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: visitor.rs
    path of file: ./repos/ruff/crates/ruff_python_formatter/src/comments
    
    the code of the file until where you have to start completion: use std::fmt::Debug;
use std::iter::Peekable;

use ruff_formatter::{SourceCode, SourceCodeSlice};
use ruff_python_ast::AnyNodeRef;
use ruff_python_ast::{Mod, Stmt};
// The interface is designed to only export the members relevant for iterating nodes in
// pre-order.
#[allow(clippy::wildcard_imports)]
use ruff_python_ast::visitor::preorder::*;
use ruff_python_trivia::{CommentLinePosition, CommentRanges};
use ruff_source_file::Locator;
use ruff_text_size::{Ranged, TextRange, TextSize};

use crate::comments::node_key::NodeRefEqualityKey;
use crate::comments::placement::place_comment;
use crate::comments::{CommentsMap, SourceComment};

/// Collect the preceding, following and enclosing node for each comment without applying
/// [`place_comment`] for debugging.
pub(crate) fn collect_comments<'a>(
    root: &'a Mod,
    source_code: SourceCode<'a>,
    comment_ranges: &'a CommentRanges,
) -> Vec<DecoratedComment<'a>> {
    let mut collector = CommentsVecBuilder::default();
    CommentsVisitor::new(source_code, comment_ranges, &mut collector).visit(AnyNodeRef::from(root));
    collector.comments
}

/// Visitor extracting the comments from an AST.
pub(super) struct CommentsVisitor<'a, 'builder> {
    builder: &'builder mut (dyn PushComment<'a> + 'a),
    source_code: SourceCode<'a>,
    parents: Vec<AnyNodeRef<'a>>,
    preceding_node: Option<AnyNodeRef<'a>>,
    comment_ranges: Peekable<std::slice::Iter<'a, TextRange>>,
}

impl<'a, 'builder> CommentsVisitor<'a, 'builder> {
    pub(super) fn new(
        source_code: SourceCode<'a>,
        comment_ranges: &'a CommentRanges,
        builder: &'builder mut (dyn PushComment<'a> + 'a),
    ) -> Self {
        Self {
            builder,
            source_code,
            parents: Vec::new(),
            preceding_node: None,
            comment_ranges: comment_ranges.iter().peekable(),
        }
    }

    pub(super) fn visit(mut self, root: AnyNodeRef<'a>) {
        if self.enter_node(root).is_traverse() {
            root.visit_preorder(&mut self);
        }

        self.leave_node(root);
    }

    // Try to skip the subtree if
    // * there are no comments
    // * if the next comment comes after this node (meaning, this nodes subtree contains no comments)
    fn can_skip(&mut self, node_end: TextSize) -> bool {
        self.comment_ranges
            .peek()
            .map_or(true, |next_comment| next_comment.start() >= node_end)
    }
}

impl<'ast> PreorderVisitor<'ast> for CommentsVisitor<'ast, '_> {
    fn enter_node(&mut self, node: AnyNodeRef<'ast>) -> TraversalSignal {
        let node_range = node.range();

        let enclosing_node = self.parents.last().copied().unwrap_or(node);

        // Process all remaining comments that end before this node's start position.
        // If the `preceding` node is set, then it process all comments ending after the `preceding`
    
    fn push_comment(&mut self, placement: DecoratedComment<'a>) {
        let placement = place_comment(placement, self.comment_ranges, &self.locator);
        match placement {
            CommentPlacement::Leading { node, comment } => {
                self.push_leading_comment(node, comment);
            }
            CommentPlacement::Trailing { node, comment } => {
                self.push_trailing_comment(node, comment);
            }
            CommentPlacement::Dangling { node, comment } => {
                self.push_dangling_comment(node, comment);
            }
            CommentPlacement::Default(comment) => {
                match comment.line_position() {
                    CommentLinePosition::EndOfLine => {
                        match (comment.preceding_node(), comment.following_node()) {
                            (Some(preceding), Some(_)) => {
                                // Attach comments with both preceding and following node to the preceding
                                // because there's a line break separating it from the following node.
                                // ```python
                                // a; # comment
                                // b
                                // ```
                                self.push_trailing_comment(preceding, comment);
                            }
                            (Some(preceding), None) => {
                                self.push_trailing_comment(preceding, comment);
                            }
                            (None, Some(following)) => {
                                self.push_leading_comment(following, comment);
                            }
                            (None, None) => {
                                self.push_dangling_comment(comment.enclosing_node(), comment);
                            }
                        }
                    }
                    CommentLinePosition::OwnLine => {
                        match (comment.preceding_node(), comment.following_node()) {
                            // Following always wins for a leading comment
                            // ```python
                            // a
                            // // python
                            // b
                            // ```
                            // attach the comment to the `b` expression statement
                            (_, Some(following)) => {
                                self.push_leading_comment(following, comment);
                            }
                            (Some(preceding), None) => {
                                self.push_trailing_comment(preceding, comment);
                            }
                            (None, None) => {
                                self.push_dangling_comment(comment.enclosing_node(), comment);
                            }
                        }
                    }
                }
            }
        }
    }