1 files changed, 19 insertions, 2 deletions

diff --git a/crates/ra_syntax/src/algo.rs b/crates/ra_syntax/src/algo.rs
index 21fca99a6..ebf59288a 100644
--- a/crates/ra_syntax/src/algo.rs
+++ b/crates/ra_syntax/src/algo.rs
@@ -4,10 +4,11 @@ use std::ops::RangeInclusive;
 
 use itertools::Itertools;
 use ra_text_edit::TextEditBuilder;
-use rustc_hash::FxHashMap;
+use rustc_hash::{FxHashMap, FxHashSet};
 
 use crate::{
-    AstNode, Direction, NodeOrToken, SyntaxElement, SyntaxNode, SyntaxNodePtr, TextRange, TextUnit,
+    AstNode, Direction, NodeOrToken, SyntaxElement, SyntaxNode, SyntaxNodePtr, SyntaxToken,
+    TextRange, TextUnit,
 };
 
 /// Returns ancestors of the node at the offset, sorted by length. This should
@@ -37,6 +38,17 @@ pub fn find_node_at_offset<N: AstNode>(syntax: &SyntaxNode, offset: TextUnit) ->
     ancestors_at_offset(syntax, offset).find_map(N::cast)
 }
 
+/// Skip to next non `trivia` token
+pub fn skip_trivia_token(mut token: SyntaxToken, direction: Direction) -> Option<SyntaxToken> {
+    while token.kind().is_trivia() {
+        token = match direction {
+            Direction::Next => token.next_token()?,
+            Direction::Prev => token.prev_token()?,
+        }
+    }
+    Some(token)
+}
+
 /// Finds the first sibling in the given direction which is not `trivia`
 pub fn non_trivia_sibling(element: SyntaxElement, direction: Direction) -> Option<SyntaxElement> {
     return match element {
@@ -56,6 +68,11 @@ pub fn find_covering_element(root: &SyntaxNode, range: TextRange) -> SyntaxEleme
     root.covering_element(range)
 }
 
+pub fn least_common_ancestor(u: &SyntaxNode, v: &SyntaxNode) -> Option<SyntaxNode> {
+    let u_ancestors = u.ancestors().collect::<FxHashSet<SyntaxNode>>();
+    v.ancestors().find(|it| u_ancestors.contains(it))
+}
+
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub enum InsertPosition<T> {
     First,