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<h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>synom</a>::<wbr><a class="macro" href=''>value</a></span><span class='out-of-band'><span id='render-detail'>
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[<span class='inner'>−</span>]
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</span><a class='srclink' href='../src/synom/lib.rs.html#871-875' title='goto source code'>[src]</a></span></h1>
<pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">value</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">res</span>:<span class="ident">expr</span>) <span class="op">=></span> { ... };
}</pre>
<div class='docblock'><p>Produce the given value without parsing anything. Useful as an argument to
<code>switch!</code>.</p>
<ul>
<li><strong>Syntax:</strong> <code>value!(VALUE)</code></li>
<li><strong>Output:</strong> <code>VALUE</code></li>
</ul>
<pre class="rust rust-example-rendered">
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">syn</span>;
<span class="attribute">#[<span class="ident">macro_use</span>]</span> <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">synom</span>;
<span class="kw">use</span> <span class="ident">syn</span>::{<span class="ident">Ident</span>, <span class="ident">Ty</span>};
<span class="kw">use</span> <span class="ident">syn</span>::<span class="ident">parse</span>::{<span class="ident">ident</span>, <span class="ident">ty</span>};
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">enum</span> <span class="ident">UnitType</span> {
<span class="ident">Struct</span> {
<span class="ident">name</span>: <span class="ident">Ident</span>,
},
<span class="ident">Enum</span> {
<span class="ident">name</span>: <span class="ident">Ident</span>,
<span class="ident">variant</span>: <span class="ident">Ident</span>,
},
}
<span class="comment">// Parse a unit struct or enum: either `struct S;` or `enum E { V }`.</span>
<span class="macro">named</span><span class="macro">!</span>(<span class="ident">unit_type</span> <span class="op">-></span> <span class="ident">UnitType</span>, <span class="macro">do_parse</span><span class="macro">!</span>(
<span class="ident">which</span>: <span class="macro">alt</span><span class="macro">!</span>(<span class="macro">keyword</span><span class="macro">!</span>(<span class="string">"struct"</span>) <span class="op">|</span> <span class="macro">keyword</span><span class="macro">!</span>(<span class="string">"enum"</span>)) <span class="op">>></span>
<span class="ident">id</span>: <span class="ident">ident</span> <span class="op">>></span>
<span class="ident">item</span>: <span class="macro">switch</span><span class="macro">!</span>(<span class="macro">value</span><span class="macro">!</span>(<span class="ident">which</span>),
<span class="string">"struct"</span> <span class="op">=></span> <span class="macro">map</span><span class="macro">!</span>(
<span class="macro">punct</span><span class="macro">!</span>(<span class="string">";"</span>),
<span class="kw">move</span> <span class="op">|</span>_<span class="op">|</span> <span class="ident">UnitType</span>::<span class="ident">Struct</span> {
<span class="ident">name</span>: <span class="ident">id</span>,
}
)
<span class="op">|</span>
<span class="string">"enum"</span> <span class="op">=></span> <span class="macro">map</span><span class="macro">!</span>(
<span class="macro">delimited</span><span class="macro">!</span>(<span class="macro">punct</span><span class="macro">!</span>(<span class="string">"{"</span>), <span class="ident">ident</span>, <span class="macro">punct</span><span class="macro">!</span>(<span class="string">"}"</span>)),
<span class="kw">move</span> <span class="op">|</span><span class="ident">variant</span><span class="op">|</span> <span class="ident">UnitType</span>::<span class="ident">Enum</span> {
<span class="ident">name</span>: <span class="ident">id</span>,
<span class="ident">variant</span>: <span class="ident">variant</span>,
}
)
) <span class="op">>></span>
(<span class="ident">item</span>)
));
<span class="kw">fn</span> <span class="ident">main</span>() {
<span class="kw">let</span> <span class="ident">input</span> <span class="op">=</span> <span class="string">"struct S;"</span>;
<span class="kw">let</span> <span class="ident">parsed</span> <span class="op">=</span> <span class="ident">unit_type</span>(<span class="ident">input</span>).<span class="ident">expect</span>(<span class="string">"unit struct or enum"</span>);
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">parsed</span>);
<span class="kw">let</span> <span class="ident">input</span> <span class="op">=</span> <span class="string">"enum E { V }"</span>;
<span class="kw">let</span> <span class="ident">parsed</span> <span class="op">=</span> <span class="ident">unit_type</span>(<span class="ident">input</span>).<span class="ident">expect</span>(<span class="string">"unit struct or enum"</span>);
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"{:?}"</span>, <span class="ident">parsed</span>);
}</pre>
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