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  45. <h1 class='fqn'><span class='in-band'>Crate <a class="mod" href=''>synstructure</a></span><span class='out-of-band'><span id='render-detail'>
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  49. </span><a class='srclink' href='../src/synstructure/lib.rs.html#1-1469' title='goto source code'>[src]</a></span></h1>
  50. <div class='docblock'><p>This crate provides helper types for matching against enum variants, and
  51. extracting bindings to each of the fields in the deriving Struct or Enum in
  52. a generic way.</p>
  53. <p>If you are writing a <code>#[derive]</code> which needs to perform some operation on
  54. every field, then you have come to the right place!</p>
  55. <h1 id="example-walkfields" class="section-header"><a href="#example-walkfields">Example: <code>WalkFields</code></a></h1>
  56. <pre class="rust rust-example-rendered">
  57. <span class="comment">/*
  58. * Trait
  59. */</span>
  60. <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">WalkFields</span>: <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">Any</span> {
  61. <span class="kw">fn</span> <span class="ident">walk_fields</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">walk</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">FnMut</span>(<span class="kw-2">&amp;</span><span class="ident">WalkFields</span>));
  62. }
  63. <span class="kw">impl</span> <span class="ident">WalkFields</span> <span class="kw">for</span> <span class="ident">i32</span> {
  64. <span class="kw">fn</span> <span class="ident">walk_fields</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">walk</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">FnMut</span>(<span class="kw-2">&amp;</span><span class="ident">WalkFields</span>)) {}
  65. }
  66. <span class="comment">/*
  67. * Derive Implementation
  68. */</span>
  69. <span class="kw">fn</span> <span class="ident">walkfields_derive</span>(<span class="ident">s</span>: <span class="ident">synstructure</span>::<span class="ident">Structure</span>) <span class="op">-&gt;</span> <span class="ident">quote</span>::<span class="ident">Tokens</span> {
  70. <span class="kw">let</span> <span class="ident">body</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">each</span>(<span class="op">|</span><span class="ident">bi</span><span class="op">|</span> <span class="macro">quote</span><span class="macro">!</span>{
  71. <span class="ident">walk</span>(#<span class="ident">bi</span>)
  72. });
  73. <span class="ident">s</span>.<span class="ident">bound_impl</span>(<span class="string">&quot;::WalkFields&quot;</span>, <span class="macro">quote</span><span class="macro">!</span>{
  74. <span class="kw">fn</span> <span class="ident">walk_fields</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">walk</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">FnMut</span>(<span class="kw-2">&amp;</span>::<span class="ident">WalkFields</span>)) {
  75. <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> { #<span class="ident">body</span> }
  76. }
  77. })
  78. }
  79. <span class="macro">decl_derive</span><span class="macro">!</span>([<span class="ident">WalkFields</span>] <span class="op">=&gt;</span> <span class="ident">walkfields_derive</span>);
  80. <span class="comment">/*
  81. * Test Case
  82. */</span>
  83. <span class="kw">fn</span> <span class="ident">main</span>() {
  84. <span class="macro">test_derive</span><span class="macro">!</span> {
  85. <span class="ident">walkfields_derive</span> {
  86. <span class="kw">enum</span> <span class="ident">A</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> {
  87. <span class="ident">B</span>(<span class="ident">i32</span>, <span class="ident">T</span>),
  88. <span class="ident">C</span>(<span class="ident">i32</span>),
  89. }
  90. }
  91. <span class="ident">expands</span> <span class="ident">to</span> {
  92. <span class="kw">impl</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> ::<span class="ident">WalkFields</span> <span class="kw">for</span> <span class="ident">A</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> <span class="kw">where</span> <span class="ident">T</span>: ::<span class="ident">WalkFields</span> {
  93. <span class="kw">fn</span> <span class="ident">walk_fields</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">walk</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">FnMut</span>(<span class="kw-2">&amp;</span>::<span class="ident">WalkFields</span>)) {
  94. <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
  95. <span class="ident">A</span>::<span class="ident">B</span>(<span class="kw-2">ref</span> <span class="ident">__binding_0</span>, <span class="kw-2">ref</span> <span class="ident">__binding_1</span>,) <span class="op">=&gt;</span> {
  96. { <span class="ident">walk</span>(<span class="ident">__binding_0</span>) }
  97. { <span class="ident">walk</span>(<span class="ident">__binding_1</span>) }
  98. }
  99. <span class="ident">A</span>::<span class="ident">C</span>(<span class="kw-2">ref</span> <span class="ident">__binding_0</span>,) <span class="op">=&gt;</span> {
  100. { <span class="ident">walk</span>(<span class="ident">__binding_0</span>) }
  101. }
  102. }
  103. }
  104. }
  105. }
  106. }
  107. }</pre>
  108. <h1 id="example-interest" class="section-header"><a href="#example-interest">Example: <code>Interest</code></a></h1>
  109. <pre class="rust rust-example-rendered">
  110. <span class="comment">/*
  111. * Trait
  112. */</span>
  113. <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">Interest</span> {
  114. <span class="kw">fn</span> <span class="ident">interesting</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span>;
  115. }
  116. <span class="kw">impl</span> <span class="ident">Interest</span> <span class="kw">for</span> <span class="ident">i32</span> {
  117. <span class="kw">fn</span> <span class="ident">interesting</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> { <span class="kw-2">*</span><span class="self">self</span> <span class="op">&gt;</span> <span class="number">0</span> }
  118. }
  119. <span class="comment">/*
  120. * Derive Implementation
  121. */</span>
  122. <span class="kw">fn</span> <span class="ident">interest_derive</span>(<span class="kw-2">mut</span> <span class="ident">s</span>: <span class="ident">synstructure</span>::<span class="ident">Structure</span>) <span class="op">-&gt;</span> <span class="ident">quote</span>::<span class="ident">Tokens</span> {
  123. <span class="kw">let</span> <span class="ident">body</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">fold</span>(<span class="bool-val">false</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">bi</span><span class="op">|</span> <span class="macro">quote</span><span class="macro">!</span>{
  124. #<span class="ident">acc</span> <span class="op">||</span> ::<span class="ident">Interest</span>::<span class="ident">interesting</span>(#<span class="ident">bi</span>)
  125. });
  126. <span class="ident">s</span>.<span class="ident">bound_impl</span>(<span class="string">&quot;::Interest&quot;</span>, <span class="macro">quote</span><span class="macro">!</span>{
  127. <span class="kw">fn</span> <span class="ident">interesting</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
  128. <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
  129. #<span class="ident">body</span>
  130. }
  131. }
  132. })
  133. }
  134. <span class="macro">decl_derive</span><span class="macro">!</span>([<span class="ident">Interest</span>] <span class="op">=&gt;</span> <span class="ident">interest_derive</span>);
  135. <span class="comment">/*
  136. * Test Case
  137. */</span>
  138. <span class="kw">fn</span> <span class="ident">main</span>() {
  139. <span class="macro">test_derive</span><span class="macro">!</span>{
  140. <span class="ident">interest_derive</span> {
  141. <span class="kw">enum</span> <span class="ident">A</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> {
  142. <span class="ident">B</span>(<span class="ident">i32</span>, <span class="ident">T</span>),
  143. <span class="ident">C</span>(<span class="ident">i32</span>),
  144. }
  145. }
  146. <span class="ident">expands</span> <span class="ident">to</span> {
  147. <span class="kw">impl</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> ::<span class="ident">Interest</span> <span class="kw">for</span> <span class="ident">A</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> <span class="kw">where</span> <span class="ident">T</span>: ::<span class="ident">Interest</span> {
  148. <span class="kw">fn</span> <span class="ident">interesting</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
  149. <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
  150. <span class="ident">A</span>::<span class="ident">B</span>(<span class="kw-2">ref</span> <span class="ident">__binding_0</span>, <span class="kw-2">ref</span> <span class="ident">__binding_1</span>,) <span class="op">=&gt;</span> {
  151. <span class="bool-val">false</span> <span class="op">||</span> ::<span class="ident">Interest</span>::<span class="ident">interesting</span>(<span class="ident">__binding_0</span>) <span class="op">||</span>
  152. ::<span class="ident">Interest</span>::<span class="ident">interesting</span>(<span class="ident">__binding_1</span>)
  153. }
  154. <span class="ident">A</span>::<span class="ident">C</span>(<span class="kw-2">ref</span> <span class="ident">__binding_0</span>,) <span class="op">=&gt;</span> {
  155. <span class="bool-val">false</span> <span class="op">||</span> ::<span class="ident">Interest</span>::<span class="ident">interesting</span>(<span class="ident">__binding_0</span>)
  156. }
  157. }
  158. }
  159. }
  160. }
  161. }
  162. }</pre>
  163. <p>For more example usage, consider investigating the <code>abomonation_derive</code> crate,
  164. which makes use of this crate, and is fairly simple.</p>
  165. </div><h2 id='macros' class='section-header'><a href="#macros">Macros</a></h2>
  166. <table>
  167. <tr class=' module-item'>
  168. <td><a class="macro" href="macro.decl_derive.html"
  169. title='macro synstructure::decl_derive'>decl_derive</a></td>
  170. <td class='docblock-short'>
  171. <p>The <code>decl_derive!</code> macro declares a custom derive wrapper. It will parse the
  172. incoming TokenStream into a <code>synstructure::Structure</code> object, and pass it
  173. into the inner function.</p>
  174. </td>
  175. </tr>
  176. <tr class=' module-item'>
  177. <td><a class="macro" href="macro.test_derive.html"
  178. title='macro synstructure::test_derive'>test_derive</a></td>
  179. <td class='docblock-short'>
  180. <p>Run a test on a custom derive. This macro expands both the original struct
  181. and the expansion to ensure that they compile correctly, and confirms that
  182. feeding the original struct into the named derive will produce the written
  183. output.</p>
  184. </td>
  185. </tr></table><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
  186. <table>
  187. <tr class=' module-item'>
  188. <td><a class="struct" href="struct.BindingInfo.html"
  189. title='struct synstructure::BindingInfo'>BindingInfo</a></td>
  190. <td class='docblock-short'>
  191. <p>Information about a specific binding. This contains both an <code>Ident</code>
  192. reference to the given field, and the syn <code>&amp;'a Field</code> descriptor for that
  193. field.</p>
  194. </td>
  195. </tr>
  196. <tr class=' module-item'>
  197. <td><a class="struct" href="struct.Structure.html"
  198. title='struct synstructure::Structure'>Structure</a></td>
  199. <td class='docblock-short'>
  200. <p>A wrapper around a <code>syn</code> <code>DeriveInput</code> which provides utilities for creating
  201. custom derive trait implementations.</p>
  202. </td>
  203. </tr>
  204. <tr class=' module-item'>
  205. <td><a class="struct" href="struct.VariantAst.html"
  206. title='struct synstructure::VariantAst'>VariantAst</a></td>
  207. <td class='docblock-short'>
  208. <p>This type is similar to <code>syn</code>'s <code>Variant</code> type, however each of the fields
  209. are references rather than owned. When this is used as the AST for a real
  210. variant, this struct simply borrows the fields of the <code>syn</code> <code>Variant</code>,
  211. however this type may also be used as the sole variant for astruct.</p>
  212. </td>
  213. </tr>
  214. <tr class=' module-item'>
  215. <td><a class="struct" href="struct.VariantInfo.html"
  216. title='struct synstructure::VariantInfo'>VariantInfo</a></td>
  217. <td class='docblock-short'>
  218. <p>A wrapper around a <code>syn</code> <code>DeriveInput</code>'s variant which provides utilities
  219. for destructuring <code>Variant</code>s with <code>match</code> expressions.</p>
  220. </td>
  221. </tr></table><h2 id='enums' class='section-header'><a href="#enums">Enums</a></h2>
  222. <table>
  223. <tr class=' module-item'>
  224. <td><a class="enum" href="enum.BindStyle.html"
  225. title='enum synstructure::BindStyle'>BindStyle</a></td>
  226. <td class='docblock-short'>
  227. <p>The type of binding to use when generating a pattern.</p>
  228. </td>
  229. </tr></table></section>
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