Type Alias TokenIter 

pub type TokenIter<'a> = ShadowCountedIter<'a, <TokenStream as IntoIterator>::IntoIter>;

Type alias for the iterator type we use for parsing. This Iterator is Clone and produces &TokenTree. The shadow counter counts tokens in the background to track progress which is used to keep the error that made the most progress in disjunctive parsers.

Aliased Type

pub struct TokenIter<'a> { /* private fields */ }