Generalize

crates/ra_assists/src/handlers/merge_imports.rs

@@ -1,7 +1,10 @@
 use std::iter::successors;
 
-use ast::{edit::AstNodeEdit, make};
-use ra_syntax::{ast, AstNode, AstToken, Direction, InsertPosition, SyntaxElement, T};
+use ra_syntax::{
+    algo::neighbor,
+    ast::{self, edit::AstNodeEdit, make},
+    AstNode, AstToken, Direction, InsertPosition, SyntaxElement, T,
+};
 
 use crate::{Assist, AssistCtx, AssistId};
 
@@ -23,7 +26,7 @@ pub(crate) fn merge_imports(ctx: AssistCtx) -> Option<Assist> {
     let (merged, to_delete) = [Direction::Prev, Direction::Next]
         .iter()
         .copied()
-        .filter_map(|dir| next_use_item(&use_item, dir))
+        .filter_map(|dir| neighbor(&use_item, dir))
         .filter_map(|it| Some((it.clone(), it.use_tree()?)))
         .find_map(|(use_item, use_tree)| {
             Some((try_merge_trees(&tree, &use_tree)?, use_item.clone()))
@@ -49,10 +52,6 @@ pub(crate) fn merge_imports(ctx: AssistCtx) -> Option<Assist> {
     })
 }
 
-fn next_use_item(this_use_item: &ast::UseItem, direction: Direction) -> Option<ast::UseItem> {
-    this_use_item.syntax().siblings(direction).skip(1).find_map(ast::UseItem::cast)
-}
-
 fn try_merge_trees(old: &ast::UseTree, new: &ast::UseTree) -> Option<ast::UseTree> {
     let lhs_path = old.path()?;
     let rhs_path = new.path()?;

crates/ra_assists/src/handlers/merge_match_arms.rs

@@ -1,6 +1,7 @@
 use std::iter::successors;
 
 use ra_syntax::{
+    algo::neighbor,
     ast::{self, AstNode},
     Direction, TextUnit,
 };
@@ -53,7 +54,7 @@ pub(crate) fn merge_match_arms(ctx: AssistCtx) -> Option<Assist> {
 
     // We check if the following match arms match this one. We could, but don't,
     // compare to the previous match arm as well.
-    let arms_to_merge = successors(Some(current_arm), next_arm)
+    let arms_to_merge = successors(Some(current_arm), |it| neighbor(it, Direction::Next))
         .take_while(|arm| {
             if arm.guard().is_some() {
                 return false;
@@ -102,15 +103,12 @@ fn contains_placeholder(a: &ast::MatchArm) -> bool {
     }
 }
 
-fn next_arm(arm: &ast::MatchArm) -> Option<ast::MatchArm> {
-    arm.syntax().siblings(Direction::Next).skip(1).find_map(ast::MatchArm::cast)
-}
-
 #[cfg(test)]
 mod tests {
-    use super::merge_match_arms;
     use crate::helpers::{check_assist, check_assist_not_applicable};
 
+    use super::*;
+
     #[test]
     fn merge_match_arms_single_patterns() {
         check_assist(

crates/ra_syntax/src/algo.rs

@@ -73,6 +73,10 @@ pub fn least_common_ancestor(u: &SyntaxNode, v: &SyntaxNode) -> Option<SyntaxNod
     v.ancestors().find(|it| u_ancestors.contains(it))
 }
 
+pub fn neighbor<T: AstNode>(me: &T, direction: Direction) -> Option<T> {
+    me.syntax().siblings(direction).skip(1).find_map(T::cast)
+}
+
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub enum InsertPosition<T> {
     First,