<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="generator" content="rustdoc">
<meta name="description" content="Source to the Rust file `libcore/result.rs`.">
<meta name="keywords" content="rust, rustlang, rust-lang">
<title>result.rs.html -- source</title>
<link rel="stylesheet" type="text/css" href="../../normalize.css">
<link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle">
<link rel="stylesheet" type="text/css" href="../../dark.css">
<link rel="stylesheet" type="text/css" href="../../main.css" id="themeStyle">
<script src="../../storage.js"></script>
<link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico">
</head>
<body class="rustdoc source">
<!--[if lte IE 8]>
<div class="warning">
This old browser is unsupported and will most likely display funky
things.
</div>
<![endif]-->
<nav class="sidebar">
<div class="sidebar-menu">☰</div>
<a href='../../core/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a>
</nav>
<div class="theme-picker">
<button id="theme-picker" aria-label="Pick another theme!">
<img src="../../brush.svg" width="18" alt="Pick another theme!">
</button>
<div id="theme-choices"></div>
</div>
<script src="../../theme.js"></script>
<nav class="sub">
<form class="search-form js-only">
<div class="search-container">
<input class="search-input" name="search"
autocomplete="off"
placeholder="Click or press ‘S’ to search, ‘?’ for more options…"
type="search">
</div>
</form>
</nav>
<section id='main' class="content"><pre class="line-numbers"><span id="1"> 1</span>
<span id="2"> 2</span>
<span id="3"> 3</span>
<span id="4"> 4</span>
<span id="5"> 5</span>
<span id="6"> 6</span>
<span id="7"> 7</span>
<span id="8"> 8</span>
<span id="9"> 9</span>
<span id="10"> 10</span>
<span id="11"> 11</span>
<span id="12"> 12</span>
<span id="13"> 13</span>
<span id="14"> 14</span>
<span id="15"> 15</span>
<span id="16"> 16</span>
<span id="17"> 17</span>
<span id="18"> 18</span>
<span id="19"> 19</span>
<span id="20"> 20</span>
<span id="21"> 21</span>
<span id="22"> 22</span>
<span id="23"> 23</span>
<span id="24"> 24</span>
<span id="25"> 25</span>
<span id="26"> 26</span>
<span id="27"> 27</span>
<span id="28"> 28</span>
<span id="29"> 29</span>
<span id="30"> 30</span>
<span id="31"> 31</span>
<span id="32"> 32</span>
<span id="33"> 33</span>
<span id="34"> 34</span>
<span id="35"> 35</span>
<span id="36"> 36</span>
<span id="37"> 37</span>
<span id="38"> 38</span>
<span id="39"> 39</span>
<span id="40"> 40</span>
<span id="41"> 41</span>
<span id="42"> 42</span>
<span id="43"> 43</span>
<span id="44"> 44</span>
<span id="45"> 45</span>
<span id="46"> 46</span>
<span id="47"> 47</span>
<span id="48"> 48</span>
<span id="49"> 49</span>
<span id="50"> 50</span>
<span id="51"> 51</span>
<span id="52"> 52</span>
<span id="53"> 53</span>
<span id="54"> 54</span>
<span id="55"> 55</span>
<span id="56"> 56</span>
<span id="57"> 57</span>
<span id="58"> 58</span>
<span id="59"> 59</span>
<span id="60"> 60</span>
<span id="61"> 61</span>
<span id="62"> 62</span>
<span id="63"> 63</span>
<span id="64"> 64</span>
<span id="65"> 65</span>
<span id="66"> 66</span>
<span id="67"> 67</span>
<span id="68"> 68</span>
<span id="69"> 69</span>
<span id="70"> 70</span>
<span id="71"> 71</span>
<span id="72"> 72</span>
<span id="73"> 73</span>
<span id="74"> 74</span>
<span id="75"> 75</span>
<span id="76"> 76</span>
<span id="77"> 77</span>
<span id="78"> 78</span>
<span id="79"> 79</span>
<span id="80"> 80</span>
<span id="81"> 81</span>
<span id="82"> 82</span>
<span id="83"> 83</span>
<span id="84"> 84</span>
<span id="85"> 85</span>
<span id="86"> 86</span>
<span id="87"> 87</span>
<span id="88"> 88</span>
<span id="89"> 89</span>
<span id="90"> 90</span>
<span id="91"> 91</span>
<span id="92"> 92</span>
<span id="93"> 93</span>
<span id="94"> 94</span>
<span id="95"> 95</span>
<span id="96"> 96</span>
<span id="97"> 97</span>
<span id="98"> 98</span>
<span id="99"> 99</span>
<span id="100"> 100</span>
<span id="101"> 101</span>
<span id="102"> 102</span>
<span id="103"> 103</span>
<span id="104"> 104</span>
<span id="105"> 105</span>
<span id="106"> 106</span>
<span id="107"> 107</span>
<span id="108"> 108</span>
<span id="109"> 109</span>
<span id="110"> 110</span>
<span id="111"> 111</span>
<span id="112"> 112</span>
<span id="113"> 113</span>
<span id="114"> 114</span>
<span id="115"> 115</span>
<span id="116"> 116</span>
<span id="117"> 117</span>
<span id="118"> 118</span>
<span id="119"> 119</span>
<span id="120"> 120</span>
<span id="121"> 121</span>
<span id="122"> 122</span>
<span id="123"> 123</span>
<span id="124"> 124</span>
<span id="125"> 125</span>
<span id="126"> 126</span>
<span id="127"> 127</span>
<span id="128"> 128</span>
<span id="129"> 129</span>
<span id="130"> 130</span>
<span id="131"> 131</span>
<span id="132"> 132</span>
<span id="133"> 133</span>
<span id="134"> 134</span>
<span id="135"> 135</span>
<span id="136"> 136</span>
<span id="137"> 137</span>
<span id="138"> 138</span>
<span id="139"> 139</span>
<span id="140"> 140</span>
<span id="141"> 141</span>
<span id="142"> 142</span>
<span id="143"> 143</span>
<span id="144"> 144</span>
<span id="145"> 145</span>
<span id="146"> 146</span>
<span id="147"> 147</span>
<span id="148"> 148</span>
<span id="149"> 149</span>
<span id="150"> 150</span>
<span id="151"> 151</span>
<span id="152"> 152</span>
<span id="153"> 153</span>
<span id="154"> 154</span>
<span id="155"> 155</span>
<span id="156"> 156</span>
<span id="157"> 157</span>
<span id="158"> 158</span>
<span id="159"> 159</span>
<span id="160"> 160</span>
<span id="161"> 161</span>
<span id="162"> 162</span>
<span id="163"> 163</span>
<span id="164"> 164</span>
<span id="165"> 165</span>
<span id="166"> 166</span>
<span id="167"> 167</span>
<span id="168"> 168</span>
<span id="169"> 169</span>
<span id="170"> 170</span>
<span id="171"> 171</span>
<span id="172"> 172</span>
<span id="173"> 173</span>
<span id="174"> 174</span>
<span id="175"> 175</span>
<span id="176"> 176</span>
<span id="177"> 177</span>
<span id="178"> 178</span>
<span id="179"> 179</span>
<span id="180"> 180</span>
<span id="181"> 181</span>
<span id="182"> 182</span>
<span id="183"> 183</span>
<span id="184"> 184</span>
<span id="185"> 185</span>
<span id="186"> 186</span>
<span id="187"> 187</span>
<span id="188"> 188</span>
<span id="189"> 189</span>
<span id="190"> 190</span>
<span id="191"> 191</span>
<span id="192"> 192</span>
<span id="193"> 193</span>
<span id="194"> 194</span>
<span id="195"> 195</span>
<span id="196"> 196</span>
<span id="197"> 197</span>
<span id="198"> 198</span>
<span id="199"> 199</span>
<span id="200"> 200</span>
<span id="201"> 201</span>
<span id="202"> 202</span>
<span id="203"> 203</span>
<span id="204"> 204</span>
<span id="205"> 205</span>
<span id="206"> 206</span>
<span id="207"> 207</span>
<span id="208"> 208</span>
<span id="209"> 209</span>
<span id="210"> 210</span>
<span id="211"> 211</span>
<span id="212"> 212</span>
<span id="213"> 213</span>
<span id="214"> 214</span>
<span id="215"> 215</span>
<span id="216"> 216</span>
<span id="217"> 217</span>
<span id="218"> 218</span>
<span id="219"> 219</span>
<span id="220"> 220</span>
<span id="221"> 221</span>
<span id="222"> 222</span>
<span id="223"> 223</span>
<span id="224"> 224</span>
<span id="225"> 225</span>
<span id="226"> 226</span>
<span id="227"> 227</span>
<span id="228"> 228</span>
<span id="229"> 229</span>
<span id="230"> 230</span>
<span id="231"> 231</span>
<span id="232"> 232</span>
<span id="233"> 233</span>
<span id="234"> 234</span>
<span id="235"> 235</span>
<span id="236"> 236</span>
<span id="237"> 237</span>
<span id="238"> 238</span>
<span id="239"> 239</span>
<span id="240"> 240</span>
<span id="241"> 241</span>
<span id="242"> 242</span>
<span id="243"> 243</span>
<span id="244"> 244</span>
<span id="245"> 245</span>
<span id="246"> 246</span>
<span id="247"> 247</span>
<span id="248"> 248</span>
<span id="249"> 249</span>
<span id="250"> 250</span>
<span id="251"> 251</span>
<span id="252"> 252</span>
<span id="253"> 253</span>
<span id="254"> 254</span>
<span id="255"> 255</span>
<span id="256"> 256</span>
<span id="257"> 257</span>
<span id="258"> 258</span>
<span id="259"> 259</span>
<span id="260"> 260</span>
<span id="261"> 261</span>
<span id="262"> 262</span>
<span id="263"> 263</span>
<span id="264"> 264</span>
<span id="265"> 265</span>
<span id="266"> 266</span>
<span id="267"> 267</span>
<span id="268"> 268</span>
<span id="269"> 269</span>
<span id="270"> 270</span>
<span id="271"> 271</span>
<span id="272"> 272</span>
<span id="273"> 273</span>
<span id="274"> 274</span>
<span id="275"> 275</span>
<span id="276"> 276</span>
<span id="277"> 277</span>
<span id="278"> 278</span>
<span id="279"> 279</span>
<span id="280"> 280</span>
<span id="281"> 281</span>
<span id="282"> 282</span>
<span id="283"> 283</span>
<span id="284"> 284</span>
<span id="285"> 285</span>
<span id="286"> 286</span>
<span id="287"> 287</span>
<span id="288"> 288</span>
<span id="289"> 289</span>
<span id="290"> 290</span>
<span id="291"> 291</span>
<span id="292"> 292</span>
<span id="293"> 293</span>
<span id="294"> 294</span>
<span id="295"> 295</span>
<span id="296"> 296</span>
<span id="297"> 297</span>
<span id="298"> 298</span>
<span id="299"> 299</span>
<span id="300"> 300</span>
<span id="301"> 301</span>
<span id="302"> 302</span>
<span id="303"> 303</span>
<span id="304"> 304</span>
<span id="305"> 305</span>
<span id="306"> 306</span>
<span id="307"> 307</span>
<span id="308"> 308</span>
<span id="309"> 309</span>
<span id="310"> 310</span>
<span id="311"> 311</span>
<span id="312"> 312</span>
<span id="313"> 313</span>
<span id="314"> 314</span>
<span id="315"> 315</span>
<span id="316"> 316</span>
<span id="317"> 317</span>
<span id="318"> 318</span>
<span id="319"> 319</span>
<span id="320"> 320</span>
<span id="321"> 321</span>
<span id="322"> 322</span>
<span id="323"> 323</span>
<span id="324"> 324</span>
<span id="325"> 325</span>
<span id="326"> 326</span>
<span id="327"> 327</span>
<span id="328"> 328</span>
<span id="329"> 329</span>
<span id="330"> 330</span>
<span id="331"> 331</span>
<span id="332"> 332</span>
<span id="333"> 333</span>
<span id="334"> 334</span>
<span id="335"> 335</span>
<span id="336"> 336</span>
<span id="337"> 337</span>
<span id="338"> 338</span>
<span id="339"> 339</span>
<span id="340"> 340</span>
<span id="341"> 341</span>
<span id="342"> 342</span>
<span id="343"> 343</span>
<span id="344"> 344</span>
<span id="345"> 345</span>
<span id="346"> 346</span>
<span id="347"> 347</span>
<span id="348"> 348</span>
<span id="349"> 349</span>
<span id="350"> 350</span>
<span id="351"> 351</span>
<span id="352"> 352</span>
<span id="353"> 353</span>
<span id="354"> 354</span>
<span id="355"> 355</span>
<span id="356"> 356</span>
<span id="357"> 357</span>
<span id="358"> 358</span>
<span id="359"> 359</span>
<span id="360"> 360</span>
<span id="361"> 361</span>
<span id="362"> 362</span>
<span id="363"> 363</span>
<span id="364"> 364</span>
<span id="365"> 365</span>
<span id="366"> 366</span>
<span id="367"> 367</span>
<span id="368"> 368</span>
<span id="369"> 369</span>
<span id="370"> 370</span>
<span id="371"> 371</span>
<span id="372"> 372</span>
<span id="373"> 373</span>
<span id="374"> 374</span>
<span id="375"> 375</span>
<span id="376"> 376</span>
<span id="377"> 377</span>
<span id="378"> 378</span>
<span id="379"> 379</span>
<span id="380"> 380</span>
<span id="381"> 381</span>
<span id="382"> 382</span>
<span id="383"> 383</span>
<span id="384"> 384</span>
<span id="385"> 385</span>
<span id="386"> 386</span>
<span id="387"> 387</span>
<span id="388"> 388</span>
<span id="389"> 389</span>
<span id="390"> 390</span>
<span id="391"> 391</span>
<span id="392"> 392</span>
<span id="393"> 393</span>
<span id="394"> 394</span>
<span id="395"> 395</span>
<span id="396"> 396</span>
<span id="397"> 397</span>
<span id="398"> 398</span>
<span id="399"> 399</span>
<span id="400"> 400</span>
<span id="401"> 401</span>
<span id="402"> 402</span>
<span id="403"> 403</span>
<span id="404"> 404</span>
<span id="405"> 405</span>
<span id="406"> 406</span>
<span id="407"> 407</span>
<span id="408"> 408</span>
<span id="409"> 409</span>
<span id="410"> 410</span>
<span id="411"> 411</span>
<span id="412"> 412</span>
<span id="413"> 413</span>
<span id="414"> 414</span>
<span id="415"> 415</span>
<span id="416"> 416</span>
<span id="417"> 417</span>
<span id="418"> 418</span>
<span id="419"> 419</span>
<span id="420"> 420</span>
<span id="421"> 421</span>
<span id="422"> 422</span>
<span id="423"> 423</span>
<span id="424"> 424</span>
<span id="425"> 425</span>
<span id="426"> 426</span>
<span id="427"> 427</span>
<span id="428"> 428</span>
<span id="429"> 429</span>
<span id="430"> 430</span>
<span id="431"> 431</span>
<span id="432"> 432</span>
<span id="433"> 433</span>
<span id="434"> 434</span>
<span id="435"> 435</span>
<span id="436"> 436</span>
<span id="437"> 437</span>
<span id="438"> 438</span>
<span id="439"> 439</span>
<span id="440"> 440</span>
<span id="441"> 441</span>
<span id="442"> 442</span>
<span id="443"> 443</span>
<span id="444"> 444</span>
<span id="445"> 445</span>
<span id="446"> 446</span>
<span id="447"> 447</span>
<span id="448"> 448</span>
<span id="449"> 449</span>
<span id="450"> 450</span>
<span id="451"> 451</span>
<span id="452"> 452</span>
<span id="453"> 453</span>
<span id="454"> 454</span>
<span id="455"> 455</span>
<span id="456"> 456</span>
<span id="457"> 457</span>
<span id="458"> 458</span>
<span id="459"> 459</span>
<span id="460"> 460</span>
<span id="461"> 461</span>
<span id="462"> 462</span>
<span id="463"> 463</span>
<span id="464"> 464</span>
<span id="465"> 465</span>
<span id="466"> 466</span>
<span id="467"> 467</span>
<span id="468"> 468</span>
<span id="469"> 469</span>
<span id="470"> 470</span>
<span id="471"> 471</span>
<span id="472"> 472</span>
<span id="473"> 473</span>
<span id="474"> 474</span>
<span id="475"> 475</span>
<span id="476"> 476</span>
<span id="477"> 477</span>
<span id="478"> 478</span>
<span id="479"> 479</span>
<span id="480"> 480</span>
<span id="481"> 481</span>
<span id="482"> 482</span>
<span id="483"> 483</span>
<span id="484"> 484</span>
<span id="485"> 485</span>
<span id="486"> 486</span>
<span id="487"> 487</span>
<span id="488"> 488</span>
<span id="489"> 489</span>
<span id="490"> 490</span>
<span id="491"> 491</span>
<span id="492"> 492</span>
<span id="493"> 493</span>
<span id="494"> 494</span>
<span id="495"> 495</span>
<span id="496"> 496</span>
<span id="497"> 497</span>
<span id="498"> 498</span>
<span id="499"> 499</span>
<span id="500"> 500</span>
<span id="501"> 501</span>
<span id="502"> 502</span>
<span id="503"> 503</span>
<span id="504"> 504</span>
<span id="505"> 505</span>
<span id="506"> 506</span>
<span id="507"> 507</span>
<span id="508"> 508</span>
<span id="509"> 509</span>
<span id="510"> 510</span>
<span id="511"> 511</span>
<span id="512"> 512</span>
<span id="513"> 513</span>
<span id="514"> 514</span>
<span id="515"> 515</span>
<span id="516"> 516</span>
<span id="517"> 517</span>
<span id="518"> 518</span>
<span id="519"> 519</span>
<span id="520"> 520</span>
<span id="521"> 521</span>
<span id="522"> 522</span>
<span id="523"> 523</span>
<span id="524"> 524</span>
<span id="525"> 525</span>
<span id="526"> 526</span>
<span id="527"> 527</span>
<span id="528"> 528</span>
<span id="529"> 529</span>
<span id="530"> 530</span>
<span id="531"> 531</span>
<span id="532"> 532</span>
<span id="533"> 533</span>
<span id="534"> 534</span>
<span id="535"> 535</span>
<span id="536"> 536</span>
<span id="537"> 537</span>
<span id="538"> 538</span>
<span id="539"> 539</span>
<span id="540"> 540</span>
<span id="541"> 541</span>
<span id="542"> 542</span>
<span id="543"> 543</span>
<span id="544"> 544</span>
<span id="545"> 545</span>
<span id="546"> 546</span>
<span id="547"> 547</span>
<span id="548"> 548</span>
<span id="549"> 549</span>
<span id="550"> 550</span>
<span id="551"> 551</span>
<span id="552"> 552</span>
<span id="553"> 553</span>
<span id="554"> 554</span>
<span id="555"> 555</span>
<span id="556"> 556</span>
<span id="557"> 557</span>
<span id="558"> 558</span>
<span id="559"> 559</span>
<span id="560"> 560</span>
<span id="561"> 561</span>
<span id="562"> 562</span>
<span id="563"> 563</span>
<span id="564"> 564</span>
<span id="565"> 565</span>
<span id="566"> 566</span>
<span id="567"> 567</span>
<span id="568"> 568</span>
<span id="569"> 569</span>
<span id="570"> 570</span>
<span id="571"> 571</span>
<span id="572"> 572</span>
<span id="573"> 573</span>
<span id="574"> 574</span>
<span id="575"> 575</span>
<span id="576"> 576</span>
<span id="577"> 577</span>
<span id="578"> 578</span>
<span id="579"> 579</span>
<span id="580"> 580</span>
<span id="581"> 581</span>
<span id="582"> 582</span>
<span id="583"> 583</span>
<span id="584"> 584</span>
<span id="585"> 585</span>
<span id="586"> 586</span>
<span id="587"> 587</span>
<span id="588"> 588</span>
<span id="589"> 589</span>
<span id="590"> 590</span>
<span id="591"> 591</span>
<span id="592"> 592</span>
<span id="593"> 593</span>
<span id="594"> 594</span>
<span id="595"> 595</span>
<span id="596"> 596</span>
<span id="597"> 597</span>
<span id="598"> 598</span>
<span id="599"> 599</span>
<span id="600"> 600</span>
<span id="601"> 601</span>
<span id="602"> 602</span>
<span id="603"> 603</span>
<span id="604"> 604</span>
<span id="605"> 605</span>
<span id="606"> 606</span>
<span id="607"> 607</span>
<span id="608"> 608</span>
<span id="609"> 609</span>
<span id="610"> 610</span>
<span id="611"> 611</span>
<span id="612"> 612</span>
<span id="613"> 613</span>
<span id="614"> 614</span>
<span id="615"> 615</span>
<span id="616"> 616</span>
<span id="617"> 617</span>
<span id="618"> 618</span>
<span id="619"> 619</span>
<span id="620"> 620</span>
<span id="621"> 621</span>
<span id="622"> 622</span>
<span id="623"> 623</span>
<span id="624"> 624</span>
<span id="625"> 625</span>
<span id="626"> 626</span>
<span id="627"> 627</span>
<span id="628"> 628</span>
<span id="629"> 629</span>
<span id="630"> 630</span>
<span id="631"> 631</span>
<span id="632"> 632</span>
<span id="633"> 633</span>
<span id="634"> 634</span>
<span id="635"> 635</span>
<span id="636"> 636</span>
<span id="637"> 637</span>
<span id="638"> 638</span>
<span id="639"> 639</span>
<span id="640"> 640</span>
<span id="641"> 641</span>
<span id="642"> 642</span>
<span id="643"> 643</span>
<span id="644"> 644</span>
<span id="645"> 645</span>
<span id="646"> 646</span>
<span id="647"> 647</span>
<span id="648"> 648</span>
<span id="649"> 649</span>
<span id="650"> 650</span>
<span id="651"> 651</span>
<span id="652"> 652</span>
<span id="653"> 653</span>
<span id="654"> 654</span>
<span id="655"> 655</span>
<span id="656"> 656</span>
<span id="657"> 657</span>
<span id="658"> 658</span>
<span id="659"> 659</span>
<span id="660"> 660</span>
<span id="661"> 661</span>
<span id="662"> 662</span>
<span id="663"> 663</span>
<span id="664"> 664</span>
<span id="665"> 665</span>
<span id="666"> 666</span>
<span id="667"> 667</span>
<span id="668"> 668</span>
<span id="669"> 669</span>
<span id="670"> 670</span>
<span id="671"> 671</span>
<span id="672"> 672</span>
<span id="673"> 673</span>
<span id="674"> 674</span>
<span id="675"> 675</span>
<span id="676"> 676</span>
<span id="677"> 677</span>
<span id="678"> 678</span>
<span id="679"> 679</span>
<span id="680"> 680</span>
<span id="681"> 681</span>
<span id="682"> 682</span>
<span id="683"> 683</span>
<span id="684"> 684</span>
<span id="685"> 685</span>
<span id="686"> 686</span>
<span id="687"> 687</span>
<span id="688"> 688</span>
<span id="689"> 689</span>
<span id="690"> 690</span>
<span id="691"> 691</span>
<span id="692"> 692</span>
<span id="693"> 693</span>
<span id="694"> 694</span>
<span id="695"> 695</span>
<span id="696"> 696</span>
<span id="697"> 697</span>
<span id="698"> 698</span>
<span id="699"> 699</span>
<span id="700"> 700</span>
<span id="701"> 701</span>
<span id="702"> 702</span>
<span id="703"> 703</span>
<span id="704"> 704</span>
<span id="705"> 705</span>
<span id="706"> 706</span>
<span id="707"> 707</span>
<span id="708"> 708</span>
<span id="709"> 709</span>
<span id="710"> 710</span>
<span id="711"> 711</span>
<span id="712"> 712</span>
<span id="713"> 713</span>
<span id="714"> 714</span>
<span id="715"> 715</span>
<span id="716"> 716</span>
<span id="717"> 717</span>
<span id="718"> 718</span>
<span id="719"> 719</span>
<span id="720"> 720</span>
<span id="721"> 721</span>
<span id="722"> 722</span>
<span id="723"> 723</span>
<span id="724"> 724</span>
<span id="725"> 725</span>
<span id="726"> 726</span>
<span id="727"> 727</span>
<span id="728"> 728</span>
<span id="729"> 729</span>
<span id="730"> 730</span>
<span id="731"> 731</span>
<span id="732"> 732</span>
<span id="733"> 733</span>
<span id="734"> 734</span>
<span id="735"> 735</span>
<span id="736"> 736</span>
<span id="737"> 737</span>
<span id="738"> 738</span>
<span id="739"> 739</span>
<span id="740"> 740</span>
<span id="741"> 741</span>
<span id="742"> 742</span>
<span id="743"> 743</span>
<span id="744"> 744</span>
<span id="745"> 745</span>
<span id="746"> 746</span>
<span id="747"> 747</span>
<span id="748"> 748</span>
<span id="749"> 749</span>
<span id="750"> 750</span>
<span id="751"> 751</span>
<span id="752"> 752</span>
<span id="753"> 753</span>
<span id="754"> 754</span>
<span id="755"> 755</span>
<span id="756"> 756</span>
<span id="757"> 757</span>
<span id="758"> 758</span>
<span id="759"> 759</span>
<span id="760"> 760</span>
<span id="761"> 761</span>
<span id="762"> 762</span>
<span id="763"> 763</span>
<span id="764"> 764</span>
<span id="765"> 765</span>
<span id="766"> 766</span>
<span id="767"> 767</span>
<span id="768"> 768</span>
<span id="769"> 769</span>
<span id="770"> 770</span>
<span id="771"> 771</span>
<span id="772"> 772</span>
<span id="773"> 773</span>
<span id="774"> 774</span>
<span id="775"> 775</span>
<span id="776"> 776</span>
<span id="777"> 777</span>
<span id="778"> 778</span>
<span id="779"> 779</span>
<span id="780"> 780</span>
<span id="781"> 781</span>
<span id="782"> 782</span>
<span id="783"> 783</span>
<span id="784"> 784</span>
<span id="785"> 785</span>
<span id="786"> 786</span>
<span id="787"> 787</span>
<span id="788"> 788</span>
<span id="789"> 789</span>
<span id="790"> 790</span>
<span id="791"> 791</span>
<span id="792"> 792</span>
<span id="793"> 793</span>
<span id="794"> 794</span>
<span id="795"> 795</span>
<span id="796"> 796</span>
<span id="797"> 797</span>
<span id="798"> 798</span>
<span id="799"> 799</span>
<span id="800"> 800</span>
<span id="801"> 801</span>
<span id="802"> 802</span>
<span id="803"> 803</span>
<span id="804"> 804</span>
<span id="805"> 805</span>
<span id="806"> 806</span>
<span id="807"> 807</span>
<span id="808"> 808</span>
<span id="809"> 809</span>
<span id="810"> 810</span>
<span id="811"> 811</span>
<span id="812"> 812</span>
<span id="813"> 813</span>
<span id="814"> 814</span>
<span id="815"> 815</span>
<span id="816"> 816</span>
<span id="817"> 817</span>
<span id="818"> 818</span>
<span id="819"> 819</span>
<span id="820"> 820</span>
<span id="821"> 821</span>
<span id="822"> 822</span>
<span id="823"> 823</span>
<span id="824"> 824</span>
<span id="825"> 825</span>
<span id="826"> 826</span>
<span id="827"> 827</span>
<span id="828"> 828</span>
<span id="829"> 829</span>
<span id="830"> 830</span>
<span id="831"> 831</span>
<span id="832"> 832</span>
<span id="833"> 833</span>
<span id="834"> 834</span>
<span id="835"> 835</span>
<span id="836"> 836</span>
<span id="837"> 837</span>
<span id="838"> 838</span>
<span id="839"> 839</span>
<span id="840"> 840</span>
<span id="841"> 841</span>
<span id="842"> 842</span>
<span id="843"> 843</span>
<span id="844"> 844</span>
<span id="845"> 845</span>
<span id="846"> 846</span>
<span id="847"> 847</span>
<span id="848"> 848</span>
<span id="849"> 849</span>
<span id="850"> 850</span>
<span id="851"> 851</span>
<span id="852"> 852</span>
<span id="853"> 853</span>
<span id="854"> 854</span>
<span id="855"> 855</span>
<span id="856"> 856</span>
<span id="857"> 857</span>
<span id="858"> 858</span>
<span id="859"> 859</span>
<span id="860"> 860</span>
<span id="861"> 861</span>
<span id="862"> 862</span>
<span id="863"> 863</span>
<span id="864"> 864</span>
<span id="865"> 865</span>
<span id="866"> 866</span>
<span id="867"> 867</span>
<span id="868"> 868</span>
<span id="869"> 869</span>
<span id="870"> 870</span>
<span id="871"> 871</span>
<span id="872"> 872</span>
<span id="873"> 873</span>
<span id="874"> 874</span>
<span id="875"> 875</span>
<span id="876"> 876</span>
<span id="877"> 877</span>
<span id="878"> 878</span>
<span id="879"> 879</span>
<span id="880"> 880</span>
<span id="881"> 881</span>
<span id="882"> 882</span>
<span id="883"> 883</span>
<span id="884"> 884</span>
<span id="885"> 885</span>
<span id="886"> 886</span>
<span id="887"> 887</span>
<span id="888"> 888</span>
<span id="889"> 889</span>
<span id="890"> 890</span>
<span id="891"> 891</span>
<span id="892"> 892</span>
<span id="893"> 893</span>
<span id="894"> 894</span>
<span id="895"> 895</span>
<span id="896"> 896</span>
<span id="897"> 897</span>
<span id="898"> 898</span>
<span id="899"> 899</span>
<span id="900"> 900</span>
<span id="901"> 901</span>
<span id="902"> 902</span>
<span id="903"> 903</span>
<span id="904"> 904</span>
<span id="905"> 905</span>
<span id="906"> 906</span>
<span id="907"> 907</span>
<span id="908"> 908</span>
<span id="909"> 909</span>
<span id="910"> 910</span>
<span id="911"> 911</span>
<span id="912"> 912</span>
<span id="913"> 913</span>
<span id="914"> 914</span>
<span id="915"> 915</span>
<span id="916"> 916</span>
<span id="917"> 917</span>
<span id="918"> 918</span>
<span id="919"> 919</span>
<span id="920"> 920</span>
<span id="921"> 921</span>
<span id="922"> 922</span>
<span id="923"> 923</span>
<span id="924"> 924</span>
<span id="925"> 925</span>
<span id="926"> 926</span>
<span id="927"> 927</span>
<span id="928"> 928</span>
<span id="929"> 929</span>
<span id="930"> 930</span>
<span id="931"> 931</span>
<span id="932"> 932</span>
<span id="933"> 933</span>
<span id="934"> 934</span>
<span id="935"> 935</span>
<span id="936"> 936</span>
<span id="937"> 937</span>
<span id="938"> 938</span>
<span id="939"> 939</span>
<span id="940"> 940</span>
<span id="941"> 941</span>
<span id="942"> 942</span>
<span id="943"> 943</span>
<span id="944"> 944</span>
<span id="945"> 945</span>
<span id="946"> 946</span>
<span id="947"> 947</span>
<span id="948"> 948</span>
<span id="949"> 949</span>
<span id="950"> 950</span>
<span id="951"> 951</span>
<span id="952"> 952</span>
<span id="953"> 953</span>
<span id="954"> 954</span>
<span id="955"> 955</span>
<span id="956"> 956</span>
<span id="957"> 957</span>
<span id="958"> 958</span>
<span id="959"> 959</span>
<span id="960"> 960</span>
<span id="961"> 961</span>
<span id="962"> 962</span>
<span id="963"> 963</span>
<span id="964"> 964</span>
<span id="965"> 965</span>
<span id="966"> 966</span>
<span id="967"> 967</span>
<span id="968"> 968</span>
<span id="969"> 969</span>
<span id="970"> 970</span>
<span id="971"> 971</span>
<span id="972"> 972</span>
<span id="973"> 973</span>
<span id="974"> 974</span>
<span id="975"> 975</span>
<span id="976"> 976</span>
<span id="977"> 977</span>
<span id="978"> 978</span>
<span id="979"> 979</span>
<span id="980"> 980</span>
<span id="981"> 981</span>
<span id="982"> 982</span>
<span id="983"> 983</span>
<span id="984"> 984</span>
<span id="985"> 985</span>
<span id="986"> 986</span>
<span id="987"> 987</span>
<span id="988"> 988</span>
<span id="989"> 989</span>
<span id="990"> 990</span>
<span id="991"> 991</span>
<span id="992"> 992</span>
<span id="993"> 993</span>
<span id="994"> 994</span>
<span id="995"> 995</span>
<span id="996"> 996</span>
<span id="997"> 997</span>
<span id="998"> 998</span>
<span id="999"> 999</span>
<span id="1000">1000</span>
<span id="1001">1001</span>
<span id="1002">1002</span>
<span id="1003">1003</span>
<span id="1004">1004</span>
<span id="1005">1005</span>
<span id="1006">1006</span>
<span id="1007">1007</span>
<span id="1008">1008</span>
<span id="1009">1009</span>
<span id="1010">1010</span>
<span id="1011">1011</span>
<span id="1012">1012</span>
<span id="1013">1013</span>
<span id="1014">1014</span>
<span id="1015">1015</span>
<span id="1016">1016</span>
<span id="1017">1017</span>
<span id="1018">1018</span>
<span id="1019">1019</span>
<span id="1020">1020</span>
<span id="1021">1021</span>
<span id="1022">1022</span>
<span id="1023">1023</span>
<span id="1024">1024</span>
<span id="1025">1025</span>
<span id="1026">1026</span>
<span id="1027">1027</span>
<span id="1028">1028</span>
<span id="1029">1029</span>
<span id="1030">1030</span>
<span id="1031">1031</span>
<span id="1032">1032</span>
<span id="1033">1033</span>
<span id="1034">1034</span>
<span id="1035">1035</span>
<span id="1036">1036</span>
<span id="1037">1037</span>
<span id="1038">1038</span>
<span id="1039">1039</span>
<span id="1040">1040</span>
<span id="1041">1041</span>
<span id="1042">1042</span>
<span id="1043">1043</span>
<span id="1044">1044</span>
<span id="1045">1045</span>
<span id="1046">1046</span>
<span id="1047">1047</span>
<span id="1048">1048</span>
<span id="1049">1049</span>
<span id="1050">1050</span>
<span id="1051">1051</span>
<span id="1052">1052</span>
<span id="1053">1053</span>
<span id="1054">1054</span>
<span id="1055">1055</span>
<span id="1056">1056</span>
<span id="1057">1057</span>
<span id="1058">1058</span>
<span id="1059">1059</span>
<span id="1060">1060</span>
<span id="1061">1061</span>
<span id="1062">1062</span>
<span id="1063">1063</span>
<span id="1064">1064</span>
<span id="1065">1065</span>
<span id="1066">1066</span>
<span id="1067">1067</span>
<span id="1068">1068</span>
<span id="1069">1069</span>
<span id="1070">1070</span>
<span id="1071">1071</span>
<span id="1072">1072</span>
<span id="1073">1073</span>
<span id="1074">1074</span>
<span id="1075">1075</span>
<span id="1076">1076</span>
<span id="1077">1077</span>
<span id="1078">1078</span>
<span id="1079">1079</span>
<span id="1080">1080</span>
<span id="1081">1081</span>
<span id="1082">1082</span>
<span id="1083">1083</span>
<span id="1084">1084</span>
<span id="1085">1085</span>
<span id="1086">1086</span>
<span id="1087">1087</span>
<span id="1088">1088</span>
<span id="1089">1089</span>
<span id="1090">1090</span>
<span id="1091">1091</span>
<span id="1092">1092</span>
<span id="1093">1093</span>
<span id="1094">1094</span>
<span id="1095">1095</span>
<span id="1096">1096</span>
<span id="1097">1097</span>
<span id="1098">1098</span>
<span id="1099">1099</span>
<span id="1100">1100</span>
<span id="1101">1101</span>
<span id="1102">1102</span>
<span id="1103">1103</span>
<span id="1104">1104</span>
<span id="1105">1105</span>
<span id="1106">1106</span>
<span id="1107">1107</span>
<span id="1108">1108</span>
<span id="1109">1109</span>
<span id="1110">1110</span>
<span id="1111">1111</span>
<span id="1112">1112</span>
<span id="1113">1113</span>
<span id="1114">1114</span>
<span id="1115">1115</span>
<span id="1116">1116</span>
<span id="1117">1117</span>
<span id="1118">1118</span>
<span id="1119">1119</span>
<span id="1120">1120</span>
<span id="1121">1121</span>
<span id="1122">1122</span>
<span id="1123">1123</span>
<span id="1124">1124</span>
<span id="1125">1125</span>
<span id="1126">1126</span>
<span id="1127">1127</span>
<span id="1128">1128</span>
<span id="1129">1129</span>
<span id="1130">1130</span>
<span id="1131">1131</span>
<span id="1132">1132</span>
<span id="1133">1133</span>
<span id="1134">1134</span>
<span id="1135">1135</span>
<span id="1136">1136</span>
<span id="1137">1137</span>
<span id="1138">1138</span>
<span id="1139">1139</span>
<span id="1140">1140</span>
<span id="1141">1141</span>
<span id="1142">1142</span>
<span id="1143">1143</span>
<span id="1144">1144</span>
<span id="1145">1145</span>
<span id="1146">1146</span>
<span id="1147">1147</span>
<span id="1148">1148</span>
<span id="1149">1149</span>
<span id="1150">1150</span>
<span id="1151">1151</span>
<span id="1152">1152</span>
<span id="1153">1153</span>
<span id="1154">1154</span>
<span id="1155">1155</span>
<span id="1156">1156</span>
<span id="1157">1157</span>
<span id="1158">1158</span>
<span id="1159">1159</span>
<span id="1160">1160</span>
<span id="1161">1161</span>
<span id="1162">1162</span>
<span id="1163">1163</span>
<span id="1164">1164</span>
<span id="1165">1165</span>
<span id="1166">1166</span>
<span id="1167">1167</span>
<span id="1168">1168</span>
<span id="1169">1169</span>
<span id="1170">1170</span>
<span id="1171">1171</span>
<span id="1172">1172</span>
<span id="1173">1173</span>
<span id="1174">1174</span>
<span id="1175">1175</span>
<span id="1176">1176</span>
<span id="1177">1177</span>
<span id="1178">1178</span>
<span id="1179">1179</span>
<span id="1180">1180</span>
<span id="1181">1181</span>
<span id="1182">1182</span>
<span id="1183">1183</span>
<span id="1184">1184</span>
<span id="1185">1185</span>
<span id="1186">1186</span>
<span id="1187">1187</span>
<span id="1188">1188</span>
<span id="1189">1189</span>
<span id="1190">1190</span>
<span id="1191">1191</span>
<span id="1192">1192</span>
<span id="1193">1193</span>
<span id="1194">1194</span>
<span id="1195">1195</span>
<span id="1196">1196</span>
<span id="1197">1197</span>
<span id="1198">1198</span>
<span id="1199">1199</span>
<span id="1200">1200</span>
<span id="1201">1201</span>
<span id="1202">1202</span>
<span id="1203">1203</span>
<span id="1204">1204</span>
<span id="1205">1205</span>
<span id="1206">1206</span>
<span id="1207">1207</span>
<span id="1208">1208</span>
<span id="1209">1209</span>
<span id="1210">1210</span>
<span id="1211">1211</span>
</pre><pre class="rust ">
<span class="comment">// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! Error handling with the `Result` type.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [`Result<T, E>`][`Result`] is the type used for returning and propagating</span>
<span class="doccomment">//! errors. It is an enum with the variants, [`Ok(T)`], representing</span>
<span class="doccomment">//! success and containing a value, and [`Err(E)`], representing error</span>
<span class="doccomment">//! and containing an error value.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! # #[allow(dead_code)]</span>
<span class="doccomment">//! enum Result<T, E> {</span>
<span class="doccomment">//! Ok(T),</span>
<span class="doccomment">//! Err(E),</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Functions return [`Result`] whenever errors are expected and</span>
<span class="doccomment">//! recoverable. In the `std` crate, [`Result`] is most prominently used</span>
<span class="doccomment">//! for [I/O](../../std/io/index.html).</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! A simple function returning [`Result`] might be</span>
<span class="doccomment">//! defined and used like so:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! #[derive(Debug)]</span>
<span class="doccomment">//! enum Version { Version1, Version2 }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! fn parse_version(header: &[u8]) -> Result<Version, &'static str> {</span>
<span class="doccomment">//! match header.get(0) {</span>
<span class="doccomment">//! None => Err("invalid header length"),</span>
<span class="doccomment">//! Some(&1) => Ok(Version::Version1),</span>
<span class="doccomment">//! Some(&2) => Ok(Version::Version2),</span>
<span class="doccomment">//! Some(_) => Err("invalid version"),</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let version = parse_version(&[1, 2, 3, 4]);</span>
<span class="doccomment">//! match version {</span>
<span class="doccomment">//! Ok(v) => println!("working with version: {:?}", v),</span>
<span class="doccomment">//! Err(e) => println!("error parsing header: {:?}", e),</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Pattern matching on [`Result`]s is clear and straightforward for</span>
<span class="doccomment">//! simple cases, but [`Result`] comes with some convenience methods</span>
<span class="doccomment">//! that make working with it more succinct.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! let good_result: Result<i32, i32> = Ok(10);</span>
<span class="doccomment">//! let bad_result: Result<i32, i32> = Err(10);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // The `is_ok` and `is_err` methods do what they say.</span>
<span class="doccomment">//! assert!(good_result.is_ok() && !good_result.is_err());</span>
<span class="doccomment">//! assert!(bad_result.is_err() && !bad_result.is_ok());</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // `map` consumes the `Result` and produces another.</span>
<span class="doccomment">//! let good_result: Result<i32, i32> = good_result.map(|i| i + 1);</span>
<span class="doccomment">//! let bad_result: Result<i32, i32> = bad_result.map(|i| i - 1);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Use `and_then` to continue the computation.</span>
<span class="doccomment">//! let good_result: Result<bool, i32> = good_result.and_then(|i| Ok(i == 11));</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Use `or_else` to handle the error.</span>
<span class="doccomment">//! let bad_result: Result<i32, i32> = bad_result.or_else(|i| Ok(i + 20));</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Consume the result and return the contents with `unwrap`.</span>
<span class="doccomment">//! let final_awesome_result = good_result.unwrap();</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Results must be used</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! A common problem with using return values to indicate errors is</span>
<span class="doccomment">//! that it is easy to ignore the return value, thus failing to handle</span>
<span class="doccomment">//! the error. [`Result`] is annotated with the `#[must_use]` attribute,</span>
<span class="doccomment">//! which will cause the compiler to issue a warning when a Result</span>
<span class="doccomment">//! value is ignored. This makes [`Result`] especially useful with</span>
<span class="doccomment">//! functions that may encounter errors but don't otherwise return a</span>
<span class="doccomment">//! useful value.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Consider the [`write_all`] method defined for I/O types</span>
<span class="doccomment">//! by the [`Write`] trait:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use std::io;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! trait Write {</span>
<span class="doccomment">//! fn write_all(&mut self, bytes: &[u8]) -> Result<(), io::Error>;</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! *Note: The actual definition of [`Write`] uses [`io::Result`], which</span>
<span class="doccomment">//! is just a synonym for [`Result`]`<T, `[`io::Error`]`>`.*</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This method doesn't produce a value, but the write may</span>
<span class="doccomment">//! fail. It's crucial to handle the error case, and *not* write</span>
<span class="doccomment">//! something like this:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```no_run</span>
<span class="doccomment">//! # #![allow(unused_must_use)] // \o/</span>
<span class="doccomment">//! use std::fs::File;</span>
<span class="doccomment">//! use std::io::prelude::*;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let mut file = File::create("valuable_data.txt").unwrap();</span>
<span class="doccomment">//! // If `write_all` errors, then we'll never know, because the return</span>
<span class="doccomment">//! // value is ignored.</span>
<span class="doccomment">//! file.write_all(b"important message");</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! If you *do* write that in Rust, the compiler will give you a</span>
<span class="doccomment">//! warning (by default, controlled by the `unused_must_use` lint).</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! You might instead, if you don't want to handle the error, simply</span>
<span class="doccomment">//! assert success with [`expect`]. This will panic if the</span>
<span class="doccomment">//! write fails, providing a marginally useful message indicating why:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```{.no_run}</span>
<span class="doccomment">//! use std::fs::File;</span>
<span class="doccomment">//! use std::io::prelude::*;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let mut file = File::create("valuable_data.txt").unwrap();</span>
<span class="doccomment">//! file.write_all(b"important message").expect("failed to write message");</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! You might also simply assert success:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```{.no_run}</span>
<span class="doccomment">//! # use std::fs::File;</span>
<span class="doccomment">//! # use std::io::prelude::*;</span>
<span class="doccomment">//! # let mut file = File::create("valuable_data.txt").unwrap();</span>
<span class="doccomment">//! assert!(file.write_all(b"important message").is_ok());</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Or propagate the error up the call stack with [`?`]:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! # use std::fs::File;</span>
<span class="doccomment">//! # use std::io::prelude::*;</span>
<span class="doccomment">//! # use std::io;</span>
<span class="doccomment">//! # #[allow(dead_code)]</span>
<span class="doccomment">//! fn write_message() -> io::Result<()> {</span>
<span class="doccomment">//! let mut file = File::create("valuable_data.txt")?;</span>
<span class="doccomment">//! file.write_all(b"important message")?;</span>
<span class="doccomment">//! Ok(())</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # The question mark operator, `?`</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! When writing code that calls many functions that return the</span>
<span class="doccomment">//! [`Result`] type, the error handling can be tedious. The question mark</span>
<span class="doccomment">//! operator, [`?`], hides some of the boilerplate of propagating errors</span>
<span class="doccomment">//! up the call stack.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! It replaces this:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! # #![allow(dead_code)]</span>
<span class="doccomment">//! use std::fs::File;</span>
<span class="doccomment">//! use std::io::prelude::*;</span>
<span class="doccomment">//! use std::io;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! struct Info {</span>
<span class="doccomment">//! name: String,</span>
<span class="doccomment">//! age: i32,</span>
<span class="doccomment">//! rating: i32,</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! fn write_info(info: &Info) -> io::Result<()> {</span>
<span class="doccomment">//! // Early return on error</span>
<span class="doccomment">//! let mut file = match File::create("my_best_friends.txt") {</span>
<span class="doccomment">//! Err(e) => return Err(e),</span>
<span class="doccomment">//! Ok(f) => f,</span>
<span class="doccomment">//! };</span>
<span class="doccomment">//! if let Err(e) = file.write_all(format!("name: {}\n", info.name).as_bytes()) {</span>
<span class="doccomment">//! return Err(e)</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! if let Err(e) = file.write_all(format!("age: {}\n", info.age).as_bytes()) {</span>
<span class="doccomment">//! return Err(e)</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! if let Err(e) = file.write_all(format!("rating: {}\n", info.rating).as_bytes()) {</span>
<span class="doccomment">//! return Err(e)</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! Ok(())</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! With this:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! # #![allow(dead_code)]</span>
<span class="doccomment">//! use std::fs::File;</span>
<span class="doccomment">//! use std::io::prelude::*;</span>
<span class="doccomment">//! use std::io;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! struct Info {</span>
<span class="doccomment">//! name: String,</span>
<span class="doccomment">//! age: i32,</span>
<span class="doccomment">//! rating: i32,</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! fn write_info(info: &Info) -> io::Result<()> {</span>
<span class="doccomment">//! let mut file = File::create("my_best_friends.txt")?;</span>
<span class="doccomment">//! // Early return on error</span>
<span class="doccomment">//! file.write_all(format!("name: {}\n", info.name).as_bytes())?;</span>
<span class="doccomment">//! file.write_all(format!("age: {}\n", info.age).as_bytes())?;</span>
<span class="doccomment">//! file.write_all(format!("rating: {}\n", info.rating).as_bytes())?;</span>
<span class="doccomment">//! Ok(())</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! *It's much nicer!*</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Ending the expression with [`?`] will result in the unwrapped</span>
<span class="doccomment">//! success ([`Ok`]) value, unless the result is [`Err`], in which case</span>
<span class="doccomment">//! [`Err`] is returned early from the enclosing function.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [`?`] can only be used in functions that return [`Result`] because of the</span>
<span class="doccomment">//! early return of [`Err`] that it provides.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [`expect`]: enum.Result.html#method.expect</span>
<span class="doccomment">//! [`Write`]: ../../std/io/trait.Write.html</span>
<span class="doccomment">//! [`write_all`]: ../../std/io/trait.Write.html#method.write_all</span>
<span class="doccomment">//! [`io::Result`]: ../../std/io/type.Result.html</span>
<span class="doccomment">//! [`?`]: ../../std/macro.try.html</span>
<span class="doccomment">//! [`Result`]: enum.Result.html</span>
<span class="doccomment">//! [`Ok(T)`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">//! [`Err(E)`]: enum.Result.html#variant.Err</span>
<span class="doccomment">//! [`io::Error`]: ../../std/io/struct.Error.html</span>
<span class="doccomment">//! [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">//! [`Err`]: enum.Result.html#variant.Err</span>
<span class="attribute">#![<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">use</span> <span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">iter</span>::{<span class="ident">FromIterator</span>, <span class="ident">FusedIterator</span>, <span class="ident">TrustedLen</span>};
<span class="kw">use</span> <span class="ident">ops</span>;
<span class="doccomment">/// `Result` is a type that represents either success ([`Ok`]) or failure ([`Err`]).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See the [`std::result`](index.html) module documentation for details.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">PartialEq</span>, <span class="ident">PartialOrd</span>, <span class="ident">Eq</span>, <span class="ident">Ord</span>, <span class="ident">Debug</span>, <span class="ident">Hash</span>)]</span>
<span class="attribute">#[<span class="ident">must_use</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="doccomment">/// Contains the success value</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="prelude-val">Ok</span>(<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="ident">T</span>),
<span class="doccomment">/// Contains the error value</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="prelude-val">Err</span>(<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="ident">E</span>),
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Type implementation</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Querying the contained values</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Returns `true` if the result is [`Ok`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<i32, &str> = Ok(-3);</span>
<span class="doccomment">/// assert_eq!(x.is_ok(), true);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<i32, &str> = Err("Some error message");</span>
<span class="doccomment">/// assert_eq!(x.is_ok(), false);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_ok</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">Ok</span>(_) <span class="op">=></span> <span class="bool-val">true</span>,
<span class="prelude-val">Err</span>(_) <span class="op">=></span> <span class="bool-val">false</span>
}
}
<span class="doccomment">/// Returns `true` if the result is [`Err`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<i32, &str> = Ok(-3);</span>
<span class="doccomment">/// assert_eq!(x.is_err(), false);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<i32, &str> = Err("Some error message");</span>
<span class="doccomment">/// assert_eq!(x.is_err(), true);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_err</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="op">!</span><span class="self">self</span>.<span class="ident">is_ok</span>()
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Adapter for each variant</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Converts from `Result<T, E>` to [`Option<T>`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Converts `self` into an [`Option<T>`], consuming `self`,</span>
<span class="doccomment">/// and discarding the error, if any.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Option<T>`]: ../../std/option/enum.Option.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// assert_eq!(x.ok(), Some(2));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("Nothing here");</span>
<span class="doccomment">/// assert_eq!(x.ok(), None);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ok</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="ident">x</span>),
<span class="prelude-val">Err</span>(_) <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// Converts from `Result<T, E>` to [`Option<E>`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Converts `self` into an [`Option<E>`], consuming `self`,</span>
<span class="doccomment">/// and discarding the success value, if any.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Option<E>`]: ../../std/option/enum.Option.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// assert_eq!(x.err(), None);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("Nothing here");</span>
<span class="doccomment">/// assert_eq!(x.err(), Some("Nothing here"));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">err</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">E</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(_) <span class="op">=></span> <span class="prelude-val">None</span>,
<span class="prelude-val">Err</span>(<span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="ident">x</span>),
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Adapter for working with references</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Converts from `Result<T, E>` to `Result<&T, &E>`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Produces a new `Result`, containing a reference</span>
<span class="doccomment">/// into the original, leaving the original in place.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// assert_eq!(x.as_ref(), Ok(&2));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("Error");</span>
<span class="doccomment">/// assert_eq!(x.as_ref(), Err(&"Error"));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">as_ref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">T</span>, <span class="kw-2">&</span><span class="ident">E</span><span class="op">></span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="kw-2">ref</span> <span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">x</span>),
<span class="prelude-val">Err</span>(<span class="kw-2">ref</span> <span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">x</span>),
}
}
<span class="doccomment">/// Converts from `Result<T, E>` to `Result<&mut T, &mut E>`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// fn mutate(r: &mut Result<i32, i32>) {</span>
<span class="doccomment">/// match r.as_mut() {</span>
<span class="doccomment">/// Ok(v) => *v = 42,</span>
<span class="doccomment">/// Err(e) => *e = 0,</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x: Result<i32, i32> = Ok(2);</span>
<span class="doccomment">/// mutate(&mut x);</span>
<span class="doccomment">/// assert_eq!(x.unwrap(), 42);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x: Result<i32, i32> = Err(13);</span>
<span class="doccomment">/// mutate(&mut x);</span>
<span class="doccomment">/// assert_eq!(x.unwrap_err(), 0);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">as_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">E</span><span class="op">></span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">x</span>),
<span class="prelude-val">Err</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">x</span>),
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Transforming contained values</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Maps a `Result<T, E>` to `Result<U, E>` by applying a function to a</span>
<span class="doccomment">/// contained [`Ok`] value, leaving an [`Err`] value untouched.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function can be used to compose the results of two functions.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Print the numbers on each line of a string multiplied by two.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let line = "1\n2\n3\n4\n";</span>
<span class="doccomment">///</span>
<span class="doccomment">/// for num in line.lines() {</span>
<span class="doccomment">/// match num.parse::<i32>().map(|i| i * 2) {</span>
<span class="doccomment">/// Ok(n) => println!("{}", n),</span>
<span class="doccomment">/// Err(..) => {}</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">map</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="ident">T</span>) <span class="op">-></span> <span class="ident">U</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">op</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">U</span>,<span class="ident">E</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">op</span>(<span class="ident">t</span>)),
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">e</span>)
}
}
<span class="doccomment">/// Maps a `Result<T, E>` to `Result<T, F>` by applying a function to a</span>
<span class="doccomment">/// contained [`Err`] value, leaving an [`Ok`] value untouched.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function can be used to pass through a successful result while handling</span>
<span class="doccomment">/// an error.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// fn stringify(x: u32) -> String { format!("error code: {}", x) }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, u32> = Ok(2);</span>
<span class="doccomment">/// assert_eq!(x.map_err(stringify), Ok(2));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, u32> = Err(13);</span>
<span class="doccomment">/// assert_eq!(x.map_err(stringify), Err("error code: 13".to_string()));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">map_err</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">O</span>: <span class="ident">FnOnce</span>(<span class="ident">E</span>) <span class="op">-></span> <span class="ident">F</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">op</span>: <span class="ident">O</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>,<span class="ident">F</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">t</span>),
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">op</span>(<span class="ident">e</span>))
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Iterator constructors</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Returns an iterator over the possibly contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The iterator yields one value if the result is [`Ok`], otherwise none.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(7);</span>
<span class="doccomment">/// assert_eq!(x.iter().next(), Some(&7));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("nothing!");</span>
<span class="doccomment">/// assert_eq!(x.iter().next(), None);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">iter</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Iter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">Iter</span> { <span class="ident">inner</span>: <span class="self">self</span>.<span class="ident">as_ref</span>().<span class="ident">ok</span>() }
}
<span class="doccomment">/// Returns a mutable iterator over the possibly contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The iterator yields one value if the result is [`Ok`], otherwise none.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let mut x: Result<u32, &str> = Ok(7);</span>
<span class="doccomment">/// match x.iter_mut().next() {</span>
<span class="doccomment">/// Some(v) => *v = 40,</span>
<span class="doccomment">/// None => {},</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// assert_eq!(x, Ok(40));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x: Result<u32, &str> = Err("nothing!");</span>
<span class="doccomment">/// assert_eq!(x.iter_mut().next(), None);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">iter_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">IterMut</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">IterMut</span> { <span class="ident">inner</span>: <span class="self">self</span>.<span class="ident">as_mut</span>().<span class="ident">ok</span>() }
}
<span class="comment">////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Boolean operations on the values, eager and lazy</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Returns `res` if the result is [`Ok`], otherwise returns the [`Err`] value of `self`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// let y: Result<&str, &str> = Err("late error");</span>
<span class="doccomment">/// assert_eq!(x.and(y), Err("late error"));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("early error");</span>
<span class="doccomment">/// let y: Result<&str, &str> = Ok("foo");</span>
<span class="doccomment">/// assert_eq!(x.and(y), Err("early error"));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("not a 2");</span>
<span class="doccomment">/// let y: Result<&str, &str> = Err("late error");</span>
<span class="doccomment">/// assert_eq!(x.and(y), Err("not a 2"));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// let y: Result<&str, &str> = Ok("different result type");</span>
<span class="doccomment">/// assert_eq!(x.and(y), Ok("different result type"));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">and</span><span class="op"><</span><span class="ident">U</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">res</span>: <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">E</span><span class="op">></span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(_) <span class="op">=></span> <span class="ident">res</span>,
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">e</span>),
}
}
<span class="doccomment">/// Calls `op` if the result is [`Ok`], otherwise returns the [`Err`] value of `self`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function can be used for control flow based on `Result` values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// fn sq(x: u32) -> Result<u32, u32> { Ok(x * x) }</span>
<span class="doccomment">/// fn err(x: u32) -> Result<u32, u32> { Err(x) }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(Ok(2).and_then(sq).and_then(sq), Ok(16));</span>
<span class="doccomment">/// assert_eq!(Ok(2).and_then(sq).and_then(err), Err(4));</span>
<span class="doccomment">/// assert_eq!(Ok(2).and_then(err).and_then(sq), Err(2));</span>
<span class="doccomment">/// assert_eq!(Err(3).and_then(sq).and_then(sq), Err(3));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">and_then</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="ident">T</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">E</span><span class="op">>></span>(<span class="self">self</span>, <span class="ident">op</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">op</span>(<span class="ident">t</span>),
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">e</span>),
}
}
<span class="doccomment">/// Returns `res` if the result is [`Err`], otherwise returns the [`Ok`] value of `self`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Arguments passed to `or` are eagerly evaluated; if you are passing the</span>
<span class="doccomment">/// result of a function call, it is recommended to use [`or_else`], which is</span>
<span class="doccomment">/// lazily evaluated.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">/// [`or_else`]: #method.or_else</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// let y: Result<u32, &str> = Err("late error");</span>
<span class="doccomment">/// assert_eq!(x.or(y), Ok(2));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("early error");</span>
<span class="doccomment">/// let y: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// assert_eq!(x.or(y), Ok(2));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("not a 2");</span>
<span class="doccomment">/// let y: Result<u32, &str> = Err("late error");</span>
<span class="doccomment">/// assert_eq!(x.or(y), Err("late error"));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// let y: Result<u32, &str> = Ok(100);</span>
<span class="doccomment">/// assert_eq!(x.or(y), Ok(2));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">or</span><span class="op"><</span><span class="ident">F</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">res</span>: <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">F</span><span class="op">></span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">F</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">v</span>) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">v</span>),
<span class="prelude-val">Err</span>(_) <span class="op">=></span> <span class="ident">res</span>,
}
}
<span class="doccomment">/// Calls `op` if the result is [`Err`], otherwise returns the [`Ok`] value of `self`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function can be used for control flow based on result values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// fn sq(x: u32) -> Result<u32, u32> { Ok(x * x) }</span>
<span class="doccomment">/// fn err(x: u32) -> Result<u32, u32> { Err(x) }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(Ok(2).or_else(sq).or_else(sq), Ok(2));</span>
<span class="doccomment">/// assert_eq!(Ok(2).or_else(err).or_else(sq), Ok(2));</span>
<span class="doccomment">/// assert_eq!(Err(3).or_else(sq).or_else(err), Ok(9));</span>
<span class="doccomment">/// assert_eq!(Err(3).or_else(err).or_else(err), Err(3));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">or_else</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">O</span>: <span class="ident">FnOnce</span>(<span class="ident">E</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">F</span><span class="op">>></span>(<span class="self">self</span>, <span class="ident">op</span>: <span class="ident">O</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">F</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">t</span>),
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="ident">op</span>(<span class="ident">e</span>),
}
}
<span class="doccomment">/// Unwraps a result, yielding the content of an [`Ok`].</span>
<span class="doccomment">/// Else, it returns `optb`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Arguments passed to `unwrap_or` are eagerly evaluated; if you are passing</span>
<span class="doccomment">/// the result of a function call, it is recommended to use [`unwrap_or_else`],</span>
<span class="doccomment">/// which is lazily evaluated.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">/// [`unwrap_or_else`]: #method.unwrap_or_else</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let optb = 2;</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(9);</span>
<span class="doccomment">/// assert_eq!(x.unwrap_or(optb), 9);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("error");</span>
<span class="doccomment">/// assert_eq!(x.unwrap_or(optb), optb);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap_or</span>(<span class="self">self</span>, <span class="ident">optb</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">t</span>,
<span class="prelude-val">Err</span>(_) <span class="op">=></span> <span class="ident">optb</span>
}
}
<span class="doccomment">/// Unwraps a result, yielding the content of an [`Ok`].</span>
<span class="doccomment">/// If the value is an [`Err`] then it calls `op` with its value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// fn count(x: &str) -> usize { x.len() }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(Ok(2).unwrap_or_else(count), 2);</span>
<span class="doccomment">/// assert_eq!(Err("foo").unwrap_or_else(count), 3);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap_or_else</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="ident">E</span>) <span class="op">-></span> <span class="ident">T</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">op</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">t</span>,
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="ident">op</span>(<span class="ident">e</span>)
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span>: <span class="ident">fmt</span>::<span class="ident">Debug</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="doccomment">/// Unwraps a result, yielding the content of an [`Ok`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if the value is an [`Err`], with a panic message provided by the</span>
<span class="doccomment">/// [`Err`]'s value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// assert_eq!(x.unwrap(), 2);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```{.should_panic}</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("emergency failure");</span>
<span class="doccomment">/// x.unwrap(); // panics with `emergency failure`</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">t</span>,
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="ident">unwrap_failed</span>(<span class="string">"called `Result::unwrap()` on an `Err` value"</span>, <span class="ident">e</span>),
}
}
<span class="doccomment">/// Unwraps a result, yielding the content of an [`Ok`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if the value is an [`Err`], with a panic message including the</span>
<span class="doccomment">/// passed message, and the content of the [`Err`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```{.should_panic}</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("emergency failure");</span>
<span class="doccomment">/// x.expect("Testing expect"); // panics with `Testing expect: emergency failure`</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"result_expect"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">expect</span>(<span class="self">self</span>, <span class="ident">msg</span>: <span class="kw-2">&</span><span class="ident">str</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">t</span>,
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="ident">unwrap_failed</span>(<span class="ident">msg</span>, <span class="ident">e</span>),
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">fmt</span>::<span class="ident">Debug</span>, <span class="ident">E</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="doccomment">/// Unwraps a result, yielding the content of an [`Err`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if the value is an [`Ok`], with a custom panic message provided</span>
<span class="doccomment">/// by the [`Ok`]'s value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```{.should_panic}</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(2);</span>
<span class="doccomment">/// x.unwrap_err(); // panics with `2`</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("emergency failure");</span>
<span class="doccomment">/// assert_eq!(x.unwrap_err(), "emergency failure");</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap_err</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">E</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">unwrap_failed</span>(<span class="string">"called `Result::unwrap_err()` on an `Ok` value"</span>, <span class="ident">t</span>),
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="ident">e</span>,
}
}
<span class="doccomment">/// Unwraps a result, yielding the content of an [`Err`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if the value is an [`Ok`], with a panic message including the</span>
<span class="doccomment">/// passed message, and the content of the [`Ok`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```{.should_panic}</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(10);</span>
<span class="doccomment">/// x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"result_expect_err"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.17.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">expect_err</span>(<span class="self">self</span>, <span class="ident">msg</span>: <span class="kw-2">&</span><span class="ident">str</span>) <span class="op">-></span> <span class="ident">E</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">unwrap_failed</span>(<span class="ident">msg</span>, <span class="ident">t</span>),
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="ident">e</span>,
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Default</span>, <span class="ident">E</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="doccomment">/// Returns the contained value or a default</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Consumes the `self` argument then, if [`Ok`], returns the contained</span>
<span class="doccomment">/// value, otherwise if [`Err`], returns the default value for that</span>
<span class="doccomment">/// type.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Convert a string to an integer, turning poorly-formed strings</span>
<span class="doccomment">/// into 0 (the default value for integers). [`parse`] converts</span>
<span class="doccomment">/// a string to any other type that implements [`FromStr`], returning an</span>
<span class="doccomment">/// [`Err`] on error.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let good_year_from_input = "1909";</span>
<span class="doccomment">/// let bad_year_from_input = "190blarg";</span>
<span class="doccomment">/// let good_year = good_year_from_input.parse().unwrap_or_default();</span>
<span class="doccomment">/// let bad_year = bad_year_from_input.parse().unwrap_or_default();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(1909, good_year);</span>
<span class="doccomment">/// assert_eq!(0, bad_year);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`parse`]: ../../std/primitive.str.html#method.parse</span>
<span class="doccomment">/// [`FromStr`]: ../../std/str/trait.FromStr.html</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err`]: enum.Result.html#variant.Err</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"result_unwrap_or_default"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.16.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap_or_default</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">x</span>) <span class="op">=></span> <span class="ident">x</span>,
<span class="prelude-val">Err</span>(_) <span class="op">=></span> <span class="ident">Default</span>::<span class="ident">default</span>(),
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="ident">E</span><span class="op">></span> {
<span class="doccomment">/// Transposes a `Result` of an `Option` into an `Option` of a `Result`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `Ok(None)` will be mapped to `None`.</span>
<span class="doccomment">/// `Ok(Some(_))` and `Err(_)` will be mapped to `Some(Ok(_))` and `Some(Err(_))`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// #![feature(transpose_result)]</span>
<span class="doccomment">///</span>
<span class="doccomment">/// #[derive(Debug, Eq, PartialEq)]</span>
<span class="doccomment">/// struct SomeErr;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<Option<i32>, SomeErr> = Ok(Some(5));</span>
<span class="doccomment">/// let y: Option<Result<i32, SomeErr>> = Some(Ok(5));</span>
<span class="doccomment">/// assert_eq!(x.transpose(), y);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"transpose_result"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"47338"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">transpose</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">>></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="ident">x</span>)) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(<span class="ident">x</span>)),
<span class="prelude-val">Ok</span>(<span class="prelude-val">None</span>) <span class="op">=></span> <span class="prelude-val">None</span>,
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="prelude-val">Err</span>(<span class="ident">e</span>)),
}
}
}
<span class="comment">// This is a separate function to reduce the code size of the methods</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">never</span>)]</span>
<span class="attribute">#[<span class="ident">cold</span>]</span>
<span class="kw">fn</span> <span class="ident">unwrap_failed</span><span class="op"><</span><span class="ident">E</span>: <span class="ident">fmt</span>::<span class="ident">Debug</span><span class="op">></span>(<span class="ident">msg</span>: <span class="kw-2">&</span><span class="ident">str</span>, <span class="ident">error</span>: <span class="ident">E</span>) <span class="op">-></span> <span class="op">!</span> {
<span class="macro">panic</span><span class="macro">!</span>(<span class="string">"{}: {:?}"</span>, <span class="ident">msg</span>, <span class="ident">error</span>)
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Trait implementations</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> <span class="ident">IntoIterator</span> <span class="kw">for</span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="kw">type</span> <span class="ident">IntoIter</span> <span class="op">=</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="doccomment">/// Returns a consuming iterator over the possibly contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The iterator yields one value if the result is [`Ok`], otherwise none.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Result<u32, &str> = Ok(5);</span>
<span class="doccomment">/// let v: Vec<u32> = x.into_iter().collect();</span>
<span class="doccomment">/// assert_eq!(v, [5]);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Result<u32, &str> = Err("nothing!");</span>
<span class="doccomment">/// let v: Vec<u32> = x.into_iter().collect();</span>
<span class="doccomment">/// assert_eq!(v, []);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">into_iter</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">IntoIter</span> { <span class="ident">inner</span>: <span class="self">self</span>.<span class="ident">ok</span>() }
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"result_iter"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> <span class="ident">IntoIterator</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span>;
<span class="kw">type</span> <span class="ident">IntoIter</span> <span class="op">=</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>;
<span class="kw">fn</span> <span class="ident">into_iter</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">iter</span>()
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"result_iter"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> <span class="ident">IntoIterator</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span>;
<span class="kw">type</span> <span class="ident">IntoIter</span> <span class="op">=</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>;
<span class="kw">fn</span> <span class="ident">into_iter</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">iter_mut</span>()
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// The Result Iterators</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// An iterator over a reference to the [`Ok`] variant of a [`Result`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The iterator yields one value if the result is [`Ok`], otherwise none.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Created by [`Result::iter`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Result`]: enum.Result.html</span>
<span class="doccomment">/// [`Result::iter`]: enum.Result.html#method.iter</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="lifetime">'a</span><span class="op">></span> { <span class="ident">inner</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span><span class="op">></span> }
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">take</span>() }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">size_hint</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>) {
<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="kw">if</span> <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">is_some</span>() {<span class="number">1</span>} <span class="kw">else</span> {<span class="number">0</span>};
(<span class="ident">n</span>, <span class="prelude-val">Some</span>(<span class="ident">n</span>))
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">DoubleEndedIterator</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">take</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">ExactSizeIterator</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"fused"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"35602"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">FusedIterator</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"trusted_len"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"37572"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">TrustedLen</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> { <span class="ident">Iter</span> { <span class="ident">inner</span>: <span class="self">self</span>.<span class="ident">inner</span> } }
}
<span class="doccomment">/// An iterator over a mutable reference to the [`Ok`] variant of a [`Result`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Created by [`Result::iter_mut`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Result`]: enum.Result.html</span>
<span class="doccomment">/// [`Result::iter_mut`]: enum.Result.html#method.iter_mut</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="lifetime">'a</span><span class="op">></span> { <span class="ident">inner</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span><span class="op">></span> }
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">take</span>() }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">size_hint</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>) {
<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="kw">if</span> <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">is_some</span>() {<span class="number">1</span>} <span class="kw">else</span> {<span class="number">0</span>};
(<span class="ident">n</span>, <span class="prelude-val">Some</span>(<span class="ident">n</span>))
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">DoubleEndedIterator</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">take</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">ExactSizeIterator</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"fused"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"35602"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">FusedIterator</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"trusted_len"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"37572"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">TrustedLen</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {}
<span class="doccomment">/// An iterator over the value in a [`Ok`] variant of a [`Result`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The iterator yields one value if the result is [`Ok`], otherwise none.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This struct is created by the [`into_iter`] method on</span>
<span class="doccomment">/// [`Result`][`Result`] (provided by the [`IntoIterator`] trait).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Ok`]: enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Result`]: enum.Result.html</span>
<span class="doccomment">/// [`into_iter`]: ../iter/trait.IntoIterator.html#tymethod.into_iter</span>
<span class="doccomment">/// [`IntoIterator`]: ../iter/trait.IntoIterator.html</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="ident">inner</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> }
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">take</span>() }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">size_hint</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>) {
<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="kw">if</span> <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">is_some</span>() {<span class="number">1</span>} <span class="kw">else</span> {<span class="number">0</span>};
(<span class="ident">n</span>, <span class="prelude-val">Some</span>(<span class="ident">n</span>))
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">DoubleEndedIterator</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">take</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">ExactSizeIterator</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"fused"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"35602"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">FusedIterator</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"trusted_len"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"37572"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">TrustedLen</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// FromIterator</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span>, <span class="ident">E</span>, <span class="ident">V</span>: <span class="ident">FromIterator</span><span class="op"><</span><span class="ident">A</span><span class="op">>></span> <span class="ident">FromIterator</span><span class="op"><</span><span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">A</span>, <span class="ident">E</span><span class="op">>></span> <span class="kw">for</span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">V</span>, <span class="ident">E</span><span class="op">></span> {
<span class="doccomment">/// Takes each element in the `Iterator`: if it is an `Err`, no further</span>
<span class="doccomment">/// elements are taken, and the `Err` is returned. Should no `Err` occur, a</span>
<span class="doccomment">/// container with the values of each `Result` is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Here is an example which increments every integer in a vector,</span>
<span class="doccomment">/// checking for overflow:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let v = vec![1, 2];</span>
<span class="doccomment">/// let res: Result<Vec<u32>, &'static str> = v.iter().map(|x: &u32|</span>
<span class="doccomment">/// x.checked_add(1).ok_or("Overflow!")</span>
<span class="doccomment">/// ).collect();</span>
<span class="doccomment">/// assert!(res == Ok(vec![2, 3]));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from_iter</span><span class="op"><</span><span class="ident">I</span>: <span class="ident">IntoIterator</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">A</span>, <span class="ident">E</span><span class="op">>></span><span class="op">></span>(<span class="ident">iter</span>: <span class="ident">I</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">V</span>, <span class="ident">E</span><span class="op">></span> {
<span class="comment">// FIXME(#11084): This could be replaced with Iterator::scan when this</span>
<span class="comment">// performance bug is closed.</span>
<span class="kw">struct</span> <span class="ident">Adapter</span><span class="op"><</span><span class="ident">Iter</span>, <span class="ident">E</span><span class="op">></span> {
<span class="ident">iter</span>: <span class="ident">Iter</span>,
<span class="ident">err</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">E</span><span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span>, <span class="ident">Iter</span>: <span class="ident">Iterator</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">>></span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">Adapter</span><span class="op"><</span><span class="ident">Iter</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">iter</span>.<span class="ident">next</span>() {
<span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(<span class="ident">value</span>)) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="ident">value</span>),
<span class="prelude-val">Some</span>(<span class="prelude-val">Err</span>(<span class="ident">err</span>)) <span class="op">=></span> {
<span class="self">self</span>.<span class="ident">err</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">err</span>);
<span class="prelude-val">None</span>
}
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="kw">fn</span> <span class="ident">size_hint</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>) {
<span class="kw">let</span> (<span class="ident">_min</span>, <span class="ident">max</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">iter</span>.<span class="ident">size_hint</span>();
(<span class="number">0</span>, <span class="ident">max</span>)
}
}
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">adapter</span> <span class="op">=</span> <span class="ident">Adapter</span> { <span class="ident">iter</span>: <span class="ident">iter</span>.<span class="ident">into_iter</span>(), <span class="ident">err</span>: <span class="prelude-val">None</span> };
<span class="kw">let</span> <span class="ident">v</span>: <span class="ident">V</span> <span class="op">=</span> <span class="ident">FromIterator</span>::<span class="ident">from_iter</span>(<span class="ident">adapter</span>.<span class="ident">by_ref</span>());
<span class="kw">match</span> <span class="ident">adapter</span>.<span class="ident">err</span> {
<span class="prelude-val">Some</span>(<span class="ident">err</span>) <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">err</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">v</span>),
}
}
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"try_trait"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"42327"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>,<span class="ident">E</span><span class="op">></span> <span class="ident">ops</span>::<span class="ident">Try</span> <span class="kw">for</span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">type</span> <span class="prelude-val">Ok</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">E</span>;
<span class="kw">fn</span> <span class="ident">into_result</span>(<span class="self">self</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="self">self</span>
}
<span class="kw">fn</span> <span class="ident">from_ok</span>(<span class="ident">v</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="prelude-val">Ok</span>(<span class="ident">v</span>)
}
<span class="kw">fn</span> <span class="ident">from_error</span>(<span class="ident">v</span>: <span class="ident">E</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="prelude-val">Err</span>(<span class="ident">v</span>)
}
}
</pre>
</section>
<section id='search' class="content hidden"></section>
<section class="footer"></section>
<aside id="help" class="hidden">
<div>
<h1 class="hidden">Help</h1>
<div class="shortcuts">
<h2>Keyboard Shortcuts</h2>
<dl>
<dt><kbd>?</kbd></dt>
<dd>Show this help dialog</dd>
<dt><kbd>S</kbd></dt>
<dd>Focus the search field</dd>
<dt><kbd>↑</kbd></dt>
<dd>Move up in search results</dd>
<dt><kbd>↓</kbd></dt>
<dd>Move down in search results</dd>
<dt><kbd>↹</kbd></dt>
<dd>Switch tab</dd>
<dt><kbd>⏎</kbd></dt>
<dd>Go to active search result</dd>
<dt><kbd>+</kbd></dt>
<dd>Expand all sections</dd>
<dt><kbd>-</kbd></dt>
<dd>Collapse all sections</dd>
</dl>
</div>
<div class="infos">
<h2>Search Tricks</h2>
<p>
Prefix searches with a type followed by a colon (e.g.
<code>fn:</code>) to restrict the search to a given type.
</p>
<p>
Accepted types are: <code>fn</code>, <code>mod</code>,
<code>struct</code>, <code>enum</code>,
<code>trait</code>, <code>type</code>, <code>macro</code>,
and <code>const</code>.
</p>
<p>
Search functions by type signature (e.g.
<code>vec -> usize</code> or <code>* -> vec</code>)
</p>
</div>
</div>
</aside>
<script>
window.rootPath = "../../";
window.currentCrate = "core";
</script>
<script src="../../main.js"></script>
<script defer src="../../search-index.js"></script>
</body>
</html>
distrib
>
Mageia
>
6
>
x86_64
>
media
>
core-updates
>
by-pkgid
>
fdedb3cf2140df9b6d419a2338ab1caa
>
files
>
3257
