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| </pre><pre class="rust"><code><span class="doccomment">/// Parse the input TokenStream of a macro, triggering a compile error if the</span> |
| <span class="doccomment">/// tokens fail to parse.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Refer to the [`parse` module] documentation for more details about parsing</span> |
| <span class="doccomment">/// in Syn.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// [`parse` module]: crate::rustdoc_workaround::parse_module</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// <br></span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # Intended usage</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This macro must be called from a function that returns</span> |
| <span class="doccomment">/// `proc_macro::TokenStream`. Usually this will be your proc macro entry point,</span> |
| <span class="doccomment">/// the function that has the #\[proc_macro\] / #\[proc_macro_derive\] /</span> |
| <span class="doccomment">/// #\[proc_macro_attribute\] attribute.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// ```</span> |
| <span class="doccomment">/// # extern crate proc_macro;</span> |
| <span class="doccomment">/// #</span> |
| <span class="doccomment">/// use proc_macro::TokenStream;</span> |
| <span class="doccomment">/// use syn::{parse_macro_input, Result};</span> |
| <span class="doccomment">/// use syn::parse::{Parse, ParseStream};</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// struct MyMacroInput {</span> |
| <span class="doccomment">/// /* ... */</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// impl Parse for MyMacroInput {</span> |
| <span class="doccomment">/// fn parse(input: ParseStream) -> Result<Self> {</span> |
| <span class="doccomment">/// /* ... */</span> |
| <span class="doccomment">/// # Ok(MyMacroInput {})</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # const IGNORE: &str = stringify! {</span> |
| <span class="doccomment">/// #[proc_macro]</span> |
| <span class="doccomment">/// # };</span> |
| <span class="doccomment">/// pub fn my_macro(tokens: TokenStream) -> TokenStream {</span> |
| <span class="doccomment">/// let input = parse_macro_input!(tokens as MyMacroInput);</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// /* ... */</span> |
| <span class="doccomment">/// # "".parse().unwrap()</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// ```</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// <br></span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # Usage with Parser</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This macro can also be used with the [`Parser` trait] for types that have</span> |
| <span class="doccomment">/// multiple ways that they can be parsed.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// [`Parser` trait]: crate::rustdoc_workaround::parse_module::Parser</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// ```</span> |
| <span class="doccomment">/// # extern crate proc_macro;</span> |
| <span class="doccomment">/// #</span> |
| <span class="doccomment">/// # use proc_macro::TokenStream;</span> |
| <span class="doccomment">/// # use syn::{parse_macro_input, Result};</span> |
| <span class="doccomment">/// # use syn::parse::ParseStream;</span> |
| <span class="doccomment">/// #</span> |
| <span class="doccomment">/// # struct MyMacroInput {}</span> |
| <span class="doccomment">/// #</span> |
| <span class="doccomment">/// impl MyMacroInput {</span> |
| <span class="doccomment">/// fn parse_alternate(input: ParseStream) -> Result<Self> {</span> |
| <span class="doccomment">/// /* ... */</span> |
| <span class="doccomment">/// # Ok(MyMacroInput {})</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # const IGNORE: &str = stringify! {</span> |
| <span class="doccomment">/// #[proc_macro]</span> |
| <span class="doccomment">/// # };</span> |
| <span class="doccomment">/// pub fn my_macro(tokens: TokenStream) -> TokenStream {</span> |
| <span class="doccomment">/// let input = parse_macro_input!(tokens with MyMacroInput::parse_alternate);</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// /* ... */</span> |
| <span class="doccomment">/// # "".parse().unwrap()</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// ```</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// <br></span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # Expansion</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// `parse_macro_input!($variable as $Type)` expands to something like:</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// ```no_run</span> |
| <span class="doccomment">/// # extern crate proc_macro;</span> |
| <span class="doccomment">/// #</span> |
| <span class="doccomment">/// # macro_rules! doc_test {</span> |
| <span class="doccomment">/// # ($variable:ident as $Type:ty) => {</span> |
| <span class="doccomment">/// match syn::parse::<$Type>($variable) {</span> |
| <span class="doccomment">/// Ok(syntax_tree) => syntax_tree,</span> |
| <span class="doccomment">/// Err(err) => return proc_macro::TokenStream::from(err.to_compile_error()),</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// # };</span> |
| <span class="doccomment">/// # }</span> |
| <span class="doccomment">/// #</span> |
| <span class="doccomment">/// # fn test(input: proc_macro::TokenStream) -> proc_macro::TokenStream {</span> |
| <span class="doccomment">/// # let _ = doc_test!(input as syn::Ident);</span> |
| <span class="doccomment">/// # proc_macro::TokenStream::new()</span> |
| <span class="doccomment">/// # }</span> |
| <span class="doccomment">/// ```</span> |
| <span class="attribute">#[<span class="ident">macro_export</span>]</span> |
| <span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">doc_cfg</span>, <span class="ident">doc</span>(<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"parsing"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"proc-macro"</span>))))]</span> |
| <span class="macro">macro_rules!</span> <span class="ident">parse_macro_input</span> { |
| (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">tokenstream</span>:<span class="ident">ident</span> <span class="kw">as</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">ty</span>:<span class="ident">ty</span>) => { |
| <span class="kw">match</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">crate::parse_macro_input::parse</span>::<span class="op"><</span><span class="macro-nonterminal">$</span><span class="macro-nonterminal">ty</span><span class="op">></span>(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">tokenstream</span>) { |
| <span class="macro-nonterminal">$</span><span class="macro-nonterminal">crate::__private::Ok</span>(<span class="ident">data</span>) => <span class="ident">data</span>, |
| <span class="macro-nonterminal">$</span><span class="macro-nonterminal">crate::__private::Err</span>(<span class="ident">err</span>) => { |
| <span class="kw">return</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">crate::__private::TokenStream::from</span>(<span class="ident">err</span>.<span class="ident">to_compile_error</span>()); |
| } |
| } |
| }; |
| (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">tokenstream</span>:<span class="ident">ident</span> <span class="ident">with</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">parser</span>:<span class="ident">path</span>) => { |
| <span class="kw">match</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">crate::parse::Parser::parse</span>(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">parser</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">tokenstream</span>) { |
| <span class="macro-nonterminal">$</span><span class="macro-nonterminal">crate::__private::Ok</span>(<span class="ident">data</span>) => <span class="ident">data</span>, |
| <span class="macro-nonterminal">$</span><span class="macro-nonterminal">crate::__private::Err</span>(<span class="ident">err</span>) => { |
| <span class="kw">return</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">crate::__private::TokenStream::from</span>(<span class="ident">err</span>.<span class="ident">to_compile_error</span>()); |
| } |
| } |
| }; |
| (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">tokenstream</span>:<span class="ident">ident</span>) => { |
| <span class="macro-nonterminal">$</span><span class="macro">crate::parse_macro_input!</span>(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">tokenstream</span> <span class="kw">as</span> <span class="kw">_</span>) |
| }; |
| } |
| |
| <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> |
| <span class="comment">// Can parse any type that implements Parse.</span> |
| |
| <span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::parse</span>::{<span class="ident">Parse</span>, <span class="ident">ParseStream</span>, <span class="ident">Parser</span>, <span class="prelude-ty">Result</span>}; |
| <span class="kw">use</span> <span class="ident">proc_macro::TokenStream</span>; |
| |
| <span class="comment">// Not public API.</span> |
| <span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span> |
| <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">parse</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">ParseMacroInput</span><span class="op">></span>(<span class="ident">token_stream</span>: <span class="ident">TokenStream</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { |
| <span class="ident">T::parse</span>.<span class="ident">parse</span>(<span class="ident">token_stream</span>) |
| } |
| |
| <span class="comment">// Not public API.</span> |
| <span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span> |
| <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">ParseMacroInput</span>: <span class="ident">Sized</span> { |
| <span class="kw">fn</span> <span class="ident">parse</span>(<span class="ident">input</span>: <span class="ident">ParseStream</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span><span class="op">></span>; |
| } |
| |
| <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Parse</span><span class="op">></span> <span class="ident">ParseMacroInput</span> <span class="kw">for</span> <span class="ident">T</span> { |
| <span class="kw">fn</span> <span class="ident">parse</span>(<span class="ident">input</span>: <span class="ident">ParseStream</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span><span class="op">></span> { |
| <span class="op"><</span><span class="ident">T</span> <span class="kw">as</span> <span class="ident">Parse</span><span class="op">></span><span class="ident">::parse</span>(<span class="ident">input</span>) |
| } |
| } |
| |
| <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> |
| <span class="comment">// Any other types that we want `parse_macro_input!` to be able to parse.</span> |
| |
| <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"full"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"derive"</span>))]</span> |
| <span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::AttributeArgs</span>; |
| |
| <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"full"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"derive"</span>))]</span> |
| <span class="kw">impl</span> <span class="ident">ParseMacroInput</span> <span class="kw">for</span> <span class="ident">AttributeArgs</span> { |
| <span class="kw">fn</span> <span class="ident">parse</span>(<span class="ident">input</span>: <span class="ident">ParseStream</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span><span class="op">></span> { |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">metas</span> <span class="op">=</span> <span class="ident">Vec::new</span>(); |
| |
| <span class="kw">loop</span> { |
| <span class="kw">if</span> <span class="ident">input</span>.<span class="ident">is_empty</span>() { |
| <span class="kw">break</span>; |
| } |
| <span class="kw">let</span> <span class="ident">value</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">parse</span>()<span class="question-mark">?</span>; |
| <span class="ident">metas</span>.<span class="ident">push</span>(<span class="ident">value</span>); |
| <span class="kw">if</span> <span class="ident">input</span>.<span class="ident">is_empty</span>() { |
| <span class="kw">break</span>; |
| } |
| <span class="ident">input</span>.<span class="ident">parse</span>::<span class="op"><</span><span class="macro">Token!</span>[,]<span class="op">></span>()<span class="question-mark">?</span>; |
| } |
| |
| <span class="prelude-val">Ok</span>(<span class="ident">metas</span>) |
| } |
| } |
| </code></pre></div> |
| </section><section id="search" class="content hidden"></section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="syn" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.60.0-nightly (1bd4fdc94 2022-01-12)" ></div> |
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