macro.ensure.html 5.6 KB

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  45. <h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>failure</a>::<wbr><a class="macro" href=''>ensure</a></span><span class='out-of-band'><span id='render-detail'>
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  50. <pre class="rust macro">
  51. <span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">ensure</span> {
  52. (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">cond</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="ident">expr</span>) <span class="op">=&gt;</span> { ... };
  53. (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">cond</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">fmt</span>:<span class="ident">expr</span>, $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">arg</span>:<span class="ident">tt</span>)<span class="op">+</span>) <span class="op">=&gt;</span> { ... };
  54. }</pre>
  55. <div class='docblock'><p>Exits a function early with an <code>Error</code> if the condition is not satisfied.</p>
  56. <p>Similar to <code>assert!</code>, <code>ensure!</code> takes a condition and exits the function
  57. if the condition fails. Unlike <code>assert!</code>, <code>ensure!</code> returns an <code>Error</code>,
  58. it does not panic.</p>
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