rustversion/
iter.rs

1use proc_macro::{token_stream, Delimiter, TokenStream, TokenTree};
2
3pub type Iter<'a> = &'a mut IterImpl;
4
5pub struct IterImpl {
6    stack: Vec<token_stream::IntoIter>,
7    peeked: Option<TokenTree>,
8}
9
10pub fn new(tokens: TokenStream) -> IterImpl {
11    IterImpl {
12        stack: vec![tokens.into_iter()],
13        peeked: None,
14    }
15}
16
17impl IterImpl {
18    pub fn peek(&mut self) -> Option<&TokenTree> {
19        self.peeked = self.next();
20        self.peeked.as_ref()
21    }
22}
23
24impl Iterator for IterImpl {
25    type Item = TokenTree;
26
27    fn next(&mut self) -> Option<Self::Item> {
28        if let Some(tt) = self.peeked.take() {
29            return Some(tt);
30        }
31        loop {
32            let top = self.stack.last_mut()?;
33            match top.next() {
34                None => drop(self.stack.pop()),
35                Some(TokenTree::Group(ref group)) if group.delimiter() == Delimiter::None => {
36                    self.stack.push(group.stream().into_iter());
37                }
38                Some(tt) => return Some(tt),
39            }
40        }
41    }
42}
rustversion/iter.rs

rustversion/
iter.rs
