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145 lines
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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="This macro declares a new struct of `$StructName` and implements traits based on `$AutomaticDerive`."><title>self_cell in self_cell - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../static.files/rustdoc-42caa33d.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="self_cell" data-themes="" data-resource-suffix="" data-rustdoc-version="1.84.0 (9fc6b4312 2025-01-07)" data-channel="1.84.0" data-search-js="search-92e6798f.js" data-settings-js="settings-0f613d39.js" ><script src="../static.files/storage-59e33391.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-5f194d8c.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-893ab5e7.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-6580c154.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-044be391.svg"></head><body class="rustdoc macro"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../self_cell/index.html">self_<wbr>cell</a><span class="version">1.1.0</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">self_<wbr>cell</a></h2><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#example" title="Example:">Example:</a></li><li><a href="#generated-api" title="Generated API:">Generated API:</a></li><li><a href="#parameters" title="Parameters:">Parameters:</a></li></ul></section><div id="rustdoc-modnav"><h2 class="in-crate"><a href="index.html">In crate self_<wbr>cell</a></h2></div></div></nav><div class="sidebar-resizer"></div><main><div class="width-limiter"><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><span class="rustdoc-breadcrumbs"><a href="index.html">self_cell</a></span><h1>Macro <span class="macro">self_cell</span><button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../src/self_cell/lib.rs.html#320-577">Source</a> </span></div><pre class="rust item-decl"><code>macro_rules! self_cell {
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(
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$(#[$StructMeta:meta])*
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$Vis:vis struct $StructName:ident $(<$OwnerLifetime:lifetime>)? {
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owner: $Owner:ty,
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#[$Covariance:ident]
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dependent: $Dependent:ident,
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}
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$(impl {$($AutomaticDerive:ident),*})?
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) => { ... };
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}</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>This macro declares a new struct of <code>$StructName</code> and implements traits
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based on <code>$AutomaticDerive</code>.</p>
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<h4 id="example"><a class="doc-anchor" href="#example">§</a>Example:</h4>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>self_cell::self_cell;
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<span class="attr">#[derive(Debug, Eq, PartialEq)]
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</span><span class="kw">struct </span>Ast<<span class="lifetime">'a</span>>(Vec<<span class="kw-2">&</span><span class="lifetime">'a </span>str>);
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<span class="macro">self_cell!</span>(
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<span class="attr">#[doc(hidden)]
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</span><span class="kw">struct </span>PackedAstCell {
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owner: String,
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<span class="attr">#[covariant]
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</span>dependent: Ast,
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}
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<span class="kw">impl </span>{Debug, PartialEq, Eq, Hash}
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);</code></pre></div>
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<p>See the crate overview to get a get an overview and a motivating example.</p>
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<h4 id="generated-api"><a class="doc-anchor" href="#generated-api">§</a>Generated API:</h4>
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<p>The macro implements these constructors:</p>
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<div class="example-wrap ignore"><a href="#" class="tooltip" title="This example is not tested">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>new(
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owner: <span class="macro-nonterminal">$Owner</span>,
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dependent_builder: <span class="kw">impl for</span><<span class="lifetime">'a</span>> ::core::ops::FnOnce(<span class="kw-2">&</span><span class="lifetime">'a </span><span class="macro-nonterminal">$Owner</span>) -> <span class="macro-nonterminal">$Dependent</span><<span class="lifetime">'a</span>>
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) -> <span class="self">Self</span></code></pre></div>
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<div class="example-wrap ignore"><a href="#" class="tooltip" title="This example is not tested">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>try_new<<span class="prelude-val">Err</span>>(
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owner: <span class="macro-nonterminal">$Owner</span>,
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dependent_builder: <span class="kw">impl for</span><<span class="lifetime">'a</span>> ::core::ops::FnOnce(<span class="kw-2">&</span><span class="lifetime">'a </span><span class="macro-nonterminal">$Owner</span>) -> <span class="prelude-ty">Result</span><<span class="macro-nonterminal">$Dependent</span><<span class="lifetime">'a</span>>, <span class="prelude-val">Err</span>>
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) -> <span class="prelude-ty">Result</span><<span class="self">Self</span>, <span class="prelude-val">Err</span>></code></pre></div>
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<div class="example-wrap ignore"><a href="#" class="tooltip" title="This example is not tested">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>try_new_or_recover<<span class="prelude-val">Err</span>>(
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owner: <span class="macro-nonterminal">$Owner</span>,
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dependent_builder: <span class="kw">impl for</span><<span class="lifetime">'a</span>> ::core::ops::FnOnce(<span class="kw-2">&</span><span class="lifetime">'a </span><span class="macro-nonterminal">$Owner</span>) -> <span class="prelude-ty">Result</span><<span class="macro-nonterminal">$Dependent</span><<span class="lifetime">'a</span>>, <span class="prelude-val">Err</span>>
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) -> <span class="prelude-ty">Result</span><<span class="self">Self</span>, (<span class="macro-nonterminal">$Owner</span>, <span class="prelude-val">Err</span>)></code></pre></div>
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<p>The macro implements these methods:</p>
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<div class="example-wrap ignore"><a href="#" class="tooltip" title="This example is not tested">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>borrow_owner<<span class="lifetime">'a</span>>(<span class="kw-2">&</span><span class="lifetime">'a </span><span class="self">self</span>) -> <span class="kw-2">&</span><span class="lifetime">'a </span><span class="macro-nonterminal">$Owner</span></code></pre></div>
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<div class="example-wrap ignore"><a href="#" class="tooltip" title="This example is not tested">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="comment">// Only available if dependent is covariant.
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</span><span class="kw">fn </span>borrow_dependent<<span class="lifetime">'a</span>>(<span class="kw-2">&</span><span class="lifetime">'a </span><span class="self">self</span>) -> <span class="kw-2">&</span><span class="lifetime">'a </span><span class="macro-nonterminal">$Dependent</span><<span class="lifetime">'a</span>></code></pre></div>
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<div class="example-wrap ignore"><a href="#" class="tooltip" title="This example is not tested">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>with_dependent<<span class="lifetime">'outer_fn</span>, Ret>(
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<span class="kw-2">&</span><span class="lifetime">'outer_fn </span><span class="self">self</span>,
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func: <span class="kw">impl for</span><<span class="lifetime">'a</span>> ::core::ops::FnOnce(<span class="kw-2">&</span><span class="lifetime">'a </span><span class="macro-nonterminal">$Owner</span>, <span class="kw-2">&</span><span class="lifetime">'outer_fn </span><span class="macro-nonterminal">$Dependent</span><<span class="lifetime">'a</span>>
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) -> Ret) -> Ret</code></pre></div>
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<div class="example-wrap ignore"><a href="#" class="tooltip" title="This example is not tested">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>with_dependent_mut<<span class="lifetime">'outer_fn</span>, Ret>(
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<span class="kw-2">&</span><span class="lifetime">'outer_fn </span><span class="kw-2">mut </span><span class="self">self</span>,
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func: <span class="kw">impl for</span><<span class="lifetime">'a</span>> ::core::ops::FnOnce(<span class="kw-2">&</span><span class="lifetime">'a </span><span class="macro-nonterminal">$Owner</span>, <span class="kw-2">&</span><span class="lifetime">'outer_fn </span><span class="kw-2">mut </span><span class="macro-nonterminal">$Dependent</span><<span class="lifetime">'a</span>>) -> Ret
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) -> Ret</code></pre></div>
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<div class="example-wrap ignore"><a href="#" class="tooltip" title="This example is not tested">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>into_owner(<span class="self">self</span>) -> <span class="macro-nonterminal">$Owner</span></code></pre></div>
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<h4 id="parameters"><a class="doc-anchor" href="#parameters">§</a>Parameters:</h4>
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<ul>
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<li>
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<p><code>$Vis:vis struct $StructName:ident</code> Name of the struct that will be
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declared, this needs to be unique for the relevant scope. Example: <code>struct AstCell</code> or <code>pub struct AstCell</code>. <code>$Vis</code> can be used to mark the struct
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and all functions implemented by the macro as public.</p>
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<p><code>$(#[$StructMeta:meta])*</code> allows you specify further meta items for this
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struct, eg. <code>#[doc(hidden)] struct AstCell</code>.</p>
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</li>
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<li>
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<p><code>$Owner:ty</code> Type of owner. This has to have a <code>'static</code> lifetime. Example:
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<code>String</code>.</p>
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</li>
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<li>
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<p><code>$Dependent:ident</code> Name of the dependent type without specified lifetime.
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This can’t be a nested type name. As workaround either create a type alias
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<code>type Dep<'a> = Option<Vec<&'a str>>;</code> or create a new-type <code>struct Dep<'a>(Option<Vec<&'a str>>);</code>. Example: <code>Ast</code>.</p>
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<p><code>$Covariance:ident</code> Marker declaring if <code>$Dependent</code> is
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<a href="https://doc.rust-lang.org/nightly/nomicon/subtyping.html">covariant</a>.
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Possible Values:</p>
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<ul>
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<li>
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<p><strong>covariant</strong>: This generates the direct reference accessor function
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<code>borrow_dependent</code>. This is only safe to do if this compiles <code>fn _assert_covariance<'x: 'y, 'y>(x: &'y $Dependent<'x>) -> &'y $Dependent<'y> {x}</code>. Otherwise you could choose a lifetime that is too short for types
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with interior mutability like <code>Cell</code>, which can lead to UB in safe code.
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Which would violate the promise of this library that it is safe-to-use.
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If you accidentally mark a type that is not covariant as covariant, you
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will get a compile time error.</p>
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</li>
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<li>
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<p><strong>not_covariant</strong>: This generates no additional code but you can use the
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<code>with_dependent</code> function. See <a href="https://github.com/Voultapher/self_cell/tree/main/examples/lazy_ast">How to build a lazy AST with
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self_cell</a>
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for a usage example.</p>
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</li>
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</ul>
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<p>In both cases you can use the <code>with_dependent_mut</code> function to mutate the
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dependent value. This is safe to do because notionally you are replacing
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pointers to a value not the other way around.</p>
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</li>
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<li>
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<p><code>impl {$($AutomaticDerive:ident),*},</code> Optional comma separated list of
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optional automatic trait implementations. Possible Values:</p>
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<ul>
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<li>
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<p><strong>Debug</strong>: Prints the debug representation of owner and dependent.
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Example: <code>AstCell { owner: "fox = cat + dog", dependent: Ast(["fox", "cat", "dog"]) }</code></p>
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</li>
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<li>
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<p><strong>PartialEq</strong>: Logic <code>*self.borrow_owner() == *other.borrow_owner()</code>,
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this assumes that <code>Dependent<'a>::From<&'a Owner></code> is deterministic, so
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that only comparing owner is enough.</p>
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</li>
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<li>
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<p><strong>Eq</strong>: Will implement the trait marker <code>Eq</code> for <code>$StructName</code>. Beware
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if you select this <code>Eq</code> will be implemented regardless if <code>$Owner</code>
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implements <code>Eq</code>, that’s an unfortunate technical limitation.</p>
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</li>
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<li>
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<p><strong>Hash</strong>: Logic <code>self.borrow_owner().hash(state);</code>, this assumes that
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<code>Dependent<'a>::From<&'a Owner></code> is deterministic, so that only hashing
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owner is enough.</p>
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</li>
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</ul>
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<p>All <code>AutomaticDerive</code> are optional and you can implement you own version
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of these traits. The declared struct is part of your module and you are
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free to implement any trait in any way you want. Access to the unsafe
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internals is only possible via unsafe functions, so you can’t accidentally
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use them in safe code.</p>
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<p>There is limited nested cell support. Eg, having an owner with non static
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references. Eg <code>struct ChildCell<'a> { owner: &'a String, ...</code>. You can
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use any lifetime name you want, except <code>_q</code> and only a single lifetime is
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supported, and can only be used in the owner. Due to macro_rules
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limitations, no <code>AutomaticDerive</code> are supported if an owner lifetime is
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provided.</p>
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</li>
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</ul>
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</div></details></section></div></main></body></html> |