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</pre><pre class="rust ">
<span class="comment">// Copyright 2018 Syn Developers</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! A stably addressed token buffer supporting efficient traversal based on a</span>
<span class="doccomment">//! cheaply copyable cursor.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! The [`Synom`] trait is implemented for syntax tree types that can be parsed</span>
<span class="doccomment">//! from one of these token cursors.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [`Synom`]: ../synom/trait.Synom.html</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! *This module is available if Syn is built with the `"parsing"` feature.*</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Example</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This example shows a basic token parser for parsing a token stream without</span>
<span class="doccomment">//! using Syn's parser combinator macros.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! #![feature(proc_macro_diagnostic)]</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! extern crate syn;</span>
<span class="doccomment">//! extern crate proc_macro;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! #[macro_use]</span>
<span class="doccomment">//! extern crate quote;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! use syn::{token, ExprTuple};</span>
<span class="doccomment">//! use syn::buffer::{Cursor, TokenBuffer};</span>
<span class="doccomment">//! use syn::spanned::Spanned;</span>
<span class="doccomment">//! use syn::synom::Synom;</span>
<span class="doccomment">//! use proc_macro::{Diagnostic, Span, TokenStream};</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! /// A basic token parser for parsing a token stream without using Syn's</span>
<span class="doccomment">//! /// parser combinator macros.</span>
<span class="doccomment">//! pub struct Parser<'a> {</span>
<span class="doccomment">//! cursor: Cursor<'a>,</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! impl<'a> Parser<'a> {</span>
<span class="doccomment">//! pub fn new(cursor: Cursor<'a>) -> Self {</span>
<span class="doccomment">//! Parser { cursor }</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! pub fn current_span(&self) -> Span {</span>
<span class="doccomment">//! self.cursor.span().unstable()</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! pub fn parse<T: Synom>(&mut self) -> Result<T, Diagnostic> {</span>
<span class="doccomment">//! let (val, rest) = T::parse(self.cursor)</span>
<span class="doccomment">//! .map_err(|e| match T::description() {</span>
<span class="doccomment">//! Some(desc) => {</span>
<span class="doccomment">//! self.current_span().error(format!("{}: expected {}", e, desc))</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! None => {</span>
<span class="doccomment">//! self.current_span().error(e.to_string())</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! })?;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! self.cursor = rest;</span>
<span class="doccomment">//! Ok(val)</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! pub fn expect_eof(&mut self) -> Result<(), Diagnostic> {</span>
<span class="doccomment">//! if !self.cursor.eof() {</span>
<span class="doccomment">//! return Err(self.current_span().error("trailing characters; expected eof"));</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Ok(())</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! fn eval(input: TokenStream) -> Result<TokenStream, Diagnostic> {</span>
<span class="doccomment">//! let buffer = TokenBuffer::new(input);</span>
<span class="doccomment">//! let mut parser = Parser::new(buffer.begin());</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Parse some syntax tree types out of the input tokens. In this case we</span>
<span class="doccomment">//! // expect something like:</span>
<span class="doccomment">//! //</span>
<span class="doccomment">//! // (a, b, c) = (1, 2, 3)</span>
<span class="doccomment">//! let a = parser.parse::<ExprTuple>()?;</span>
<span class="doccomment">//! parser.parse::<token::Eq>()?;</span>
<span class="doccomment">//! let b = parser.parse::<ExprTuple>()?;</span>
<span class="doccomment">//! parser.expect_eof()?;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Perform some validation and report errors.</span>
<span class="doccomment">//! let (a_len, b_len) = (a.elems.len(), b.elems.len());</span>
<span class="doccomment">//! if a_len != b_len {</span>
<span class="doccomment">//! let diag = b.span().unstable()</span>
<span class="doccomment">//! .error(format!("expected {} element(s), got {}", a_len, b_len))</span>
<span class="doccomment">//! .span_note(a.span().unstable(), "because of this");</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! return Err(diag);</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Build the output tokens.</span>
<span class="doccomment">//! let out = quote! {</span>
<span class="doccomment">//! println!("All good! Received two tuples of size {}", #a_len);</span>
<span class="doccomment">//! };</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Ok(out.into())</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! #</span>
<span class="doccomment">//! # extern crate proc_macro2;</span>
<span class="doccomment">//! #</span>
<span class="doccomment">//! # // This method exists on proc_macro2::Span but is behind the "nightly"</span>
<span class="doccomment">//! # // feature.</span>
<span class="doccomment">//! # trait ToUnstableSpan {</span>
<span class="doccomment">//! # fn unstable(&self) -> Span;</span>
<span class="doccomment">//! # }</span>
<span class="doccomment">//! #</span>
<span class="doccomment">//! # impl ToUnstableSpan for proc_macro2::Span {</span>
<span class="doccomment">//! # fn unstable(&self) -> Span {</span>
<span class="doccomment">//! # unimplemented!()</span>
<span class="doccomment">//! # }</span>
<span class="doccomment">//! # }</span>
<span class="doccomment">//! #</span>
<span class="doccomment">//! # fn main() {}</span>
<span class="doccomment">//! ```</span>
<span class="comment">// This module is heavily commented as it contains the only unsafe code in Syn,</span>
<span class="comment">// and caution should be used when editing it. The public-facing interface is</span>
<span class="comment">// 100% safe but the implementation is fragile internally.</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(
<span class="ident">not</span>(<span class="ident">all</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"wasm32"</span>, <span class="ident">target_os</span> <span class="op">=</span> <span class="string">"unknown"</span>)),
<span class="ident">feature</span> <span class="op">=</span> <span class="string">"proc-macro"</span>
))]</span>
<span class="kw">use</span> <span class="ident">proc_macro</span> <span class="kw">as</span> <span class="ident">pm</span>;
<span class="kw">use</span> <span class="ident">proc_macro2</span>::{<span class="ident">Delimiter</span>, <span class="ident">Ident</span>, <span class="ident">Literal</span>, <span class="ident">Span</span>, <span class="ident">TokenStream</span>};
<span class="kw">use</span> <span class="ident">proc_macro2</span>::{<span class="ident">Group</span>, <span class="ident">Punct</span>, <span class="ident">TokenTree</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">marker</span>::<span class="ident">PhantomData</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ptr</span>;
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">synom_verbose_trace</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>::{<span class="self">self</span>, <span class="ident">Debug</span>};
<span class="doccomment">/// Internal type which is used instead of `TokenTree` to represent a token tree</span>
<span class="doccomment">/// within a `TokenBuffer`.</span>
<span class="kw">enum</span> <span class="ident">Entry</span> {
<span class="comment">// Mimicking types from proc-macro.</span>
<span class="ident">Group</span>(<span class="ident">Span</span>, <span class="ident">Delimiter</span>, <span class="ident">TokenBuffer</span>),
<span class="ident">Ident</span>(<span class="ident">Ident</span>),
<span class="ident">Punct</span>(<span class="ident">Punct</span>),
<span class="ident">Literal</span>(<span class="ident">Literal</span>),
<span class="comment">// End entries contain a raw pointer to the entry from the containing</span>
<span class="comment">// token tree, or null if this is the outermost level.</span>
<span class="ident">End</span>(<span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Entry</span>),
}
<span class="doccomment">/// A buffer that can be efficiently traversed multiple times, unlike</span>
<span class="doccomment">/// `TokenStream` which requires a deep copy in order to traverse more than</span>
<span class="doccomment">/// once.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See the [module documentation] for an example of `TokenBuffer` in action.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [module documentation]: index.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// *This type is available if Syn is built with the `"parsing"` feature.*</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">TokenBuffer</span> {
<span class="comment">// NOTE: Do not derive clone on this - there are raw pointers inside which</span>
<span class="comment">// will be messed up. Moving the `TokenBuffer` itself is safe as the actual</span>
<span class="comment">// backing slices won't be moved.</span>
<span class="ident">data</span>: <span class="ident">Box</span><span class="op"><</span>[<span class="ident">Entry</span>]<span class="op">></span>,
}
<span class="kw">impl</span> <span class="ident">TokenBuffer</span> {
<span class="comment">// NOTE: DO NOT MUTATE THE `Vec` RETURNED FROM THIS FUNCTION ONCE IT</span>
<span class="comment">// RETURNS, THE ADDRESS OF ITS BACKING MEMORY MUST REMAIN STABLE.</span>
<span class="kw">fn</span> <span class="ident">inner_new</span>(<span class="ident">stream</span>: <span class="ident">TokenStream</span>, <span class="ident">up</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Entry</span>) <span class="op">-></span> <span class="ident">TokenBuffer</span> {
<span class="comment">// Build up the entries list, recording the locations of any Groups</span>
<span class="comment">// in the list to be processed later.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">entries</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">new</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">seqs</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">new</span>();
<span class="kw">for</span> <span class="ident">tt</span> <span class="kw">in</span> <span class="ident">stream</span> {
<span class="kw">match</span> <span class="ident">tt</span> {
<span class="ident">TokenTree</span>::<span class="ident">Ident</span>(<span class="ident">sym</span>) <span class="op">=></span> {
<span class="ident">entries</span>.<span class="ident">push</span>(<span class="ident">Entry</span>::<span class="ident">Ident</span>(<span class="ident">sym</span>));
}
<span class="ident">TokenTree</span>::<span class="ident">Punct</span>(<span class="ident">op</span>) <span class="op">=></span> {
<span class="ident">entries</span>.<span class="ident">push</span>(<span class="ident">Entry</span>::<span class="ident">Punct</span>(<span class="ident">op</span>));
}
<span class="ident">TokenTree</span>::<span class="ident">Literal</span>(<span class="ident">l</span>) <span class="op">=></span> {
<span class="ident">entries</span>.<span class="ident">push</span>(<span class="ident">Entry</span>::<span class="ident">Literal</span>(<span class="ident">l</span>));
}
<span class="ident">TokenTree</span>::<span class="ident">Group</span>(<span class="ident">g</span>) <span class="op">=></span> {
<span class="comment">// Record the index of the interesting entry, and store an</span>
<span class="comment">// `End(null)` there temporarially.</span>
<span class="ident">seqs</span>.<span class="ident">push</span>((<span class="ident">entries</span>.<span class="ident">len</span>(), <span class="ident">g</span>.<span class="ident">span</span>(), <span class="ident">g</span>.<span class="ident">delimiter</span>(), <span class="ident">g</span>.<span class="ident">stream</span>().<span class="ident">clone</span>()));
<span class="ident">entries</span>.<span class="ident">push</span>(<span class="ident">Entry</span>::<span class="ident">End</span>(<span class="ident">ptr</span>::<span class="ident">null</span>()));
}
}
}
<span class="comment">// Add an `End` entry to the end with a reference to the enclosing token</span>
<span class="comment">// stream which was passed in.</span>
<span class="ident">entries</span>.<span class="ident">push</span>(<span class="ident">Entry</span>::<span class="ident">End</span>(<span class="ident">up</span>));
<span class="comment">// NOTE: This is done to ensure that we don't accidentally modify the</span>
<span class="comment">// length of the backing buffer. The backing buffer must remain at a</span>
<span class="comment">// constant address after this point, as we are going to store a raw</span>
<span class="comment">// pointer into it.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">entries</span> <span class="op">=</span> <span class="ident">entries</span>.<span class="ident">into_boxed_slice</span>();
<span class="kw">for</span> (<span class="ident">idx</span>, <span class="ident">span</span>, <span class="ident">delim</span>, <span class="ident">seq_stream</span>) <span class="kw">in</span> <span class="ident">seqs</span> {
<span class="comment">// We know that this index refers to one of the temporary</span>
<span class="comment">// `End(null)` entries, and we know that the last entry is</span>
<span class="comment">// `End(up)`, so the next index is also valid.</span>
<span class="kw">let</span> <span class="ident">seq_up</span> <span class="op">=</span> <span class="kw-2">&</span><span class="ident">entries</span>[<span class="ident">idx</span> <span class="op">+</span> <span class="number">1</span>] <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Entry</span>;
<span class="comment">// The end entry stored at the end of this Entry::Group should</span>
<span class="comment">// point to the Entry which follows the Group in the list.</span>
<span class="kw">let</span> <span class="ident">inner</span> <span class="op">=</span> <span class="self">Self</span>::<span class="ident">inner_new</span>(<span class="ident">seq_stream</span>, <span class="ident">seq_up</span>);
<span class="ident">entries</span>[<span class="ident">idx</span>] <span class="op">=</span> <span class="ident">Entry</span>::<span class="ident">Group</span>(<span class="ident">span</span>, <span class="ident">delim</span>, <span class="ident">inner</span>);
}
<span class="ident">TokenBuffer</span> { <span class="ident">data</span>: <span class="ident">entries</span> }
}
<span class="doccomment">/// Creates a `TokenBuffer` containing all the tokens from the input</span>
<span class="doccomment">/// `TokenStream`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// *This method is available if Syn is built with both the `"parsing"` and</span>
<span class="doccomment">/// `"proc-macro"` features.*</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(
<span class="ident">not</span>(<span class="ident">all</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"wasm32"</span>, <span class="ident">target_os</span> <span class="op">=</span> <span class="string">"unknown"</span>)),
<span class="ident">feature</span> <span class="op">=</span> <span class="string">"proc-macro"</span>
))]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">stream</span>: <span class="ident">pm</span>::<span class="ident">TokenStream</span>) <span class="op">-></span> <span class="ident">TokenBuffer</span> {
<span class="self">Self</span>::<span class="ident">new2</span>(<span class="ident">stream</span>.<span class="ident">into</span>())
}
<span class="doccomment">/// Creates a `TokenBuffer` containing all the tokens from the input</span>
<span class="doccomment">/// `TokenStream`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new2</span>(<span class="ident">stream</span>: <span class="ident">TokenStream</span>) <span class="op">-></span> <span class="ident">TokenBuffer</span> {
<span class="self">Self</span>::<span class="ident">inner_new</span>(<span class="ident">stream</span>, <span class="ident">ptr</span>::<span class="ident">null</span>())
}
<span class="doccomment">/// Creates a cursor referencing the first token in the buffer and able to</span>
<span class="doccomment">/// traverse until the end of the buffer.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">begin</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Cursor</span> {
<span class="kw">unsafe</span> { <span class="ident">Cursor</span>::<span class="ident">create</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">data</span>[<span class="number">0</span>], <span class="kw-2">&</span><span class="self">self</span>.<span class="ident">data</span>[<span class="self">self</span>.<span class="ident">data</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">1</span>]) }
}
}
<span class="doccomment">/// A cheaply copyable cursor into a `TokenBuffer`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This cursor holds a shared reference into the immutable data which is used</span>
<span class="doccomment">/// internally to represent a `TokenStream`, and can be efficiently manipulated</span>
<span class="doccomment">/// and copied around.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An empty `Cursor` can be created directly, or one may create a `TokenBuffer`</span>
<span class="doccomment">/// object and get a cursor to its first token with `begin()`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Two cursors are equal if they have the same location in the same input</span>
<span class="doccomment">/// stream, and have the same scope.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See the [module documentation] for an example of a `Cursor` in action.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [module documentation]: index.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// *This type is available if Syn is built with the `"parsing"` feature.*</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Copy</span>, <span class="ident">Clone</span>, <span class="ident">Eq</span>, <span class="ident">PartialEq</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="doccomment">/// The current entry which the `Cursor` is pointing at.</span>
<span class="ident">ptr</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Entry</span>,
<span class="doccomment">/// This is the only `Entry::End(..)` object which this cursor is allowed to</span>
<span class="doccomment">/// point at. All other `End` objects are skipped over in `Cursor::create`.</span>
<span class="ident">scope</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Entry</span>,
<span class="doccomment">/// This uses the &'a reference which guarantees that these pointers are</span>
<span class="doccomment">/// still valid.</span>
<span class="ident">marker</span>: <span class="ident">PhantomData</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Entry</span><span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="doccomment">/// Creates a cursor referencing a static empty TokenStream.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">empty</span>() <span class="op">-></span> <span class="self">Self</span> {
<span class="comment">// It's safe in this situation for us to put an `Entry` object in global</span>
<span class="comment">// storage, despite it not actually being safe to send across threads</span>
<span class="comment">// (`Ident` is a reference into a thread-local table). This is because</span>
<span class="comment">// this entry never includes a `Ident` object.</span>
<span class="comment">//</span>
<span class="comment">// This wrapper struct allows us to break the rules and put a `Sync`</span>
<span class="comment">// object in global storage.</span>
<span class="kw">struct</span> <span class="ident">UnsafeSyncEntry</span>(<span class="ident">Entry</span>);
<span class="kw">unsafe</span> <span class="kw">impl</span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">UnsafeSyncEntry</span> {}
<span class="kw">static</span> <span class="ident">EMPTY_ENTRY</span>: <span class="ident">UnsafeSyncEntry</span> <span class="op">=</span> <span class="ident">UnsafeSyncEntry</span>(<span class="ident">Entry</span>::<span class="ident">End</span>(<span class="number">0</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Entry</span>));
<span class="ident">Cursor</span> {
<span class="ident">ptr</span>: <span class="kw-2">&</span><span class="ident">EMPTY_ENTRY</span>.<span class="number">0</span>,
<span class="ident">scope</span>: <span class="kw-2">&</span><span class="ident">EMPTY_ENTRY</span>.<span class="number">0</span>,
<span class="ident">marker</span>: <span class="ident">PhantomData</span>,
}
}
<span class="doccomment">/// This create method intelligently exits non-explicitly-entered</span>
<span class="doccomment">/// `None`-delimited scopes when the cursor reaches the end of them,</span>
<span class="doccomment">/// allowing for them to be treated transparently.</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">create</span>(<span class="kw-2">mut</span> <span class="ident">ptr</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Entry</span>, <span class="ident">scope</span>: <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Entry</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="comment">// NOTE: If we're looking at a `End(..)`, we want to advance the cursor</span>
<span class="comment">// past it, unless `ptr == scope`, which means that we're at the edge of</span>
<span class="comment">// our cursor's scope. We should only have `ptr != scope` at the exit</span>
<span class="comment">// from None-delimited groups entered with `ignore_none`.</span>
<span class="kw">while</span> <span class="kw">let</span> <span class="ident">Entry</span>::<span class="ident">End</span>(<span class="ident">exit</span>) <span class="op">=</span> <span class="kw-2">*</span><span class="ident">ptr</span> {
<span class="kw">if</span> <span class="ident">ptr</span> <span class="op">==</span> <span class="ident">scope</span> {
<span class="kw">break</span>;
}
<span class="ident">ptr</span> <span class="op">=</span> <span class="ident">exit</span>;
}
<span class="ident">Cursor</span> {
<span class="ident">ptr</span>: <span class="ident">ptr</span>,
<span class="ident">scope</span>: <span class="ident">scope</span>,
<span class="ident">marker</span>: <span class="ident">PhantomData</span>,
}
}
<span class="doccomment">/// Get the current entry.</span>
<span class="kw">fn</span> <span class="ident">entry</span>(<span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">Entry</span> {
<span class="kw">unsafe</span> { <span class="kw-2">&</span><span class="kw-2">*</span><span class="self">self</span>.<span class="ident">ptr</span> }
}
<span class="doccomment">/// Bump the cursor to point at the next token after the current one. This</span>
<span class="doccomment">/// is undefined behavior if the cursor is currently looking at an</span>
<span class="doccomment">/// `Entry::End`.</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">bump</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="ident">Cursor</span>::<span class="ident">create</span>(<span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">offset</span>(<span class="number">1</span>), <span class="self">self</span>.<span class="ident">scope</span>)
}
<span class="doccomment">/// If the cursor is looking at a `None`-delimited group, move it to look at</span>
<span class="doccomment">/// the first token inside instead. If the group is empty, this will move</span>
<span class="doccomment">/// the cursor past the `None`-delimited group.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// WARNING: This mutates its argument.</span>
<span class="kw">fn</span> <span class="ident">ignore_none</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">if</span> <span class="kw">let</span> <span class="ident">Entry</span>::<span class="ident">Group</span>(<span class="kw">_</span>, <span class="ident">Delimiter</span>::<span class="prelude-val">None</span>, <span class="kw-2">ref</span> <span class="ident">buf</span>) <span class="op">=</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">entry</span>() {
<span class="comment">// NOTE: We call `Cursor::create` here to make sure that situations</span>
<span class="comment">// where we should immediately exit the span after entering it are</span>
<span class="comment">// handled correctly.</span>
<span class="kw">unsafe</span> {
<span class="kw-2">*</span><span class="self">self</span> <span class="op">=</span> <span class="ident">Cursor</span>::<span class="ident">create</span>(<span class="kw-2">&</span><span class="ident">buf</span>.<span class="ident">data</span>[<span class="number">0</span>], <span class="self">self</span>.<span class="ident">scope</span>);
}
}
}
<span class="doccomment">/// Checks whether the cursor is currently pointing at the end of its valid</span>
<span class="doccomment">/// scope.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">eof</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="comment">// We're at eof if we're at the end of our scope.</span>
<span class="self">self</span>.<span class="ident">ptr</span> <span class="op">==</span> <span class="self">self</span>.<span class="ident">scope</span>
}
<span class="doccomment">/// If the cursor is pointing at a `Group` with the given delimiter, returns</span>
<span class="doccomment">/// a cursor into that group and one pointing to the next `TokenTree`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">group</span>(<span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">delim</span>: <span class="ident">Delimiter</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>, <span class="ident">Span</span>, <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>)<span class="op">></span> {
<span class="comment">// If we're not trying to enter a none-delimited group, we want to</span>
<span class="comment">// ignore them. We have to make sure to _not_ ignore them when we want</span>
<span class="comment">// to enter them, of course. For obvious reasons.</span>
<span class="kw">if</span> <span class="ident">delim</span> <span class="op">!=</span> <span class="ident">Delimiter</span>::<span class="prelude-val">None</span> {
<span class="self">self</span>.<span class="ident">ignore_none</span>();
}
<span class="kw">if</span> <span class="kw">let</span> <span class="ident">Entry</span>::<span class="ident">Group</span>(<span class="ident">span</span>, <span class="ident">group_delim</span>, <span class="kw-2">ref</span> <span class="ident">buf</span>) <span class="op">=</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">entry</span>() {
<span class="kw">if</span> <span class="ident">group_delim</span> <span class="op">==</span> <span class="ident">delim</span> {
<span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">buf</span>.<span class="ident">begin</span>(), <span class="ident">span</span>, <span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">bump</span>() }));
}
}
<span class="prelude-val">None</span>
}
<span class="doccomment">/// If the cursor is pointing at a `Ident`, returns it along with a cursor</span>
<span class="doccomment">/// pointing at the next `TokenTree`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ident</span>(<span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">Ident</span>, <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>)<span class="op">></span> {
<span class="self">self</span>.<span class="ident">ignore_none</span>();
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">entry</span>() {
<span class="ident">Entry</span>::<span class="ident">Ident</span>(<span class="kw-2">ref</span> <span class="ident">ident</span>) <span class="op">=></span> <span class="prelude-val">Some</span>((<span class="ident">ident</span>.<span class="ident">clone</span>(), <span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">bump</span>() })),
<span class="kw">_</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// If the cursor is pointing at an `Punct`, returns it along with a cursor</span>
<span class="doccomment">/// pointing at the next `TokenTree`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">punct</span>(<span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">Punct</span>, <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>)<span class="op">></span> {
<span class="self">self</span>.<span class="ident">ignore_none</span>();
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">entry</span>() {
<span class="ident">Entry</span>::<span class="ident">Punct</span>(<span class="kw-2">ref</span> <span class="ident">op</span>) <span class="op">=></span> <span class="prelude-val">Some</span>((<span class="ident">op</span>.<span class="ident">clone</span>(), <span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">bump</span>() })),
<span class="kw">_</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// If the cursor is pointing at a `Literal`, return it along with a cursor</span>
<span class="doccomment">/// pointing at the next `TokenTree`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">literal</span>(<span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">Literal</span>, <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>)<span class="op">></span> {
<span class="self">self</span>.<span class="ident">ignore_none</span>();
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">entry</span>() {
<span class="ident">Entry</span>::<span class="ident">Literal</span>(<span class="kw-2">ref</span> <span class="ident">lit</span>) <span class="op">=></span> <span class="prelude-val">Some</span>((<span class="ident">lit</span>.<span class="ident">clone</span>(), <span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">bump</span>() })),
<span class="kw">_</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// Copies all remaining tokens visible from this cursor into a</span>
<span class="doccomment">/// `TokenStream`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">token_stream</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">TokenStream</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">tts</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">new</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="self">self</span>;
<span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>((<span class="ident">tt</span>, <span class="ident">rest</span>)) <span class="op">=</span> <span class="ident">cursor</span>.<span class="ident">token_tree</span>() {
<span class="ident">tts</span>.<span class="ident">push</span>(<span class="ident">tt</span>);
<span class="ident">cursor</span> <span class="op">=</span> <span class="ident">rest</span>;
}
<span class="ident">tts</span>.<span class="ident">into_iter</span>().<span class="ident">collect</span>()
}
<span class="doccomment">/// If the cursor is pointing at a `TokenTree`, returns it along with a</span>
<span class="doccomment">/// cursor pointing at the next `TokenTree`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns `None` if the cursor has reached the end of its stream.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method does not treat `None`-delimited groups as transparent, and</span>
<span class="doccomment">/// will return a `Group(None, ..)` if the cursor is looking at one.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">token_tree</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">TokenTree</span>, <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>)<span class="op">></span> {
<span class="kw">let</span> <span class="ident">tree</span> <span class="op">=</span> <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">entry</span>() {
<span class="ident">Entry</span>::<span class="ident">Group</span>(<span class="ident">span</span>, <span class="ident">delim</span>, <span class="kw-2">ref</span> <span class="ident">buf</span>) <span class="op">=></span> {
<span class="kw">let</span> <span class="ident">stream</span> <span class="op">=</span> <span class="ident">buf</span>.<span class="ident">begin</span>().<span class="ident">token_stream</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">g</span> <span class="op">=</span> <span class="ident">Group</span>::<span class="ident">new</span>(<span class="ident">delim</span>, <span class="ident">stream</span>);
<span class="ident">g</span>.<span class="ident">set_span</span>(<span class="ident">span</span>);
<span class="ident">TokenTree</span>::<span class="ident">from</span>(<span class="ident">g</span>)
}
<span class="ident">Entry</span>::<span class="ident">Literal</span>(<span class="kw-2">ref</span> <span class="ident">lit</span>) <span class="op">=></span> <span class="ident">lit</span>.<span class="ident">clone</span>().<span class="ident">into</span>(),
<span class="ident">Entry</span>::<span class="ident">Ident</span>(<span class="kw-2">ref</span> <span class="ident">ident</span>) <span class="op">=></span> <span class="ident">ident</span>.<span class="ident">clone</span>().<span class="ident">into</span>(),
<span class="ident">Entry</span>::<span class="ident">Punct</span>(<span class="kw-2">ref</span> <span class="ident">op</span>) <span class="op">=></span> <span class="ident">op</span>.<span class="ident">clone</span>().<span class="ident">into</span>(),
<span class="ident">Entry</span>::<span class="ident">End</span>(..) <span class="op">=></span> {
<span class="kw">return</span> <span class="prelude-val">None</span>;
}
};
<span class="prelude-val">Some</span>((<span class="ident">tree</span>, <span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">bump</span>() }))
}
<span class="doccomment">/// Returns the `Span` of the current token, or `Span::call_site()` if this</span>
<span class="doccomment">/// cursor points to eof.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">span</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Span</span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">entry</span>() {
<span class="ident">Entry</span>::<span class="ident">Group</span>(<span class="ident">span</span>, ..) <span class="op">=></span> <span class="ident">span</span>,
<span class="ident">Entry</span>::<span class="ident">Literal</span>(<span class="kw-2">ref</span> <span class="ident">l</span>) <span class="op">=></span> <span class="ident">l</span>.<span class="ident">span</span>(),
<span class="ident">Entry</span>::<span class="ident">Ident</span>(<span class="kw-2">ref</span> <span class="ident">t</span>) <span class="op">=></span> <span class="ident">t</span>.<span class="ident">span</span>(),
<span class="ident">Entry</span>::<span class="ident">Punct</span>(<span class="kw-2">ref</span> <span class="ident">o</span>) <span class="op">=></span> <span class="ident">o</span>.<span class="ident">span</span>(),
<span class="ident">Entry</span>::<span class="ident">End</span>(..) <span class="op">=></span> <span class="ident">Span</span>::<span class="ident">call_site</span>(),
}
}
}
<span class="comment">// We do a custom implementation for `Debug` as the default implementation is</span>
<span class="comment">// pretty useless.</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">synom_verbose_trace</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Cursor</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="comment">// Print what the cursor is currently looking at.</span>
<span class="comment">// This will look like Cursor("some remaining tokens here")</span>
<span class="ident">f</span>.<span class="ident">debug_tuple</span>(<span class="string">"Cursor"</span>)
.<span class="ident">field</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">token_stream</span>().<span class="ident">to_string</span>())
.<span class="ident">finish</span>()
}
}
</pre>
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