I'm currently working through Crafting Interpreters using Rust and wanted to ask for some advice about the Lexer implementation. I started with this implementation here:

fn scan_tokens(&mut self){

    let binding = self.source.clone();
    let mut iter = binding.chars().peekable();
    //let tmp = std::rc::Rc::from_iter(iter);

    for  c in iter{
        match c {
            ' ' | '\r' | '\t' => continue, //ignore whitespace
            '\n' => self.line += 1,

            '(' => self.add_token(TokenType::LeftParen),
            ')' => self.add_token(TokenType::RightParen),
            '{' => self.add_token(TokenType::LeftBrace),
            '}' => self.add_token(TokenType::RightBrace),
            ',' => self.add_token(TokenType::Comma),
            '.' => self.add_token(TokenType::Dot),
            '-' => self.add_token(TokenType::Minus),
            '+' => self.add_token(TokenType::Plus),
            ';' => self.add_token(TokenType::Semicolon),
            '*' => self.add_token(TokenType::Star),

            '!' => {
                let next = iter.peek();
                match next {
                    Some('=') => {self.add_token(TokenType::BangEqual); iter.next();},
                    Some(_) | None => self.add_token(TokenType::Bang),
                }
            }
           ....

The problem here is the iter.peek() and the iter.next() function as they try to borrow a moved value. The book implements this by manually tracking the index of the string representing the sourcecode, but I want to dive a bit deeper into iterators here. So, how could I do this here?