| <!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 of the Rust file `crates/parser/src/event.rs`."><title>event.rs - source</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../static.files/rustdoc-b7b9f40b.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="parser" data-themes="" data-resource-suffix="" data-rustdoc-version="1.95.0 (59807616e 2026-04-14)" data-channel="1.95.0" data-search-js="search-63369b7b.js" data-stringdex-js="stringdex-b897f86f.js" data-settings-js="settings-170eb4bf.js" ><script src="../../static.files/storage-41dd4d93.js"></script><script defer src="../../static.files/src-script-813739b1.js"></script><script defer src="../../src-files.js"></script><script defer src="../../static.files/main-5013f961.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-f7c3ffd8.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-eab170b8.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-044be391.svg"></head><body class="rustdoc src"><a class="skip-main-content" href="#main-content">Skip to main content</a><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="src-sidebar-title"><h2>Files</h2></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><section id="main-content" class="content" tabindex="-1"><div class="main-heading"><h1><div class="sub-heading">parser/</div>event.rs</h1><rustdoc-toolbar></rustdoc-toolbar></div><div class="example-wrap digits-3"><pre class="rust"><code><a href=#1 id=1 data-nosnippet>1</a><span class="doccomment">//! This module provides a way to construct a `File`. |
| <a href=#2 id=2 data-nosnippet>2</a>//! It is intended to be completely decoupled from the |
| <a href=#3 id=3 data-nosnippet>3</a>//! parser, so as to allow to evolve the tree representation |
| <a href=#4 id=4 data-nosnippet>4</a>//! and the parser algorithm independently. |
| <a href=#5 id=5 data-nosnippet>5</a></span><span class="kw">use </span>std::{mem, num::NonZeroU32}; |
| <a href=#6 id=6 data-nosnippet>6</a> |
| <a href=#7 id=7 data-nosnippet>7</a><span class="kw">use </span>crate::{ |
| <a href=#8 id=8 data-nosnippet>8</a> SyntaxKind::{<span class="self">self</span>, <span class="kw-2">*</span>}, |
| <a href=#9 id=9 data-nosnippet>9</a> output::Output, |
| <a href=#10 id=10 data-nosnippet>10</a>}; |
| <a href=#11 id=11 data-nosnippet>11</a> |
| <a href=#12 id=12 data-nosnippet>12</a><span class="doccomment">/// `Parser` produces a flat list of `Event`s. |
| <a href=#13 id=13 data-nosnippet>13</a>/// They are converted to a tree-structure in |
| <a href=#14 id=14 data-nosnippet>14</a>/// a separate pass, via `TreeBuilder`. |
| <a href=#15 id=15 data-nosnippet>15</a>/// |
| <a href=#16 id=16 data-nosnippet>16</a>/// Kept to 8 bytes: error messages live in a side table on the `Parser` |
| <a href=#17 id=17 data-nosnippet>17</a>/// (the `errors` vec) and `Event::Error` only stores an index into it. |
| <a href=#18 id=18 data-nosnippet>18</a>/// `forward_parent` uses `NonZeroU32` so `Option` is niche-optimised away |
| <a href=#19 id=19 data-nosnippet>19</a>/// (the offset is always ≥ 1 because the forward parent sits later in the |
| <a href=#20 id=20 data-nosnippet>20</a>/// event stream). |
| <a href=#21 id=21 data-nosnippet>21</a></span><span class="attr">#[derive(Debug, PartialEq, Clone, Copy)] |
| <a href=#22 id=22 data-nosnippet>22</a></span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">enum </span>Event { |
| <a href=#23 id=23 data-nosnippet>23</a> <span class="doccomment">/// This event signifies the start of the node. |
| <a href=#24 id=24 data-nosnippet>24</a> /// It should be either abandoned (in which case the |
| <a href=#25 id=25 data-nosnippet>25</a> /// `kind` is `TOMBSTONE`, and the event is ignored), |
| <a href=#26 id=26 data-nosnippet>26</a> /// or completed via a `Finish` event. |
| <a href=#27 id=27 data-nosnippet>27</a> /// |
| <a href=#28 id=28 data-nosnippet>28</a> /// All tokens between a `Start` and a `Finish` would |
| <a href=#29 id=29 data-nosnippet>29</a> /// become the children of the respective node. |
| <a href=#30 id=30 data-nosnippet>30</a> /// |
| <a href=#31 id=31 data-nosnippet>31</a> /// For left-recursive syntactic constructs, the parser produces |
| <a href=#32 id=32 data-nosnippet>32</a> /// a child node before it sees a parent. `forward_parent` |
| <a href=#33 id=33 data-nosnippet>33</a> /// saves the position of current event's parent. |
| <a href=#34 id=34 data-nosnippet>34</a> /// |
| <a href=#35 id=35 data-nosnippet>35</a> /// Consider this path |
| <a href=#36 id=36 data-nosnippet>36</a> /// |
| <a href=#37 id=37 data-nosnippet>37</a> /// foo::bar |
| <a href=#38 id=38 data-nosnippet>38</a> /// |
| <a href=#39 id=39 data-nosnippet>39</a> /// The events for it would look like this: |
| <a href=#40 id=40 data-nosnippet>40</a> /// |
| <a href=#41 id=41 data-nosnippet>41</a> /// ```text |
| <a href=#42 id=42 data-nosnippet>42</a> /// START(PATH) IDENT('foo') FINISH START(PATH) T![::] IDENT('bar') FINISH |
| <a href=#43 id=43 data-nosnippet>43</a> /// | /\ |
| <a href=#44 id=44 data-nosnippet>44</a> /// | | |
| <a href=#45 id=45 data-nosnippet>45</a> /// +------forward-parent------+ |
| <a href=#46 id=46 data-nosnippet>46</a> /// ``` |
| <a href=#47 id=47 data-nosnippet>47</a> /// |
| <a href=#48 id=48 data-nosnippet>48</a> /// And the tree would look like this |
| <a href=#49 id=49 data-nosnippet>49</a> /// |
| <a href=#50 id=50 data-nosnippet>50</a> /// ```text |
| <a href=#51 id=51 data-nosnippet>51</a> /// +--PATH---------+ |
| <a href=#52 id=52 data-nosnippet>52</a> /// | | | |
| <a href=#53 id=53 data-nosnippet>53</a> /// | | | |
| <a href=#54 id=54 data-nosnippet>54</a> /// | '::' 'bar' |
| <a href=#55 id=55 data-nosnippet>55</a> /// | |
| <a href=#56 id=56 data-nosnippet>56</a> /// PATH |
| <a href=#57 id=57 data-nosnippet>57</a> /// | |
| <a href=#58 id=58 data-nosnippet>58</a> /// 'foo' |
| <a href=#59 id=59 data-nosnippet>59</a> /// ``` |
| <a href=#60 id=60 data-nosnippet>60</a> /// |
| <a href=#61 id=61 data-nosnippet>61</a> /// See also `CompletedMarker::precede`. |
| <a href=#62 id=62 data-nosnippet>62</a> </span>Start { kind: SyntaxKind, forward_parent: <span class="prelude-ty">Option</span><NonZeroU32> }, |
| <a href=#63 id=63 data-nosnippet>63</a> |
| <a href=#64 id=64 data-nosnippet>64</a> <span class="doccomment">/// Complete the previous `Start` event |
| <a href=#65 id=65 data-nosnippet>65</a> </span>Finish, |
| <a href=#66 id=66 data-nosnippet>66</a> |
| <a href=#67 id=67 data-nosnippet>67</a> <span class="doccomment">/// Produce a single leaf-element. |
| <a href=#68 id=68 data-nosnippet>68</a> /// `n_raw_tokens` is used to glue complex contextual tokens. |
| <a href=#69 id=69 data-nosnippet>69</a> /// For example, lexer tokenizes `>>` as `>`, `>`, and |
| <a href=#70 id=70 data-nosnippet>70</a> /// `n_raw_tokens = 2` is used to produced a single `>>`. |
| <a href=#71 id=71 data-nosnippet>71</a> </span>Token { kind: SyntaxKind, n_raw_tokens: u8 }, |
| <a href=#72 id=72 data-nosnippet>72</a> <span class="doccomment">/// When we parse `foo.0.0` or `foo. 0. 0` the lexer will hand us a float literal |
| <a href=#73 id=73 data-nosnippet>73</a> /// instead of an integer literal followed by a dot as the lexer has no contextual knowledge. |
| <a href=#74 id=74 data-nosnippet>74</a> /// This event instructs whatever consumes the events to split the float literal into |
| <a href=#75 id=75 data-nosnippet>75</a> /// the corresponding parts. |
| <a href=#76 id=76 data-nosnippet>76</a> </span>FloatSplitHack { ends_in_dot: bool }, |
| <a href=#77 id=77 data-nosnippet>77</a> <span class="doccomment">/// Index into the parser's side `errors` vec. |
| <a href=#78 id=78 data-nosnippet>78</a> </span>Error { err: u32 }, |
| <a href=#79 id=79 data-nosnippet>79</a>} |
| <a href=#80 id=80 data-nosnippet>80</a> |
| <a href=#81 id=81 data-nosnippet>81</a><span class="kw">impl </span>Event { |
| <a href=#82 id=82 data-nosnippet>82</a> <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>tombstone() -> <span class="self">Self </span>{ |
| <a href=#83 id=83 data-nosnippet>83</a> Event::Start { kind: TOMBSTONE, forward_parent: <span class="prelude-val">None </span>} |
| <a href=#84 id=84 data-nosnippet>84</a> } |
| <a href=#85 id=85 data-nosnippet>85</a>} |
| <a href=#86 id=86 data-nosnippet>86</a> |
| <a href=#87 id=87 data-nosnippet>87</a><span class="doccomment">/// Generate the syntax tree with the control of events. `errors` is the |
| <a href=#88 id=88 data-nosnippet>88</a>/// side table of error messages built up alongside the `events` stream. |
| <a href=#89 id=89 data-nosnippet>89</a></span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>process(<span class="kw-2">mut </span>events: Vec<Event>, <span class="kw-2">mut </span>errors: Vec<String>) -> Output { |
| <a href=#90 id=90 data-nosnippet>90</a> <span class="comment">// Each event becomes roughly one u32 in Output, so preallocate to avoid |
| <a href=#91 id=91 data-nosnippet>91</a> // the amortized grow-one churn we used to see in Output::enter_node. |
| <a href=#92 id=92 data-nosnippet>92</a> </span><span class="kw">let </span><span class="kw-2">mut </span>res = Output::with_event_capacity(events.len()); |
| <a href=#93 id=93 data-nosnippet>93</a> <span class="kw">let </span><span class="kw-2">mut </span>forward_parents = Vec::new(); |
| <a href=#94 id=94 data-nosnippet>94</a> |
| <a href=#95 id=95 data-nosnippet>95</a> <span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..events.len() { |
| <a href=#96 id=96 data-nosnippet>96</a> <span class="kw">match </span>events[i] { |
| <a href=#97 id=97 data-nosnippet>97</a> Event::Start { kind, forward_parent } => { |
| <a href=#98 id=98 data-nosnippet>98</a> <span class="comment">// For events[A, B, C], B is A's forward_parent, C is B's forward_parent, |
| <a href=#99 id=99 data-nosnippet>99</a> // in the normal control flow, the parent-child relation: `A -> B -> C`, |
| <a href=#100 id=100 data-nosnippet>100</a> // while with the magic forward_parent, it writes: `C <- B <- A`. |
| <a href=#101 id=101 data-nosnippet>101</a> |
| <a href=#102 id=102 data-nosnippet>102</a> // append `A` into parents. |
| <a href=#103 id=103 data-nosnippet>103</a> </span>forward_parents.push(kind); |
| <a href=#104 id=104 data-nosnippet>104</a> <span class="kw">let </span><span class="kw-2">mut </span>idx = i; |
| <a href=#105 id=105 data-nosnippet>105</a> <span class="kw">let </span><span class="kw-2">mut </span>fp = forward_parent; |
| <a href=#106 id=106 data-nosnippet>106</a> <span class="kw">while let </span><span class="prelude-val">Some</span>(fwd) = fp { |
| <a href=#107 id=107 data-nosnippet>107</a> idx += fwd.get() <span class="kw">as </span>usize; |
| <a href=#108 id=108 data-nosnippet>108</a> <span class="comment">// append `A`'s forward_parent `B` |
| <a href=#109 id=109 data-nosnippet>109</a> </span>fp = <span class="kw">match </span>mem::replace(<span class="kw-2">&mut </span>events[idx], Event::tombstone()) { |
| <a href=#110 id=110 data-nosnippet>110</a> Event::Start { kind, forward_parent } => { |
| <a href=#111 id=111 data-nosnippet>111</a> forward_parents.push(kind); |
| <a href=#112 id=112 data-nosnippet>112</a> forward_parent |
| <a href=#113 id=113 data-nosnippet>113</a> } |
| <a href=#114 id=114 data-nosnippet>114</a> <span class="kw">_ </span>=> <span class="macro">unreachable!</span>(), |
| <a href=#115 id=115 data-nosnippet>115</a> }; |
| <a href=#116 id=116 data-nosnippet>116</a> <span class="comment">// append `B`'s forward_parent `C` in the next stage. |
| <a href=#117 id=117 data-nosnippet>117</a> </span>} |
| <a href=#118 id=118 data-nosnippet>118</a> |
| <a href=#119 id=119 data-nosnippet>119</a> <span class="kw">for </span>kind <span class="kw">in </span>forward_parents.drain(..).rev() { |
| <a href=#120 id=120 data-nosnippet>120</a> <span class="kw">if </span>kind != TOMBSTONE { |
| <a href=#121 id=121 data-nosnippet>121</a> res.enter_node(kind); |
| <a href=#122 id=122 data-nosnippet>122</a> } |
| <a href=#123 id=123 data-nosnippet>123</a> } |
| <a href=#124 id=124 data-nosnippet>124</a> } |
| <a href=#125 id=125 data-nosnippet>125</a> Event::Finish => res.leave_node(), |
| <a href=#126 id=126 data-nosnippet>126</a> Event::Token { kind, n_raw_tokens } => { |
| <a href=#127 id=127 data-nosnippet>127</a> res.token(kind, n_raw_tokens); |
| <a href=#128 id=128 data-nosnippet>128</a> } |
| <a href=#129 id=129 data-nosnippet>129</a> Event::FloatSplitHack { ends_in_dot } => { |
| <a href=#130 id=130 data-nosnippet>130</a> res.float_split_hack(ends_in_dot); |
| <a href=#131 id=131 data-nosnippet>131</a> <span class="kw">let </span>ev = mem::replace(<span class="kw-2">&mut </span>events[i + <span class="number">1</span>], Event::tombstone()); |
| <a href=#132 id=132 data-nosnippet>132</a> <span class="macro">assert!</span>(<span class="macro">matches!</span>(ev, Event::Finish), <span class="string">"{ev:?}"</span>); |
| <a href=#133 id=133 data-nosnippet>133</a> } |
| <a href=#134 id=134 data-nosnippet>134</a> Event::Error { err } => { |
| <a href=#135 id=135 data-nosnippet>135</a> <span class="comment">// Move the string out of the side table; each index is visited |
| <a href=#136 id=136 data-nosnippet>136</a> // exactly once, so swapping with an empty String is cheap and |
| <a href=#137 id=137 data-nosnippet>137</a> // avoids any clone. |
| <a href=#138 id=138 data-nosnippet>138</a> </span><span class="kw">let </span>msg = mem::take(<span class="kw-2">&mut </span>errors[err <span class="kw">as </span>usize]); |
| <a href=#139 id=139 data-nosnippet>139</a> res.error(msg); |
| <a href=#140 id=140 data-nosnippet>140</a> } |
| <a href=#141 id=141 data-nosnippet>141</a> } |
| <a href=#142 id=142 data-nosnippet>142</a> } |
| <a href=#143 id=143 data-nosnippet>143</a> |
| <a href=#144 id=144 data-nosnippet>144</a> res |
| <a href=#145 id=145 data-nosnippet>145</a>} |
| </code></pre></div></section></main></body></html> |
