<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="API documentation for the Rust `proc_macro2` crate."><metaname="keywords"content="rust, rustlang, rust-lang, proc_macro2"><title>proc_macro2 - Rust</title><linkrel="stylesheet"type="text/css"href="../normalize.css"><linkrel="stylesheet"type="text/css"href="../rustdoc.css"id="mainThemeStyle"><linkrel="stylesheet"type="text/css"href="../dark.css"><linkrel="stylesheet"type="text/css"href="../light.css"id="themeStyle"><scriptsrc="../storage.js"></script><noscript><linkrel="stylesheet"href="../noscript.css"></noscript><linkrel="shortcut icon"href="../favicon.ico"><styletype="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><bodyclass="rustdoc mod"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="sidebar"><divclass="sidebar-menu">☰</div><ahref='../proc_macro2/index.html'><divclass='logo-container'><imgsrc='../rust-logo.png'alt='logo'></div></a><pclass='location'>Crate proc_macro2</p><divclass="sidebar-elems"><aid='all-types'href='all.html'><p>See all proc_macro2's items</p></a><divclass="block items"><ul><li><ahref="#modules">Modules</a></li><li><ahref="#structs">Structs</a></li><li><ahref="#enums">Enums</a></li></ul></div><pclass='location'></p><script>window.sidebarCurrent={name:'proc_macro2',ty:'mod',relpath:'../'};</script></div></nav><divclass="theme-picker"><buttonid="theme-picker"aria-label="Pick another theme!"><imgsrc="../brush.svg"width="18"alt="Pick another theme!"></button><divid="theme-choices"></div></div><scriptsrc="../theme.js"></script><navclass="sub"><formclass="search-form js-only"><divclass="search-container"><div><selectid="crate-search"><optionvalue="All crates">All crates</option></select><inputclass="search-input"name="search"autocomplete="off"spellcheck="false"placeholder="Click or press ‘S’ to search, ‘?’ for more options…"type="search"></div><aid="settings-menu"href="../settings.html"><imgsrc="../wheel.svg"width="18"alt="Change settings"></a></div></form></nav><sectionid="main"class="content"><h1class='fqn'><spanclass='out-of-band'><spanid='render-detail'><aid="toggle-all-docs"href="javascript:void(0)"title="collapse all docs">[<spanclass='inner'>−</span>]</a></span><aclass='srclink'href='../src/proc_macro2/lib.rs.html#1-1156'title='goto source code'>[src]</a></span><spanclass='in-band'>Crate <aclass="mod"href=''>proc_macro2</a></span></h1><divclass='docblock'><p>A wrapper around the procedural macro API of the compiler's <ahref="https://doc.rust-lang.org/proc_macro/"><code>proc_macro</code></a>
<p><strong>Bring proc-macro-like functionality to other contexts like build.rs and
main.rs.</strong> Types from <code>proc_macro</code> are entirely specific to procedural
macros and cannot ever exist in code outside of a procedural macro.
Meanwhile <code>proc_macro2</code> types may exist anywhere including non-macro code.
By developing foundational libraries like <ahref="https://github.com/dtolnay/syn">syn</a> and <ahref="https://github.com/dtolnay/quote">quote</a> against
<code>proc_macro2</code> rather than <code>proc_macro</code>, the procedural macro ecosystem
becomes easily applicable to many other use cases and we avoid
reimplementing non-macro equivalents of those libraries.</p>
</li>
<li>
<p><strong>Make procedural macros unit testable.</strong> As a consequence of being
specific to procedural macros, nothing that uses <code>proc_macro</code> can be
executed from a unit test. In order for helper libraries or components of
a macro to be testable in isolation, they must be implemented using
<p>If parsing with <ahref="https://github.com/dtolnay/syn">Syn</a>, you'll use <ahref="https://docs.rs/syn/0.15/syn/macro.parse_macro_input.html"><code>parse_macro_input!</code></a> instead to
<table><trclass='module-item'><td><aclass="mod"href="token_stream/index.html"title='proc_macro2::token_stream mod'>token_stream</a></td><tdclass='docblock-short'><p>Public implementation details for the <code>TokenStream</code> type, such as iterators.</p>
</td></tr><trclass='module-item'><td><aclass="struct"href="struct.Ident.html"title='proc_macro2::Ident struct'>Ident</a></td><tdclass='docblock-short'><p>A word of Rust code, which may be a keyword or legal variable name.</p>
</td></tr><trclass='module-item'><td><aclass="struct"href="struct.LexError.html"title='proc_macro2::LexError struct'>LexError</a></td><tdclass='docblock-short'><p>Error returned from <code>TokenStream::from_str</code>.</p>
</td></tr><trclass='module-item'><td><aclass="struct"href="struct.Literal.html"title='proc_macro2::Literal struct'>Literal</a></td><tdclass='docblock-short'><p>A literal string (<code>"hello"</code>), byte string (<code>b"hello"</code>), character (<code>'a'</code>),
byte character (<code>b'a'</code>), an integer or floating point number with or without
a suffix (<code>1</code>, <code>1u8</code>, <code>2.3</code>, <code>2.3f32</code>).</p>
</td></tr><trclass='module-item'><td><aclass="struct"href="struct.Punct.html"title='proc_macro2::Punct struct'>Punct</a></td><tdclass='docblock-short'><p>An <code>Punct</code> is an single punctuation character like <code>+</code>, <code>-</code> or <code>#</code>.</p>
</td></tr><trclass='module-item'><td><aclass="struct"href="struct.Span.html"title='proc_macro2::Span struct'>Span</a></td><tdclass='docblock-short'><p>A region of source code, along with macro expansion information.</p>
</td></tr><trclass='module-item'><td><aclass="struct"href="struct.TokenStream.html"title='proc_macro2::TokenStream struct'>TokenStream</a></td><tdclass='docblock-short'><p>An abstract stream of tokens, or more concretely a sequence of token trees.</p>
<table><trclass='module-item'><td><aclass="enum"href="enum.Delimiter.html"title='proc_macro2::Delimiter enum'>Delimiter</a></td><tdclass='docblock-short'><p>Describes how a sequence of token trees is delimited.</p>
</td></tr><trclass='module-item'><td><aclass="enum"href="enum.Spacing.html"title='proc_macro2::Spacing enum'>Spacing</a></td><tdclass='docblock-short'><p>Whether an <code>Punct</code> is followed immediately by another <code>Punct</code> or followed by
another token or whitespace.</p>
</td></tr><trclass='module-item'><td><aclass="enum"href="enum.TokenTree.html"title='proc_macro2::TokenTree enum'>TokenTree</a></td><tdclass='docblock-short'><p>A single token or a delimited sequence of token trees (e.g. <code>[1, (), ..]</code>).</p>
</td></tr></table></section><sectionid="search"class="content hidden"></section><sectionclass="footer"></section><asideid="help"class="hidden"><div><h1class="hidden">Help</h1><divclass="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>⏎</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><divclass="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g., <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g., <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g., <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath="../";window.currentCrate="proc_macro2";</script><scriptsrc="../aliases.js"></script><scriptsrc="../main.js"></script><scriptdefersrc="../search-index.js"></script></body></html>
