_struct</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_struct_field' class='fnname'>emit_struct_field</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f_name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f_idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_tuple' class='fnname'>emit_tuple</a>&lt;F&gt;(&amp;mut self, len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_tuple_arg' class='fnname'>emit_tuple_arg</a>&lt;F&gt;(&amp;mut self, idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_tuple_struct' class='fnname'>emit_tuple_struct</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_tuple_struct_arg' class='fnname'>emit_tuple_struct_arg</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f_idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_option' class='fnname'>emit_option</a>&lt;F&gt;(&amp;mut self, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_option_none' class='fnname'>emit_option_none</a>(&amp;mut self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_option_some' class='fnname'>emit_option_some</a>&lt;F&gt;(&amp;mut self, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_seq' class='fnname'>emit_seq</a>&lt;F&gt;(&amp;mut self, len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_seq_elt' class='fnname'>emit_seq_elt</a>&lt;F&gt;(&amp;mut self, idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_map' class='fnname'>emit_map</a>&lt;F&gt;(&amp;mut self, len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_map_elt_key' class='fnname'>emit_map_elt_key</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
<div class='item-spacer'></div>    fn <a href='#tymethod.emit_map_elt_val' class='fnname'>emit_map_elt_val</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>&nbsp;&nbsp;&nbsp;&nbsp;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;<br>&nbsp;&nbsp;&nbsp; <span class="where">where<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</span>;
}</pre><div class='docblock'><p>Trait for writing out an encoding when serializing.</p>
<p>This trait provides methods to encode basic types and generic forms of
collections.  Implementations of <code>Encodable</code> use it to perform the actual
encoding of a type.</p>
<p>It is unspecified what is done with the encoding - it could be stored in a
variable, or written directly to a file, for example.</p>
<p>Encoders can expect to only have a single &quot;root&quot; method call made on this
trait. Non-trivial types will call one of the collection-emitting methods,
passing a function that may call other methods on the trait, but once the
collection-emitting method has returned, encoding should be complete.</p>
</div>
            <h2 id='associated-types' class='small-section-header'>
              Associated Types<a href='#associated-types' class='anchor'></a>
            </h2>
            <div class='methods'>
        <h3 id='associatedtype.Error' class='method'><span id='Error.t' class='invisible'><code>type <a href='#associatedtype.Error' class="type">Error</a></code></span></h3><div class='docblock'><p>The error type for method results.</p>
</div></div>
            <h2 id='required-methods' class='small-section-header'>
              Required Methods<a href='#required-methods' class='anchor'></a>
            </h2>
            <div class='methods'>
        <h3 id='tymethod.emit_nil' class='method'><span id='emit_nil.v' class='invisible'><code>fn <a href='#tymethod.emit_nil' class='fnname'>emit_nil</a>(&amp;mut self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a nil value.</p>
<p>For example, this might be stored as the null keyword in JSON.</p>
</div><h3 id='tymethod.emit_usize' class='method'><span id='emit_usize.v' class='invisible'><code>fn <a href='#tymethod.emit_usize' class='fnname'>emit_usize</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a usize value.</p>
</div><h3 id='tymethod.emit_u64' class='method'><span id='emit_u64.v' class='invisible'><code>fn <a href='#tymethod.emit_u64' class='fnname'>emit_u64</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u64.html">u64</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a u64 value.</p>
</div><h3 id='tymethod.emit_u32' class='method'><span id='emit_u32.v' class='invisible'><code>fn <a href='#tymethod.emit_u32' class='fnname'>emit_u32</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u32.html">u32</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a u32 value.</p>
</div><h3 id='tymethod.emit_u16' class='method'><span id='emit_u16.v' class='invisible'><code>fn <a href='#tymethod.emit_u16' class='fnname'>emit_u16</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u16.html">u16</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a u16 value.</p>
</div><h3 id='tymethod.emit_u8' class='method'><span id='emit_u8.v' class='invisible'><code>fn <a href='#tymethod.emit_u8' class='fnname'>emit_u8</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a u8 value.</p>
</div><h3 id='tymethod.emit_isize' class='method'><span id='emit_isize.v' class='invisible'><code>fn <a href='#tymethod.emit_isize' class='fnname'>emit_isize</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.isize.html">isize</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a isize value.</p>
</div><h3 id='tymethod.emit_i64' class='method'><span id='emit_i64.v' class='invisible'><code>fn <a href='#tymethod.emit_i64' class='fnname'>emit_i64</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i64.html">i64</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a i64 value.</p>
</div><h3 id='tymethod.emit_i32' class='method'><span id='emit_i32.v' class='invisible'><code>fn <a href='#tymethod.emit_i32' class='fnname'>emit_i32</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i32.html">i32</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a i32 value.</p>
</div><h3 id='tymethod.emit_i16' class='method'><span id='emit_i16.v' class='invisible'><code>fn <a href='#tymethod.emit_i16' class='fnname'>emit_i16</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i16.html">i16</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a i16 value.</p>
</div><h3 id='tymethod.emit_i8' class='method'><span id='emit_i8.v' class='invisible'><code>fn <a href='#tymethod.emit_i8' class='fnname'>emit_i8</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.i8.html">i8</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a i8 value.</p>
</div><h3 id='tymethod.emit_bool' class='method'><span id='emit_bool.v' class='invisible'><code>fn <a href='#tymethod.emit_bool' class='fnname'>emit_bool</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a bool value.</p>
<p>For example, this might be stored as the true and false keywords in
JSON.</p>
</div><h3 id='tymethod.emit_f64' class='method'><span id='emit_f64.v' class='invisible'><code>fn <a href='#tymethod.emit_f64' class='fnname'>emit_f64</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f64.html">f64</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a f64 value.</p>
</div><h3 id='tymethod.emit_f32' class='method'><span id='emit_f32.v' class='invisible'><code>fn <a href='#tymethod.emit_f32' class='fnname'>emit_f32</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.f32.html">f32</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a f32 value.</p>
</div><h3 id='tymethod.emit_char' class='method'><span id='emit_char.v' class='invisible'><code>fn <a href='#tymethod.emit_char' class='fnname'>emit_char</a>(&amp;mut self, v: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.char.html">char</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a char value.</p>
<p>Note that strings should be emitted using <code>emit_str</code>, not as a sequence
of <code>emit_char</code> calls.</p>
</div><h3 id='tymethod.emit_str' class='method'><span id='emit_str.v' class='invisible'><code>fn <a href='#tymethod.emit_str' class='fnname'>emit_str</a>(&amp;mut self, v: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit a string value.</p>
</div><h3 id='tymethod.emit_enum' class='method'><span id='emit_enum.v' class='invisible'><code>fn <a href='#tymethod.emit_enum' class='fnname'>emit_enum</a>&lt;F&gt;(&amp;mut self, name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit an enumeration value.</p>
<ul>
<li><code>name</code> indicates the enumeration type name.</li>
<li><code>f</code> is a function that will call <code>emit_enum_variant</code> or
<code>emit_enum_struct_variant</code> as appropriate to write the actual value.</li>
</ul>
</div><h3 id='tymethod.emit_enum_variant' class='method'><span id='emit_enum_variant.v' class='invisible'><code>fn <a href='#tymethod.emit_enum_variant' class='fnname'>emit_enum_variant</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;v_name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;v_id: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a enumeration variant value with no or unnamed data.</p>
<p>This should only be called from a function passed to <code>emit_enum</code>.
Variants with named data should use <code>emit_enum_struct_variant</code>.</p>
<ul>
<li><code>v_name</code> is the variant name</li>
<li><code>v_id</code> is the numeric identifier for the variant.</li>
<li><code>len</code> is the number of data items associated with the variant.</li>
<li><code>f</code> is a function that will call <code>emit_enum_variant_arg</code> for each data
item. It may not be called if len is 0.</li>
</ul>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encodable</span>;
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encoder</span>;

<span class="kw">enum</span> <span class="ident">Message</span> {
    <span class="ident">Quit</span>,
    <span class="ident">ChangeColor</span>(<span class="ident">i32</span>, <span class="ident">i32</span>, <span class="ident">i32</span>),
}

<span class="kw">impl</span> <span class="ident">Encodable</span> <span class="kw">for</span> <span class="ident">Message</span> {
    <span class="kw">fn</span> <span class="ident">encode</span><span class="op">&lt;</span><span class="ident">S</span>: <span class="ident">Encoder</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">s</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">S</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span>(), <span class="ident">S</span>::<span class="ident">Error</span><span class="op">&gt;</span> {
        <span class="ident">s</span>.<span class="ident">emit_enum</span>(<span class="string">&quot;Message&quot;</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
            <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
                <span class="ident">Message</span>::<span class="ident">Quit</span> <span class="op">=&gt;</span> {
                    <span class="ident">s</span>.<span class="ident">emit_enum_variant</span>(<span class="string">&quot;Quit&quot;</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> <span class="prelude-val">Ok</span>(()))
                }
                <span class="ident">Message</span>::<span class="ident">ChangeColor</span>(<span class="ident">r</span>, <span class="ident">g</span>, <span class="ident">b</span>) <span class="op">=&gt;</span> {
                    <span class="ident">s</span>.<span class="ident">emit_enum_variant</span>(<span class="string">&quot;ChangeColor&quot;</span>, <span class="number">1</span>, <span class="number">3</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                        <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_enum_variant_arg</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                            <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="ident">r</span>)
                        }));
                        <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_enum_variant_arg</span>(<span class="number">1</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                            <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="ident">g</span>)
                        }));
                        <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_enum_variant_arg</span>(<span class="number">2</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                            <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="ident">b</span>)
                        }));
                        <span class="prelude-val">Ok</span>(())
                    })
                }
            }
        })
    }
}</pre>
</div><h3 id='tymethod.emit_enum_variant_arg' class='method'><span id='emit_enum_variant_arg.v' class='invisible'><code>fn <a href='#tymethod.emit_enum_variant_arg' class='fnname'>emit_enum_variant_arg</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;a_idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit an unnamed data item for an enumeration variant.</p>
<p>This should only be called from a function passed to
<code>emit_enum_variant</code>.</p>
<ul>
<li><code>a_idx</code> is the (zero-based) index of the data item.</li>
<li><code>f</code> is a function that will call the appropriate emit method to encode
the data object.</li>
</ul>
<p>Note that variant data items must be emitted in order - starting with
index <code>0</code> and finishing with index <code>len-1</code>.</p>
</div><h3 id='tymethod.emit_enum_struct_variant' class='method'><span id='emit_enum_struct_variant.v' class='invisible'><code>fn <a href='#tymethod.emit_enum_struct_variant' class='fnname'>emit_enum_struct_variant</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;v_name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;v_id: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a enumeration variant value with no or named data.</p>
<p>This should only be called from a function passed to <code>emit_enum</code>.
Variants with unnamed data should use <code>emit_enum_variant</code>.</p>
<ul>
<li><code>v_name</code> is the variant name.</li>
<li><code>v_id</code> is the numeric identifier for the variant.</li>
<li><code>len</code> is the number of data items associated with the variant.</li>
<li><code>f</code> is a function that will call <code>emit_enum_struct_variant_field</code> for
each data item. It may not be called if <code>len</code> is <code>0</code>.</li>
</ul>
<h1 id="examples-1" class="section-header"><a href="#examples-1">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encodable</span>;
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encoder</span>;

<span class="kw">enum</span> <span class="ident">Message</span> {
    <span class="ident">Quit</span>,
    <span class="ident">Move</span> { <span class="ident">x</span>: <span class="ident">i32</span>, <span class="ident">y</span>: <span class="ident">i32</span> },
}

<span class="kw">impl</span> <span class="ident">Encodable</span> <span class="kw">for</span> <span class="ident">Message</span> {
    <span class="kw">fn</span> <span class="ident">encode</span><span class="op">&lt;</span><span class="ident">S</span>: <span class="ident">Encoder</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">s</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">S</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span>(), <span class="ident">S</span>::<span class="ident">Error</span><span class="op">&gt;</span> {
        <span class="ident">s</span>.<span class="ident">emit_enum</span>(<span class="string">&quot;Message&quot;</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
            <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
                <span class="ident">Message</span>::<span class="ident">Quit</span> <span class="op">=&gt;</span> {
                    <span class="ident">s</span>.<span class="ident">emit_enum_struct_variant</span>(<span class="string">&quot;Quit&quot;</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> <span class="prelude-val">Ok</span>(()))
                }
                <span class="ident">Message</span>::<span class="ident">Move</span> { <span class="ident">x</span>: <span class="ident">x</span>, <span class="ident">y</span>: <span class="ident">y</span> } <span class="op">=&gt;</span> {
                    <span class="ident">s</span>.<span class="ident">emit_enum_struct_variant</span>(<span class="string">&quot;Move&quot;</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                        <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_enum_struct_variant_field</span>(<span class="string">&quot;x&quot;</span>, <span class="number">0</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                            <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="ident">x</span>)
                        }));
                        <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_enum_struct_variant_field</span>(<span class="string">&quot;y&quot;</span>, <span class="number">1</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                            <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="ident">y</span>)
                        }));
                        <span class="prelude-val">Ok</span>(())
                    })
                }
            }
        })
    }
}</pre>
</div><h3 id='tymethod.emit_enum_struct_variant_field' class='method'><span id='emit_enum_struct_variant_field.v' class='invisible'><code>fn <a href='#tymethod.emit_enum_struct_variant_field' class='fnname'>emit_enum_struct_variant_field</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;f_name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f_idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a named data item for an enumeration variant.</p>
<p>This should only be called from a function passed to
<code>emit_enum_struct_variant</code>.</p>
<ul>
<li><code>f_name</code> is the name of the data item field.</li>
<li><code>f_idx</code> is its (zero-based) index.</li>
<li><code>f</code> is a function that will call the appropriate emit method to encode
the data object.</li>
</ul>
<p>Note that fields must be emitted in order - starting with index <code>0</code> and
finishing with index <code>len-1</code>.</p>
</div><h3 id='tymethod.emit_struct' class='method'><span id='emit_struct.v' class='invisible'><code>fn <a href='#tymethod.emit_struct' class='fnname'>emit_struct</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a struct value.</p>
<ul>
<li><code>name</code> is the name of the struct.</li>
<li><code>len</code> is the number of members.</li>
<li><code>f</code> is a function that calls <code>emit_struct_field</code> for each member.</li>
</ul>
<h1 id="examples-2" class="section-header"><a href="#examples-2">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encodable</span>;
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encoder</span>;

<span class="kw">struct</span> <span class="ident">Point</span> {
    <span class="ident">x</span>: <span class="ident">i32</span>,
    <span class="ident">y</span>: <span class="ident">i32</span>,
}

<span class="kw">impl</span> <span class="ident">Encodable</span> <span class="kw">for</span> <span class="ident">Point</span> {
    <span class="kw">fn</span> <span class="ident">encode</span><span class="op">&lt;</span><span class="ident">S</span>: <span class="ident">Encoder</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">s</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">S</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span>(), <span class="ident">S</span>::<span class="ident">Error</span><span class="op">&gt;</span> {
        <span class="ident">s</span>.<span class="ident">emit_struct</span>(<span class="string">&quot;Point&quot;</span>, <span class="number">2</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
            <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_struct_field</span>(<span class="string">&quot;x&quot;</span>, <span class="number">0</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="self">self</span>.<span class="ident">x</span>)
            }));
            <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_struct_field</span>(<span class="string">&quot;y&quot;</span>, <span class="number">1</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="self">self</span>.<span class="ident">y</span>)
            }));
            <span class="prelude-val">Ok</span>(())
        })
    }
}</pre>
</div><h3 id='tymethod.emit_struct_field' class='method'><span id='emit_struct_field.v' class='invisible'><code>fn <a href='#tymethod.emit_struct_field' class='fnname'>emit_struct_field</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;f_name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f_idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a field item for a struct.</p>
<p>This should only be called from a function passed to <code>emit_struct</code>.</p>
<ul>
<li><code>f_name</code> is the name of the data item field.</li>
<li><code>f_idx</code> is its (zero-based) index.</li>
<li><code>f</code> is a function that will call the appropriate emit method to encode
the data object.</li>
</ul>
<p>Note that fields must be emitted in order - starting with index <code>0</code> and
finishing with index <code>len-1</code>.</p>
</div><h3 id='tymethod.emit_tuple' class='method'><span id='emit_tuple.v' class='invisible'><code>fn <a href='#tymethod.emit_tuple' class='fnname'>emit_tuple</a>&lt;F&gt;(&amp;mut self, len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a tuple value.</p>
<ul>
<li><code>len</code> is the number of items in the tuple.</li>
<li><code>f</code> is a function that calls <code>emit_tuple_arg</code> for each member.</li>
</ul>
<p>Note that external <code>Encodable</code> implementations should not normally need
to use this method directly; it is meant for the use of this module's
own implementation of <code>Encodable</code> for tuples.</p>
</div><h3 id='tymethod.emit_tuple_arg' class='method'><span id='emit_tuple_arg.v' class='invisible'><code>fn <a href='#tymethod.emit_tuple_arg' class='fnname'>emit_tuple_arg</a>&lt;F&gt;(&amp;mut self, idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a data item for a tuple.</p>
<p>This should only be called from a function passed to <code>emit_tuple</code>.</p>
<ul>
<li><code>idx</code> is the (zero-based) index of the data item.</li>
<li><code>f</code> is a function that will call the appropriate emit method to encode
the data object.</li>
</ul>
<p>Note that tuple items must be emitted in order - starting with index <code>0</code>
and finishing with index <code>len-1</code>.</p>
</div><h3 id='tymethod.emit_tuple_struct' class='method'><span id='emit_tuple_struct.v' class='invisible'><code>fn <a href='#tymethod.emit_tuple_struct' class='fnname'>emit_tuple_struct</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;name: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a tuple struct value.</p>
<ul>
<li><code>name</code> is the name of the tuple struct.</li>
<li><code>len</code> is the number of items in the tuple struct.</li>
<li><code>f</code> is a function that calls <code>emit_tuple_struct_arg</code> for each member.</li>
</ul>
<h1 id="examples-3" class="section-header"><a href="#examples-3">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encodable</span>;
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encoder</span>;

<span class="kw">struct</span> <span class="ident">Pair</span>(<span class="ident">i32</span>,<span class="ident">i32</span>);

<span class="kw">impl</span> <span class="ident">Encodable</span> <span class="kw">for</span> <span class="ident">Pair</span> {
    <span class="kw">fn</span> <span class="ident">encode</span><span class="op">&lt;</span><span class="ident">S</span>: <span class="ident">Encoder</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">s</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">S</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span>(), <span class="ident">S</span>::<span class="ident">Error</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="ident">Pair</span>(<span class="ident">first</span>,<span class="ident">second</span>) <span class="op">=</span> <span class="kw-2">*</span><span class="self">self</span>;
        <span class="ident">s</span>.<span class="ident">emit_tuple_struct</span>(<span class="string">&quot;Pair&quot;</span>, <span class="number">2</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
            <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_tuple_arg</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="ident">first</span>)
            }));
            <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_tuple_arg</span>(<span class="number">1</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
                <span class="ident">s</span>.<span class="ident">emit_i32</span>(<span class="ident">second</span>)
            }));
            <span class="prelude-val">Ok</span>(())
        })
    }
}</pre>
</div><h3 id='tymethod.emit_tuple_struct_arg' class='method'><span id='emit_tuple_struct_arg.v' class='invisible'><code>fn <a href='#tymethod.emit_tuple_struct_arg' class='fnname'>emit_tuple_struct_arg</a>&lt;F&gt;(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;f_idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, <br>&nbsp;&nbsp;&nbsp;&nbsp;f: F<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a data item for a tuple struct.</p>
<p>This should only be called from a function passed to
<code>emit_tuple_struct</code>.</p>
<ul>
<li><code>f_idx</code> is the (zero-based) index of the data item.</li>
<li><code>f</code> is a function that will call the appropriate emit method to encode
the data object.</li>
</ul>
<p>Note that tuple items must be emitted in order - starting with index <code>0</code>
and finishing with index <code>len-1</code>.</p>
</div><h3 id='tymethod.emit_option' class='method'><span id='emit_option.v' class='invisible'><code>fn <a href='#tymethod.emit_option' class='fnname'>emit_option</a>&lt;F&gt;(&amp;mut self, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit an optional value.</p>
<p><code>f</code> is a function that will call either <code>emit_option_none</code> or
<code>emit_option_some</code> as appropriate.</p>
<p>This method allows encoders to handle <code>Option&lt;T&gt;</code> values specially,
rather than using the generic enum methods, because many encoding
formats have a built-in &quot;optional&quot; concept.</p>
<p>Note that external <code>Encodable</code> implementations should not normally need
to use this method directly; it is meant for the use of this module's
own implementation of <code>Encodable</code> for <code>Option&lt;T&gt;</code>.</p>
</div><h3 id='tymethod.emit_option_none' class='method'><span id='emit_option_none.v' class='invisible'><code>fn <a href='#tymethod.emit_option_none' class='fnname'>emit_option_none</a>(&amp;mut self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;</code></span></h3><div class='docblock'><p>Emit the <code>None</code> optional value.</p>
<p>This should only be called from a function passed to <code>emit_option</code>.</p>
</div><h3 id='tymethod.emit_option_some' class='method'><span id='emit_option_some.v' class='invisible'><code>fn <a href='#tymethod.emit_option_some' class='fnname'>emit_option_some</a>&lt;F&gt;(&amp;mut self, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit the <code>Some(x)</code> optional value.</p>
<p><code>f</code> is a function that will call the appropriate emit method to encode
the data object.</p>
<p>This should only be called from a function passed to <code>emit_option</code>.</p>
</div><h3 id='tymethod.emit_seq' class='method'><span id='emit_seq.v' class='invisible'><code>fn <a href='#tymethod.emit_seq' class='fnname'>emit_seq</a>&lt;F&gt;(&amp;mut self, len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit a sequence of values.</p>
<p>This should be used for both array-like ordered sequences and set-like
unordered ones.</p>
<ul>
<li><code>len</code> is the number of values in the sequence.</li>
<li><code>f</code> is a function that will call <code>emit_seq_elt</code> for each value in the
sequence.</li>
</ul>
</div><h3 id='tymethod.emit_seq_elt' class='method'><span id='emit_seq_elt.v' class='invisible'><code>fn <a href='#tymethod.emit_seq_elt' class='fnname'>emit_seq_elt</a>&lt;F&gt;(&amp;mut self, idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit an element in a sequence.</p>
<p>This should only be called from a function passed to <code>emit_seq</code>.</p>
<ul>
<li><code>idx</code> is the (zero-based) index of the value in the sequence.</li>
<li><code>f</code> is a function that will call the appropriate emit method to encode
the data object.</li>
</ul>
<p>Note that sequence elements must be emitted in order - starting with
index <code>0</code> and finishing with index <code>len-1</code>.</p>
</div><h3 id='tymethod.emit_map' class='method'><span id='emit_map.v' class='invisible'><code>fn <a href='#tymethod.emit_map' class='fnname'>emit_map</a>&lt;F&gt;(&amp;mut self, len: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit an associative container (map).</p>
<ul>
<li><code>len</code> is the number of entries in the map.</li>
<li><code>f</code> is a function that will call <code>emit_map_elt_key</code> and
<code>emit_map_elt_val</code> for each entry in the map.</li>
</ul>
<h1 id="examples-4" class="section-header"><a href="#examples-4">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encodable</span>;
<span class="kw">use</span> <span class="ident">rustc_serialize</span>::<span class="ident">Encoder</span>;

<span class="kw">struct</span> <span class="ident">SimpleMap</span><span class="op">&lt;</span><span class="ident">K</span>,<span class="ident">V</span><span class="op">&gt;</span> {
    <span class="ident">entries</span>: <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">K</span>,<span class="ident">V</span>)<span class="op">&gt;</span>,
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">K</span>:<span class="ident">Encodable</span>,<span class="ident">V</span>:<span class="ident">Encodable</span><span class="op">&gt;</span> <span class="ident">Encodable</span> <span class="kw">for</span> <span class="ident">SimpleMap</span><span class="op">&lt;</span><span class="ident">K</span>,<span class="ident">V</span><span class="op">&gt;</span> {
    <span class="kw">fn</span> <span class="ident">encode</span><span class="op">&lt;</span><span class="ident">S</span>: <span class="ident">Encoder</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">s</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">S</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span>(), <span class="ident">S</span>::<span class="ident">Error</span><span class="op">&gt;</span> {
        <span class="ident">s</span>.<span class="ident">emit_map</span>(<span class="self">self</span>.<span class="ident">entries</span>.<span class="ident">len</span>(), <span class="op">|</span><span class="ident">s</span><span class="op">|</span> {
            <span class="kw">for</span> (<span class="ident">i</span>, <span class="ident">e</span>) <span class="kw">in</span> <span class="self">self</span>.<span class="ident">entries</span>.<span class="ident">iter</span>().<span class="ident">enumerate</span>() {
                <span class="kw">let</span> (<span class="kw-2">ref</span> <span class="ident">k</span>, <span class="kw-2">ref</span> <span class="ident">v</span>) <span class="op">=</span> <span class="kw-2">*</span><span class="ident">e</span>;
                <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_map_elt_key</span>(<span class="ident">i</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> <span class="ident">k</span>.<span class="ident">encode</span>(<span class="ident">s</span>)));
                <span class="macro">try</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">emit_map_elt_val</span>(<span class="ident">i</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">encode</span>(<span class="ident">s</span>)));
            }
            <span class="prelude-val">Ok</span>(())
        })
    }
}</pre>
</div><h3 id='tymethod.emit_map_elt_key' class='method'><span id='emit_map_elt_key.v' class='invisible'><code>fn <a href='#tymethod.emit_map_elt_key' class='fnname'>emit_map_elt_key</a>&lt;F&gt;(&amp;mut self, idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit the key for an entry in a map.</p>
<p>This should only be called from a function passed to <code>emit_map</code>.</p>
<ul>
<li><code>idx</code> is the (zero-based) index of the entry in the map</li>
<li><code>f</code> is a function that will call the appropriate emit method to encode
the key.</li>
</ul>
<p>Note that map entries must be emitted in order - starting with index <code>0</code>
and finishing with index <code>len-1</code> - and for each entry, the key should be
emitted followed immediately by the value.</p>
</div><h3 id='tymethod.emit_map_elt_val' class='method'><span id='emit_map_elt_val.v' class='invisible'><code>fn <a href='#tymethod.emit_map_elt_val' class='fnname'>emit_map_elt_val</a>&lt;F&gt;(&amp;mut self, idx: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>, f: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>Self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, Self::<a class="type" href="../rustc_serialize/trait.Encoder.html#associatedtype.Error" title="type rustc_serialize::Encoder::Error">Error</a>&gt;,&nbsp;</span></code></span></h3><div class='docblock'><p>Emit the value for an entry in a map.</p>
<p>This should only be called from a function passed to <code>emit_map</code>.</p>
<ul>
<li><code>idx</code> is the (zero-based) index of the entry in the map</li>
<li><code>f</code> is a function that will call the appropriate emit method to encode
the value.</li>
</ul>
<p>Note that map entries must be emitted in order - starting with index <code>0</code>
and finishing with index <code>len-1</code> - and for each entry, the key should be
emitted followed immediately by the value.</p>
</div></div>
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    <li><div class='out-of-band'><a class='srclink' href='../src/rustc_serialize/json.rs.html#622-928' title='goto source code'>[src]</a></div><code>impl&lt;'a&gt; Encoder for <a class="struct" href="../rustc_serialize/json/struct.Encoder.html" title="struct rustc_serialize::json::Encoder">Encoder</a>&lt;'a&gt;<span class="where fmt-newline">  type <a href='#associatedtype.Error' class="type">Error</a> = <a class="enum" href="../rustc_serialize/json/enum.EncoderError.html" title="enum rustc_serialize::json::EncoderError">EncoderError</a>;</span></code></li>
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