rustversion_msrv/
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 Iterator for IterImpl {
18    type Item = TokenTree;
19
20    fn next(&mut self) -> Option<Self::Item> {
21        if let Some(tt) = self.peeked.take() {
22            return Some(tt);
23        }
24        loop {
25            let top = self.stack.last_mut()?;
26            match top.next() {
27                None => drop(self.stack.pop()),
28                Some(TokenTree::Group(ref group)) if group.delimiter() == Delimiter::None => {
29                    self.stack.push(group.stream().into_iter());
30                }
31                Some(tt) => return Some(tt),
32            }
33        }
34    }
35}