You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: parse.rs
    path of file: ./repos/maud/maud_macros/src
    
    the code of the file until where you have to start completion: use proc_macro2::{Delimiter, Ident, Literal, Spacing, Span, TokenStream, TokenTree};
use proc_macro_error::{abort, abort_call_site, emit_error, SpanRange};
use std::collections::HashMap;

use syn::Lit;

use crate::ast;

pub fn parse(input: TokenStream) -> Vec<ast::Markup> {
    Parser::new(input).markups()
}

#[derive(Clone)]
struct Parser {
    /// If we're inside an attribute, then this contains the attribute name.
    current_attr: Option<String>,
    input: <TokenStream as IntoIterator>::IntoIter,
}

impl Iterator for Parser {
    type Item = TokenTree;

    fn next(&mut self) -> Option<TokenTree> {
        self.input.next()
    }
}

impl Parser {
    fn new(input: TokenStream) -> Parser {
        Parser {
            current_attr: None,
            input: input.into_iter(),
        }
    }

    fn with_input(&self, input: TokenStream) -> Parser {
        Parser {
            current_attr: self.current_attr.clone(),
            input: input.into_iter(),
        }
    }

    /// Returns the next token in the stream without consuming it.
    fn peek(&mut self) -> Option<TokenTree> {
        self.clone().next()
    }

    /// Returns the next two tokens in the stream without consuming them.
    fn peek2(&mut self) -> Option<(TokenTree, Option<TokenTree>)> {
        let mut clone = self.cl
    
    fn for_expr(&mut self, at_span: Span, keyword: TokenTree) -> ast::Markup {
        let keyword_span = keyword.span();
        let mut head = vec![keyword];
        loop {
            match self.next() {
                Some(TokenTree::Ident(ref in_keyword)) if *in_keyword == "in" => {
                    head.push(TokenTree::Ident(in_keyword.clone()));
                    break;
                }
                Some(token) => head.push(token),
                None => {
                    let span = SpanRange {
                        first: at_span,
                        last: keyword_span,
                    };
                    abort!(span, "missing `in` in `@for` loop");
                }
            }
        }
        let body = loop {
            match self.next() {
                Some(TokenTree::Group(ref block)) if block.delimiter() == Delimiter::Brace => {
                    break self.block(block.stream(), SpanRange::single_span(block.span()));
                }
                Some(token) => head.push(token),
                None => {
                    let span = SpanRange {
                        first: at_span,
                        last: keyword_span,
                    };
                    abort!(span, "expected body for this `@for`");
                }
            }
        };
        ast::Markup::Special {
            segments: vec![ast::Special {
                at_span: SpanRange::single_span(at_span),
                head: head.into_iter().collect(),
                body,
            }],
        }
    }