Move highlighting and matching_brace

crates/ra_ide_api/src/matching_brace.rs

@@ -0,0 +1,45 @@
+use ra_syntax::{
+    SourceFile, TextUnit,
+    algo::find_leaf_at_offset,
+    SyntaxKind::{self, *},
+    ast::AstNode,
+};
+
+pub fn matching_brace(file: &SourceFile, offset: TextUnit) -> Option<TextUnit> {
+    const BRACES: &[SyntaxKind] =
+        &[L_CURLY, R_CURLY, L_BRACK, R_BRACK, L_PAREN, R_PAREN, L_ANGLE, R_ANGLE];
+    let (brace_node, brace_idx) = find_leaf_at_offset(file.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())
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::{add_cursor, assert_eq_text, extract_offset};
+
+    use super::*;
+
+    #[test]
+    fn test_matching_brace() {
+        fn do_check(before: &str, after: &str) {
+            let (pos, before) = extract_offset(before);
+            let file = SourceFile::parse(&before);
+            let new_pos = match matching_brace(&file, pos) {
+                None => pos,
+                Some(pos) => pos,
+            };
+            let actual = add_cursor(&before, new_pos);
+            assert_eq_text!(after, &actual);
+        }
+
+        do_check("struct Foo { a: i32, }<|>", "struct Foo <|>{ a: i32, }");
+    }
+
+}