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Remove allocations from LCA

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I haven't actually profiled this, but not allocating a hash map (or
anything, really) seems like a good idea
This commit is contained in:
Aleksey Kladov 2020-04-09 13:56:45 +02:00
parent 1647d5ac60
commit 738fc79c92
1 changed files with 13 additions and 3 deletions
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16
crates/ra_syntax/src/algo.rs
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@ -7,7 +7,7 @@ use std::{
use itertools::Itertools; use itertools::Itertools;
use ra_text_edit::TextEditBuilder; use ra_text_edit::TextEditBuilder;
use rustc_hash::{FxHashMap, FxHashSet}; use rustc_hash::FxHashMap;
use crate::{ use crate::{
AstNode, Direction, NodeOrToken, SyntaxElement, SyntaxNode, SyntaxNodePtr, SyntaxToken, AstNode, Direction, NodeOrToken, SyntaxElement, SyntaxNode, SyntaxNodePtr, SyntaxToken,
@ -72,8 +72,18 @@ pub fn find_covering_element(root: &SyntaxNode, range: TextRange) -> SyntaxEleme
} }
pub fn least_common_ancestor(u: &SyntaxNode, v: &SyntaxNode) -> Option<SyntaxNode> { pub fn least_common_ancestor(u: &SyntaxNode, v: &SyntaxNode) -> Option<SyntaxNode> {
let u_ancestors = u.ancestors().collect::<FxHashSet<SyntaxNode>>(); if u == v {
v.ancestors().find(|it| u_ancestors.contains(it)) return Some(u.clone());
}
let u_depth = u.ancestors().count();
let v_depth = v.ancestors().count();
let keep = u_depth.min(v_depth);
let u_candidates = u.ancestors().skip(u_depth - keep);
let v_canidates = v.ancestors().skip(v_depth - keep);
let (res, _) = u_candidates.zip(v_canidates).find(|(x, y)| x == y)?;
Some(res)
} }
pub fn neighbor<T: AstNode>(me: &T, direction: Direction) -> Option<T> { pub fn neighbor<T: AstNode>(me: &T, direction: Direction) -> Option<T> {