From c631b585a7358d1569a051f2529ecaae222e95cd Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Thu, 16 Aug 2018 00:23:22 +0300
Subject: matching brace

---
 crates/libeditor/src/lib.rs | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

(limited to 'crates/libeditor/src/lib.rs')

diff --git a/crates/libeditor/src/lib.rs b/crates/libeditor/src/lib.rs
index 9e44f5d92..28da457d1 100644
--- a/crates/libeditor/src/lib.rs
+++ b/crates/libeditor/src/lib.rs
@@ -12,8 +12,8 @@ mod code_actions;
 use libsyntax2::{
     ast::{self, NameOwner},
     AstNode,
-    algo::walk,
-    SyntaxKind::*,
+    algo::{walk, find_leaf_at_offset},
+    SyntaxKind::{self, *},
 };
 pub use libsyntax2::{File, TextRange, TextUnit};
 pub use self::{
@@ -52,6 +52,28 @@ pub fn parse(text: &str) -> ast::File {
     ast::File::parse(text)
 }
 
+pub fn matching_brace(file: &ast::File, offset: TextUnit) -> Option<TextUnit> {
+    const BRACES: &[SyntaxKind] = &[
+        L_CURLY, R_CURLY,
+        L_BRACK, R_BRACK,
+        L_PAREN, R_PAREN,
+        L_ANGLE, R_ANGLE,
+    ];
+    let syntax = file.syntax();
+    let syntax = syntax.as_ref();
+    let (brace_node, brace_idx) = find_leaf_at_offset(syntax, offset)
+        .filter_map(|node| {
+            let idx = BRACES.iter().position(|&brace| brace == node.kind())?;
+            Some((node, idx))
+        })
+        .next()?;
+    let parent = brace_node.parent()?;
+    let matching_kind = BRACES[brace_idx ^ 1];
+    let matching_node = parent.children()
+        .find(|node| node.kind() == matching_kind)?;
+    Some(matching_node.range().start())
+}
+
 pub fn highlight(file: &ast::File) -> Vec<HighlightedRange> {
     let syntax = file.syntax();
     let mut res = Vec::new();
-- 
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