179 lines
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179 lines
11 KiB
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<meta name="description" content="API documentation for the Rust `custom_derive` crate.">
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<meta name="keywords" content="rust, rustlang, rust-lang, custom_derive">
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<title>custom_derive - Rust</title>
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things.
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<![endif]-->
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<nav class="sidebar">
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<p class='location'></p><script>window.sidebarCurrent = {name: 'custom_derive', ty: 'mod', relpath: '../'};</script>
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autocomplete="off"
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placeholder="Click or press ‘S’ to search, ‘?’ for more options…"
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type="search">
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<section id='main' class="content mod">
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<h1 class='fqn'><span class='in-band'>Crate <a class='mod' href=''>custom_derive</a></span><span class='out-of-band'><span id='render-detail'>
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<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
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[<span class='inner'>−</span>]
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</a>
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</span><a id='src-0' class='srclink' href='../src/custom_derive/lib.rs.html#10-437' title='goto source code'>[src]</a></span></h1>
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<div class='docblock'><p>This crate provides a macro that enables the use of custom <code>derive</code> attributes.</p>
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<p>To use it, make sure you link to the crate like so:</p>
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<pre class='rust rust-example-rendered'>
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<span class='attribute'>#[<span class='ident'>macro_use</span>]</span> <span class='kw'>extern</span> <span class='kw'>crate</span> <span class='ident'>custom_derive</span>;</pre>
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<blockquote>
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<p><strong>Note</strong>: the <code>custom_derive!</code> macro itself is not documented, as the automatic documentation for it would be uselessly huge and incomprehensible.</p>
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</blockquote>
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<h1 id='usage' class='section-header'><a href='#usage'>Usage</a></h1>
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<p>The macro should be used to wrap an entire <em>single</em> <code>enum</code> or <code>struct</code> declaration, including its attributes (both <code>derive</code> and others). All derivation attributes which the macro does <em>not</em> recognise will be assumed to be custom, and treated accordingly.</p>
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<p><code>custom_derive!</code> assumes that custom derivations are implemented as macros (of the same name). For example, here is a simple derivation macro:</p>
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<pre class='rust rust-example-rendered'>
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<span class='attribute'>#[<span class='ident'>macro_use</span>]</span> <span class='kw'>extern</span> <span class='kw'>crate</span> <span class='ident'>custom_derive</span>;
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<span class='kw'>trait</span> <span class='ident'>TypeName</span> {
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<span class='kw'>fn</span> <span class='ident'>type_name</span>() <span class='op'>-></span> <span class='kw-2'>&</span><span class='lifetime'>'static</span> <span class='ident'>str</span>;
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}
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<span class='kw'>trait</span> <span class='ident'>ReprType</span> {
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<span class='kw'>type</span> <span class='ident'>Repr</span>;
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}
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<span class='macro'>macro_rules</span><span class='macro'>!</span> <span class='ident'>TypeName</span> {
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(() $(<span class='kw'>pub</span>)<span class='op'>*</span> <span class='kw'>enum</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span>:<span class='ident'>ident</span> $(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>tail</span>:<span class='ident'>tt</span>)<span class='op'>*</span>) <span class='op'>=></span> { <span class='macro'>TypeName</span><span class='macro'>!</span> { <span class='kw-2'>@</span><span class='kw'>impl</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span> } };
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(() $(<span class='kw'>pub</span>)<span class='op'>*</span> <span class='kw'>struct</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span>:<span class='ident'>ident</span> $(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>tail</span>:<span class='ident'>tt</span>)<span class='op'>*</span>) <span class='op'>=></span> { <span class='macro'>TypeName</span><span class='macro'>!</span> { <span class='kw-2'>@</span><span class='kw'>impl</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span> } };
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(<span class='kw-2'>@</span><span class='kw'>impl</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span>:<span class='ident'>ident</span>) <span class='op'>=></span> {
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<span class='kw'>impl</span> <span class='ident'>TypeName</span> <span class='kw'>for</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span> {
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<span class='kw'>fn</span> <span class='ident'>type_name</span>() <span class='op'>-></span> <span class='kw-2'>&</span><span class='lifetime'>'static</span> <span class='ident'>str</span> { <span class='macro'>stringify</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span>) }
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}
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};
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}
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<span class='macro'>macro_rules</span><span class='macro'>!</span> <span class='ident'>TryFrom</span> {
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((<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>repr</span>:<span class='ident'>ty</span>) $(<span class='kw'>pub</span>)<span class='op'>*</span> <span class='kw'>enum</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span>:<span class='ident'>ident</span> $(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>tail</span>:<span class='ident'>tt</span>)<span class='op'>*</span>) <span class='op'>=></span> {
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<span class='kw'>impl</span> <span class='ident'>ReprType</span> <span class='kw'>for</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>name</span> {
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<span class='kw'>type</span> <span class='ident'>Repr</span> <span class='op'>=</span> <span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>repr</span>;
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}
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};
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}
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<span class='macro'>custom_derive</span><span class='macro'>!</span> {
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<span class='attribute'>#[<span class='ident'>allow</span>(<span class='ident'>dead_code</span>)]</span>
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<span class='attribute'>#[<span class='ident'>repr</span>(<span class='ident'>u8</span>)]</span>
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<span class='attribute'>#[<span class='ident'>derive</span>(<span class='ident'>Clone</span>, <span class='ident'>Copy</span>, <span class='ident'>Debug</span>, <span class='ident'>TryFrom</span>(<span class='ident'>u8</span>), <span class='ident'>TypeName</span>)]</span>
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<span class='kw'>enum</span> <span class='ident'>Foo</span> { <span class='ident'>A</span>, <span class='ident'>B</span> }
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}
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<span class='kw'>fn</span> <span class='ident'>main</span>() {
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<span class='kw'>let</span> <span class='ident'>foo</span> <span class='op'>=</span> <span class='ident'>Foo</span>::<span class='ident'>B</span>;
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<span class='kw'>let</span> <span class='ident'>v</span> <span class='op'>=</span> <span class='ident'>foo</span> <span class='kw'>as</span> <span class='op'><</span><span class='ident'>Foo</span> <span class='kw'>as</span> <span class='ident'>ReprType</span><span class='op'>></span>::<span class='ident'>Repr</span>;
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<span class='kw'>let</span> <span class='ident'>msg</span> <span class='op'>=</span> <span class='macro'>format</span><span class='macro'>!</span>(<span class='string'>"{}: {:?} ({:?})"</span>, <span class='ident'>Foo</span>::<span class='ident'>type_name</span>(), <span class='ident'>foo</span>, <span class='ident'>v</span>);
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<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>msg</span>, <span class='string'>"Foo: B (1)"</span>);
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}</pre>
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<p>First, note that <code>custom_derive!</code> passes any arguments on the derivation attribute to the macro. In the case of attributes <em>without</em> any arguments, <code>()</code> is passed instead.</p>
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<p>Secondly, the macro is passed the entire item, <em>sans</em> attributes. It is the derivation macro's job to parse the item correctly.</p>
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<p>Third, each derivation macro is expected to result in zero or more items, not including the item itself. As a result, it is <em>not</em> possible to mutate the item in any way, or attach additional attributes to it.</p>
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<p>Finally, <code>@impl</code> is merely a trick to pack multiple, different functions into a single macro. The sequence has no special meaning; it is simply <em>distinct</em> from the usual invocation syntax.</p>
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</div></table></section>
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<section id='search' class="content hidden"></section>
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<h2>Search Tricks</h2>
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Prefix searches with a type followed by a colon (e.g.
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<code>fn:</code>) to restrict the search to a given type.
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<p>
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Accepted types are: <code>fn</code>, <code>mod</code>,
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<code>struct</code>, <code>enum</code>,
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<code>trait</code>, <code>type</code>, <code>macro</code>,
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and <code>const</code>.
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<p>
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Search functions by type signature (e.g.
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<code>vec -> usize</code> or <code>* -> vec</code>)
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window.rootPath = "../";
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window.currentCrate = "custom_derive";
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