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<a href=#2 id=2 data-nosnippet>2</a>//!
<a href=#3 id=3 data-nosnippet>3</a>//! Whenever there is a closure expression, we need to determine how each
<a href=#4 id=4 data-nosnippet>4</a>//! upvar is used. We do this by initially assigning each upvar an
<a href=#5 id=5 data-nosnippet>5</a>//! immutable "borrow kind" (see `BorrowKind` for details) and then
<a href=#6 id=6 data-nosnippet>6</a>//! "escalating" the kind as needed. The borrow kind proceeds according to
<a href=#7 id=7 data-nosnippet>7</a>//! the following lattice:
<a href=#8 id=8 data-nosnippet>8</a>//! ```ignore (not-rust)
<a href=#9 id=9 data-nosnippet>9</a>//! ty::ImmBorrow -&gt; ty::UniqueImmBorrow -&gt; ty::MutBorrow
<a href=#10 id=10 data-nosnippet>10</a>//! ```
<a href=#11 id=11 data-nosnippet>11</a>//! So, for example, if we see an assignment `x = 5` to an upvar `x`, we
<a href=#12 id=12 data-nosnippet>12</a>//! will promote its borrow kind to mutable borrow. If we see an `&amp;mut x`
<a href=#13 id=13 data-nosnippet>13</a>//! we'll do the same. Naturally, this applies not just to the upvar, but
<a href=#14 id=14 data-nosnippet>14</a>//! to everything owned by `x`, so the result is the same for something
<a href=#15 id=15 data-nosnippet>15</a>//! like `x.f = 5` and so on (presuming `x` is not a borrowed pointer to a
<a href=#16 id=16 data-nosnippet>16</a>//! struct). These adjustments are performed in
<a href=#17 id=17 data-nosnippet>17</a>//! `adjust_for_non_move_closure` (you can trace backwards through the code
<a href=#18 id=18 data-nosnippet>18</a>//! from there).
<a href=#19 id=19 data-nosnippet>19</a>//!
<a href=#20 id=20 data-nosnippet>20</a>//! The fact that we are inferring borrow kinds as we go results in a
<a href=#21 id=21 data-nosnippet>21</a>//! semi-hacky interaction with the way `ExprUseVisitor` is computing
<a href=#22 id=22 data-nosnippet>22</a>//! `Place`s. In particular, it will query the current borrow kind as it
<a href=#23 id=23 data-nosnippet>23</a>//! goes, and we'll return the *current* value, but this may get
<a href=#24 id=24 data-nosnippet>24</a>//! adjusted later. Therefore, in this module, we generally ignore the
<a href=#25 id=25 data-nosnippet>25</a>//! borrow kind (and derived mutabilities) that `ExprUseVisitor` returns
<a href=#26 id=26 data-nosnippet>26</a>//! within `Place`s, since they may be inaccurate. (Another option
<a href=#27 id=27 data-nosnippet>27</a>//! would be to use a unification scheme, where instead of returning a
<a href=#28 id=28 data-nosnippet>28</a>//! concrete borrow kind like `ty::ImmBorrow`, we return a
<a href=#29 id=29 data-nosnippet>29</a>//! `ty::InferBorrow(upvar_id)` or something like that, but this would
<a href=#30 id=30 data-nosnippet>30</a>//! then mean that all later passes would have to check for these figments
<a href=#31 id=31 data-nosnippet>31</a>//! and report an error, and it just seems like more mess in the end.)
<a href=#32 id=32 data-nosnippet>32</a>
<a href=#33 id=33 data-nosnippet>33</a></span><span class="kw">use </span>std::{cmp, iter, mem};
<a href=#34 id=34 data-nosnippet>34</a>
<a href=#35 id=35 data-nosnippet>35</a><span class="kw">use </span>hir_def::{
<a href=#36 id=36 data-nosnippet>36</a> expr_store::ExpressionStore,
<a href=#37 id=37 data-nosnippet>37</a> hir::{
<a href=#38 id=38 data-nosnippet>38</a> BindingAnnotation, BindingId, CaptureBy, CoroutineSource, Expr, ExprId, ExprOrPatIdPacked,
<a href=#39 id=39 data-nosnippet>39</a> Pat, PatId, Statement,
<a href=#40 id=40 data-nosnippet>40</a> },
<a href=#41 id=41 data-nosnippet>41</a> resolver::ValueNs,
<a href=#42 id=42 data-nosnippet>42</a>};
<a href=#43 id=43 data-nosnippet>43</a><span class="kw">use </span>macros::{TypeFoldable, TypeVisitable};
<a href=#44 id=44 data-nosnippet>44</a><span class="kw">use </span>rustc_abi::ExternAbi;
<a href=#45 id=45 data-nosnippet>45</a><span class="kw">use </span>rustc_ast_ir::Mutability;
<a href=#46 id=46 data-nosnippet>46</a><span class="kw">use </span>rustc_hash::{FxBuildHasher, FxHashMap};
<a href=#47 id=47 data-nosnippet>47</a><span class="kw">use </span>rustc_type_ir::{
<a href=#48 id=48 data-nosnippet>48</a> BoundVar, ClosureKind,
<a href=#49 id=49 data-nosnippet>49</a> inherent::{AdtDef <span class="kw">as _</span>, GenericArgs <span class="kw">as _</span>, IntoKind <span class="kw">as _</span>, Ty <span class="kw">as _</span>},
<a href=#50 id=50 data-nosnippet>50</a>};
<a href=#51 id=51 data-nosnippet>51</a><span class="kw">use </span>smallvec::{SmallVec, smallvec};
<a href=#52 id=52 data-nosnippet>52</a><span class="kw">use </span>span::Edition;
<a href=#53 id=53 data-nosnippet>53</a><span class="kw">use </span>tracing::{debug, instrument};
<a href=#54 id=54 data-nosnippet>54</a>
<a href=#55 id=55 data-nosnippet>55</a><span class="kw">use crate</span>::{
<a href=#56 id=56 data-nosnippet>56</a> Span,
<a href=#57 id=57 data-nosnippet>57</a> infer::{
<a href=#58 id=58 data-nosnippet>58</a> CaptureInfo, CaptureSourceStack, CapturedPlace, InferenceContext, UpvarCapture,
<a href=#59 id=59 data-nosnippet>59</a> closure::analysis::expr_use_visitor::{
<a href=#60 id=60 data-nosnippet>60</a> <span class="self">self </span><span class="kw">as </span>euv, FakeReadCause, Place, PlaceBase, PlaceWithOrigin, Projection,
<a href=#61 id=61 data-nosnippet>61</a> ProjectionKind,
<a href=#62 id=62 data-nosnippet>62</a> },
<a href=#63 id=63 data-nosnippet>63</a> },
<a href=#64 id=64 data-nosnippet>64</a> next_solver::{
<a href=#65 id=65 data-nosnippet>65</a> Binder, BoundRegion, BoundRegionKind, DbInterner, GenericArgs, Region, Ty, TyKind,
<a href=#66 id=66 data-nosnippet>66</a> abi::Safety, infer::traits::ObligationCause, normalize,
<a href=#67 id=67 data-nosnippet>67</a> },
<a href=#68 id=68 data-nosnippet>68</a> upvars::{Upvars, UpvarsRef},
<a href=#69 id=69 data-nosnippet>69</a>};
<a href=#70 id=70 data-nosnippet>70</a>
<a href=#71 id=71 data-nosnippet>71</a><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">mod </span>expr_use_visitor;
<a href=#72 id=72 data-nosnippet>72</a>
<a href=#73 id=73 data-nosnippet>73</a><span class="attr">#[derive(Debug, Copy, Clone, TypeVisitable, TypeFoldable)]
<a href=#74 id=74 data-nosnippet>74</a></span><span class="kw">enum </span>UpvarArgs&lt;<span class="lifetime">'db</span>&gt; {
<a href=#75 id=75 data-nosnippet>75</a> Closure(GenericArgs&lt;<span class="lifetime">'db</span>&gt;),
<a href=#76 id=76 data-nosnippet>76</a> Coroutine(GenericArgs&lt;<span class="lifetime">'db</span>&gt;),
<a href=#77 id=77 data-nosnippet>77</a> CoroutineClosure(GenericArgs&lt;<span class="lifetime">'db</span>&gt;),
<a href=#78 id=78 data-nosnippet>78</a>}
<a href=#79 id=79 data-nosnippet>79</a>
<a href=#80 id=80 data-nosnippet>80</a><span class="kw">impl</span>&lt;<span class="lifetime">'db</span>&gt; UpvarArgs&lt;<span class="lifetime">'db</span>&gt; {
<a href=#81 id=81 data-nosnippet>81</a> <span class="attr">#[inline]
<a href=#82 id=82 data-nosnippet>82</a> </span><span class="kw">fn </span>tupled_upvars_ty(<span class="self">self</span>) -&gt; Ty&lt;<span class="lifetime">'db</span>&gt; {
<a href=#83 id=83 data-nosnippet>83</a> <span class="kw">match </span><span class="self">self </span>{
<a href=#84 id=84 data-nosnippet>84</a> UpvarArgs::Closure(args) =&gt; args.as_closure().tupled_upvars_ty(),
<a href=#85 id=85 data-nosnippet>85</a> UpvarArgs::Coroutine(args) =&gt; args.as_coroutine().tupled_upvars_ty(),
<a href=#86 id=86 data-nosnippet>86</a> UpvarArgs::CoroutineClosure(args) =&gt; args.as_coroutine_closure().tupled_upvars_ty(),
<a href=#87 id=87 data-nosnippet>87</a> }
<a href=#88 id=88 data-nosnippet>88</a> }
<a href=#89 id=89 data-nosnippet>89</a>}
<a href=#90 id=90 data-nosnippet>90</a>
<a href=#91 id=91 data-nosnippet>91</a><span class="attr">#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
<a href=#92 id=92 data-nosnippet>92</a></span><span class="kw">pub enum </span>BorrowKind {
<a href=#93 id=93 data-nosnippet>93</a> <span class="doccomment">/// Data must be immutable and is aliasable.
<a href=#94 id=94 data-nosnippet>94</a> </span>Immutable,
<a href=#95 id=95 data-nosnippet>95</a>
<a href=#96 id=96 data-nosnippet>96</a> <span class="doccomment">/// Data must be immutable but not aliasable. This kind of borrow
<a href=#97 id=97 data-nosnippet>97</a> /// cannot currently be expressed by the user and is used only in
<a href=#98 id=98 data-nosnippet>98</a> /// implicit closure bindings. It is needed when the closure
<a href=#99 id=99 data-nosnippet>99</a> /// is borrowing or mutating a mutable referent, e.g.:
<a href=#100 id=100 data-nosnippet>100</a> ///
<a href=#101 id=101 data-nosnippet>101</a> /// ```
<a href=#102 id=102 data-nosnippet>102</a> /// let mut z = 3;
<a href=#103 id=103 data-nosnippet>103</a> /// let x: &amp;mut isize = &amp;mut z;
<a href=#104 id=104 data-nosnippet>104</a> /// let y = || *x += 5;
<a href=#105 id=105 data-nosnippet>105</a> /// ```
<a href=#106 id=106 data-nosnippet>106</a> ///
<a href=#107 id=107 data-nosnippet>107</a> /// If we were to try to translate this closure into a more explicit
<a href=#108 id=108 data-nosnippet>108</a> /// form, we'd encounter an error with the code as written:
<a href=#109 id=109 data-nosnippet>109</a> ///
<a href=#110 id=110 data-nosnippet>110</a> /// ```compile_fail,E0594
<a href=#111 id=111 data-nosnippet>111</a> /// struct Env&lt;'a&gt; { x: &amp;'a &amp;'a mut isize }
<a href=#112 id=112 data-nosnippet>112</a> /// let mut z = 3;
<a href=#113 id=113 data-nosnippet>113</a> /// let x: &amp;mut isize = &amp;mut z;
<a href=#114 id=114 data-nosnippet>114</a> /// let y = (&amp;mut Env { x: &amp;x }, fn_ptr); // Closure is pair of env and fn
<a href=#115 id=115 data-nosnippet>115</a> /// fn fn_ptr(env: &amp;mut Env) { **env.x += 5; }
<a href=#116 id=116 data-nosnippet>116</a> /// ```
<a href=#117 id=117 data-nosnippet>117</a> ///
<a href=#118 id=118 data-nosnippet>118</a> /// This is then illegal because you cannot mutate a `&amp;mut` found
<a href=#119 id=119 data-nosnippet>119</a> /// in an aliasable location. To solve, you'd have to translate with
<a href=#120 id=120 data-nosnippet>120</a> /// an `&amp;mut` borrow:
<a href=#121 id=121 data-nosnippet>121</a> ///
<a href=#122 id=122 data-nosnippet>122</a> /// ```compile_fail,E0596
<a href=#123 id=123 data-nosnippet>123</a> /// struct Env&lt;'a&gt; { x: &amp;'a mut &amp;'a mut isize }
<a href=#124 id=124 data-nosnippet>124</a> /// let mut z = 3;
<a href=#125 id=125 data-nosnippet>125</a> /// let x: &amp;mut isize = &amp;mut z;
<a href=#126 id=126 data-nosnippet>126</a> /// let y = (&amp;mut Env { x: &amp;mut x }, fn_ptr); // changed from &amp;x to &amp;mut x
<a href=#127 id=127 data-nosnippet>127</a> /// fn fn_ptr(env: &amp;mut Env) { **env.x += 5; }
<a href=#128 id=128 data-nosnippet>128</a> /// ```
<a href=#129 id=129 data-nosnippet>129</a> ///
<a href=#130 id=130 data-nosnippet>130</a> /// Now the assignment to `**env.x` is legal, but creating a
<a href=#131 id=131 data-nosnippet>131</a> /// mutable pointer to `x` is not because `x` is not mutable. We
<a href=#132 id=132 data-nosnippet>132</a> /// could fix this by declaring `x` as `let mut x`. This is ok in
<a href=#133 id=133 data-nosnippet>133</a> /// user code, if awkward, but extra weird for closures, since the
<a href=#134 id=134 data-nosnippet>134</a> /// borrow is hidden.
<a href=#135 id=135 data-nosnippet>135</a> ///
<a href=#136 id=136 data-nosnippet>136</a> /// So we introduce a "unique imm" borrow -- the referent is
<a href=#137 id=137 data-nosnippet>137</a> /// immutable, but not aliasable. This solves the problem. For
<a href=#138 id=138 data-nosnippet>138</a> /// simplicity, we don't give users the way to express this
<a href=#139 id=139 data-nosnippet>139</a> /// borrow, it's just used when translating closures.
<a href=#140 id=140 data-nosnippet>140</a> ///
<a href=#141 id=141 data-nosnippet>141</a> /// FIXME: Rename this to indicate the borrow is actually not immutable.
<a href=#142 id=142 data-nosnippet>142</a> </span>UniqueImmutable,
<a href=#143 id=143 data-nosnippet>143</a>
<a href=#144 id=144 data-nosnippet>144</a> <span class="doccomment">/// Data is mutable and not aliasable.
<a href=#145 id=145 data-nosnippet>145</a> </span>Mutable,
<a href=#146 id=146 data-nosnippet>146</a>}
<a href=#147 id=147 data-nosnippet>147</a>
<a href=#148 id=148 data-nosnippet>148</a><span class="kw">impl </span>BorrowKind {
<a href=#149 id=149 data-nosnippet>149</a> <span class="kw">pub fn </span>from_hir_mutbl(m: hir_def::hir::type_ref::Mutability) -&gt; BorrowKind {
<a href=#150 id=150 data-nosnippet>150</a> <span class="kw">match </span>m {
<a href=#151 id=151 data-nosnippet>151</a> hir_def::hir::type_ref::Mutability::Mut =&gt; BorrowKind::Mutable,
<a href=#152 id=152 data-nosnippet>152</a> hir_def::hir::type_ref::Mutability::Shared =&gt; BorrowKind::Immutable,
<a href=#153 id=153 data-nosnippet>153</a> }
<a href=#154 id=154 data-nosnippet>154</a> }
<a href=#155 id=155 data-nosnippet>155</a>
<a href=#156 id=156 data-nosnippet>156</a> <span class="kw">pub fn </span>from_mutbl(m: Mutability) -&gt; BorrowKind {
<a href=#157 id=157 data-nosnippet>157</a> <span class="kw">match </span>m {
<a href=#158 id=158 data-nosnippet>158</a> Mutability::Mut =&gt; BorrowKind::Mutable,
<a href=#159 id=159 data-nosnippet>159</a> Mutability::Not =&gt; BorrowKind::Immutable,
<a href=#160 id=160 data-nosnippet>160</a> }
<a href=#161 id=161 data-nosnippet>161</a> }
<a href=#162 id=162 data-nosnippet>162</a>
<a href=#163 id=163 data-nosnippet>163</a> <span class="doccomment">/// Returns a mutability `m` such that an `&amp;m T` pointer could be used to obtain this borrow
<a href=#164 id=164 data-nosnippet>164</a> /// kind. Because borrow kinds are richer than mutabilities, we sometimes have to pick a
<a href=#165 id=165 data-nosnippet>165</a> /// mutability that is stronger than necessary so that it at least *would permit* the borrow in
<a href=#166 id=166 data-nosnippet>166</a> /// question.
<a href=#167 id=167 data-nosnippet>167</a> </span><span class="kw">pub fn </span>to_mutbl_lossy(<span class="self">self</span>) -&gt; Mutability {
<a href=#168 id=168 data-nosnippet>168</a> <span class="kw">match </span><span class="self">self </span>{
<a href=#169 id=169 data-nosnippet>169</a> BorrowKind::Mutable =&gt; Mutability::Mut,
<a href=#170 id=170 data-nosnippet>170</a> BorrowKind::Immutable =&gt; Mutability::Not,
<a href=#171 id=171 data-nosnippet>171</a>
<a href=#172 id=172 data-nosnippet>172</a> <span class="comment">// We have no type corresponding to a unique imm borrow, so
<a href=#173 id=173 data-nosnippet>173</a> // use `&amp;mut`. It gives all the capabilities of a `&amp;uniq`
<a href=#174 id=174 data-nosnippet>174</a> // and hence is a safe "over approximation".
<a href=#175 id=175 data-nosnippet>175</a> </span>BorrowKind::UniqueImmutable =&gt; Mutability::Mut,
<a href=#176 id=176 data-nosnippet>176</a> }
<a href=#177 id=177 data-nosnippet>177</a> }
<a href=#178 id=178 data-nosnippet>178</a>}
<a href=#179 id=179 data-nosnippet>179</a>
<a href=#180 id=180 data-nosnippet>180</a><span class="doccomment">/// Describe the relationship between the paths of two places
<a href=#181 id=181 data-nosnippet>181</a>/// eg:
<a href=#182 id=182 data-nosnippet>182</a>/// - `foo` is ancestor of `foo.bar.baz`
<a href=#183 id=183 data-nosnippet>183</a>/// - `foo.bar.baz` is an descendant of `foo.bar`
<a href=#184 id=184 data-nosnippet>184</a>/// - `foo.bar` and `foo.baz` are divergent
<a href=#185 id=185 data-nosnippet>185</a></span><span class="kw">enum </span>PlaceAncestryRelation {
<a href=#186 id=186 data-nosnippet>186</a> Ancestor,
<a href=#187 id=187 data-nosnippet>187</a> Descendant,
<a href=#188 id=188 data-nosnippet>188</a> SamePlace,
<a href=#189 id=189 data-nosnippet>189</a> Divergent,
<a href=#190 id=190 data-nosnippet>190</a>}
<a href=#191 id=191 data-nosnippet>191</a>
<a href=#192 id=192 data-nosnippet>192</a><span class="doccomment">/// Intermediate format to store a captured `Place` and associated `CaptureInfo`
<a href=#193 id=193 data-nosnippet>193</a>/// during capture analysis. Information in this map feeds into the minimum capture
<a href=#194 id=194 data-nosnippet>194</a>/// analysis pass.
<a href=#195 id=195 data-nosnippet>195</a></span><span class="kw">type </span>InferredCaptureInformation = Vec&lt;(Place, CaptureInfo)&gt;;
<a href=#196 id=196 data-nosnippet>196</a>
<a href=#197 id=197 data-nosnippet>197</a><span class="kw">impl</span>&lt;<span class="lifetime">'db</span>&gt; InferenceContext&lt;<span class="lifetime">'db</span>&gt; {
<a href=#198 id=198 data-nosnippet>198</a> <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>closure_analyze(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
<a href=#199 id=199 data-nosnippet>199</a> <span class="kw">let </span>upvars = <span class="kw">crate</span>::upvars::upvars_mentioned(<span class="self">self</span>.db, <span class="self">self</span>.store_owner)
<a href=#200 id=200 data-nosnippet>200</a> .unwrap_or(<span class="kw">const </span>{ <span class="kw-2">&amp;</span>FxHashMap::with_hasher(FxBuildHasher) });
<a href=#201 id=201 data-nosnippet>201</a> <span class="kw">for </span>root_expr <span class="kw">in </span><span class="self">self</span>.store.expr_roots() {
<a href=#202 id=202 data-nosnippet>202</a> <span class="self">self</span>.analyze_closures_in_expr(root_expr, upvars);
<a href=#203 id=203 data-nosnippet>203</a> }
<a href=#204 id=204 data-nosnippet>204</a>
<a href=#205 id=205 data-nosnippet>205</a> <span class="comment">// it's our job to process these.
<a href=#206 id=206 data-nosnippet>206</a> </span><span class="macro">assert!</span>(<span class="self">self</span>.deferred_call_resolutions.is_empty());
<a href=#207 id=207 data-nosnippet>207</a> }
<a href=#208 id=208 data-nosnippet>208</a>
<a href=#209 id=209 data-nosnippet>209</a> <span class="kw">fn </span>analyze_closures_in_expr(<span class="kw-2">&amp;mut </span><span class="self">self</span>, expr: ExprId, upvars: <span class="kw-2">&amp;</span><span class="lifetime">'db </span>FxHashMap&lt;ExprId, Upvars&gt;) {
<a href=#210 id=210 data-nosnippet>210</a> <span class="self">self</span>.store.walk_child_exprs(expr, |expr| <span class="self">self</span>.analyze_closures_in_expr(expr, upvars));
<a href=#211 id=211 data-nosnippet>211</a>
<a href=#212 id=212 data-nosnippet>212</a> <span class="kw">match </span><span class="kw-2">&amp;</span><span class="self">self</span>.store[expr] {
<a href=#213 id=213 data-nosnippet>213</a> Expr::Closure { args, body, closure_kind, capture_by, .. } =&gt; {
<a href=#214 id=214 data-nosnippet>214</a> <span class="self">self</span>.analyze_closure(
<a href=#215 id=215 data-nosnippet>215</a> expr,
<a href=#216 id=216 data-nosnippet>216</a> args,
<a href=#217 id=217 data-nosnippet>217</a> <span class="kw-2">*</span>body,
<a href=#218 id=218 data-nosnippet>218</a> <span class="kw-2">*</span>capture_by,
<a href=#219 id=219 data-nosnippet>219</a> <span class="kw-2">*</span>closure_kind,
<a href=#220 id=220 data-nosnippet>220</a> upvars.get(<span class="kw-2">&amp;</span>expr).map(|upvars| upvars.as_ref()).unwrap_or_default(),
<a href=#221 id=221 data-nosnippet>221</a> );
<a href=#222 id=222 data-nosnippet>222</a> }
<a href=#223 id=223 data-nosnippet>223</a> <span class="kw">_ </span>=&gt; {}
<a href=#224 id=224 data-nosnippet>224</a> }
<a href=#225 id=225 data-nosnippet>225</a> }
<a href=#226 id=226 data-nosnippet>226</a>
<a href=#227 id=227 data-nosnippet>227</a> <span class="doccomment">/// Analysis starting point.
<a href=#228 id=228 data-nosnippet>228</a> </span><span class="attr">#[instrument(skip(<span class="self">self</span>, body), level = <span class="string">"debug"</span>)]
<a href=#229 id=229 data-nosnippet>229</a> </span><span class="kw">fn </span>analyze_closure(
<a href=#230 id=230 data-nosnippet>230</a> <span class="kw-2">&amp;mut </span><span class="self">self</span>,
<a href=#231 id=231 data-nosnippet>231</a> closure_expr_id: ExprId,
<a href=#232 id=232 data-nosnippet>232</a> params: <span class="kw-2">&amp;</span>[PatId],
<a href=#233 id=233 data-nosnippet>233</a> body: ExprId,
<a href=#234 id=234 data-nosnippet>234</a> <span class="kw-2">mut </span>capture_clause: CaptureBy,
<a href=#235 id=235 data-nosnippet>235</a> closure_kind: hir_def::hir::ClosureKind,
<a href=#236 id=236 data-nosnippet>236</a> upvars: UpvarsRef&lt;<span class="lifetime">'db</span>&gt;,
<a href=#237 id=237 data-nosnippet>237</a> ) {
<a href=#238 id=238 data-nosnippet>238</a> <span class="comment">// Extract the type of the closure.
<a href=#239 id=239 data-nosnippet>239</a> </span><span class="kw">let </span>ty = <span class="self">self</span>.expr_ty(closure_expr_id);
<a href=#240 id=240 data-nosnippet>240</a> <span class="kw">let </span>(args, infer_kind) = <span class="kw">match </span>ty.kind() {
<a href=#241 id=241 data-nosnippet>241</a> TyKind::Closure(_def_id, args) =&gt; {
<a href=#242 id=242 data-nosnippet>242</a> (UpvarArgs::Closure(args), <span class="self">self</span>.infcx().closure_kind(ty).is_none())
<a href=#243 id=243 data-nosnippet>243</a> }
<a href=#244 id=244 data-nosnippet>244</a> TyKind::CoroutineClosure(_def_id, args) =&gt; {
<a href=#245 id=245 data-nosnippet>245</a> (UpvarArgs::CoroutineClosure(args), <span class="self">self</span>.infcx().closure_kind(ty).is_none())
<a href=#246 id=246 data-nosnippet>246</a> }
<a href=#247 id=247 data-nosnippet>247</a> TyKind::Coroutine(_def_id, args) =&gt; (UpvarArgs::Coroutine(args), <span class="bool-val">false</span>),
<a href=#248 id=248 data-nosnippet>248</a> TyKind::Error(<span class="kw">_</span>) =&gt; {
<a href=#249 id=249 data-nosnippet>249</a> <span class="comment">// #51714: skip analysis when we have already encountered type errors
<a href=#250 id=250 data-nosnippet>250</a> </span><span class="kw">return</span>;
<a href=#251 id=251 data-nosnippet>251</a> }
<a href=#252 id=252 data-nosnippet>252</a> <span class="kw">_ </span>=&gt; {
<a href=#253 id=253 data-nosnippet>253</a> <span class="macro">panic!</span>(<span class="string">"type of closure expr {:?} is not a closure {:?}"</span>, closure_expr_id, ty);
<a href=#254 id=254 data-nosnippet>254</a> }
<a href=#255 id=255 data-nosnippet>255</a> };
<a href=#256 id=256 data-nosnippet>256</a> <span class="kw">let </span>args = <span class="self">self</span>.infcx().resolve_vars_if_possible(args);
<a href=#257 id=257 data-nosnippet>257</a>
<a href=#258 id=258 data-nosnippet>258</a> <span class="kw">let </span><span class="kw-2">mut </span>delegate = InferBorrowKind {
<a href=#259 id=259 data-nosnippet>259</a> closure_def_id: closure_expr_id,
<a href=#260 id=260 data-nosnippet>260</a> capture_information: Default::default(),
<a href=#261 id=261 data-nosnippet>261</a> fake_reads: Default::default(),
<a href=#262 id=262 data-nosnippet>262</a> };
<a href=#263 id=263 data-nosnippet>263</a>
<a href=#264 id=264 data-nosnippet>264</a> <span class="kw">let _ </span>= euv::ExprUseVisitor::new(<span class="self">self</span>, closure_expr_id, upvars, <span class="kw-2">&amp;mut </span>delegate)
<a href=#265 id=265 data-nosnippet>265</a> .consume_closure_body(params, body);
<a href=#266 id=266 data-nosnippet>266</a>
<a href=#267 id=267 data-nosnippet>267</a> <span class="comment">// There are several curious situations with coroutine-closures where
<a href=#268 id=268 data-nosnippet>268</a> // analysis is too aggressive with borrows when the coroutine-closure is
<a href=#269 id=269 data-nosnippet>269</a> // marked `move`. Specifically:
<a href=#270 id=270 data-nosnippet>270</a> //
<a href=#271 id=271 data-nosnippet>271</a> // 1. If the coroutine-closure was inferred to be `FnOnce` during signature
<a href=#272 id=272 data-nosnippet>272</a> // inference, then it's still possible that we try to borrow upvars from
<a href=#273 id=273 data-nosnippet>273</a> // the coroutine-closure because they are not used by the coroutine body
<a href=#274 id=274 data-nosnippet>274</a> // in a way that forces a move. See the test:
<a href=#275 id=275 data-nosnippet>275</a> // `async-await/async-closures/force-move-due-to-inferred-kind.rs`.
<a href=#276 id=276 data-nosnippet>276</a> //
<a href=#277 id=277 data-nosnippet>277</a> // 2. If the coroutine-closure is forced to be `FnOnce` due to the way it
<a href=#278 id=278 data-nosnippet>278</a> // uses its upvars (e.g. it consumes a non-copy value), but not *all* upvars
<a href=#279 id=279 data-nosnippet>279</a> // would force the closure to `FnOnce`.
<a href=#280 id=280 data-nosnippet>280</a> // See the test: `async-await/async-closures/force-move-due-to-actually-fnonce.rs`.
<a href=#281 id=281 data-nosnippet>281</a> //
<a href=#282 id=282 data-nosnippet>282</a> // This would lead to an impossible to satisfy situation, since `AsyncFnOnce`
<a href=#283 id=283 data-nosnippet>283</a> // coroutine bodies can't borrow from their parent closure. To fix this,
<a href=#284 id=284 data-nosnippet>284</a> // we force the inner coroutine to also be `move`. This only matters for
<a href=#285 id=285 data-nosnippet>285</a> // coroutine-closures that are `move` since otherwise they themselves will
<a href=#286 id=286 data-nosnippet>286</a> // be borrowing from the outer environment, so there's no self-borrows occurring.
<a href=#287 id=287 data-nosnippet>287</a> </span><span class="kw">if let </span>UpvarArgs::Coroutine(..) = args
<a href=#288 id=288 data-nosnippet>288</a> &amp;&amp; <span class="kw">let </span>hir_def::hir::ClosureKind::Coroutine { source: CoroutineSource::Closure, .. } =
<a href=#289 id=289 data-nosnippet>289</a> closure_kind
<a href=#290 id=290 data-nosnippet>290</a> &amp;&amp; <span class="kw">let </span>parent_hir_id = ExpressionStore::closure_for_coroutine(closure_expr_id)
<a href=#291 id=291 data-nosnippet>291</a> &amp;&amp; <span class="kw">let </span>parent_ty = <span class="self">self</span>.result.expr_ty(parent_hir_id)
<a href=#292 id=292 data-nosnippet>292</a> &amp;&amp; <span class="kw">let </span>Expr::Closure { capture_by: CaptureBy::Value, .. } = <span class="self">self</span>.store[parent_hir_id]
<a href=#293 id=293 data-nosnippet>293</a> {
<a href=#294 id=294 data-nosnippet>294</a> <span class="comment">// (1.) Closure signature inference forced this closure to `FnOnce`.
<a href=#295 id=295 data-nosnippet>295</a> </span><span class="kw">if let </span><span class="prelude-val">Some</span>(ClosureKind::FnOnce) = <span class="self">self</span>.infcx().closure_kind(parent_ty) {
<a href=#296 id=296 data-nosnippet>296</a> capture_clause = CaptureBy::Value;
<a href=#297 id=297 data-nosnippet>297</a> }
<a href=#298 id=298 data-nosnippet>298</a> <span class="comment">// (2.) The way that the closure uses its upvars means it's `FnOnce`.
<a href=#299 id=299 data-nosnippet>299</a> </span><span class="kw">else if </span><span class="self">self</span>.coroutine_body_consumes_upvars(closure_expr_id, body, upvars) {
<a href=#300 id=300 data-nosnippet>300</a> capture_clause = CaptureBy::Value;
<a href=#301 id=301 data-nosnippet>301</a> }
<a href=#302 id=302 data-nosnippet>302</a> }
<a href=#303 id=303 data-nosnippet>303</a>
<a href=#304 id=304 data-nosnippet>304</a> <span class="comment">// As noted in `lower_coroutine_body_with_moved_arguments`, we default the capture mode
<a href=#305 id=305 data-nosnippet>305</a> // to `ByRef` for the `async {}` block internal to async fns/closure. This means
<a href=#306 id=306 data-nosnippet>306</a> // that we would *not* be moving all of the parameters into the async block in all cases.
<a href=#307 id=307 data-nosnippet>307</a> // For example, when one of the arguments is `Copy`, we turn a consuming use into a copy of
<a href=#308 id=308 data-nosnippet>308</a> // a reference, so for `async fn x(t: i32) {}`, we'd only take a reference to `t`.
<a href=#309 id=309 data-nosnippet>309</a> //
<a href=#310 id=310 data-nosnippet>310</a> // We force all of these arguments to be captured by move before we do expr use analysis.
<a href=#311 id=311 data-nosnippet>311</a> //
<a href=#312 id=312 data-nosnippet>312</a> // FIXME(async_closures): This could be cleaned up. It's a bit janky that we're just
<a href=#313 id=313 data-nosnippet>313</a> // moving all of the `LocalSource::AsyncFn` locals here.
<a href=#314 id=314 data-nosnippet>314</a> </span><span class="kw">if let </span>hir_def::hir::ClosureKind::Coroutine {
<a href=#315 id=315 data-nosnippet>315</a> source: CoroutineSource::Fn | CoroutineSource::Closure,
<a href=#316 id=316 data-nosnippet>316</a> ..
<a href=#317 id=317 data-nosnippet>317</a> } = closure_kind
<a href=#318 id=318 data-nosnippet>318</a> {
<a href=#319 id=319 data-nosnippet>319</a> <span class="kw">let </span>Expr::Block { statements, .. } = <span class="kw-2">&amp;</span><span class="self">self</span>.store[body] <span class="kw">else </span>{
<a href=#320 id=320 data-nosnippet>320</a> <span class="macro">panic!</span>();
<a href=#321 id=321 data-nosnippet>321</a> };
<a href=#322 id=322 data-nosnippet>322</a> <span class="kw">for </span>stmt <span class="kw">in </span>statements {
<a href=#323 id=323 data-nosnippet>323</a> <span class="kw">let </span>Statement::Let { pat, initializer: <span class="prelude-val">Some</span>(init), .. } = <span class="kw-2">*</span>stmt <span class="kw">else </span>{
<a href=#324 id=324 data-nosnippet>324</a> <span class="macro">panic!</span>();
<a href=#325 id=325 data-nosnippet>325</a> };
<a href=#326 id=326 data-nosnippet>326</a> <span class="kw">let </span>Pat::Bind { .. } = <span class="self">self</span>.store[pat] <span class="kw">else </span>{
<a href=#327 id=327 data-nosnippet>327</a> <span class="comment">// Complex pattern, skip the non-upvar local.
<a href=#328 id=328 data-nosnippet>328</a> </span><span class="kw">continue</span>;
<a href=#329 id=329 data-nosnippet>329</a> };
<a href=#330 id=330 data-nosnippet>330</a> <span class="kw">let </span>Expr::Path(path) = <span class="kw-2">&amp;</span><span class="self">self</span>.store[init] <span class="kw">else </span>{
<a href=#331 id=331 data-nosnippet>331</a> <span class="macro">panic!</span>();
<a href=#332 id=332 data-nosnippet>332</a> };
<a href=#333 id=333 data-nosnippet>333</a> <span class="kw">let </span>update_guard =
<a href=#334 id=334 data-nosnippet>334</a> <span class="self">self</span>.resolver.update_to_inner_scope(<span class="self">self</span>.db, <span class="self">self</span>.store_owner, init);
<a href=#335 id=335 data-nosnippet>335</a> <span class="kw">let </span><span class="prelude-val">Some</span>(ValueNs::LocalBinding(local_id)) =
<a href=#336 id=336 data-nosnippet>336</a> <span class="self">self</span>.resolver.resolve_path_in_value_ns_fully(
<a href=#337 id=337 data-nosnippet>337</a> <span class="self">self</span>.db,
<a href=#338 id=338 data-nosnippet>338</a> path,
<a href=#339 id=339 data-nosnippet>339</a> <span class="self">self</span>.store.expr_path_hygiene(init),
<a href=#340 id=340 data-nosnippet>340</a> )
<a href=#341 id=341 data-nosnippet>341</a> <span class="kw">else </span>{
<a href=#342 id=342 data-nosnippet>342</a> <span class="macro">panic!</span>();
<a href=#343 id=343 data-nosnippet>343</a> };
<a href=#344 id=344 data-nosnippet>344</a> <span class="self">self</span>.resolver.reset_to_guard(update_guard);
<a href=#345 id=345 data-nosnippet>345</a> <span class="kw">let </span>place = <span class="self">self</span>.place_for_root_variable(closure_expr_id, local_id);
<a href=#346 id=346 data-nosnippet>346</a> delegate.capture_information.push((
<a href=#347 id=347 data-nosnippet>347</a> place,
<a href=#348 id=348 data-nosnippet>348</a> CaptureInfo {
<a href=#349 id=349 data-nosnippet>349</a> sources: <span class="macro">smallvec!</span>[CaptureSourceStack::from_single(init.into())],
<a href=#350 id=350 data-nosnippet>350</a> capture_kind: UpvarCapture::ByValue,
<a href=#351 id=351 data-nosnippet>351</a> },
<a href=#352 id=352 data-nosnippet>352</a> ));
<a href=#353 id=353 data-nosnippet>353</a> }
<a href=#354 id=354 data-nosnippet>354</a> }
<a href=#355 id=355 data-nosnippet>355</a>
<a href=#356 id=356 data-nosnippet>356</a> <span class="macro">debug!</span>(
<a href=#357 id=357 data-nosnippet>357</a> <span class="string">"For closure={:?}, capture_information={:#?}"</span>,
<a href=#358 id=358 data-nosnippet>358</a> closure_expr_id, delegate.capture_information
<a href=#359 id=359 data-nosnippet>359</a> );
<a href=#360 id=360 data-nosnippet>360</a>
<a href=#361 id=361 data-nosnippet>361</a> <span class="kw">let </span>(capture_information, closure_kind, _origin) = <span class="self">self
<a href=#362 id=362 data-nosnippet>362</a> </span>.process_collected_capture_information(capture_clause, <span class="kw-2">&amp;</span>delegate.capture_information);
<a href=#363 id=363 data-nosnippet>363</a>
<a href=#364 id=364 data-nosnippet>364</a> <span class="self">self</span>.compute_min_captures(closure_expr_id, capture_information);
<a href=#365 id=365 data-nosnippet>365</a>
<a href=#366 id=366 data-nosnippet>366</a> <span class="comment">// We now fake capture information for all variables that are mentioned within the closure
<a href=#367 id=367 data-nosnippet>367</a> // We do this after handling migrations so that min_captures computes before
<a href=#368 id=368 data-nosnippet>368</a> </span><span class="kw">if </span>!enable_precise_capture(<span class="self">self</span>.edition) {
<a href=#369 id=369 data-nosnippet>369</a> <span class="kw">let </span><span class="kw-2">mut </span>capture_information: InferredCaptureInformation = Default::default();
<a href=#370 id=370 data-nosnippet>370</a>
<a href=#371 id=371 data-nosnippet>371</a> <span class="kw">for </span>var_hir_id <span class="kw">in </span>upvars.iter() {
<a href=#372 id=372 data-nosnippet>372</a> <span class="kw">let </span>place = Place {
<a href=#373 id=373 data-nosnippet>373</a> base_ty: <span class="self">self</span>.result.binding_ty(var_hir_id).store(),
<a href=#374 id=374 data-nosnippet>374</a> base: PlaceBase::Upvar { closure: closure_expr_id, var_id: var_hir_id },
<a href=#375 id=375 data-nosnippet>375</a> projections: Vec::new(),
<a href=#376 id=376 data-nosnippet>376</a> };
<a href=#377 id=377 data-nosnippet>377</a>
<a href=#378 id=378 data-nosnippet>378</a> <span class="macro">debug!</span>(<span class="string">"seed place {:?}"</span>, place);
<a href=#379 id=379 data-nosnippet>379</a>
<a href=#380 id=380 data-nosnippet>380</a> <span class="kw">let </span>capture_kind = <span class="self">self</span>.init_capture_kind_for_place(<span class="kw-2">&amp;</span>place, capture_clause);
<a href=#381 id=381 data-nosnippet>381</a> <span class="kw">let </span>fake_info = CaptureInfo { sources: SmallVec::new(), capture_kind };
<a href=#382 id=382 data-nosnippet>382</a>
<a href=#383 id=383 data-nosnippet>383</a> capture_information.push((place, fake_info));
<a href=#384 id=384 data-nosnippet>384</a> }
<a href=#385 id=385 data-nosnippet>385</a>
<a href=#386 id=386 data-nosnippet>386</a> <span class="comment">// This will update the min captures based on this new fake information.
<a href=#387 id=387 data-nosnippet>387</a> </span><span class="self">self</span>.compute_min_captures(closure_expr_id, capture_information);
<a href=#388 id=388 data-nosnippet>388</a> }
<a href=#389 id=389 data-nosnippet>389</a>
<a href=#390 id=390 data-nosnippet>390</a> <span class="kw">if </span>infer_kind {
<a href=#391 id=391 data-nosnippet>391</a> <span class="comment">// Unify the (as yet unbound) type variable in the closure
<a href=#392 id=392 data-nosnippet>392</a> // args with the kind we inferred.
<a href=#393 id=393 data-nosnippet>393</a> </span><span class="kw">let </span>closure_kind_ty = <span class="kw">match </span>args {
<a href=#394 id=394 data-nosnippet>394</a> UpvarArgs::Closure(args) =&gt; args.as_closure().kind_ty(),
<a href=#395 id=395 data-nosnippet>395</a> UpvarArgs::CoroutineClosure(args) =&gt; args.as_coroutine_closure().kind_ty(),
<a href=#396 id=396 data-nosnippet>396</a> UpvarArgs::Coroutine(<span class="kw">_</span>) =&gt; <span class="macro">unreachable!</span>(<span class="string">"coroutines don't have an inferred kind"</span>),
<a href=#397 id=397 data-nosnippet>397</a> };
<a href=#398 id=398 data-nosnippet>398</a> <span class="kw">_ </span>= <span class="self">self</span>.demand_eqtype(
<a href=#399 id=399 data-nosnippet>399</a> closure_expr_id.into(),
<a href=#400 id=400 data-nosnippet>400</a> Ty::from_closure_kind(<span class="self">self</span>.interner(), closure_kind),
<a href=#401 id=401 data-nosnippet>401</a> closure_kind_ty,
<a href=#402 id=402 data-nosnippet>402</a> );
<a href=#403 id=403 data-nosnippet>403</a> }
<a href=#404 id=404 data-nosnippet>404</a>
<a href=#405 id=405 data-nosnippet>405</a> <span class="comment">// For coroutine-closures, we additionally must compute the
<a href=#406 id=406 data-nosnippet>406</a> // `coroutine_captures_by_ref_ty` type, which is used to generate the by-ref
<a href=#407 id=407 data-nosnippet>407</a> // version of the coroutine-closure's output coroutine.
<a href=#408 id=408 data-nosnippet>408</a> </span><span class="kw">if let </span>UpvarArgs::CoroutineClosure(args) = args {
<a href=#409 id=409 data-nosnippet>409</a> <span class="kw">let </span>closure_env_region: Region&lt;<span class="lifetime">'_</span>&gt; = Region::new_bound(
<a href=#410 id=410 data-nosnippet>410</a> <span class="self">self</span>.interner(),
<a href=#411 id=411 data-nosnippet>411</a> rustc_type_ir::INNERMOST,
<a href=#412 id=412 data-nosnippet>412</a> BoundRegion { var: BoundVar::ZERO, kind: BoundRegionKind::ClosureEnv },
<a href=#413 id=413 data-nosnippet>413</a> );
<a href=#414 id=414 data-nosnippet>414</a>
<a href=#415 id=415 data-nosnippet>415</a> <span class="kw">let </span>num_args = args
<a href=#416 id=416 data-nosnippet>416</a> .as_coroutine_closure()
<a href=#417 id=417 data-nosnippet>417</a> .coroutine_closure_sig()
<a href=#418 id=418 data-nosnippet>418</a> .skip_binder()
<a href=#419 id=419 data-nosnippet>419</a> .tupled_inputs_ty
<a href=#420 id=420 data-nosnippet>420</a> .tuple_fields()
<a href=#421 id=421 data-nosnippet>421</a> .len();
<a href=#422 id=422 data-nosnippet>422</a>
<a href=#423 id=423 data-nosnippet>423</a> <span class="kw">let </span>tupled_upvars_ty_for_borrow = Ty::new_tup_from_iter(
<a href=#424 id=424 data-nosnippet>424</a> <span class="self">self</span>.interner(),
<a href=#425 id=425 data-nosnippet>425</a> analyze_coroutine_closure_captures(
<a href=#426 id=426 data-nosnippet>426</a> <span class="self">self</span>.closure_min_captures_flattened(closure_expr_id),
<a href=#427 id=427 data-nosnippet>427</a> <span class="self">self</span>.closure_min_captures_flattened(ExpressionStore::coroutine_for_closure(
<a href=#428 id=428 data-nosnippet>428</a> closure_expr_id,
<a href=#429 id=429 data-nosnippet>429</a> ))
<a href=#430 id=430 data-nosnippet>430</a> <span class="comment">// Skip the captures that are just moving the closure's args
<a href=#431 id=431 data-nosnippet>431</a> // into the coroutine. These are always by move, and we append
<a href=#432 id=432 data-nosnippet>432</a> // those later in the `CoroutineClosureSignature` helper functions.
<a href=#433 id=433 data-nosnippet>433</a> </span>.skip(num_args),
<a href=#434 id=434 data-nosnippet>434</a> |(<span class="kw">_</span>, parent_capture), (<span class="kw">_</span>, child_capture)| {
<a href=#435 id=435 data-nosnippet>435</a> <span class="comment">// This is subtle. See documentation on function.
<a href=#436 id=436 data-nosnippet>436</a> </span><span class="kw">let </span>needs_ref = should_reborrow_from_env_of_parent_coroutine_closure(
<a href=#437 id=437 data-nosnippet>437</a> parent_capture,
<a href=#438 id=438 data-nosnippet>438</a> child_capture,
<a href=#439 id=439 data-nosnippet>439</a> );
<a href=#440 id=440 data-nosnippet>440</a>
<a href=#441 id=441 data-nosnippet>441</a> <span class="kw">let </span>upvar_ty = child_capture.place.ty();
<a href=#442 id=442 data-nosnippet>442</a> <span class="kw">let </span>capture = child_capture.info.capture_kind;
<a href=#443 id=443 data-nosnippet>443</a> <span class="comment">// Not all upvars are captured by ref, so use
<a href=#444 id=444 data-nosnippet>444</a> // `apply_capture_kind_on_capture_ty` to ensure that we
<a href=#445 id=445 data-nosnippet>445</a> // compute the right captured type.
<a href=#446 id=446 data-nosnippet>446</a> </span>apply_capture_kind_on_capture_ty(
<a href=#447 id=447 data-nosnippet>447</a> <span class="self">self</span>.interner(),
<a href=#448 id=448 data-nosnippet>448</a> upvar_ty,
<a href=#449 id=449 data-nosnippet>449</a> capture,
<a href=#450 id=450 data-nosnippet>450</a> <span class="kw">if </span>needs_ref { closure_env_region } <span class="kw">else </span>{ <span class="self">self</span>.types.regions.erased },
<a href=#451 id=451 data-nosnippet>451</a> )
<a href=#452 id=452 data-nosnippet>452</a> },
<a href=#453 id=453 data-nosnippet>453</a> ),
<a href=#454 id=454 data-nosnippet>454</a> );
<a href=#455 id=455 data-nosnippet>455</a> <span class="kw">let </span>coroutine_captures_by_ref_ty = Ty::new_fn_ptr(
<a href=#456 id=456 data-nosnippet>456</a> <span class="self">self</span>.interner(),
<a href=#457 id=457 data-nosnippet>457</a> Binder::bind_with_vars(
<a href=#458 id=458 data-nosnippet>458</a> <span class="self">self</span>.interner().mk_fn_sig(
<a href=#459 id=459 data-nosnippet>459</a> [],
<a href=#460 id=460 data-nosnippet>460</a> tupled_upvars_ty_for_borrow,
<a href=#461 id=461 data-nosnippet>461</a> <span class="bool-val">false</span>,
<a href=#462 id=462 data-nosnippet>462</a> Safety::Safe,
<a href=#463 id=463 data-nosnippet>463</a> ExternAbi::Rust,
<a href=#464 id=464 data-nosnippet>464</a> ),
<a href=#465 id=465 data-nosnippet>465</a> <span class="self">self</span>.types.coroutine_captures_by_ref_bound_var_kinds,
<a href=#466 id=466 data-nosnippet>466</a> ),
<a href=#467 id=467 data-nosnippet>467</a> );
<a href=#468 id=468 data-nosnippet>468</a> <span class="kw">_ </span>= <span class="self">self</span>.demand_eqtype(
<a href=#469 id=469 data-nosnippet>469</a> closure_expr_id.into(),
<a href=#470 id=470 data-nosnippet>470</a> args.as_coroutine_closure().coroutine_captures_by_ref_ty(),
<a href=#471 id=471 data-nosnippet>471</a> coroutine_captures_by_ref_ty,
<a href=#472 id=472 data-nosnippet>472</a> );
<a href=#473 id=473 data-nosnippet>473</a>
<a href=#474 id=474 data-nosnippet>474</a> <span class="comment">// Additionally, we can now constrain the coroutine's kind type.
<a href=#475 id=475 data-nosnippet>475</a> //
<a href=#476 id=476 data-nosnippet>476</a> // We only do this if `infer_kind`, because if we have constrained
<a href=#477 id=477 data-nosnippet>477</a> // the kind from closure signature inference, the kind inferred
<a href=#478 id=478 data-nosnippet>478</a> // for the inner coroutine may actually be more restrictive.
<a href=#479 id=479 data-nosnippet>479</a> </span><span class="kw">if </span>infer_kind {
<a href=#480 id=480 data-nosnippet>480</a> <span class="kw">let </span>TyKind::Coroutine(<span class="kw">_</span>, coroutine_args) = <span class="self">self</span>.result.expr_ty(body).kind() <span class="kw">else </span>{
<a href=#481 id=481 data-nosnippet>481</a> <span class="macro">panic!</span>();
<a href=#482 id=482 data-nosnippet>482</a> };
<a href=#483 id=483 data-nosnippet>483</a> <span class="kw">_ </span>= <span class="self">self</span>.demand_eqtype(
<a href=#484 id=484 data-nosnippet>484</a> closure_expr_id.into(),
<a href=#485 id=485 data-nosnippet>485</a> coroutine_args.as_coroutine().kind_ty(),
<a href=#486 id=486 data-nosnippet>486</a> Ty::from_coroutine_closure_kind(<span class="self">self</span>.interner(), closure_kind),
<a href=#487 id=487 data-nosnippet>487</a> );
<a href=#488 id=488 data-nosnippet>488</a> }
<a href=#489 id=489 data-nosnippet>489</a> }
<a href=#490 id=490 data-nosnippet>490</a>
<a href=#491 id=491 data-nosnippet>491</a> <span class="comment">// Now that we've analyzed the closure, we know how each
<a href=#492 id=492 data-nosnippet>492</a> // variable is borrowed, and we know what traits the closure
<a href=#493 id=493 data-nosnippet>493</a> // implements (Fn vs FnMut etc). We now have some updates to do
<a href=#494 id=494 data-nosnippet>494</a> // with that information.
<a href=#495 id=495 data-nosnippet>495</a> //
<a href=#496 id=496 data-nosnippet>496</a> // Note that no closure type C may have an upvar of type C
<a href=#497 id=497 data-nosnippet>497</a> // (though it may reference itself via a trait object). This
<a href=#498 id=498 data-nosnippet>498</a> // results from the desugaring of closures to a struct like
<a href=#499 id=499 data-nosnippet>499</a> // `Foo&lt;..., UV0...UVn&gt;`. If one of those upvars referenced
<a href=#500 id=500 data-nosnippet>500</a> // C, then the type would have infinite size (and the
<a href=#501 id=501 data-nosnippet>501</a> // inference algorithm will reject it).
<a href=#502 id=502 data-nosnippet>502</a>
<a href=#503 id=503 data-nosnippet>503</a> // Equate the type variables for the upvars with the actual types.
<a href=#504 id=504 data-nosnippet>504</a> </span><span class="kw">let </span>final_upvar_tys = <span class="self">self</span>.final_upvar_tys(closure_expr_id);
<a href=#505 id=505 data-nosnippet>505</a> <span class="macro">debug!</span>(<span class="question-mark">?</span>closure_expr_id, <span class="question-mark">?</span>args, <span class="question-mark">?</span>final_upvar_tys);
<a href=#506 id=506 data-nosnippet>506</a>
<a href=#507 id=507 data-nosnippet>507</a> <span class="comment">// Build a tuple (U0..Un) of the final upvar types U0..Un
<a href=#508 id=508 data-nosnippet>508</a> // and unify the upvar tuple type in the closure with it:
<a href=#509 id=509 data-nosnippet>509</a> </span><span class="kw">let </span>final_tupled_upvars_type = Ty::new_tup(<span class="self">self</span>.interner(), <span class="kw-2">&amp;</span>final_upvar_tys);
<a href=#510 id=510 data-nosnippet>510</a> <span class="kw">_ </span>= <span class="self">self</span>.demand_suptype(
<a href=#511 id=511 data-nosnippet>511</a> closure_expr_id.into(),
<a href=#512 id=512 data-nosnippet>512</a> args.tupled_upvars_ty(),
<a href=#513 id=513 data-nosnippet>513</a> final_tupled_upvars_type,
<a href=#514 id=514 data-nosnippet>514</a> );
<a href=#515 id=515 data-nosnippet>515</a>
<a href=#516 id=516 data-nosnippet>516</a> <span class="kw">let </span>fake_reads = delegate.fake_reads;
<a href=#517 id=517 data-nosnippet>517</a>
<a href=#518 id=518 data-nosnippet>518</a> <span class="self">self</span>.result.closures_data.get_mut(<span class="kw-2">&amp;</span>closure_expr_id).unwrap().fake_reads =
<a href=#519 id=519 data-nosnippet>519</a> fake_reads.into_boxed_slice();
<a href=#520 id=520 data-nosnippet>520</a>
<a href=#521 id=521 data-nosnippet>521</a> <span class="comment">// If we are also inferred the closure kind here,
<a href=#522 id=522 data-nosnippet>522</a> // process any deferred resolutions.
<a href=#523 id=523 data-nosnippet>523</a> </span><span class="kw">let </span>deferred_call_resolutions = <span class="self">self</span>.remove_deferred_call_resolutions(closure_expr_id);
<a href=#524 id=524 data-nosnippet>524</a> <span class="kw">for </span>deferred_call_resolution <span class="kw">in </span>deferred_call_resolutions {
<a href=#525 id=525 data-nosnippet>525</a> deferred_call_resolution.resolve(<span class="self">self</span>);
<a href=#526 id=526 data-nosnippet>526</a> }
<a href=#527 id=527 data-nosnippet>527</a> }
<a href=#528 id=528 data-nosnippet>528</a>
<a href=#529 id=529 data-nosnippet>529</a> <span class="doccomment">/// Determines whether the body of the coroutine uses its upvars in a way that
<a href=#530 id=530 data-nosnippet>530</a> /// consumes (i.e. moves) the value, which would force the coroutine to `FnOnce`.
<a href=#531 id=531 data-nosnippet>531</a> /// In a more detailed comment above, we care whether this happens, since if
<a href=#532 id=532 data-nosnippet>532</a> /// this happens, we want to force the coroutine to move all of the upvars it
<a href=#533 id=533 data-nosnippet>533</a> /// would've borrowed from the parent coroutine-closure.
<a href=#534 id=534 data-nosnippet>534</a> ///
<a href=#535 id=535 data-nosnippet>535</a> /// This only really makes sense to be called on the child coroutine of a
<a href=#536 id=536 data-nosnippet>536</a> /// coroutine-closure.
<a href=#537 id=537 data-nosnippet>537</a> </span><span class="kw">fn </span>coroutine_body_consumes_upvars(
<a href=#538 id=538 data-nosnippet>538</a> <span class="kw-2">&amp;mut </span><span class="self">self</span>,
<a href=#539 id=539 data-nosnippet>539</a> coroutine_def_id: ExprId,
<a href=#540 id=540 data-nosnippet>540</a> body: ExprId,
<a href=#541 id=541 data-nosnippet>541</a> upvars: UpvarsRef&lt;<span class="lifetime">'db</span>&gt;,
<a href=#542 id=542 data-nosnippet>542</a> ) -&gt; bool {
<a href=#543 id=543 data-nosnippet>543</a> <span class="kw">let </span><span class="kw-2">mut </span>delegate = InferBorrowKind {
<a href=#544 id=544 data-nosnippet>544</a> closure_def_id: coroutine_def_id,
<a href=#545 id=545 data-nosnippet>545</a> capture_information: Default::default(),
<a href=#546 id=546 data-nosnippet>546</a> fake_reads: Default::default(),
<a href=#547 id=547 data-nosnippet>547</a> };
<a href=#548 id=548 data-nosnippet>548</a>
<a href=#549 id=549 data-nosnippet>549</a> <span class="kw">let _ </span>= euv::ExprUseVisitor::new(<span class="self">self</span>, coroutine_def_id, upvars, <span class="kw-2">&amp;mut </span>delegate)
<a href=#550 id=550 data-nosnippet>550</a> .consume_expr(body);
<a href=#551 id=551 data-nosnippet>551</a>
<a href=#552 id=552 data-nosnippet>552</a> <span class="kw">let </span>(<span class="kw">_</span>, kind, <span class="kw">_</span>) = <span class="self">self
<a href=#553 id=553 data-nosnippet>553</a> </span>.process_collected_capture_information(CaptureBy::Ref, <span class="kw-2">&amp;</span>delegate.capture_information);
<a href=#554 id=554 data-nosnippet>554</a>
<a href=#555 id=555 data-nosnippet>555</a> <span class="macro">matches!</span>(kind, ClosureKind::FnOnce)
<a href=#556 id=556 data-nosnippet>556</a> }
<a href=#557 id=557 data-nosnippet>557</a>
<a href=#558 id=558 data-nosnippet>558</a> <span class="comment">// Returns a list of `Ty`s for each upvar.
<a href=#559 id=559 data-nosnippet>559</a> </span><span class="kw">fn </span>final_upvar_tys(<span class="kw-2">&amp;</span><span class="self">self</span>, closure_id: ExprId) -&gt; Vec&lt;Ty&lt;<span class="lifetime">'db</span>&gt;&gt; {
<a href=#560 id=560 data-nosnippet>560</a> <span class="self">self</span>.closure_min_captures_flattened(closure_id)
<a href=#561 id=561 data-nosnippet>561</a> .map(|captured_place| {
<a href=#562 id=562 data-nosnippet>562</a> <span class="kw">let </span>upvar_ty = captured_place.place.ty();
<a href=#563 id=563 data-nosnippet>563</a> <span class="kw">let </span>capture = captured_place.info.capture_kind;
<a href=#564 id=564 data-nosnippet>564</a>
<a href=#565 id=565 data-nosnippet>565</a> <span class="macro">debug!</span>(<span class="question-mark">?</span>captured_place.place, <span class="question-mark">?</span>upvar_ty, <span class="question-mark">?</span>capture, <span class="question-mark">?</span>captured_place.mutability);
<a href=#566 id=566 data-nosnippet>566</a>
<a href=#567 id=567 data-nosnippet>567</a> apply_capture_kind_on_capture_ty(
<a href=#568 id=568 data-nosnippet>568</a> <span class="self">self</span>.interner(),
<a href=#569 id=569 data-nosnippet>569</a> upvar_ty,
<a href=#570 id=570 data-nosnippet>570</a> capture,
<a href=#571 id=571 data-nosnippet>571</a> <span class="self">self</span>.types.regions.erased,
<a href=#572 id=572 data-nosnippet>572</a> )
<a href=#573 id=573 data-nosnippet>573</a> })
<a href=#574 id=574 data-nosnippet>574</a> .collect()
<a href=#575 id=575 data-nosnippet>575</a> }
<a href=#576 id=576 data-nosnippet>576</a>
<a href=#577 id=577 data-nosnippet>577</a> <span class="doccomment">/// Adjusts the closure capture information to ensure that the operations aren't unsafe,
<a href=#578 id=578 data-nosnippet>578</a> /// and that the path can be captured with required capture kind (depending on use in closure,
<a href=#579 id=579 data-nosnippet>579</a> /// move closure etc.)
<a href=#580 id=580 data-nosnippet>580</a> ///
<a href=#581 id=581 data-nosnippet>581</a> /// Returns the set of adjusted information along with the inferred closure kind and span
<a href=#582 id=582 data-nosnippet>582</a> /// associated with the closure kind inference.
<a href=#583 id=583 data-nosnippet>583</a> ///
<a href=#584 id=584 data-nosnippet>584</a> /// Note that we *always* infer a minimal kind, even if
<a href=#585 id=585 data-nosnippet>585</a> /// we don't always *use* that in the final result (i.e., sometimes
<a href=#586 id=586 data-nosnippet>586</a> /// we've taken the closure kind from the expectations instead, and
<a href=#587 id=587 data-nosnippet>587</a> /// for coroutines we don't even implement the closure traits
<a href=#588 id=588 data-nosnippet>588</a> /// really).
<a href=#589 id=589 data-nosnippet>589</a> ///
<a href=#590 id=590 data-nosnippet>590</a> /// If we inferred that the closure needs to be FnMut/FnOnce, last element of the returned tuple
<a href=#591 id=591 data-nosnippet>591</a> /// contains a `Some()` with the `Place` that caused us to do so.
<a href=#592 id=592 data-nosnippet>592</a> </span><span class="kw">fn </span>process_collected_capture_information(
<a href=#593 id=593 data-nosnippet>593</a> <span class="kw-2">&amp;mut </span><span class="self">self</span>,
<a href=#594 id=594 data-nosnippet>594</a> capture_clause: CaptureBy,
<a href=#595 id=595 data-nosnippet>595</a> capture_information: <span class="kw-2">&amp;</span>InferredCaptureInformation,
<a href=#596 id=596 data-nosnippet>596</a> ) -&gt; (InferredCaptureInformation, ClosureKind, <span class="prelude-ty">Option</span>&lt;Place&gt;) {
<a href=#597 id=597 data-nosnippet>597</a> <span class="kw">let </span><span class="kw-2">mut </span>closure_kind = ClosureKind::LATTICE_BOTTOM;
<a href=#598 id=598 data-nosnippet>598</a> <span class="kw">let </span><span class="kw-2">mut </span>origin: <span class="prelude-ty">Option</span>&lt;Place&gt; = <span class="prelude-val">None</span>;
<a href=#599 id=599 data-nosnippet>599</a>
<a href=#600 id=600 data-nosnippet>600</a> <span class="kw">let </span>processed = capture_information
<a href=#601 id=601 data-nosnippet>601</a> .iter()
<a href=#602 id=602 data-nosnippet>602</a> .cloned()
<a href=#603 id=603 data-nosnippet>603</a> .map(|(place, <span class="kw-2">mut </span>capture_info)| {
<a href=#604 id=604 data-nosnippet>604</a> <span class="comment">// Apply rules for safety before inferring closure kind
<a href=#605 id=605 data-nosnippet>605</a> </span><span class="kw">let </span>place = restrict_capture_precision(place, <span class="kw-2">&amp;mut </span>capture_info);
<a href=#606 id=606 data-nosnippet>606</a>
<a href=#607 id=607 data-nosnippet>607</a> <span class="kw">let </span>place = truncate_capture_for_optimization(place, <span class="kw-2">&amp;mut </span>capture_info);
<a href=#608 id=608 data-nosnippet>608</a>
<a href=#609 id=609 data-nosnippet>609</a> <span class="kw">let </span>updated = <span class="kw">match </span>capture_info.capture_kind {
<a href=#610 id=610 data-nosnippet>610</a> UpvarCapture::ByValue =&gt; <span class="kw">match </span>closure_kind {
<a href=#611 id=611 data-nosnippet>611</a> ClosureKind::Fn | ClosureKind::FnMut =&gt; {
<a href=#612 id=612 data-nosnippet>612</a> (ClosureKind::FnOnce, <span class="prelude-val">Some</span>(place.clone()))
<a href=#613 id=613 data-nosnippet>613</a> }
<a href=#614 id=614 data-nosnippet>614</a> <span class="comment">// If closure is already FnOnce, don't update
<a href=#615 id=615 data-nosnippet>615</a> </span>ClosureKind::FnOnce =&gt; (closure_kind, origin.take()),
<a href=#616 id=616 data-nosnippet>616</a> },
<a href=#617 id=617 data-nosnippet>617</a>
<a href=#618 id=618 data-nosnippet>618</a> UpvarCapture::ByRef(BorrowKind::Mutable | BorrowKind::UniqueImmutable) =&gt; {
<a href=#619 id=619 data-nosnippet>619</a> <span class="kw">match </span>closure_kind {
<a href=#620 id=620 data-nosnippet>620</a> ClosureKind::Fn =&gt; (ClosureKind::FnMut, <span class="prelude-val">Some</span>(place.clone())),
<a href=#621 id=621 data-nosnippet>621</a> <span class="comment">// Don't update the origin
<a href=#622 id=622 data-nosnippet>622</a> </span>ClosureKind::FnMut | ClosureKind::FnOnce =&gt; {
<a href=#623 id=623 data-nosnippet>623</a> (closure_kind, origin.take())
<a href=#624 id=624 data-nosnippet>624</a> }
<a href=#625 id=625 data-nosnippet>625</a> }
<a href=#626 id=626 data-nosnippet>626</a> }
<a href=#627 id=627 data-nosnippet>627</a>
<a href=#628 id=628 data-nosnippet>628</a> <span class="kw">_ </span>=&gt; (closure_kind, origin.take()),
<a href=#629 id=629 data-nosnippet>629</a> };
<a href=#630 id=630 data-nosnippet>630</a>
<a href=#631 id=631 data-nosnippet>631</a> closure_kind = updated.<span class="number">0</span>;
<a href=#632 id=632 data-nosnippet>632</a> origin = updated.<span class="number">1</span>;
<a href=#633 id=633 data-nosnippet>633</a>
<a href=#634 id=634 data-nosnippet>634</a> <span class="kw">let </span>place = <span class="kw">match </span>capture_clause {
<a href=#635 id=635 data-nosnippet>635</a> CaptureBy::Value =&gt; adjust_for_move_closure(place, <span class="kw-2">&amp;mut </span>capture_info),
<a href=#636 id=636 data-nosnippet>636</a> CaptureBy::Ref =&gt; adjust_for_non_move_closure(place, <span class="kw-2">&amp;mut </span>capture_info),
<a href=#637 id=637 data-nosnippet>637</a> };
<a href=#638 id=638 data-nosnippet>638</a>
<a href=#639 id=639 data-nosnippet>639</a> <span class="comment">// This restriction needs to be applied after we have handled adjustments for `move`
<a href=#640 id=640 data-nosnippet>640</a> // closures. We want to make sure any adjustment that might make us move the place into
<a href=#641 id=641 data-nosnippet>641</a> // the closure gets handled.
<a href=#642 id=642 data-nosnippet>642</a> </span><span class="kw">let </span>place = restrict_precision_for_drop_types(<span class="self">self</span>, place, <span class="kw-2">&amp;mut </span>capture_info);
<a href=#643 id=643 data-nosnippet>643</a>
<a href=#644 id=644 data-nosnippet>644</a> (place, capture_info)
<a href=#645 id=645 data-nosnippet>645</a> })
<a href=#646 id=646 data-nosnippet>646</a> .collect();
<a href=#647 id=647 data-nosnippet>647</a>
<a href=#648 id=648 data-nosnippet>648</a> (processed, closure_kind, origin)
<a href=#649 id=649 data-nosnippet>649</a> }
<a href=#650 id=650 data-nosnippet>650</a>
<a href=#651 id=651 data-nosnippet>651</a> <span class="doccomment">/// Analyzes the information collected by `InferBorrowKind` to compute the min number of
<a href=#652 id=652 data-nosnippet>652</a> /// Places (and corresponding capture kind) that we need to keep track of to support all
<a href=#653 id=653 data-nosnippet>653</a> /// the required captured paths.
<a href=#654 id=654 data-nosnippet>654</a> ///
<a href=#655 id=655 data-nosnippet>655</a> ///
<a href=#656 id=656 data-nosnippet>656</a> /// Note: If this function is called multiple times for the same closure, it will update
<a href=#657 id=657 data-nosnippet>657</a> /// the existing min_capture map that is stored in TypeckResults.
<a href=#658 id=658 data-nosnippet>658</a> ///
<a href=#659 id=659 data-nosnippet>659</a> /// Eg:
<a href=#660 id=660 data-nosnippet>660</a> /// ```
<a href=#661 id=661 data-nosnippet>661</a> /// #[derive(Debug)]
<a href=#662 id=662 data-nosnippet>662</a> /// struct Point { x: i32, y: i32 }
<a href=#663 id=663 data-nosnippet>663</a> ///
<a href=#664 id=664 data-nosnippet>664</a> /// let s = String::from("s"); // hir_id_s
<a href=#665 id=665 data-nosnippet>665</a> /// let mut p = Point { x: 2, y: -2 }; // his_id_p
<a href=#666 id=666 data-nosnippet>666</a> /// let c = || {
<a href=#667 id=667 data-nosnippet>667</a> /// println!("{s:?}"); // L1
<a href=#668 id=668 data-nosnippet>668</a> /// p.x += 10; // L2
<a href=#669 id=669 data-nosnippet>669</a> /// println!("{}" , p.y); // L3
<a href=#670 id=670 data-nosnippet>670</a> /// println!("{p:?}"); // L4
<a href=#671 id=671 data-nosnippet>671</a> /// drop(s); // L5
<a href=#672 id=672 data-nosnippet>672</a> /// };
<a href=#673 id=673 data-nosnippet>673</a> /// ```
<a href=#674 id=674 data-nosnippet>674</a> /// and let hir_id_L1..5 be the expressions pointing to use of a captured variable on
<a href=#675 id=675 data-nosnippet>675</a> /// the lines L1..5 respectively.
<a href=#676 id=676 data-nosnippet>676</a> ///
<a href=#677 id=677 data-nosnippet>677</a> /// InferBorrowKind results in a structure like this:
<a href=#678 id=678 data-nosnippet>678</a> ///
<a href=#679 id=679 data-nosnippet>679</a> /// ```ignore (illustrative)
<a href=#680 id=680 data-nosnippet>680</a> /// {
<a href=#681 id=681 data-nosnippet>681</a> /// Place(base: hir_id_s, projections: [], ....) -&gt; {
<a href=#682 id=682 data-nosnippet>682</a> /// capture_kind_expr: hir_id_L5,
<a href=#683 id=683 data-nosnippet>683</a> /// path_expr_id: hir_id_L5,
<a href=#684 id=684 data-nosnippet>684</a> /// capture_kind: ByValue
<a href=#685 id=685 data-nosnippet>685</a> /// },
<a href=#686 id=686 data-nosnippet>686</a> /// Place(base: hir_id_p, projections: [Field(0, 0)], ...) -&gt; {
<a href=#687 id=687 data-nosnippet>687</a> /// capture_kind_expr: hir_id_L2,
<a href=#688 id=688 data-nosnippet>688</a> /// path_expr_id: hir_id_L2,
<a href=#689 id=689 data-nosnippet>689</a> /// capture_kind: ByValue
<a href=#690 id=690 data-nosnippet>690</a> /// },
<a href=#691 id=691 data-nosnippet>691</a> /// Place(base: hir_id_p, projections: [Field(1, 0)], ...) -&gt; {
<a href=#692 id=692 data-nosnippet>692</a> /// capture_kind_expr: hir_id_L3,
<a href=#693 id=693 data-nosnippet>693</a> /// path_expr_id: hir_id_L3,
<a href=#694 id=694 data-nosnippet>694</a> /// capture_kind: ByValue
<a href=#695 id=695 data-nosnippet>695</a> /// },
<a href=#696 id=696 data-nosnippet>696</a> /// Place(base: hir_id_p, projections: [], ...) -&gt; {
<a href=#697 id=697 data-nosnippet>697</a> /// capture_kind_expr: hir_id_L4,
<a href=#698 id=698 data-nosnippet>698</a> /// path_expr_id: hir_id_L4,
<a href=#699 id=699 data-nosnippet>699</a> /// capture_kind: ByValue
<a href=#700 id=700 data-nosnippet>700</a> /// },
<a href=#701 id=701 data-nosnippet>701</a> /// }
<a href=#702 id=702 data-nosnippet>702</a> /// ```
<a href=#703 id=703 data-nosnippet>703</a> ///
<a href=#704 id=704 data-nosnippet>704</a> /// After the min capture analysis, we get:
<a href=#705 id=705 data-nosnippet>705</a> /// ```ignore (illustrative)
<a href=#706 id=706 data-nosnippet>706</a> /// {
<a href=#707 id=707 data-nosnippet>707</a> /// hir_id_s -&gt; [
<a href=#708 id=708 data-nosnippet>708</a> /// Place(base: hir_id_s, projections: [], ....) -&gt; {
<a href=#709 id=709 data-nosnippet>709</a> /// capture_kind_expr: hir_id_L5,
<a href=#710 id=710 data-nosnippet>710</a> /// path_expr_id: hir_id_L5,
<a href=#711 id=711 data-nosnippet>711</a> /// capture_kind: ByValue
<a href=#712 id=712 data-nosnippet>712</a> /// },
<a href=#713 id=713 data-nosnippet>713</a> /// ],
<a href=#714 id=714 data-nosnippet>714</a> /// hir_id_p -&gt; [
<a href=#715 id=715 data-nosnippet>715</a> /// Place(base: hir_id_p, projections: [], ...) -&gt; {
<a href=#716 id=716 data-nosnippet>716</a> /// capture_kind_expr: hir_id_L2,
<a href=#717 id=717 data-nosnippet>717</a> /// path_expr_id: hir_id_L4,
<a href=#718 id=718 data-nosnippet>718</a> /// capture_kind: ByValue
<a href=#719 id=719 data-nosnippet>719</a> /// },
<a href=#720 id=720 data-nosnippet>720</a> /// ],
<a href=#721 id=721 data-nosnippet>721</a> /// }
<a href=#722 id=722 data-nosnippet>722</a> /// ```
<a href=#723 id=723 data-nosnippet>723</a> </span><span class="attr">#[instrument(level = <span class="string">"debug"</span>, skip(<span class="self">self</span>))]
<a href=#724 id=724 data-nosnippet>724</a> </span><span class="kw">fn </span>compute_min_captures(
<a href=#725 id=725 data-nosnippet>725</a> <span class="kw-2">&amp;mut </span><span class="self">self</span>,
<a href=#726 id=726 data-nosnippet>726</a> closure_def_id: ExprId,
<a href=#727 id=727 data-nosnippet>727</a> capture_information: InferredCaptureInformation,
<a href=#728 id=728 data-nosnippet>728</a> ) {
<a href=#729 id=729 data-nosnippet>729</a> <span class="kw">if </span>capture_information.is_empty() {
<a href=#730 id=730 data-nosnippet>730</a> <span class="kw">return</span>;
<a href=#731 id=731 data-nosnippet>731</a> }
<a href=#732 id=732 data-nosnippet>732</a>
<a href=#733 id=733 data-nosnippet>733</a> <span class="kw">let </span><span class="kw-2">mut </span>closure_data = <span class="self">self</span>.result.closures_data.remove(<span class="kw-2">&amp;</span>closure_def_id).unwrap();
<a href=#734 id=734 data-nosnippet>734</a> <span class="kw">let </span>root_var_min_capture_list = <span class="kw-2">&amp;mut </span>closure_data.min_captures;
<a href=#735 id=735 data-nosnippet>735</a> <span class="kw">let </span><span class="kw-2">mut </span>dedup_sources_scratch = FxHashMap::default();
<a href=#736 id=736 data-nosnippet>736</a>
<a href=#737 id=737 data-nosnippet>737</a> <span class="kw">for </span>(<span class="kw-2">mut </span>place, capture_info) <span class="kw">in </span>capture_information.into_iter() {
<a href=#738 id=738 data-nosnippet>738</a> <span class="kw">let </span>var_hir_id = <span class="kw">match </span>place.base {
<a href=#739 id=739 data-nosnippet>739</a> PlaceBase::Upvar { var_id, .. } =&gt; var_id,
<a href=#740 id=740 data-nosnippet>740</a> base =&gt; <span class="macro">panic!</span>(<span class="string">"Expected upvar, found={:?}"</span>, base),
<a href=#741 id=741 data-nosnippet>741</a> };
<a href=#742 id=742 data-nosnippet>742</a>
<a href=#743 id=743 data-nosnippet>743</a> <span class="kw">let </span><span class="prelude-val">Some</span>(min_cap_list) = root_var_min_capture_list.get_mut(<span class="kw-2">&amp;</span>var_hir_id) <span class="kw">else </span>{
<a href=#744 id=744 data-nosnippet>744</a> <span class="kw">let </span>mutability = <span class="self">self</span>.determine_capture_mutability(closure_def_id, <span class="kw-2">&amp;</span>place);
<a href=#745 id=745 data-nosnippet>745</a> <span class="kw">let </span>min_cap_list = <span class="macro">vec!</span>[CapturedPlace { place, info: capture_info, mutability }];
<a href=#746 id=746 data-nosnippet>746</a> root_var_min_capture_list.insert(var_hir_id, min_cap_list);
<a href=#747 id=747 data-nosnippet>747</a> <span class="kw">continue</span>;
<a href=#748 id=748 data-nosnippet>748</a> };
<a href=#749 id=749 data-nosnippet>749</a>
<a href=#750 id=750 data-nosnippet>750</a> <span class="comment">// Go through each entry in the current list of min_captures
<a href=#751 id=751 data-nosnippet>751</a> // - if ancestor is found, update its capture kind to account for current place's
<a href=#752 id=752 data-nosnippet>752</a> // capture information.
<a href=#753 id=753 data-nosnippet>753</a> //
<a href=#754 id=754 data-nosnippet>754</a> // - if descendant is found, remove it from the list, and update the current place's
<a href=#755 id=755 data-nosnippet>755</a> // capture information to account for the descendant's capture kind.
<a href=#756 id=756 data-nosnippet>756</a> //
<a href=#757 id=757 data-nosnippet>757</a> // We can never be in a case where the list contains both an ancestor and a descendant
<a href=#758 id=758 data-nosnippet>758</a> // Also there can only be ancestor but in case of descendants there might be
<a href=#759 id=759 data-nosnippet>759</a> // multiple.
<a href=#760 id=760 data-nosnippet>760</a>
<a href=#761 id=761 data-nosnippet>761</a> </span><span class="kw">let </span><span class="kw-2">mut </span>descendant_found = <span class="bool-val">false</span>;
<a href=#762 id=762 data-nosnippet>762</a> <span class="kw">let </span><span class="kw-2">mut </span>updated_capture_info = capture_info;
<a href=#763 id=763 data-nosnippet>763</a> min_cap_list.retain(|possible_descendant| {
<a href=#764 id=764 data-nosnippet>764</a> <span class="kw">match </span>determine_place_ancestry_relation(<span class="kw-2">&amp;</span>place, <span class="kw-2">&amp;</span>possible_descendant.place) {
<a href=#765 id=765 data-nosnippet>765</a> <span class="comment">// current place is ancestor of possible_descendant
<a href=#766 id=766 data-nosnippet>766</a> </span>PlaceAncestryRelation::Ancestor =&gt; {
<a href=#767 id=767 data-nosnippet>767</a> descendant_found = <span class="bool-val">true</span>;
<a href=#768 id=768 data-nosnippet>768</a>
<a href=#769 id=769 data-nosnippet>769</a> <span class="kw">let </span><span class="kw-2">mut </span>possible_descendant = possible_descendant.clone();
<a href=#770 id=770 data-nosnippet>770</a>
<a href=#771 id=771 data-nosnippet>771</a> <span class="comment">// Truncate the descendant (already in min_captures) to be same as the ancestor to handle any
<a href=#772 id=772 data-nosnippet>772</a> // possible change in capture mode.
<a href=#773 id=773 data-nosnippet>773</a> </span>truncate_place_to_len_and_update_capture_kind(
<a href=#774 id=774 data-nosnippet>774</a> <span class="kw-2">&amp;mut </span>possible_descendant.place,
<a href=#775 id=775 data-nosnippet>775</a> <span class="kw-2">&amp;mut </span>possible_descendant.info,
<a href=#776 id=776 data-nosnippet>776</a> place.projections.len(),
<a href=#777 id=777 data-nosnippet>777</a> );
<a href=#778 id=778 data-nosnippet>778</a>
<a href=#779 id=779 data-nosnippet>779</a> <span class="kw">let </span>backup_path_sources = determine_capture_sources(
<a href=#780 id=780 data-nosnippet>780</a> <span class="kw-2">&amp;mut </span>updated_capture_info,
<a href=#781 id=781 data-nosnippet>781</a> <span class="kw-2">&amp;mut </span>possible_descendant.info,
<a href=#782 id=782 data-nosnippet>782</a> <span class="kw-2">&amp;mut </span>dedup_sources_scratch,
<a href=#783 id=783 data-nosnippet>783</a> );
<a href=#784 id=784 data-nosnippet>784</a> determine_capture_info(
<a href=#785 id=785 data-nosnippet>785</a> <span class="kw-2">&amp;mut </span>updated_capture_info,
<a href=#786 id=786 data-nosnippet>786</a> <span class="kw-2">&amp;mut </span>possible_descendant.info,
<a href=#787 id=787 data-nosnippet>787</a> );
<a href=#788 id=788 data-nosnippet>788</a>
<a href=#789 id=789 data-nosnippet>789</a> <span class="comment">// we need to keep the ancestor's `path_expr_id`
<a href=#790 id=790 data-nosnippet>790</a> </span>updated_capture_info.sources = backup_path_sources;
<a href=#791 id=791 data-nosnippet>791</a> <span class="bool-val">false
<a href=#792 id=792 data-nosnippet>792</a> </span>}
<a href=#793 id=793 data-nosnippet>793</a>
<a href=#794 id=794 data-nosnippet>794</a> <span class="kw">_ </span>=&gt; <span class="bool-val">true</span>,
<a href=#795 id=795 data-nosnippet>795</a> }
<a href=#796 id=796 data-nosnippet>796</a> });
<a href=#797 id=797 data-nosnippet>797</a>
<a href=#798 id=798 data-nosnippet>798</a> <span class="kw">let </span><span class="kw-2">mut </span>ancestor_found = <span class="bool-val">false</span>;
<a href=#799 id=799 data-nosnippet>799</a> <span class="kw">if </span>!descendant_found {
<a href=#800 id=800 data-nosnippet>800</a> <span class="kw">for </span>possible_ancestor <span class="kw">in </span>min_cap_list.iter_mut() {
<a href=#801 id=801 data-nosnippet>801</a> <span class="kw">match </span>determine_place_ancestry_relation(<span class="kw-2">&amp;</span>place, <span class="kw-2">&amp;</span>possible_ancestor.place) {
<a href=#802 id=802 data-nosnippet>802</a> PlaceAncestryRelation::SamePlace =&gt; {
<a href=#803 id=803 data-nosnippet>803</a> ancestor_found = <span class="bool-val">true</span>;
<a href=#804 id=804 data-nosnippet>804</a> <span class="kw">let </span>backup_path_sources = determine_capture_sources(
<a href=#805 id=805 data-nosnippet>805</a> <span class="kw-2">&amp;mut </span>updated_capture_info,
<a href=#806 id=806 data-nosnippet>806</a> <span class="kw-2">&amp;mut </span>possible_ancestor.info,
<a href=#807 id=807 data-nosnippet>807</a> <span class="kw-2">&amp;mut </span>dedup_sources_scratch,
<a href=#808 id=808 data-nosnippet>808</a> );
<a href=#809 id=809 data-nosnippet>809</a> determine_capture_info(
<a href=#810 id=810 data-nosnippet>810</a> <span class="kw-2">&amp;mut </span>possible_ancestor.info,
<a href=#811 id=811 data-nosnippet>811</a> <span class="kw-2">&amp;mut </span>updated_capture_info,
<a href=#812 id=812 data-nosnippet>812</a> );
<a href=#813 id=813 data-nosnippet>813</a> possible_ancestor.info.sources = backup_path_sources;
<a href=#814 id=814 data-nosnippet>814</a>
<a href=#815 id=815 data-nosnippet>815</a> <span class="comment">// Only one related place will be in the list.
<a href=#816 id=816 data-nosnippet>816</a> </span><span class="kw">break</span>;
<a href=#817 id=817 data-nosnippet>817</a> }
<a href=#818 id=818 data-nosnippet>818</a> <span class="comment">// current place is descendant of possible_ancestor
<a href=#819 id=819 data-nosnippet>819</a> </span>PlaceAncestryRelation::Descendant =&gt; {
<a href=#820 id=820 data-nosnippet>820</a> ancestor_found = <span class="bool-val">true</span>;
<a href=#821 id=821 data-nosnippet>821</a>
<a href=#822 id=822 data-nosnippet>822</a> <span class="comment">// Truncate the descendant (current place) to be same as the ancestor to handle any
<a href=#823 id=823 data-nosnippet>823</a> // possible change in capture mode.
<a href=#824 id=824 data-nosnippet>824</a> </span>truncate_place_to_len_and_update_capture_kind(
<a href=#825 id=825 data-nosnippet>825</a> <span class="kw-2">&amp;mut </span>place,
<a href=#826 id=826 data-nosnippet>826</a> <span class="kw-2">&amp;mut </span>updated_capture_info,
<a href=#827 id=827 data-nosnippet>827</a> possible_ancestor.place.projections.len(),
<a href=#828 id=828 data-nosnippet>828</a> );
<a href=#829 id=829 data-nosnippet>829</a>
<a href=#830 id=830 data-nosnippet>830</a> <span class="kw">let </span>backup_path_sources = determine_capture_sources(
<a href=#831 id=831 data-nosnippet>831</a> <span class="kw-2">&amp;mut </span>updated_capture_info,
<a href=#832 id=832 data-nosnippet>832</a> <span class="kw-2">&amp;mut </span>possible_ancestor.info,
<a href=#833 id=833 data-nosnippet>833</a> <span class="kw-2">&amp;mut </span>dedup_sources_scratch,
<a href=#834 id=834 data-nosnippet>834</a> );
<a href=#835 id=835 data-nosnippet>835</a> determine_capture_info(
<a href=#836 id=836 data-nosnippet>836</a> <span class="kw-2">&amp;mut </span>possible_ancestor.info,
<a href=#837 id=837 data-nosnippet>837</a> <span class="kw-2">&amp;mut </span>updated_capture_info,
<a href=#838 id=838 data-nosnippet>838</a> );
<a href=#839 id=839 data-nosnippet>839</a>
<a href=#840 id=840 data-nosnippet>840</a> <span class="comment">// we need to keep the ancestor's `sources`
<a href=#841 id=841 data-nosnippet>841</a> </span>possible_ancestor.info.sources = backup_path_sources;
<a href=#842 id=842 data-nosnippet>842</a>
<a href=#843 id=843 data-nosnippet>843</a> <span class="comment">// Only one related place will be in the list.
<a href=#844 id=844 data-nosnippet>844</a> </span><span class="kw">break</span>;
<a href=#845 id=845 data-nosnippet>845</a> }
<a href=#846 id=846 data-nosnippet>846</a> <span class="kw">_ </span>=&gt; {}
<a href=#847 id=847 data-nosnippet>847</a> }
<a href=#848 id=848 data-nosnippet>848</a> }
<a href=#849 id=849 data-nosnippet>849</a> }
<a href=#850 id=850 data-nosnippet>850</a>
<a href=#851 id=851 data-nosnippet>851</a> <span class="comment">// Only need to insert when we don't have an ancestor in the existing min capture list
<a href=#852 id=852 data-nosnippet>852</a> </span><span class="kw">if </span>!ancestor_found {
<a href=#853 id=853 data-nosnippet>853</a> <span class="kw">let </span>mutability = <span class="self">self</span>.determine_capture_mutability(closure_def_id, <span class="kw-2">&amp;</span>place);
<a href=#854 id=854 data-nosnippet>854</a> <span class="kw">let </span>captured_place =
<a href=#855 id=855 data-nosnippet>855</a> CapturedPlace { place, info: updated_capture_info, mutability };
<a href=#856 id=856 data-nosnippet>856</a> min_cap_list.push(captured_place);
<a href=#857 id=857 data-nosnippet>857</a> }
<a href=#858 id=858 data-nosnippet>858</a> }
<a href=#859 id=859 data-nosnippet>859</a>
<a href=#860 id=860 data-nosnippet>860</a> <span class="macro">debug!</span>(
<a href=#861 id=861 data-nosnippet>861</a> <span class="string">"For closure={:?}, min_captures before sorting={:?}"</span>,
<a href=#862 id=862 data-nosnippet>862</a> closure_def_id, root_var_min_capture_list
<a href=#863 id=863 data-nosnippet>863</a> );
<a href=#864 id=864 data-nosnippet>864</a>
<a href=#865 id=865 data-nosnippet>865</a> <span class="comment">// Now that we have the minimized list of captures, sort the captures by field id.
<a href=#866 id=866 data-nosnippet>866</a> // This causes the closure to capture the upvars in the same order as the fields are
<a href=#867 id=867 data-nosnippet>867</a> // declared which is also the drop order. Thus, in situations where we capture all the
<a href=#868 id=868 data-nosnippet>868</a> // fields of some type, the observable drop order will remain the same as it previously
<a href=#869 id=869 data-nosnippet>869</a> // was even though we're dropping each capture individually.
<a href=#870 id=870 data-nosnippet>870</a> // See https://github.com/rust-lang/project-rfc-2229/issues/42 and
<a href=#871 id=871 data-nosnippet>871</a> // `tests/ui/closures/2229_closure_analysis/preserve_field_drop_order.rs`.
<a href=#872 id=872 data-nosnippet>872</a> </span><span class="kw">for </span>(<span class="kw">_</span>, captures) <span class="kw">in </span><span class="kw-2">&amp;mut *</span>root_var_min_capture_list {
<a href=#873 id=873 data-nosnippet>873</a> captures.sort_by(|capture1, capture2| {
<a href=#874 id=874 data-nosnippet>874</a> <span class="kw">fn </span>is_field(p: &amp;&amp;Projection) -&gt; bool {
<a href=#875 id=875 data-nosnippet>875</a> <span class="kw">match </span>p.kind {
<a href=#876 id=876 data-nosnippet>876</a> ProjectionKind::Field { .. } =&gt; <span class="bool-val">true</span>,
<a href=#877 id=877 data-nosnippet>877</a> ProjectionKind::Deref | ProjectionKind::UnwrapUnsafeBinder =&gt; <span class="bool-val">false</span>,
<a href=#878 id=878 data-nosnippet>878</a> p @ (ProjectionKind::Subslice | ProjectionKind::Index) =&gt; {
<a href=#879 id=879 data-nosnippet>879</a> <span class="macro">panic!</span>(<span class="string">"ProjectionKind {:?} was unexpected"</span>, p)
<a href=#880 id=880 data-nosnippet>880</a> }
<a href=#881 id=881 data-nosnippet>881</a> }
<a href=#882 id=882 data-nosnippet>882</a> }
<a href=#883 id=883 data-nosnippet>883</a>
<a href=#884 id=884 data-nosnippet>884</a> <span class="comment">// Need to sort only by Field projections, so filter away others.
<a href=#885 id=885 data-nosnippet>885</a> // A previous implementation considered other projection types too
<a href=#886 id=886 data-nosnippet>886</a> // but that caused ICE #118144
<a href=#887 id=887 data-nosnippet>887</a> </span><span class="kw">let </span>capture1_field_projections = capture1.place.projections.iter().filter(is_field);
<a href=#888 id=888 data-nosnippet>888</a> <span class="kw">let </span>capture2_field_projections = capture2.place.projections.iter().filter(is_field);
<a href=#889 id=889 data-nosnippet>889</a>
<a href=#890 id=890 data-nosnippet>890</a> <span class="kw">for </span>(p1, p2) <span class="kw">in </span>capture1_field_projections.zip(capture2_field_projections) {
<a href=#891 id=891 data-nosnippet>891</a> <span class="comment">// We do not need to look at the `Projection.ty` fields here because at each
<a href=#892 id=892 data-nosnippet>892</a> // step of the iteration, the projections will either be the same and therefore
<a href=#893 id=893 data-nosnippet>893</a> // the types must be as well or the current projection will be different and
<a href=#894 id=894 data-nosnippet>894</a> // we will return the result of comparing the field indexes.
<a href=#895 id=895 data-nosnippet>895</a> </span><span class="kw">match </span>(p1.kind, p2.kind) {
<a href=#896 id=896 data-nosnippet>896</a> (
<a href=#897 id=897 data-nosnippet>897</a> ProjectionKind::Field { field_idx: i1, .. },
<a href=#898 id=898 data-nosnippet>898</a> ProjectionKind::Field { field_idx: i2, .. },
<a href=#899 id=899 data-nosnippet>899</a> ) =&gt; {
<a href=#900 id=900 data-nosnippet>900</a> <span class="comment">// Compare only if paths are different.
<a href=#901 id=901 data-nosnippet>901</a> // Otherwise continue to the next iteration
<a href=#902 id=902 data-nosnippet>902</a> </span><span class="kw">if </span>i1 != i2 {
<a href=#903 id=903 data-nosnippet>903</a> <span class="kw">return </span>i1.cmp(<span class="kw-2">&amp;</span>i2);
<a href=#904 id=904 data-nosnippet>904</a> }
<a href=#905 id=905 data-nosnippet>905</a> }
<a href=#906 id=906 data-nosnippet>906</a> <span class="comment">// Given the filter above, this arm should never be hit
<a href=#907 id=907 data-nosnippet>907</a> </span>(l, r) =&gt; <span class="macro">panic!</span>(<span class="string">"ProjectionKinds {:?} or {:?} were unexpected"</span>, l, r),
<a href=#908 id=908 data-nosnippet>908</a> }
<a href=#909 id=909 data-nosnippet>909</a> }
<a href=#910 id=910 data-nosnippet>910</a>
<a href=#911 id=911 data-nosnippet>911</a> std::cmp::Ordering::Equal
<a href=#912 id=912 data-nosnippet>912</a> });
<a href=#913 id=913 data-nosnippet>913</a> }
<a href=#914 id=914 data-nosnippet>914</a>
<a href=#915 id=915 data-nosnippet>915</a> <span class="macro">debug!</span>(
<a href=#916 id=916 data-nosnippet>916</a> <span class="string">"For closure={:?}, min_captures after sorting={:#?}"</span>,
<a href=#917 id=917 data-nosnippet>917</a> closure_def_id, root_var_min_capture_list
<a href=#918 id=918 data-nosnippet>918</a> );
<a href=#919 id=919 data-nosnippet>919</a> <span class="self">self</span>.result.closures_data.insert(closure_def_id, closure_data);
<a href=#920 id=920 data-nosnippet>920</a> }
<a href=#921 id=921 data-nosnippet>921</a>
<a href=#922 id=922 data-nosnippet>922</a> <span class="kw">fn </span>normalize_capture_place(<span class="kw-2">&amp;mut </span><span class="self">self</span>, span: Span, place: Place) -&gt; Place {
<a href=#923 id=923 data-nosnippet>923</a> <span class="kw">let </span>place = <span class="self">self</span>.infcx().resolve_vars_if_possible(place);
<a href=#924 id=924 data-nosnippet>924</a>
<a href=#925 id=925 data-nosnippet>925</a> <span class="comment">// In the new solver, types in HIR `Place`s can contain unnormalized aliases,
<a href=#926 id=926 data-nosnippet>926</a> // which can ICE later (e.g. when projecting fields for diagnostics).
<a href=#927 id=927 data-nosnippet>927</a> </span><span class="kw">let </span>cause = ObligationCause::new(span);
<a href=#928 id=928 data-nosnippet>928</a> <span class="kw">let </span>at = <span class="self">self</span>.table.at(<span class="kw-2">&amp;</span>cause);
<a href=#929 id=929 data-nosnippet>929</a> <span class="kw">match </span>normalize::deeply_normalize_with_skipped_universes_and_ambiguous_coroutine_goals(
<a href=#930 id=930 data-nosnippet>930</a> at,
<a href=#931 id=931 data-nosnippet>931</a> place.clone(),
<a href=#932 id=932 data-nosnippet>932</a> <span class="macro">vec!</span>[],
<a href=#933 id=933 data-nosnippet>933</a> ) {
<a href=#934 id=934 data-nosnippet>934</a> <span class="prelude-val">Ok</span>((normalized, goals)) =&gt; {
<a href=#935 id=935 data-nosnippet>935</a> <span class="kw">if </span>!goals.is_empty() {
<a href=#936 id=936 data-nosnippet>936</a> <span class="comment">// FIXME: Insert coroutine stalled predicates, this matters for MIR.
<a href=#937 id=937 data-nosnippet>937</a> // let mut typeck_results = self.typeck_results.borrow_mut();
<a href=#938 id=938 data-nosnippet>938</a> // typeck_results.coroutine_stalled_predicates.extend(
<a href=#939 id=939 data-nosnippet>939</a> // goals
<a href=#940 id=940 data-nosnippet>940</a> // .into_iter()
<a href=#941 id=941 data-nosnippet>941</a> // // FIXME: throwing away the param-env :(
<a href=#942 id=942 data-nosnippet>942</a> // .map(|goal| (goal.predicate, self.misc(span))),
<a href=#943 id=943 data-nosnippet>943</a> // );
<a href=#944 id=944 data-nosnippet>944</a> </span>}
<a href=#945 id=945 data-nosnippet>945</a> normalized
<a href=#946 id=946 data-nosnippet>946</a> }
<a href=#947 id=947 data-nosnippet>947</a> <span class="prelude-val">Err</span>(errors) =&gt; {
<a href=#948 id=948 data-nosnippet>948</a> <span class="self">self</span>.table.trait_errors.extend(errors);
<a href=#949 id=949 data-nosnippet>949</a> place
<a href=#950 id=950 data-nosnippet>950</a> }
<a href=#951 id=951 data-nosnippet>951</a> }
<a href=#952 id=952 data-nosnippet>952</a> }
<a href=#953 id=953 data-nosnippet>953</a>
<a href=#954 id=954 data-nosnippet>954</a> <span class="kw">fn </span>closure_min_captures_flattened(
<a href=#955 id=955 data-nosnippet>955</a> <span class="kw-2">&amp;</span><span class="self">self</span>,
<a href=#956 id=956 data-nosnippet>956</a> closure_expr_id: ExprId,
<a href=#957 id=957 data-nosnippet>957</a> ) -&gt; <span class="kw">impl </span>Iterator&lt;Item = <span class="kw-2">&amp;</span>CapturedPlace&gt; {
<a href=#958 id=958 data-nosnippet>958</a> <span class="self">self</span>.result
<a href=#959 id=959 data-nosnippet>959</a> .closures_data
<a href=#960 id=960 data-nosnippet>960</a> .get(<span class="kw-2">&amp;</span>closure_expr_id)
<a href=#961 id=961 data-nosnippet>961</a> .map(|closure_data| closure_data.min_captures.values().flatten())
<a href=#962 id=962 data-nosnippet>962</a> .into_iter()
<a href=#963 id=963 data-nosnippet>963</a> .flatten()
<a href=#964 id=964 data-nosnippet>964</a> }
<a href=#965 id=965 data-nosnippet>965</a>
<a href=#966 id=966 data-nosnippet>966</a> <span class="kw">fn </span>init_capture_kind_for_place(
<a href=#967 id=967 data-nosnippet>967</a> <span class="kw-2">&amp;</span><span class="self">self</span>,
<a href=#968 id=968 data-nosnippet>968</a> place: <span class="kw-2">&amp;</span>Place,
<a href=#969 id=969 data-nosnippet>969</a> capture_clause: CaptureBy,
<a href=#970 id=970 data-nosnippet>970</a> ) -&gt; UpvarCapture {
<a href=#971 id=971 data-nosnippet>971</a> <span class="kw">match </span>capture_clause {
<a href=#972 id=972 data-nosnippet>972</a> <span class="comment">// In case of a move closure if the data is accessed through a reference we
<a href=#973 id=973 data-nosnippet>973</a> // want to capture by ref to allow precise capture using reborrows.
<a href=#974 id=974 data-nosnippet>974</a> //
<a href=#975 id=975 data-nosnippet>975</a> // If the data will be moved out of this place, then the place will be truncated
<a href=#976 id=976 data-nosnippet>976</a> // at the first Deref in `adjust_for_move_closure` and then moved into the closure.
<a href=#977 id=977 data-nosnippet>977</a> //
<a href=#978 id=978 data-nosnippet>978</a> // For example:
<a href=#979 id=979 data-nosnippet>979</a> //
<a href=#980 id=980 data-nosnippet>980</a> // struct Buffer&lt;'a&gt; {
<a href=#981 id=981 data-nosnippet>981</a> // x: &amp;'a String,
<a href=#982 id=982 data-nosnippet>982</a> // y: Vec&lt;u8&gt;,
<a href=#983 id=983 data-nosnippet>983</a> // }
<a href=#984 id=984 data-nosnippet>984</a> //
<a href=#985 id=985 data-nosnippet>985</a> // fn get&lt;'a&gt;(b: Buffer&lt;'a&gt;) -&gt; impl Sized + 'a {
<a href=#986 id=986 data-nosnippet>986</a> // let c = move || b.x;
<a href=#987 id=987 data-nosnippet>987</a> // drop(b);
<a href=#988 id=988 data-nosnippet>988</a> // c
<a href=#989 id=989 data-nosnippet>989</a> // }
<a href=#990 id=990 data-nosnippet>990</a> //
<a href=#991 id=991 data-nosnippet>991</a> // Even though the closure is declared as move, when we are capturing borrowed data (in
<a href=#992 id=992 data-nosnippet>992</a> // this case, *b.x) we prefer to capture by reference.
<a href=#993 id=993 data-nosnippet>993</a> // Otherwise you'd get an error in 2021 immediately because you'd be trying to take
<a href=#994 id=994 data-nosnippet>994</a> // ownership of the (borrowed) String or else you'd take ownership of b, as in 2018 and
<a href=#995 id=995 data-nosnippet>995</a> // before, which is also an error.
<a href=#996 id=996 data-nosnippet>996</a> </span>CaptureBy::Value <span class="kw">if </span>!place.deref_tys().any(Ty::is_ref) =&gt; UpvarCapture::ByValue,
<a href=#997 id=997 data-nosnippet>997</a> CaptureBy::Value | CaptureBy::Ref =&gt; UpvarCapture::ByRef(BorrowKind::Immutable),
<a href=#998 id=998 data-nosnippet>998</a> }
<a href=#999 id=999 data-nosnippet>999</a> }
<a href=#1000 id=1000 data-nosnippet>1000</a>
<a href=#1001 id=1001 data-nosnippet>1001</a> <span class="kw">fn </span>place_for_root_variable(<span class="kw-2">&amp;mut </span><span class="self">self</span>, closure_def_id: ExprId, var_hir_id: BindingId) -&gt; Place {
<a href=#1002 id=1002 data-nosnippet>1002</a> <span class="kw">let </span>place = Place {
<a href=#1003 id=1003 data-nosnippet>1003</a> base_ty: <span class="self">self</span>.result.binding_ty(var_hir_id).store(),
<a href=#1004 id=1004 data-nosnippet>1004</a> base: PlaceBase::Upvar { closure: closure_def_id, var_id: var_hir_id },
<a href=#1005 id=1005 data-nosnippet>1005</a> projections: Default::default(),
<a href=#1006 id=1006 data-nosnippet>1006</a> };
<a href=#1007 id=1007 data-nosnippet>1007</a>
<a href=#1008 id=1008 data-nosnippet>1008</a> <span class="comment">// Normalize eagerly when inserting into `capture_information`, so all downstream
<a href=#1009 id=1009 data-nosnippet>1009</a> // capture analysis can assume a normalized `Place`.
<a href=#1010 id=1010 data-nosnippet>1010</a> </span><span class="self">self</span>.normalize_capture_place(var_hir_id.into(), place)
<a href=#1011 id=1011 data-nosnippet>1011</a> }
<a href=#1012 id=1012 data-nosnippet>1012</a>
<a href=#1013 id=1013 data-nosnippet>1013</a> <span class="doccomment">/// A captured place is mutable if
<a href=#1014 id=1014 data-nosnippet>1014</a> /// 1. Projections don't include a Deref of an immut-borrow, **and**
<a href=#1015 id=1015 data-nosnippet>1015</a> /// 2. PlaceBase is mut or projections include a Deref of a mut-borrow.
<a href=#1016 id=1016 data-nosnippet>1016</a> </span><span class="kw">fn </span>determine_capture_mutability(<span class="kw-2">&amp;mut </span><span class="self">self</span>, closure_expr: ExprId, place: <span class="kw-2">&amp;</span>Place) -&gt; Mutability {
<a href=#1017 id=1017 data-nosnippet>1017</a> <span class="kw">let </span>var_hir_id = <span class="kw">match </span>place.base {
<a href=#1018 id=1018 data-nosnippet>1018</a> PlaceBase::Upvar { var_id, .. } =&gt; var_id,
<a href=#1019 id=1019 data-nosnippet>1019</a> <span class="kw">_ </span>=&gt; <span class="macro">unreachable!</span>(),
<a href=#1020 id=1020 data-nosnippet>1020</a> };
<a href=#1021 id=1021 data-nosnippet>1021</a>
<a href=#1022 id=1022 data-nosnippet>1022</a> <span class="kw">let </span><span class="kw-2">mut </span>is_mutbl = <span class="kw">if </span><span class="self">self</span>.store[var_hir_id].mode == BindingAnnotation::Mutable {
<a href=#1023 id=1023 data-nosnippet>1023</a> Mutability::Mut
<a href=#1024 id=1024 data-nosnippet>1024</a> } <span class="kw">else </span>{
<a href=#1025 id=1025 data-nosnippet>1025</a> Mutability::Not
<a href=#1026 id=1026 data-nosnippet>1026</a> };
<a href=#1027 id=1027 data-nosnippet>1027</a>
<a href=#1028 id=1028 data-nosnippet>1028</a> <span class="kw">for </span>pointer_ty <span class="kw">in </span>place.deref_tys() {
<a href=#1029 id=1029 data-nosnippet>1029</a> <span class="kw">match </span><span class="self">self</span>.structurally_resolve_type(closure_expr.into(), pointer_ty).kind() {
<a href=#1030 id=1030 data-nosnippet>1030</a> <span class="comment">// We don't capture derefs of raw ptrs
<a href=#1031 id=1031 data-nosnippet>1031</a> </span>TyKind::RawPtr(<span class="kw">_</span>, <span class="kw">_</span>) =&gt; <span class="macro">unreachable!</span>(),
<a href=#1032 id=1032 data-nosnippet>1032</a>
<a href=#1033 id=1033 data-nosnippet>1033</a> <span class="comment">// Dereferencing a mut-ref allows us to mut the Place if we don't deref
<a href=#1034 id=1034 data-nosnippet>1034</a> // an immut-ref after on top of this.
<a href=#1035 id=1035 data-nosnippet>1035</a> </span>TyKind::Ref(.., Mutability::Mut) =&gt; is_mutbl = Mutability::Mut,
<a href=#1036 id=1036 data-nosnippet>1036</a>
<a href=#1037 id=1037 data-nosnippet>1037</a> <span class="comment">// The place isn't mutable once we dereference an immutable reference.
<a href=#1038 id=1038 data-nosnippet>1038</a> </span>TyKind::Ref(.., Mutability::Not) =&gt; <span class="kw">return </span>Mutability::Not,
<a href=#1039 id=1039 data-nosnippet>1039</a>
<a href=#1040 id=1040 data-nosnippet>1040</a> <span class="comment">// Dereferencing a box doesn't change mutability
<a href=#1041 id=1041 data-nosnippet>1041</a> </span>TyKind::Adt(def, ..) <span class="kw">if </span>def.is_box() =&gt; {}
<a href=#1042 id=1042 data-nosnippet>1042</a>
<a href=#1043 id=1043 data-nosnippet>1043</a> unexpected_ty =&gt; <span class="macro">panic!</span>(<span class="string">"deref of unexpected pointer type {:?}"</span>, unexpected_ty),
<a href=#1044 id=1044 data-nosnippet>1044</a> }
<a href=#1045 id=1045 data-nosnippet>1045</a> }
<a href=#1046 id=1046 data-nosnippet>1046</a>
<a href=#1047 id=1047 data-nosnippet>1047</a> is_mutbl
<a href=#1048 id=1048 data-nosnippet>1048</a> }
<a href=#1049 id=1049 data-nosnippet>1049</a>}
<a href=#1050 id=1050 data-nosnippet>1050</a>
<a href=#1051 id=1051 data-nosnippet>1051</a><span class="doccomment">/// Determines whether a child capture that is derived from a parent capture
<a href=#1052 id=1052 data-nosnippet>1052</a>/// should be borrowed with the lifetime of the parent coroutine-closure's env.
<a href=#1053 id=1053 data-nosnippet>1053</a>///
<a href=#1054 id=1054 data-nosnippet>1054</a>/// There are two cases when this needs to happen:
<a href=#1055 id=1055 data-nosnippet>1055</a>///
<a href=#1056 id=1056 data-nosnippet>1056</a>/// (1.) Are we borrowing data owned by the parent closure? We can determine if
<a href=#1057 id=1057 data-nosnippet>1057</a>/// that is the case by checking if the parent capture is by move, EXCEPT if we
<a href=#1058 id=1058 data-nosnippet>1058</a>/// apply a deref projection of an immutable reference, reborrows of immutable
<a href=#1059 id=1059 data-nosnippet>1059</a>/// references which aren't restricted to the LUB of the lifetimes of the deref
<a href=#1060 id=1060 data-nosnippet>1060</a>/// chain. This is why `&amp;'short mut &amp;'long T` can be reborrowed as `&amp;'long T`.
<a href=#1061 id=1061 data-nosnippet>1061</a>///
<a href=#1062 id=1062 data-nosnippet>1062</a>/// ```rust
<a href=#1063 id=1063 data-nosnippet>1063</a>/// let x = &amp;1i32; // Let's call this lifetime `'1`.
<a href=#1064 id=1064 data-nosnippet>1064</a>/// let c = async move || {
<a href=#1065 id=1065 data-nosnippet>1065</a>/// println!("{:?}", *x);
<a href=#1066 id=1066 data-nosnippet>1066</a>/// // Even though the inner coroutine borrows by ref, we're only capturing `*x`,
<a href=#1067 id=1067 data-nosnippet>1067</a>/// // not `x`, so the inner closure is allowed to reborrow the data for `'1`.
<a href=#1068 id=1068 data-nosnippet>1068</a>/// };
<a href=#1069 id=1069 data-nosnippet>1069</a>/// ```
<a href=#1070 id=1070 data-nosnippet>1070</a>///
<a href=#1071 id=1071 data-nosnippet>1071</a>/// (2.) If a coroutine is mutably borrowing from a parent capture, then that
<a href=#1072 id=1072 data-nosnippet>1072</a>/// mutable borrow cannot live for longer than either the parent *or* the borrow
<a href=#1073 id=1073 data-nosnippet>1073</a>/// that we have on the original upvar. Therefore we always need to borrow the
<a href=#1074 id=1074 data-nosnippet>1074</a>/// child capture with the lifetime of the parent coroutine-closure's env.
<a href=#1075 id=1075 data-nosnippet>1075</a>///
<a href=#1076 id=1076 data-nosnippet>1076</a>/// ```rust
<a href=#1077 id=1077 data-nosnippet>1077</a>/// let mut x = 1i32;
<a href=#1078 id=1078 data-nosnippet>1078</a>/// let c = async || {
<a href=#1079 id=1079 data-nosnippet>1079</a>/// x = 1;
<a href=#1080 id=1080 data-nosnippet>1080</a>/// // The parent borrows `x` for some `&amp;'1 mut i32`.
<a href=#1081 id=1081 data-nosnippet>1081</a>/// // However, when we call `c()`, we implicitly autoref for the signature of
<a href=#1082 id=1082 data-nosnippet>1082</a>/// // `AsyncFnMut::async_call_mut`. Let's call that lifetime `'call`. Since
<a href=#1083 id=1083 data-nosnippet>1083</a>/// // the maximum that `&amp;'call mut &amp;'1 mut i32` can be reborrowed is `&amp;'call mut i32`,
<a href=#1084 id=1084 data-nosnippet>1084</a>/// // the inner coroutine should capture w/ the lifetime of the coroutine-closure.
<a href=#1085 id=1085 data-nosnippet>1085</a>/// };
<a href=#1086 id=1086 data-nosnippet>1086</a>/// ```
<a href=#1087 id=1087 data-nosnippet>1087</a>///
<a href=#1088 id=1088 data-nosnippet>1088</a>/// If either of these cases apply, then we should capture the borrow with the
<a href=#1089 id=1089 data-nosnippet>1089</a>/// lifetime of the parent coroutine-closure's env. Luckily, if this function is
<a href=#1090 id=1090 data-nosnippet>1090</a>/// not correct, then the program is not unsound, since we still borrowck and validate
<a href=#1091 id=1091 data-nosnippet>1091</a>/// the choices made from this function -- the only side-effect is that the user
<a href=#1092 id=1092 data-nosnippet>1092</a>/// may receive unnecessary borrowck errors.
<a href=#1093 id=1093 data-nosnippet>1093</a></span><span class="kw">fn </span>should_reborrow_from_env_of_parent_coroutine_closure(
<a href=#1094 id=1094 data-nosnippet>1094</a> parent_capture: <span class="kw-2">&amp;</span>CapturedPlace,
<a href=#1095 id=1095 data-nosnippet>1095</a> child_capture: <span class="kw-2">&amp;</span>CapturedPlace,
<a href=#1096 id=1096 data-nosnippet>1096</a>) -&gt; bool {
<a href=#1097 id=1097 data-nosnippet>1097</a> <span class="comment">// (1.)
<a href=#1098 id=1098 data-nosnippet>1098</a> </span>(!parent_capture.is_by_ref()
<a href=#1099 id=1099 data-nosnippet>1099</a> <span class="comment">// This is just inlined `place.deref_tys()` but truncated to just
<a href=#1100 id=1100 data-nosnippet>1100</a> // the child projections. Namely, look for a `&amp;T` deref, since we
<a href=#1101 id=1101 data-nosnippet>1101</a> // can always extend `&amp;'short mut &amp;'long T` to `&amp;'long T`.
<a href=#1102 id=1102 data-nosnippet>1102</a> </span>&amp;&amp; !child_capture
<a href=#1103 id=1103 data-nosnippet>1103</a> .place
<a href=#1104 id=1104 data-nosnippet>1104</a> .projections
<a href=#1105 id=1105 data-nosnippet>1105</a> .iter()
<a href=#1106 id=1106 data-nosnippet>1106</a> .enumerate()
<a href=#1107 id=1107 data-nosnippet>1107</a> .skip(parent_capture.place.projections.len())
<a href=#1108 id=1108 data-nosnippet>1108</a> .any(|(idx, proj)| {
<a href=#1109 id=1109 data-nosnippet>1109</a> <span class="macro">matches!</span>(proj.kind, ProjectionKind::Deref)
<a href=#1110 id=1110 data-nosnippet>1110</a> &amp;&amp; <span class="macro">matches!</span>(
<a href=#1111 id=1111 data-nosnippet>1111</a> child_capture.place.ty_before_projection(idx).kind(),
<a href=#1112 id=1112 data-nosnippet>1112</a> TyKind::Ref(.., Mutability::Not)
<a href=#1113 id=1113 data-nosnippet>1113</a> )
<a href=#1114 id=1114 data-nosnippet>1114</a> }))
<a href=#1115 id=1115 data-nosnippet>1115</a> <span class="comment">// (2.)
<a href=#1116 id=1116 data-nosnippet>1116</a> </span>|| <span class="macro">matches!</span>(child_capture.info.capture_kind, UpvarCapture::ByRef(BorrowKind::Mutable))
<a href=#1117 id=1117 data-nosnippet>1117</a>}
<a href=#1118 id=1118 data-nosnippet>1118</a>
<a href=#1119 id=1119 data-nosnippet>1119</a><span class="doccomment">/// Truncate the capture so that the place being borrowed is in accordance with RFC 1240,
<a href=#1120 id=1120 data-nosnippet>1120</a>/// which states that it's unsafe to take a reference into a struct marked `repr(packed)`.
<a href=#1121 id=1121 data-nosnippet>1121</a></span><span class="kw">fn </span>restrict_repr_packed_field_ref_capture(
<a href=#1122 id=1122 data-nosnippet>1122</a> <span class="kw-2">mut </span>place: Place,
<a href=#1123 id=1123 data-nosnippet>1123</a> capture_info: <span class="kw-2">&amp;mut </span>CaptureInfo,
<a href=#1124 id=1124 data-nosnippet>1124</a>) -&gt; Place {
<a href=#1125 id=1125 data-nosnippet>1125</a> <span class="kw">let </span>pos = place.projections.iter().enumerate().position(|(i, p)| {
<a href=#1126 id=1126 data-nosnippet>1126</a> <span class="kw">let </span>ty = place.ty_before_projection(i);
<a href=#1127 id=1127 data-nosnippet>1127</a>
<a href=#1128 id=1128 data-nosnippet>1128</a> <span class="comment">// Return true for fields of packed structs.
<a href=#1129 id=1129 data-nosnippet>1129</a> </span><span class="kw">match </span>p.kind {
<a href=#1130 id=1130 data-nosnippet>1130</a> ProjectionKind::Field { .. } =&gt; <span class="kw">match </span>ty.kind() {
<a href=#1131 id=1131 data-nosnippet>1131</a> TyKind::Adt(def, <span class="kw">_</span>) <span class="kw">if </span>def.is_packed() =&gt; {
<a href=#1132 id=1132 data-nosnippet>1132</a> <span class="comment">// We stop here regardless of field alignment. Field alignment can change as
<a href=#1133 id=1133 data-nosnippet>1133</a> // types change, including the types of private fields in other crates, and that
<a href=#1134 id=1134 data-nosnippet>1134</a> // shouldn't affect how we compute our captures.
<a href=#1135 id=1135 data-nosnippet>1135</a> </span><span class="bool-val">true
<a href=#1136 id=1136 data-nosnippet>1136</a> </span>}
<a href=#1137 id=1137 data-nosnippet>1137</a>
<a href=#1138 id=1138 data-nosnippet>1138</a> <span class="kw">_ </span>=&gt; <span class="bool-val">false</span>,
<a href=#1139 id=1139 data-nosnippet>1139</a> },
<a href=#1140 id=1140 data-nosnippet>1140</a> <span class="kw">_ </span>=&gt; <span class="bool-val">false</span>,
<a href=#1141 id=1141 data-nosnippet>1141</a> }
<a href=#1142 id=1142 data-nosnippet>1142</a> });
<a href=#1143 id=1143 data-nosnippet>1143</a>
<a href=#1144 id=1144 data-nosnippet>1144</a> <span class="kw">if let </span><span class="prelude-val">Some</span>(pos) = pos {
<a href=#1145 id=1145 data-nosnippet>1145</a> truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, pos);
<a href=#1146 id=1146 data-nosnippet>1146</a> }
<a href=#1147 id=1147 data-nosnippet>1147</a>
<a href=#1148 id=1148 data-nosnippet>1148</a> place
<a href=#1149 id=1149 data-nosnippet>1149</a>}
<a href=#1150 id=1150 data-nosnippet>1150</a>
<a href=#1151 id=1151 data-nosnippet>1151</a><span class="doccomment">/// Returns a Ty that applies the specified capture kind on the provided capture Ty
<a href=#1152 id=1152 data-nosnippet>1152</a></span><span class="kw">fn </span>apply_capture_kind_on_capture_ty&lt;<span class="lifetime">'db</span>&gt;(
<a href=#1153 id=1153 data-nosnippet>1153</a> interner: DbInterner&lt;<span class="lifetime">'db</span>&gt;,
<a href=#1154 id=1154 data-nosnippet>1154</a> ty: Ty&lt;<span class="lifetime">'db</span>&gt;,
<a href=#1155 id=1155 data-nosnippet>1155</a> capture_kind: UpvarCapture,
<a href=#1156 id=1156 data-nosnippet>1156</a> region: Region&lt;<span class="lifetime">'db</span>&gt;,
<a href=#1157 id=1157 data-nosnippet>1157</a>) -&gt; Ty&lt;<span class="lifetime">'db</span>&gt; {
<a href=#1158 id=1158 data-nosnippet>1158</a> <span class="kw">match </span>capture_kind {
<a href=#1159 id=1159 data-nosnippet>1159</a> UpvarCapture::ByValue | UpvarCapture::ByUse =&gt; ty,
<a href=#1160 id=1160 data-nosnippet>1160</a> UpvarCapture::ByRef(kind) =&gt; Ty::new_ref(interner, region, ty, kind.to_mutbl_lossy()),
<a href=#1161 id=1161 data-nosnippet>1161</a> }
<a href=#1162 id=1162 data-nosnippet>1162</a>}
<a href=#1163 id=1163 data-nosnippet>1163</a>
<a href=#1164 id=1164 data-nosnippet>1164</a><span class="kw">struct </span>InferBorrowKind {
<a href=#1165 id=1165 data-nosnippet>1165</a> <span class="comment">// The def-id of the closure whose kind and upvar accesses are being inferred.
<a href=#1166 id=1166 data-nosnippet>1166</a> </span>closure_def_id: ExprId,
<a href=#1167 id=1167 data-nosnippet>1167</a>
<a href=#1168 id=1168 data-nosnippet>1168</a> <span class="doccomment">/// For each Place that is captured by the closure, we track the minimal kind of
<a href=#1169 id=1169 data-nosnippet>1169</a> /// access we need (ref, ref mut, move, etc) and the expression that resulted in such access.
<a href=#1170 id=1170 data-nosnippet>1170</a> ///
<a href=#1171 id=1171 data-nosnippet>1171</a> /// Consider closure where s.str1 is captured via an ImmutableBorrow and
<a href=#1172 id=1172 data-nosnippet>1172</a> /// s.str2 via a MutableBorrow
<a href=#1173 id=1173 data-nosnippet>1173</a> ///
<a href=#1174 id=1174 data-nosnippet>1174</a> /// ```rust,no_run
<a href=#1175 id=1175 data-nosnippet>1175</a> /// struct SomeStruct { str1: String, str2: String };
<a href=#1176 id=1176 data-nosnippet>1176</a> ///
<a href=#1177 id=1177 data-nosnippet>1177</a> /// // Assume that the HirId for the variable definition is `V1`
<a href=#1178 id=1178 data-nosnippet>1178</a> /// let mut s = SomeStruct { str1: format!("s1"), str2: format!("s2") };
<a href=#1179 id=1179 data-nosnippet>1179</a> ///
<a href=#1180 id=1180 data-nosnippet>1180</a> /// let fix_s = |new_s2| {
<a href=#1181 id=1181 data-nosnippet>1181</a> /// // Assume that the HirId for the expression `s.str1` is `E1`
<a href=#1182 id=1182 data-nosnippet>1182</a> /// println!("Updating SomeStruct with str1={0}", s.str1);
<a href=#1183 id=1183 data-nosnippet>1183</a> /// // Assume that the HirId for the expression `*s.str2` is `E2`
<a href=#1184 id=1184 data-nosnippet>1184</a> /// s.str2 = new_s2;
<a href=#1185 id=1185 data-nosnippet>1185</a> /// };
<a href=#1186 id=1186 data-nosnippet>1186</a> /// ```
<a href=#1187 id=1187 data-nosnippet>1187</a> ///
<a href=#1188 id=1188 data-nosnippet>1188</a> /// For closure `fix_s`, (at a high level) the map contains
<a href=#1189 id=1189 data-nosnippet>1189</a> ///
<a href=#1190 id=1190 data-nosnippet>1190</a> /// ```ignore (illustrative)
<a href=#1191 id=1191 data-nosnippet>1191</a> /// Place { V1, [ProjectionKind::Field(Index=0, Variant=0)] } : CaptureKind { E1, ImmutableBorrow }
<a href=#1192 id=1192 data-nosnippet>1192</a> /// Place { V1, [ProjectionKind::Field(Index=1, Variant=0)] } : CaptureKind { E2, MutableBorrow }
<a href=#1193 id=1193 data-nosnippet>1193</a> /// ```
<a href=#1194 id=1194 data-nosnippet>1194</a> </span>capture_information: InferredCaptureInformation,
<a href=#1195 id=1195 data-nosnippet>1195</a> fake_reads: Vec&lt;(Place, FakeReadCause, SmallVec&lt;[CaptureSourceStack; <span class="number">2</span>]&gt;)&gt;,
<a href=#1196 id=1196 data-nosnippet>1196</a>}
<a href=#1197 id=1197 data-nosnippet>1197</a>
<a href=#1198 id=1198 data-nosnippet>1198</a><span class="kw">impl</span>&lt;<span class="lifetime">'db</span>&gt; euv::Delegate&lt;<span class="lifetime">'db</span>&gt; <span class="kw">for </span>InferBorrowKind {
<a href=#1199 id=1199 data-nosnippet>1199</a> <span class="attr">#[instrument(skip(<span class="self">self</span>), level = <span class="string">"debug"</span>)]
<a href=#1200 id=1200 data-nosnippet>1200</a> </span><span class="kw">fn </span>fake_read(
<a href=#1201 id=1201 data-nosnippet>1201</a> <span class="kw-2">&amp;mut </span><span class="self">self</span>,
<a href=#1202 id=1202 data-nosnippet>1202</a> place_with_id: PlaceWithOrigin,
<a href=#1203 id=1203 data-nosnippet>1203</a> cause: FakeReadCause,
<a href=#1204 id=1204 data-nosnippet>1204</a> ctx: <span class="kw-2">&amp;mut </span>InferenceContext&lt;<span class="lifetime">'db</span>&gt;,
<a href=#1205 id=1205 data-nosnippet>1205</a> ) {
<a href=#1206 id=1206 data-nosnippet>1206</a> <span class="kw">let </span>PlaceBase::Upvar { .. } = place_with_id.place.base <span class="kw">else </span>{ <span class="kw">return </span>};
<a href=#1207 id=1207 data-nosnippet>1207</a>
<a href=#1208 id=1208 data-nosnippet>1208</a> <span class="comment">// We need to restrict Fake Read precision to avoid fake reading unsafe code,
<a href=#1209 id=1209 data-nosnippet>1209</a> // such as deref of a raw pointer.
<a href=#1210 id=1210 data-nosnippet>1210</a> </span><span class="kw">let </span>dummy_capture_kind = UpvarCapture::ByRef(BorrowKind::Immutable);
<a href=#1211 id=1211 data-nosnippet>1211</a> <span class="kw">let </span><span class="kw-2">mut </span>dummy_capture_info =
<a href=#1212 id=1212 data-nosnippet>1212</a> CaptureInfo { sources: SmallVec::new(), capture_kind: dummy_capture_kind };
<a href=#1213 id=1213 data-nosnippet>1213</a>
<a href=#1214 id=1214 data-nosnippet>1214</a> <span class="kw">let </span>place = ctx.normalize_capture_place(place_with_id.span(), place_with_id.place.clone());
<a href=#1215 id=1215 data-nosnippet>1215</a>
<a href=#1216 id=1216 data-nosnippet>1216</a> <span class="kw">let </span>place = restrict_capture_precision(place, <span class="kw-2">&amp;mut </span>dummy_capture_info);
<a href=#1217 id=1217 data-nosnippet>1217</a>
<a href=#1218 id=1218 data-nosnippet>1218</a> dummy_capture_info.capture_kind = dummy_capture_kind;
<a href=#1219 id=1219 data-nosnippet>1219</a> <span class="kw">let </span>place = restrict_repr_packed_field_ref_capture(place, <span class="kw-2">&amp;mut </span>dummy_capture_info);
<a href=#1220 id=1220 data-nosnippet>1220</a> <span class="self">self</span>.fake_reads.push((place, cause, place_with_id.origins));
<a href=#1221 id=1221 data-nosnippet>1221</a> }
<a href=#1222 id=1222 data-nosnippet>1222</a>
<a href=#1223 id=1223 data-nosnippet>1223</a> <span class="attr">#[instrument(skip(<span class="self">self</span>), level = <span class="string">"debug"</span>)]
<a href=#1224 id=1224 data-nosnippet>1224</a> </span><span class="kw">fn </span>consume(<span class="kw-2">&amp;mut </span><span class="self">self</span>, place_with_id: PlaceWithOrigin, ctx: <span class="kw-2">&amp;mut </span>InferenceContext&lt;<span class="lifetime">'db</span>&gt;) {
<a href=#1225 id=1225 data-nosnippet>1225</a> <span class="kw">let </span>PlaceBase::Upvar { closure: upvar_closure, .. } = place_with_id.place.base <span class="kw">else </span>{
<a href=#1226 id=1226 data-nosnippet>1226</a> <span class="kw">return</span>;
<a href=#1227 id=1227 data-nosnippet>1227</a> };
<a href=#1228 id=1228 data-nosnippet>1228</a> <span class="macro">assert_eq!</span>(<span class="self">self</span>.closure_def_id, upvar_closure);
<a href=#1229 id=1229 data-nosnippet>1229</a>
<a href=#1230 id=1230 data-nosnippet>1230</a> <span class="kw">let </span>place = ctx.normalize_capture_place(place_with_id.span(), place_with_id.place.clone());
<a href=#1231 id=1231 data-nosnippet>1231</a>
<a href=#1232 id=1232 data-nosnippet>1232</a> <span class="self">self</span>.capture_information.push((
<a href=#1233 id=1233 data-nosnippet>1233</a> place,
<a href=#1234 id=1234 data-nosnippet>1234</a> CaptureInfo { sources: place_with_id.origins, capture_kind: UpvarCapture::ByValue },
<a href=#1235 id=1235 data-nosnippet>1235</a> ));
<a href=#1236 id=1236 data-nosnippet>1236</a> }
<a href=#1237 id=1237 data-nosnippet>1237</a>
<a href=#1238 id=1238 data-nosnippet>1238</a> <span class="attr">#[instrument(skip(<span class="self">self</span>), level = <span class="string">"debug"</span>)]
<a href=#1239 id=1239 data-nosnippet>1239</a> </span><span class="kw">fn </span>use_cloned(<span class="kw-2">&amp;mut </span><span class="self">self</span>, place_with_id: PlaceWithOrigin, ctx: <span class="kw-2">&amp;mut </span>InferenceContext&lt;<span class="lifetime">'db</span>&gt;) {
<a href=#1240 id=1240 data-nosnippet>1240</a> <span class="kw">let </span>PlaceBase::Upvar { closure: upvar_closure, .. } = place_with_id.place.base <span class="kw">else </span>{
<a href=#1241 id=1241 data-nosnippet>1241</a> <span class="kw">return</span>;
<a href=#1242 id=1242 data-nosnippet>1242</a> };
<a href=#1243 id=1243 data-nosnippet>1243</a> <span class="macro">assert_eq!</span>(<span class="self">self</span>.closure_def_id, upvar_closure);
<a href=#1244 id=1244 data-nosnippet>1244</a>
<a href=#1245 id=1245 data-nosnippet>1245</a> <span class="kw">let </span>place = ctx.normalize_capture_place(place_with_id.span(), place_with_id.place.clone());
<a href=#1246 id=1246 data-nosnippet>1246</a>
<a href=#1247 id=1247 data-nosnippet>1247</a> <span class="self">self</span>.capture_information.push((
<a href=#1248 id=1248 data-nosnippet>1248</a> place,
<a href=#1249 id=1249 data-nosnippet>1249</a> CaptureInfo { sources: place_with_id.origins, capture_kind: UpvarCapture::ByUse },
<a href=#1250 id=1250 data-nosnippet>1250</a> ));
<a href=#1251 id=1251 data-nosnippet>1251</a> }
<a href=#1252 id=1252 data-nosnippet>1252</a>
<a href=#1253 id=1253 data-nosnippet>1253</a> <span class="attr">#[instrument(skip(<span class="self">self</span>), level = <span class="string">"debug"</span>)]
<a href=#1254 id=1254 data-nosnippet>1254</a> </span><span class="kw">fn </span>borrow(
<a href=#1255 id=1255 data-nosnippet>1255</a> <span class="kw-2">&amp;mut </span><span class="self">self</span>,
<a href=#1256 id=1256 data-nosnippet>1256</a> place_with_id: PlaceWithOrigin,
<a href=#1257 id=1257 data-nosnippet>1257</a> bk: BorrowKind,
<a href=#1258 id=1258 data-nosnippet>1258</a> ctx: <span class="kw-2">&amp;mut </span>InferenceContext&lt;<span class="lifetime">'db</span>&gt;,
<a href=#1259 id=1259 data-nosnippet>1259</a> ) {
<a href=#1260 id=1260 data-nosnippet>1260</a> <span class="kw">let </span>PlaceBase::Upvar { closure: upvar_closure, .. } = place_with_id.place.base <span class="kw">else </span>{
<a href=#1261 id=1261 data-nosnippet>1261</a> <span class="kw">return</span>;
<a href=#1262 id=1262 data-nosnippet>1262</a> };
<a href=#1263 id=1263 data-nosnippet>1263</a> <span class="macro">assert_eq!</span>(<span class="self">self</span>.closure_def_id, upvar_closure);
<a href=#1264 id=1264 data-nosnippet>1264</a>
<a href=#1265 id=1265 data-nosnippet>1265</a> <span class="comment">// The region here will get discarded/ignored
<a href=#1266 id=1266 data-nosnippet>1266</a> </span><span class="kw">let </span>capture_kind = UpvarCapture::ByRef(bk);
<a href=#1267 id=1267 data-nosnippet>1267</a> <span class="kw">let </span><span class="kw-2">mut </span>capture_info =
<a href=#1268 id=1268 data-nosnippet>1268</a> CaptureInfo { sources: place_with_id.origins.iter().cloned().collect(), capture_kind };
<a href=#1269 id=1269 data-nosnippet>1269</a>
<a href=#1270 id=1270 data-nosnippet>1270</a> <span class="kw">let </span>place = ctx.normalize_capture_place(place_with_id.span(), place_with_id.place.clone());
<a href=#1271 id=1271 data-nosnippet>1271</a>
<a href=#1272 id=1272 data-nosnippet>1272</a> <span class="comment">// We only want repr packed restriction to be applied to reading references into a packed
<a href=#1273 id=1273 data-nosnippet>1273</a> // struct, and not when the data is being moved. Therefore we call this method here instead
<a href=#1274 id=1274 data-nosnippet>1274</a> // of in `restrict_capture_precision`.
<a href=#1275 id=1275 data-nosnippet>1275</a> </span><span class="kw">let </span>place = restrict_repr_packed_field_ref_capture(place, <span class="kw-2">&amp;mut </span>capture_info);
<a href=#1276 id=1276 data-nosnippet>1276</a>
<a href=#1277 id=1277 data-nosnippet>1277</a> <span class="comment">// Raw pointers don't inherit mutability
<a href=#1278 id=1278 data-nosnippet>1278</a> </span><span class="kw">if </span>place.deref_tys().any(Ty::is_raw_ptr) {
<a href=#1279 id=1279 data-nosnippet>1279</a> capture_info.capture_kind = UpvarCapture::ByRef(BorrowKind::Immutable);
<a href=#1280 id=1280 data-nosnippet>1280</a> }
<a href=#1281 id=1281 data-nosnippet>1281</a>
<a href=#1282 id=1282 data-nosnippet>1282</a> <span class="self">self</span>.capture_information.push((place, capture_info));
<a href=#1283 id=1283 data-nosnippet>1283</a> }
<a href=#1284 id=1284 data-nosnippet>1284</a>
<a href=#1285 id=1285 data-nosnippet>1285</a> <span class="attr">#[instrument(skip(<span class="self">self</span>), level = <span class="string">"debug"</span>)]
<a href=#1286 id=1286 data-nosnippet>1286</a> </span><span class="kw">fn </span>mutate(<span class="kw-2">&amp;mut </span><span class="self">self</span>, assignee_place: PlaceWithOrigin, ctx: <span class="kw-2">&amp;mut </span>InferenceContext&lt;<span class="lifetime">'db</span>&gt;) {
<a href=#1287 id=1287 data-nosnippet>1287</a> <span class="self">self</span>.borrow(assignee_place, BorrowKind::Mutable, ctx);
<a href=#1288 id=1288 data-nosnippet>1288</a> }
<a href=#1289 id=1289 data-nosnippet>1289</a>}
<a href=#1290 id=1290 data-nosnippet>1290</a>
<a href=#1291 id=1291 data-nosnippet>1291</a><span class="doccomment">/// Rust doesn't permit moving fields out of a type that implements drop
<a href=#1292 id=1292 data-nosnippet>1292</a></span><span class="attr">#[instrument(skip(fcx), ret, level = <span class="string">"debug"</span>)]
<a href=#1293 id=1293 data-nosnippet>1293</a></span><span class="kw">fn </span>restrict_precision_for_drop_types&lt;<span class="lifetime">'db</span>&gt;(
<a href=#1294 id=1294 data-nosnippet>1294</a> fcx: <span class="kw-2">&amp;mut </span>InferenceContext&lt;<span class="lifetime">'db</span>&gt;,
<a href=#1295 id=1295 data-nosnippet>1295</a> <span class="kw-2">mut </span>place: Place,
<a href=#1296 id=1296 data-nosnippet>1296</a> capture_info: <span class="kw-2">&amp;mut </span>CaptureInfo,
<a href=#1297 id=1297 data-nosnippet>1297</a>) -&gt; Place {
<a href=#1298 id=1298 data-nosnippet>1298</a> <span class="kw">if </span>capture_info.capture_kind == UpvarCapture::ByValue
<a href=#1299 id=1299 data-nosnippet>1299</a> &amp;&amp; !fcx.infcx().type_is_copy_modulo_regions(fcx.table.param_env, place.ty())
<a href=#1300 id=1300 data-nosnippet>1300</a> {
<a href=#1301 id=1301 data-nosnippet>1301</a> <span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..place.projections.len() {
<a href=#1302 id=1302 data-nosnippet>1302</a> <span class="kw">match </span>place.ty_before_projection(i).kind() {
<a href=#1303 id=1303 data-nosnippet>1303</a> TyKind::Adt(def, <span class="kw">_</span>) <span class="kw">if </span>def.destructor(fcx.interner()).is_some() =&gt; {
<a href=#1304 id=1304 data-nosnippet>1304</a> truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, i);
<a href=#1305 id=1305 data-nosnippet>1305</a> <span class="kw">break</span>;
<a href=#1306 id=1306 data-nosnippet>1306</a> }
<a href=#1307 id=1307 data-nosnippet>1307</a> <span class="kw">_ </span>=&gt; {}
<a href=#1308 id=1308 data-nosnippet>1308</a> }
<a href=#1309 id=1309 data-nosnippet>1309</a> }
<a href=#1310 id=1310 data-nosnippet>1310</a> }
<a href=#1311 id=1311 data-nosnippet>1311</a>
<a href=#1312 id=1312 data-nosnippet>1312</a> place
<a href=#1313 id=1313 data-nosnippet>1313</a>}
<a href=#1314 id=1314 data-nosnippet>1314</a>
<a href=#1315 id=1315 data-nosnippet>1315</a><span class="doccomment">/// Truncate `place` so that an `unsafe` block isn't required to capture it.
<a href=#1316 id=1316 data-nosnippet>1316</a>/// - No projections are applied to raw pointers, since these require unsafe blocks. We capture
<a href=#1317 id=1317 data-nosnippet>1317</a>/// them completely.
<a href=#1318 id=1318 data-nosnippet>1318</a>/// - No projections are applied on top of Union ADTs, since these require unsafe blocks.
<a href=#1319 id=1319 data-nosnippet>1319</a></span><span class="kw">fn </span>restrict_precision_for_unsafe(<span class="kw-2">mut </span>place: Place, capture_info: <span class="kw-2">&amp;mut </span>CaptureInfo) -&gt; Place {
<a href=#1320 id=1320 data-nosnippet>1320</a> <span class="kw">if </span>place.base_ty.as_ref().is_raw_ptr() {
<a href=#1321 id=1321 data-nosnippet>1321</a> truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, <span class="number">0</span>);
<a href=#1322 id=1322 data-nosnippet>1322</a> }
<a href=#1323 id=1323 data-nosnippet>1323</a>
<a href=#1324 id=1324 data-nosnippet>1324</a> <span class="kw">if </span>place.base_ty.as_ref().is_union() {
<a href=#1325 id=1325 data-nosnippet>1325</a> truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, <span class="number">0</span>);
<a href=#1326 id=1326 data-nosnippet>1326</a> }
<a href=#1327 id=1327 data-nosnippet>1327</a>
<a href=#1328 id=1328 data-nosnippet>1328</a> <span class="kw">for </span>(i, proj) <span class="kw">in </span>place.projections.iter().enumerate() {
<a href=#1329 id=1329 data-nosnippet>1329</a> <span class="kw">if </span>proj.ty.as_ref().is_raw_ptr() {
<a href=#1330 id=1330 data-nosnippet>1330</a> <span class="comment">// Don't apply any projections on top of a raw ptr.
<a href=#1331 id=1331 data-nosnippet>1331</a> </span>truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, i + <span class="number">1</span>);
<a href=#1332 id=1332 data-nosnippet>1332</a> <span class="kw">break</span>;
<a href=#1333 id=1333 data-nosnippet>1333</a> }
<a href=#1334 id=1334 data-nosnippet>1334</a>
<a href=#1335 id=1335 data-nosnippet>1335</a> <span class="kw">if </span>proj.ty.as_ref().is_union() {
<a href=#1336 id=1336 data-nosnippet>1336</a> <span class="comment">// Don't capture precise fields of a union.
<a href=#1337 id=1337 data-nosnippet>1337</a> </span>truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, i + <span class="number">1</span>);
<a href=#1338 id=1338 data-nosnippet>1338</a> <span class="kw">break</span>;
<a href=#1339 id=1339 data-nosnippet>1339</a> }
<a href=#1340 id=1340 data-nosnippet>1340</a> }
<a href=#1341 id=1341 data-nosnippet>1341</a>
<a href=#1342 id=1342 data-nosnippet>1342</a> place
<a href=#1343 id=1343 data-nosnippet>1343</a>}
<a href=#1344 id=1344 data-nosnippet>1344</a>
<a href=#1345 id=1345 data-nosnippet>1345</a><span class="doccomment">/// Truncate projections so that the following rules are obeyed by the captured `place`:
<a href=#1346 id=1346 data-nosnippet>1346</a>/// - No Index projections are captured, since arrays are captured completely.
<a href=#1347 id=1347 data-nosnippet>1347</a>/// - No unsafe block is required to capture `place`.
<a href=#1348 id=1348 data-nosnippet>1348</a>///
<a href=#1349 id=1349 data-nosnippet>1349</a>/// Returns the truncated place and updated capture mode.
<a href=#1350 id=1350 data-nosnippet>1350</a></span><span class="attr">#[instrument(ret, level = <span class="string">"debug"</span>)]
<a href=#1351 id=1351 data-nosnippet>1351</a></span><span class="kw">fn </span>restrict_capture_precision(place: Place, capture_info: <span class="kw-2">&amp;mut </span>CaptureInfo) -&gt; Place {
<a href=#1352 id=1352 data-nosnippet>1352</a> <span class="kw">let </span><span class="kw-2">mut </span>place = restrict_precision_for_unsafe(place, capture_info);
<a href=#1353 id=1353 data-nosnippet>1353</a>
<a href=#1354 id=1354 data-nosnippet>1354</a> <span class="kw">if </span>place.projections.is_empty() {
<a href=#1355 id=1355 data-nosnippet>1355</a> <span class="comment">// Nothing to do here
<a href=#1356 id=1356 data-nosnippet>1356</a> </span><span class="kw">return </span>place;
<a href=#1357 id=1357 data-nosnippet>1357</a> }
<a href=#1358 id=1358 data-nosnippet>1358</a>
<a href=#1359 id=1359 data-nosnippet>1359</a> <span class="kw">for </span>(i, proj) <span class="kw">in </span>place.projections.iter().enumerate() {
<a href=#1360 id=1360 data-nosnippet>1360</a> <span class="kw">match </span>proj.kind {
<a href=#1361 id=1361 data-nosnippet>1361</a> ProjectionKind::Index | ProjectionKind::Subslice =&gt; {
<a href=#1362 id=1362 data-nosnippet>1362</a> <span class="comment">// Arrays are completely captured, so we drop Index and Subslice projections
<a href=#1363 id=1363 data-nosnippet>1363</a> </span>truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, i);
<a href=#1364 id=1364 data-nosnippet>1364</a> <span class="kw">return </span>place;
<a href=#1365 id=1365 data-nosnippet>1365</a> }
<a href=#1366 id=1366 data-nosnippet>1366</a> ProjectionKind::Deref =&gt; {}
<a href=#1367 id=1367 data-nosnippet>1367</a> ProjectionKind::Field { .. } =&gt; {}
<a href=#1368 id=1368 data-nosnippet>1368</a> ProjectionKind::UnwrapUnsafeBinder =&gt; {}
<a href=#1369 id=1369 data-nosnippet>1369</a> }
<a href=#1370 id=1370 data-nosnippet>1370</a> }
<a href=#1371 id=1371 data-nosnippet>1371</a>
<a href=#1372 id=1372 data-nosnippet>1372</a> place
<a href=#1373 id=1373 data-nosnippet>1373</a>}
<a href=#1374 id=1374 data-nosnippet>1374</a>
<a href=#1375 id=1375 data-nosnippet>1375</a><span class="doccomment">/// Truncate deref of any reference.
<a href=#1376 id=1376 data-nosnippet>1376</a></span><span class="attr">#[instrument(ret, level = <span class="string">"debug"</span>)]
<a href=#1377 id=1377 data-nosnippet>1377</a></span><span class="kw">fn </span>adjust_for_move_closure(<span class="kw-2">mut </span>place: Place, capture_info: <span class="kw-2">&amp;mut </span>CaptureInfo) -&gt; Place {
<a href=#1378 id=1378 data-nosnippet>1378</a> <span class="kw">let </span>first_deref = place.projections.iter().position(|proj| proj.kind == ProjectionKind::Deref);
<a href=#1379 id=1379 data-nosnippet>1379</a>
<a href=#1380 id=1380 data-nosnippet>1380</a> <span class="kw">if let </span><span class="prelude-val">Some</span>(idx) = first_deref {
<a href=#1381 id=1381 data-nosnippet>1381</a> truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, idx);
<a href=#1382 id=1382 data-nosnippet>1382</a> }
<a href=#1383 id=1383 data-nosnippet>1383</a>
<a href=#1384 id=1384 data-nosnippet>1384</a> capture_info.capture_kind = UpvarCapture::ByValue;
<a href=#1385 id=1385 data-nosnippet>1385</a> place
<a href=#1386 id=1386 data-nosnippet>1386</a>}
<a href=#1387 id=1387 data-nosnippet>1387</a>
<a href=#1388 id=1388 data-nosnippet>1388</a><span class="doccomment">/// Adjust closure capture just that if taking ownership of data, only move data
<a href=#1389 id=1389 data-nosnippet>1389</a>/// from enclosing stack frame.
<a href=#1390 id=1390 data-nosnippet>1390</a></span><span class="attr">#[instrument(ret, level = <span class="string">"debug"</span>)]
<a href=#1391 id=1391 data-nosnippet>1391</a></span><span class="kw">fn </span>adjust_for_non_move_closure(<span class="kw-2">mut </span>place: Place, capture_info: <span class="kw-2">&amp;mut </span>CaptureInfo) -&gt; Place {
<a href=#1392 id=1392 data-nosnippet>1392</a> <span class="kw">let </span>contains_deref =
<a href=#1393 id=1393 data-nosnippet>1393</a> place.projections.iter().position(|proj| proj.kind == ProjectionKind::Deref);
<a href=#1394 id=1394 data-nosnippet>1394</a>
<a href=#1395 id=1395 data-nosnippet>1395</a> <span class="kw">match </span>capture_info.capture_kind {
<a href=#1396 id=1396 data-nosnippet>1396</a> UpvarCapture::ByValue | UpvarCapture::ByUse =&gt; {
<a href=#1397 id=1397 data-nosnippet>1397</a> <span class="kw">if let </span><span class="prelude-val">Some</span>(idx) = contains_deref {
<a href=#1398 id=1398 data-nosnippet>1398</a> truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, capture_info, idx);
<a href=#1399 id=1399 data-nosnippet>1399</a> }
<a href=#1400 id=1400 data-nosnippet>1400</a> }
<a href=#1401 id=1401 data-nosnippet>1401</a>
<a href=#1402 id=1402 data-nosnippet>1402</a> UpvarCapture::ByRef(..) =&gt; {}
<a href=#1403 id=1403 data-nosnippet>1403</a> }
<a href=#1404 id=1404 data-nosnippet>1404</a>
<a href=#1405 id=1405 data-nosnippet>1405</a> place
<a href=#1406 id=1406 data-nosnippet>1406</a>}
<a href=#1407 id=1407 data-nosnippet>1407</a>
<a href=#1408 id=1408 data-nosnippet>1408</a><span class="doccomment">/// At the end, `capture_info_a` will contain the selected info.
<a href=#1409 id=1409 data-nosnippet>1409</a></span><span class="kw">fn </span>determine_capture_info(capture_info_a: <span class="kw-2">&amp;mut </span>CaptureInfo, capture_info_b: <span class="kw-2">&amp;mut </span>CaptureInfo) {
<a href=#1410 id=1410 data-nosnippet>1410</a> <span class="comment">// We select the CaptureKind which ranks higher based the following priority order:
<a href=#1411 id=1411 data-nosnippet>1411</a> // (ByUse | ByValue) &gt; MutBorrow &gt; UniqueImmBorrow &gt; ImmBorrow
<a href=#1412 id=1412 data-nosnippet>1412</a> </span><span class="kw">match </span>capture_info_a.capture_kind.partial_cmp(<span class="kw-2">&amp;</span>capture_info_b.capture_kind) {
<a href=#1413 id=1413 data-nosnippet>1413</a> <span class="prelude-val">Some</span>(cmp::Ordering::Equal) | <span class="prelude-val">Some</span>(cmp::Ordering::Greater) =&gt; {}
<a href=#1414 id=1414 data-nosnippet>1414</a> <span class="prelude-val">Some</span>(cmp::Ordering::Less) =&gt; mem::swap(capture_info_a, capture_info_b),
<a href=#1415 id=1415 data-nosnippet>1415</a> <span class="prelude-val">None </span>=&gt; <span class="macro">panic!</span>(<span class="string">"Same capture can't be ByUse and ByValue at the same time"</span>),
<a href=#1416 id=1416 data-nosnippet>1416</a> }
<a href=#1417 id=1417 data-nosnippet>1417</a>}
<a href=#1418 id=1418 data-nosnippet>1418</a>
<a href=#1419 id=1419 data-nosnippet>1419</a><span class="kw">fn </span>determine_capture_sources(
<a href=#1420 id=1420 data-nosnippet>1420</a> capture_info_a: <span class="kw-2">&amp;mut </span>CaptureInfo,
<a href=#1421 id=1421 data-nosnippet>1421</a> capture_info_b: <span class="kw-2">&amp;mut </span>CaptureInfo,
<a href=#1422 id=1422 data-nosnippet>1422</a> dedup_sources_scratch: <span class="kw-2">&amp;mut </span>FxHashMap&lt;ExprOrPatIdPacked, CaptureSourceStack&gt;,
<a href=#1423 id=1423 data-nosnippet>1423</a>) -&gt; SmallVec&lt;[CaptureSourceStack; <span class="number">2</span>]&gt; {
<a href=#1424 id=1424 data-nosnippet>1424</a> dedup_sources_scratch.clear();
<a href=#1425 id=1425 data-nosnippet>1425</a> dedup_sources_scratch.extend(
<a href=#1426 id=1426 data-nosnippet>1426</a> mem::take(<span class="kw-2">&amp;mut </span>capture_info_a.sources).into_iter().map(|it| (it.final_source(), it)),
<a href=#1427 id=1427 data-nosnippet>1427</a> );
<a href=#1428 id=1428 data-nosnippet>1428</a> dedup_sources_scratch.extend(
<a href=#1429 id=1429 data-nosnippet>1429</a> mem::take(<span class="kw-2">&amp;mut </span>capture_info_b.sources).into_iter().map(|it| (it.final_source(), it)),
<a href=#1430 id=1430 data-nosnippet>1430</a> );
<a href=#1431 id=1431 data-nosnippet>1431</a>
<a href=#1432 id=1432 data-nosnippet>1432</a> <span class="kw">let </span><span class="kw-2">mut </span>result = mem::take(<span class="kw-2">&amp;mut </span>capture_info_a.sources);
<a href=#1433 id=1433 data-nosnippet>1433</a> result.clear();
<a href=#1434 id=1434 data-nosnippet>1434</a> result.extend(dedup_sources_scratch.values().cloned());
<a href=#1435 id=1435 data-nosnippet>1435</a> result
<a href=#1436 id=1436 data-nosnippet>1436</a>}
<a href=#1437 id=1437 data-nosnippet>1437</a>
<a href=#1438 id=1438 data-nosnippet>1438</a><span class="doccomment">/// Truncates `place` to have up to `len` projections.
<a href=#1439 id=1439 data-nosnippet>1439</a>/// `curr_mode` is the current required capture kind for the place.
<a href=#1440 id=1440 data-nosnippet>1440</a>/// Returns the truncated `place` and the updated required capture kind.
<a href=#1441 id=1441 data-nosnippet>1441</a>///
<a href=#1442 id=1442 data-nosnippet>1442</a>/// Note: Capture kind changes from `MutBorrow` to `UniqueImmBorrow` if the truncated part of the `place`
<a href=#1443 id=1443 data-nosnippet>1443</a>/// contained `Deref` of `&amp;mut`.
<a href=#1444 id=1444 data-nosnippet>1444</a></span><span class="kw">fn </span>truncate_place_to_len_and_update_capture_kind(
<a href=#1445 id=1445 data-nosnippet>1445</a> place: <span class="kw-2">&amp;mut </span>Place,
<a href=#1446 id=1446 data-nosnippet>1446</a> info: <span class="kw-2">&amp;mut </span>CaptureInfo,
<a href=#1447 id=1447 data-nosnippet>1447</a> len: usize,
<a href=#1448 id=1448 data-nosnippet>1448</a>) {
<a href=#1449 id=1449 data-nosnippet>1449</a> <span class="kw">let </span>is_mut_ref = |ty: Ty&lt;<span class="lifetime">'_</span>&gt;| <span class="macro">matches!</span>(ty.kind(), TyKind::Ref(.., Mutability::Mut));
<a href=#1450 id=1450 data-nosnippet>1450</a>
<a href=#1451 id=1451 data-nosnippet>1451</a> <span class="comment">// If the truncated part of the place contains `Deref` of a `&amp;mut` then convert MutBorrow -&gt;
<a href=#1452 id=1452 data-nosnippet>1452</a> // UniqueImmBorrow
<a href=#1453 id=1453 data-nosnippet>1453</a> // Note that if the place contained Deref of a raw pointer it would've not been MutBorrow, so
<a href=#1454 id=1454 data-nosnippet>1454</a> // we don't need to worry about that case here.
<a href=#1455 id=1455 data-nosnippet>1455</a> </span><span class="kw">match </span>info.capture_kind {
<a href=#1456 id=1456 data-nosnippet>1456</a> UpvarCapture::ByRef(BorrowKind::Mutable) =&gt; {
<a href=#1457 id=1457 data-nosnippet>1457</a> <span class="kw">for </span>i <span class="kw">in </span>len..place.projections.len() {
<a href=#1458 id=1458 data-nosnippet>1458</a> <span class="kw">if </span>place.projections[i].kind == ProjectionKind::Deref
<a href=#1459 id=1459 data-nosnippet>1459</a> &amp;&amp; is_mut_ref(place.ty_before_projection(i))
<a href=#1460 id=1460 data-nosnippet>1460</a> {
<a href=#1461 id=1461 data-nosnippet>1461</a> info.capture_kind = UpvarCapture::ByRef(BorrowKind::UniqueImmutable);
<a href=#1462 id=1462 data-nosnippet>1462</a> <span class="kw">break</span>;
<a href=#1463 id=1463 data-nosnippet>1463</a> }
<a href=#1464 id=1464 data-nosnippet>1464</a> }
<a href=#1465 id=1465 data-nosnippet>1465</a> }
<a href=#1466 id=1466 data-nosnippet>1466</a>
<a href=#1467 id=1467 data-nosnippet>1467</a> UpvarCapture::ByRef(..) =&gt; {}
<a href=#1468 id=1468 data-nosnippet>1468</a> UpvarCapture::ByValue | UpvarCapture::ByUse =&gt; {}
<a href=#1469 id=1469 data-nosnippet>1469</a> }
<a href=#1470 id=1470 data-nosnippet>1470</a>
<a href=#1471 id=1471 data-nosnippet>1471</a> <span class="comment">// Now fix the sources, to point at the smaller place.
<a href=#1472 id=1472 data-nosnippet>1472</a> </span><span class="kw">for </span>source <span class="kw">in </span><span class="kw-2">&amp;mut </span>info.sources {
<a href=#1473 id=1473 data-nosnippet>1473</a> <span class="comment">// +1 because the first place is the base.
<a href=#1474 id=1474 data-nosnippet>1474</a> </span>source.truncate(len + <span class="number">1</span>);
<a href=#1475 id=1475 data-nosnippet>1475</a> }
<a href=#1476 id=1476 data-nosnippet>1476</a>
<a href=#1477 id=1477 data-nosnippet>1477</a> place.projections.truncate(len);
<a href=#1478 id=1478 data-nosnippet>1478</a>}
<a href=#1479 id=1479 data-nosnippet>1479</a>
<a href=#1480 id=1480 data-nosnippet>1480</a><span class="doccomment">/// Determines the Ancestry relationship of Place A relative to Place B
<a href=#1481 id=1481 data-nosnippet>1481</a>///
<a href=#1482 id=1482 data-nosnippet>1482</a>/// `PlaceAncestryRelation::Ancestor` implies Place A is ancestor of Place B
<a href=#1483 id=1483 data-nosnippet>1483</a>/// `PlaceAncestryRelation::Descendant` implies Place A is descendant of Place B
<a href=#1484 id=1484 data-nosnippet>1484</a>/// `PlaceAncestryRelation::Divergent` implies neither of them is the ancestor of the other.
<a href=#1485 id=1485 data-nosnippet>1485</a></span><span class="kw">fn </span>determine_place_ancestry_relation(place_a: <span class="kw-2">&amp;</span>Place, place_b: <span class="kw-2">&amp;</span>Place) -&gt; PlaceAncestryRelation {
<a href=#1486 id=1486 data-nosnippet>1486</a> <span class="comment">// If Place A and Place B don't start off from the same root variable, they are divergent.
<a href=#1487 id=1487 data-nosnippet>1487</a> </span><span class="kw">if </span>place_a.base != place_b.base {
<a href=#1488 id=1488 data-nosnippet>1488</a> <span class="kw">return </span>PlaceAncestryRelation::Divergent;
<a href=#1489 id=1489 data-nosnippet>1489</a> }
<a href=#1490 id=1490 data-nosnippet>1490</a>
<a href=#1491 id=1491 data-nosnippet>1491</a> <span class="comment">// Assume of length of projections_a = n
<a href=#1492 id=1492 data-nosnippet>1492</a> </span><span class="kw">let </span>projections_a = <span class="kw-2">&amp;</span>place_a.projections;
<a href=#1493 id=1493 data-nosnippet>1493</a>
<a href=#1494 id=1494 data-nosnippet>1494</a> <span class="comment">// Assume of length of projections_b = m
<a href=#1495 id=1495 data-nosnippet>1495</a> </span><span class="kw">let </span>projections_b = <span class="kw-2">&amp;</span>place_b.projections;
<a href=#1496 id=1496 data-nosnippet>1496</a>
<a href=#1497 id=1497 data-nosnippet>1497</a> <span class="kw">let </span>same_initial_projections =
<a href=#1498 id=1498 data-nosnippet>1498</a> iter::zip(projections_a, projections_b).all(|(proj_a, proj_b)| proj_a.kind == proj_b.kind);
<a href=#1499 id=1499 data-nosnippet>1499</a>
<a href=#1500 id=1500 data-nosnippet>1500</a> <span class="kw">if </span>same_initial_projections {
<a href=#1501 id=1501 data-nosnippet>1501</a> <span class="kw">use </span>std::cmp::Ordering;
<a href=#1502 id=1502 data-nosnippet>1502</a>
<a href=#1503 id=1503 data-nosnippet>1503</a> <span class="comment">// First min(n, m) projections are the same
<a href=#1504 id=1504 data-nosnippet>1504</a> // Select Ancestor/Descendant
<a href=#1505 id=1505 data-nosnippet>1505</a> </span><span class="kw">match </span>projections_b.len().cmp(<span class="kw-2">&amp;</span>projections_a.len()) {
<a href=#1506 id=1506 data-nosnippet>1506</a> Ordering::Greater =&gt; PlaceAncestryRelation::Ancestor,
<a href=#1507 id=1507 data-nosnippet>1507</a> Ordering::Equal =&gt; PlaceAncestryRelation::SamePlace,
<a href=#1508 id=1508 data-nosnippet>1508</a> Ordering::Less =&gt; PlaceAncestryRelation::Descendant,
<a href=#1509 id=1509 data-nosnippet>1509</a> }
<a href=#1510 id=1510 data-nosnippet>1510</a> } <span class="kw">else </span>{
<a href=#1511 id=1511 data-nosnippet>1511</a> PlaceAncestryRelation::Divergent
<a href=#1512 id=1512 data-nosnippet>1512</a> }
<a href=#1513 id=1513 data-nosnippet>1513</a>}
<a href=#1514 id=1514 data-nosnippet>1514</a>
<a href=#1515 id=1515 data-nosnippet>1515</a><span class="doccomment">/// Reduces the precision of the captured place when the precision doesn't yield any benefit from
<a href=#1516 id=1516 data-nosnippet>1516</a>/// borrow checking perspective, allowing us to save us on the size of the capture.
<a href=#1517 id=1517 data-nosnippet>1517</a>///
<a href=#1518 id=1518 data-nosnippet>1518</a>///
<a href=#1519 id=1519 data-nosnippet>1519</a>/// Fields that are read through a shared reference will always be read via a shared ref or a copy,
<a href=#1520 id=1520 data-nosnippet>1520</a>/// and therefore capturing precise paths yields no benefit. This optimization truncates the
<a href=#1521 id=1521 data-nosnippet>1521</a>/// rightmost deref of the capture if the deref is applied to a shared ref.
<a href=#1522 id=1522 data-nosnippet>1522</a>///
<a href=#1523 id=1523 data-nosnippet>1523</a>/// Reason we only drop the last deref is because of the following edge case:
<a href=#1524 id=1524 data-nosnippet>1524</a>///
<a href=#1525 id=1525 data-nosnippet>1525</a>/// ```
<a href=#1526 id=1526 data-nosnippet>1526</a>/// # struct A { field_of_a: Box&lt;i32&gt; }
<a href=#1527 id=1527 data-nosnippet>1527</a>/// # struct B {}
<a href=#1528 id=1528 data-nosnippet>1528</a>/// # struct C&lt;'a&gt;(&amp;'a i32);
<a href=#1529 id=1529 data-nosnippet>1529</a>/// struct MyStruct&lt;'a&gt; {
<a href=#1530 id=1530 data-nosnippet>1530</a>/// a: &amp;'static A,
<a href=#1531 id=1531 data-nosnippet>1531</a>/// b: B,
<a href=#1532 id=1532 data-nosnippet>1532</a>/// c: C&lt;'a&gt;,
<a href=#1533 id=1533 data-nosnippet>1533</a>/// }
<a href=#1534 id=1534 data-nosnippet>1534</a>///
<a href=#1535 id=1535 data-nosnippet>1535</a>/// fn foo&lt;'a, 'b&gt;(m: &amp;'a MyStruct&lt;'b&gt;) -&gt; impl FnMut() + 'static {
<a href=#1536 id=1536 data-nosnippet>1536</a>/// || drop(&amp;*m.a.field_of_a)
<a href=#1537 id=1537 data-nosnippet>1537</a>/// // Here we really do want to capture `*m.a` because that outlives `'static`
<a href=#1538 id=1538 data-nosnippet>1538</a>///
<a href=#1539 id=1539 data-nosnippet>1539</a>/// // If we capture `m`, then the closure no longer outlives `'static`
<a href=#1540 id=1540 data-nosnippet>1540</a>/// // it is constrained to `'a`
<a href=#1541 id=1541 data-nosnippet>1541</a>/// }
<a href=#1542 id=1542 data-nosnippet>1542</a>/// ```
<a href=#1543 id=1543 data-nosnippet>1543</a></span><span class="attr">#[instrument(ret, level = <span class="string">"debug"</span>)]
<a href=#1544 id=1544 data-nosnippet>1544</a></span><span class="kw">fn </span>truncate_capture_for_optimization(<span class="kw-2">mut </span>place: Place, info: <span class="kw-2">&amp;mut </span>CaptureInfo) -&gt; Place {
<a href=#1545 id=1545 data-nosnippet>1545</a> <span class="kw">let </span>is_shared_ref = |ty: Ty&lt;<span class="lifetime">'_</span>&gt;| <span class="macro">matches!</span>(ty.kind(), TyKind::Ref(.., Mutability::Not));
<a href=#1546 id=1546 data-nosnippet>1546</a>
<a href=#1547 id=1547 data-nosnippet>1547</a> <span class="comment">// Find the rightmost deref (if any). All the projections that come after this
<a href=#1548 id=1548 data-nosnippet>1548</a> // are fields or other "in-place pointer adjustments"; these refer therefore to
<a href=#1549 id=1549 data-nosnippet>1549</a> // data owned by whatever pointer is being dereferenced here.
<a href=#1550 id=1550 data-nosnippet>1550</a> </span><span class="kw">let </span>idx = place.projections.iter().rposition(|proj| ProjectionKind::Deref == proj.kind);
<a href=#1551 id=1551 data-nosnippet>1551</a>
<a href=#1552 id=1552 data-nosnippet>1552</a> <span class="kw">match </span>idx {
<a href=#1553 id=1553 data-nosnippet>1553</a> <span class="comment">// If that pointer is a shared reference, then we don't need those fields.
<a href=#1554 id=1554 data-nosnippet>1554</a> </span><span class="prelude-val">Some</span>(idx) <span class="kw">if </span>is_shared_ref(place.ty_before_projection(idx)) =&gt; {
<a href=#1555 id=1555 data-nosnippet>1555</a> truncate_place_to_len_and_update_capture_kind(<span class="kw-2">&amp;mut </span>place, info, idx + <span class="number">1</span>)
<a href=#1556 id=1556 data-nosnippet>1556</a> }
<a href=#1557 id=1557 data-nosnippet>1557</a> <span class="prelude-val">None </span>| <span class="prelude-val">Some</span>(<span class="kw">_</span>) =&gt; {}
<a href=#1558 id=1558 data-nosnippet>1558</a> }
<a href=#1559 id=1559 data-nosnippet>1559</a>
<a href=#1560 id=1560 data-nosnippet>1560</a> place
<a href=#1561 id=1561 data-nosnippet>1561</a>}
<a href=#1562 id=1562 data-nosnippet>1562</a>
<a href=#1563 id=1563 data-nosnippet>1563</a><span class="doccomment">/// Precise capture is enabled if user is using Rust Edition 2021 or higher.
<a href=#1564 id=1564 data-nosnippet>1564</a>/// `span` is the span of the closure.
<a href=#1565 id=1565 data-nosnippet>1565</a></span><span class="kw">fn </span>enable_precise_capture(edition: Edition) -&gt; bool {
<a href=#1566 id=1566 data-nosnippet>1566</a> <span class="comment">// FIXME: We should use the edition from the closure expr.
<a href=#1567 id=1567 data-nosnippet>1567</a> </span>edition.at_least_2021()
<a href=#1568 id=1568 data-nosnippet>1568</a>}
<a href=#1569 id=1569 data-nosnippet>1569</a>
<a href=#1570 id=1570 data-nosnippet>1570</a><span class="kw">fn </span>analyze_coroutine_closure_captures&lt;<span class="lifetime">'a</span>, T&gt;(
<a href=#1571 id=1571 data-nosnippet>1571</a> parent_captures: <span class="kw">impl </span>IntoIterator&lt;Item = <span class="kw-2">&amp;</span><span class="lifetime">'a </span>CapturedPlace&gt;,
<a href=#1572 id=1572 data-nosnippet>1572</a> child_captures: <span class="kw">impl </span>IntoIterator&lt;Item = <span class="kw-2">&amp;</span><span class="lifetime">'a </span>CapturedPlace&gt;,
<a href=#1573 id=1573 data-nosnippet>1573</a> <span class="kw-2">mut </span>for_each: <span class="kw">impl </span>FnMut((usize, <span class="kw-2">&amp;</span><span class="lifetime">'a </span>CapturedPlace), (usize, <span class="kw-2">&amp;</span><span class="lifetime">'a </span>CapturedPlace)) -&gt; T,
<a href=#1574 id=1574 data-nosnippet>1574</a>) -&gt; <span class="kw">impl </span>Iterator&lt;Item = T&gt; {
<a href=#1575 id=1575 data-nosnippet>1575</a> <span class="kw">let </span><span class="kw-2">mut </span>result = SmallVec::&lt;[<span class="kw">_</span>; <span class="number">10</span>]&gt;::new();
<a href=#1576 id=1576 data-nosnippet>1576</a>
<a href=#1577 id=1577 data-nosnippet>1577</a> <span class="kw">let </span><span class="kw-2">mut </span>child_captures = child_captures.into_iter().enumerate().peekable();
<a href=#1578 id=1578 data-nosnippet>1578</a>
<a href=#1579 id=1579 data-nosnippet>1579</a> <span class="comment">// One parent capture may correspond to several child captures if we end up
<a href=#1580 id=1580 data-nosnippet>1580</a> // refining the set of captures via edition-2021 precise captures. We want to
<a href=#1581 id=1581 data-nosnippet>1581</a> // match up any number of child captures with one parent capture, so we keep
<a href=#1582 id=1582 data-nosnippet>1582</a> // peeking off this `Peekable` until the child doesn't match anymore.
<a href=#1583 id=1583 data-nosnippet>1583</a> </span><span class="kw">for </span>(parent_field_idx, parent_capture) <span class="kw">in </span>parent_captures.into_iter().enumerate() {
<a href=#1584 id=1584 data-nosnippet>1584</a> <span class="comment">// Make sure we use every field at least once, b/c why are we capturing something
<a href=#1585 id=1585 data-nosnippet>1585</a> // if it's not used in the inner coroutine.
<a href=#1586 id=1586 data-nosnippet>1586</a> </span><span class="kw">let </span><span class="kw-2">mut </span>field_used_at_least_once = <span class="bool-val">false</span>;
<a href=#1587 id=1587 data-nosnippet>1587</a>
<a href=#1588 id=1588 data-nosnippet>1588</a> <span class="comment">// A parent matches a child if they share the same prefix of projections.
<a href=#1589 id=1589 data-nosnippet>1589</a> // The child may have more, if it is capturing sub-fields out of
<a href=#1590 id=1590 data-nosnippet>1590</a> // something that is captured by-move in the parent closure.
<a href=#1591 id=1591 data-nosnippet>1591</a> </span><span class="kw">while </span>child_captures.peek().is_some_and(|(<span class="kw">_</span>, child_capture)| {
<a href=#1592 id=1592 data-nosnippet>1592</a> child_prefix_matches_parent_projections(parent_capture, child_capture)
<a href=#1593 id=1593 data-nosnippet>1593</a> }) {
<a href=#1594 id=1594 data-nosnippet>1594</a> <span class="kw">let </span>(child_field_idx, child_capture) = child_captures.next().unwrap();
<a href=#1595 id=1595 data-nosnippet>1595</a> <span class="comment">// This analysis only makes sense if the parent capture is a
<a href=#1596 id=1596 data-nosnippet>1596</a> // prefix of the child capture.
<a href=#1597 id=1597 data-nosnippet>1597</a> </span><span class="macro">assert!</span>(
<a href=#1598 id=1598 data-nosnippet>1598</a> child_capture.place.projections.len() &gt;= parent_capture.place.projections.len(),
<a href=#1599 id=1599 data-nosnippet>1599</a> <span class="string">"parent capture ({parent_capture:#?}) expected to be prefix of \
<a href=#1600 id=1600 data-nosnippet>1600</a> child capture ({child_capture:#?})"
<a href=#1601 id=1601 data-nosnippet>1601</a> </span>);
<a href=#1602 id=1602 data-nosnippet>1602</a>
<a href=#1603 id=1603 data-nosnippet>1603</a> result.push(for_each(
<a href=#1604 id=1604 data-nosnippet>1604</a> (parent_field_idx, parent_capture),
<a href=#1605 id=1605 data-nosnippet>1605</a> (child_field_idx, child_capture),
<a href=#1606 id=1606 data-nosnippet>1606</a> ));
<a href=#1607 id=1607 data-nosnippet>1607</a>
<a href=#1608 id=1608 data-nosnippet>1608</a> field_used_at_least_once = <span class="bool-val">true</span>;
<a href=#1609 id=1609 data-nosnippet>1609</a> }
<a href=#1610 id=1610 data-nosnippet>1610</a>
<a href=#1611 id=1611 data-nosnippet>1611</a> <span class="comment">// Make sure the field was used at least once.
<a href=#1612 id=1612 data-nosnippet>1612</a> </span><span class="macro">assert!</span>(
<a href=#1613 id=1613 data-nosnippet>1613</a> field_used_at_least_once,
<a href=#1614 id=1614 data-nosnippet>1614</a> <span class="string">"we captured {parent_capture:#?} but it was not used in the child coroutine?"
<a href=#1615 id=1615 data-nosnippet>1615</a> </span>);
<a href=#1616 id=1616 data-nosnippet>1616</a> }
<a href=#1617 id=1617 data-nosnippet>1617</a> <span class="macro">assert_eq!</span>(child_captures.next(), <span class="prelude-val">None</span>, <span class="string">"leftover child captures?"</span>);
<a href=#1618 id=1618 data-nosnippet>1618</a>
<a href=#1619 id=1619 data-nosnippet>1619</a> result.into_iter()
<a href=#1620 id=1620 data-nosnippet>1620</a>}
<a href=#1621 id=1621 data-nosnippet>1621</a>
<a href=#1622 id=1622 data-nosnippet>1622</a><span class="kw">fn </span>child_prefix_matches_parent_projections(
<a href=#1623 id=1623 data-nosnippet>1623</a> parent_capture: <span class="kw-2">&amp;</span>CapturedPlace,
<a href=#1624 id=1624 data-nosnippet>1624</a> child_capture: <span class="kw-2">&amp;</span>CapturedPlace,
<a href=#1625 id=1625 data-nosnippet>1625</a>) -&gt; bool {
<a href=#1626 id=1626 data-nosnippet>1626</a> <span class="kw">let </span>PlaceBase::Upvar { var_id: parent_base, .. } = parent_capture.place.base <span class="kw">else </span>{
<a href=#1627 id=1627 data-nosnippet>1627</a> <span class="macro">panic!</span>(<span class="string">"expected capture to be an upvar"</span>);
<a href=#1628 id=1628 data-nosnippet>1628</a> };
<a href=#1629 id=1629 data-nosnippet>1629</a> <span class="kw">let </span>PlaceBase::Upvar { var_id: child_base, .. } = child_capture.place.base <span class="kw">else </span>{
<a href=#1630 id=1630 data-nosnippet>1630</a> <span class="macro">panic!</span>(<span class="string">"expected capture to be an upvar"</span>);
<a href=#1631 id=1631 data-nosnippet>1631</a> };
<a href=#1632 id=1632 data-nosnippet>1632</a>
<a href=#1633 id=1633 data-nosnippet>1633</a> parent_base == child_base
<a href=#1634 id=1634 data-nosnippet>1634</a> &amp;&amp; std::iter::zip(<span class="kw-2">&amp;</span>child_capture.place.projections, <span class="kw-2">&amp;</span>parent_capture.place.projections)
<a href=#1635 id=1635 data-nosnippet>1635</a> .all(|(child, parent)| child.kind == parent.kind)
<a href=#1636 id=1636 data-nosnippet>1636</a>}
</code></pre></div></section></main></body></html>