| use proc_macro2::Ident; |
| use std::cmp::Ordering; |
| |
| use crate::atom::iter_atoms; |
| |
| #[derive(Copy, Clone, PartialEq)] |
| pub enum UnderscoreOrder { |
| First, |
| Last, |
| } |
| |
| pub struct Path { |
| pub segments: Vec<Ident>, |
| } |
| |
| pub fn cmp(lhs: &Path, rhs: &Path, mode: UnderscoreOrder) -> Ordering { |
| // Lexicographic ordering across path segments. |
| for (lhs, rhs) in lhs.segments.iter().zip(&rhs.segments) { |
| match cmp_segment(&lhs.to_string(), &rhs.to_string(), mode) { |
| Ordering::Equal => {} |
| non_eq => return non_eq, |
| } |
| } |
| |
| lhs.segments.len().cmp(&rhs.segments.len()) |
| } |
| |
| fn cmp_segment(lhs: &str, rhs: &str, mode: UnderscoreOrder) -> Ordering { |
| // Sort `_` last. |
| match (lhs, rhs) { |
| ("_", "_") => return Ordering::Equal, |
| ("_", _) => return Ordering::Greater, |
| (_, "_") => return Ordering::Less, |
| (_, _) => {} |
| } |
| |
| let mut lhs_atoms = iter_atoms(lhs); |
| let mut rhs_atoms = iter_atoms(rhs); |
| |
| // Path segments can't be empty. |
| let mut left = lhs_atoms.next().unwrap(); |
| let mut right = rhs_atoms.next().unwrap(); |
| |
| if mode == UnderscoreOrder::Last { |
| // Compare leading underscores. |
| match left.underscores().cmp(&right.underscores()) { |
| Ordering::Equal => {} |
| non_eq => return non_eq, |
| } |
| } |
| |
| loop { |
| match left.cmp(&right) { |
| Ordering::Equal => {} |
| non_eq => return non_eq, |
| } |
| |
| match (lhs_atoms.next(), rhs_atoms.next()) { |
| (None, None) => return Ordering::Equal, |
| (None, Some(_)) => return Ordering::Less, |
| (Some(_), None) => return Ordering::Greater, |
| (Some(nextl), Some(nextr)) => { |
| left = nextl; |
| right = nextr; |
| } |
| } |
| } |
| } |