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use proc_macro::{token_stream, Delimiter, TokenStream, TokenTree};
pub type Iter<'a> = &'a mut IterImpl;
pub struct IterImpl {
stack: Vec<token_stream::IntoIter>,
peeked: Option<TokenTree>,
}
pub fn new(tokens: TokenStream) -> IterImpl {
IterImpl {
stack: vec![tokens.into_iter()],
peeked: None,
}
}
impl IterImpl {
pub fn peek(&mut self) -> Option<&TokenTree> {
self.peeked = self.next();
self.peeked.as_ref()
}
}
impl Iterator for IterImpl {
type Item = TokenTree;
fn next(&mut self) -> Option<Self::Item> {
if let Some(tt) = self.peeked.take() {
return Some(tt);
}
loop {
let top = self.stack.last_mut()?;
match top.next() {
None => drop(self.stack.pop()),
Some(TokenTree::Group(ref group)) if group.delimiter() == Delimiter::None => {
self.stack.push(group.stream().into_iter());
}
Some(tt) => return Some(tt),
}
}
}
}
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