1mod buffer;
2mod diagnostic_set;
3mod highlight_map;
4mod outline;
5pub mod proto;
6#[cfg(test)]
7mod tests;
8
9use anyhow::{anyhow, Context, Result};
10use client::http::HttpClient;
11use collections::HashMap;
12use futures::{
13 future::{BoxFuture, Shared},
14 FutureExt, TryFutureExt,
15};
16use gpui::{MutableAppContext, Task};
17use highlight_map::HighlightMap;
18use lazy_static::lazy_static;
19use parking_lot::{Mutex, RwLock};
20use regex::Regex;
21use serde::{de, Deserialize, Deserializer};
22use serde_json::Value;
23use std::{
24 any::Any,
25 cell::RefCell,
26 mem,
27 ops::Range,
28 path::{Path, PathBuf},
29 str,
30 sync::Arc,
31};
32use theme::SyntaxTheme;
33use tree_sitter::{self, Query};
34use util::ResultExt;
35
36#[cfg(any(test, feature = "test-support"))]
37use futures::channel::mpsc;
38
39pub use buffer::Operation;
40pub use buffer::*;
41pub use diagnostic_set::DiagnosticEntry;
42pub use outline::{Outline, OutlineItem};
43pub use tree_sitter::{Parser, Tree};
44
45thread_local! {
46 static PARSER: RefCell<Parser> = RefCell::new(Parser::new());
47}
48
49lazy_static! {
50 pub static ref PLAIN_TEXT: Arc<Language> = Arc::new(Language::new(
51 LanguageConfig {
52 name: "Plain Text".into(),
53 ..Default::default()
54 },
55 None,
56 ));
57}
58
59pub trait ToLspPosition {
60 fn to_lsp_position(self) -> lsp::Position;
61}
62
63#[derive(Clone, Debug, PartialEq, Eq, Hash)]
64pub struct LanguageServerName(pub Arc<str>);
65
66use async_trait::async_trait;
67
68// pub struct LspAdapter {
69// name: LanguageServerName,
70// adapter: Arc<dyn LspAdapter>,
71// }
72
73// impl LspAdapter {
74// async fn new(adapter: Arc<dyn LspAdapter>) -> Self {
75// let name = adapter.name().await;
76
77// LspAdapter { name, adapter }
78// }
79
80// fn name(&self) -> LanguageServerName {
81// self.name
82// }
83// }
84
85#[async_trait]
86pub trait LspAdapter: 'static + Send + Sync {
87 async fn name(&self) -> LanguageServerName;
88 async fn fetch_latest_server_version(
89 &self,
90 http: Arc<dyn HttpClient>,
91 ) -> Result<Box<dyn 'static + Send + Any>>;
92 async fn fetch_server_binary(
93 &self,
94 version: Box<dyn 'static + Send + Any>,
95 http: Arc<dyn HttpClient>,
96 container_dir: PathBuf,
97 ) -> Result<PathBuf>;
98 async fn cached_server_binary(&self, container_dir: PathBuf) -> Option<PathBuf>;
99
100 async fn process_diagnostics(&self, _: &mut lsp::PublishDiagnosticsParams) {}
101
102 async fn label_for_completion(
103 &self,
104 _: &lsp::CompletionItem,
105 _: &Language,
106 ) -> Option<CodeLabel> {
107 None
108 }
109
110 async fn label_for_symbol(
111 &self,
112 _: &str,
113 _: lsp::SymbolKind,
114 _: &Language,
115 ) -> Option<CodeLabel> {
116 None
117 }
118
119 async fn server_args(&self) -> Vec<String> {
120 Vec::new()
121 }
122
123 async fn initialization_options(&self) -> Option<Value> {
124 None
125 }
126
127 async fn disk_based_diagnostic_sources(&self) -> Vec<String> {
128 Default::default()
129 }
130
131 async fn disk_based_diagnostics_progress_token(&self) -> Option<String> {
132 None
133 }
134
135 async fn id_for_language(&self, _name: &str) -> Option<String> {
136 None
137 }
138}
139
140#[derive(Clone, Debug, PartialEq, Eq)]
141pub struct CodeLabel {
142 pub text: String,
143 pub runs: Vec<(Range<usize>, HighlightId)>,
144 pub filter_range: Range<usize>,
145}
146
147#[derive(Deserialize)]
148pub struct LanguageConfig {
149 pub name: Arc<str>,
150 pub path_suffixes: Vec<String>,
151 pub brackets: Vec<BracketPair>,
152 #[serde(default = "auto_indent_using_last_non_empty_line_default")]
153 pub auto_indent_using_last_non_empty_line: bool,
154 #[serde(default, deserialize_with = "deserialize_regex")]
155 pub increase_indent_pattern: Option<Regex>,
156 #[serde(default, deserialize_with = "deserialize_regex")]
157 pub decrease_indent_pattern: Option<Regex>,
158 #[serde(default)]
159 pub autoclose_before: String,
160 pub line_comment: Option<String>,
161}
162
163impl Default for LanguageConfig {
164 fn default() -> Self {
165 Self {
166 name: "".into(),
167 path_suffixes: Default::default(),
168 brackets: Default::default(),
169 auto_indent_using_last_non_empty_line: auto_indent_using_last_non_empty_line_default(),
170 increase_indent_pattern: Default::default(),
171 decrease_indent_pattern: Default::default(),
172 autoclose_before: Default::default(),
173 line_comment: Default::default(),
174 }
175 }
176}
177
178fn auto_indent_using_last_non_empty_line_default() -> bool {
179 true
180}
181
182fn deserialize_regex<'de, D: Deserializer<'de>>(d: D) -> Result<Option<Regex>, D::Error> {
183 let source = Option::<String>::deserialize(d)?;
184 if let Some(source) = source {
185 Ok(Some(regex::Regex::new(&source).map_err(de::Error::custom)?))
186 } else {
187 Ok(None)
188 }
189}
190
191#[cfg(any(test, feature = "test-support"))]
192pub struct FakeLspAdapter {
193 pub name: &'static str,
194 pub capabilities: lsp::ServerCapabilities,
195 pub initializer: Option<Box<dyn 'static + Send + Sync + Fn(&mut lsp::FakeLanguageServer)>>,
196 pub disk_based_diagnostics_progress_token: Option<String>,
197 pub disk_based_diagnostics_sources: Vec<String>,
198}
199
200#[derive(Clone, Debug, Deserialize)]
201pub struct BracketPair {
202 pub start: String,
203 pub end: String,
204 pub close: bool,
205 pub newline: bool,
206}
207
208pub struct Language {
209 pub(crate) config: LanguageConfig,
210 pub(crate) grammar: Option<Arc<Grammar>>,
211 pub(crate) adapter: Option<Arc<dyn LspAdapter>>,
212
213 #[cfg(any(test, feature = "test-support"))]
214 fake_adapter: Option<(
215 mpsc::UnboundedSender<lsp::FakeLanguageServer>,
216 Arc<FakeLspAdapter>,
217 )>,
218}
219
220pub struct Grammar {
221 pub(crate) ts_language: tree_sitter::Language,
222 pub(crate) highlights_query: Option<Query>,
223 pub(crate) brackets_query: Option<Query>,
224 pub(crate) indents_query: Option<Query>,
225 pub(crate) outline_query: Option<Query>,
226 pub(crate) highlight_map: Mutex<HighlightMap>,
227}
228
229#[derive(Clone)]
230pub enum LanguageServerBinaryStatus {
231 CheckingForUpdate,
232 Downloading,
233 Downloaded,
234 Cached,
235 Failed { error: String },
236}
237
238pub struct LanguageRegistry {
239 languages: RwLock<Vec<Arc<Language>>>,
240 language_server_download_dir: Option<Arc<Path>>,
241 lsp_binary_statuses_tx: async_broadcast::Sender<(Arc<Language>, LanguageServerBinaryStatus)>,
242 lsp_binary_statuses_rx: async_broadcast::Receiver<(Arc<Language>, LanguageServerBinaryStatus)>,
243 login_shell_env_loaded: Shared<Task<()>>,
244 lsp_binary_paths: Mutex<
245 HashMap<
246 LanguageServerName,
247 Shared<BoxFuture<'static, Result<PathBuf, Arc<anyhow::Error>>>>,
248 >,
249 >,
250}
251
252impl LanguageRegistry {
253 pub fn new(login_shell_env_loaded: Task<()>) -> Self {
254 let (lsp_binary_statuses_tx, lsp_binary_statuses_rx) = async_broadcast::broadcast(16);
255 Self {
256 language_server_download_dir: None,
257 languages: Default::default(),
258 lsp_binary_statuses_tx,
259 lsp_binary_statuses_rx,
260 login_shell_env_loaded: login_shell_env_loaded.shared(),
261 lsp_binary_paths: Default::default(),
262 }
263 }
264
265 #[cfg(any(test, feature = "test-support"))]
266 pub fn test() -> Self {
267 Self::new(Task::ready(()))
268 }
269
270 pub fn add(&self, language: Arc<Language>) {
271 self.languages.write().push(language.clone());
272 }
273
274 pub fn set_theme(&self, theme: &SyntaxTheme) {
275 for language in self.languages.read().iter() {
276 language.set_theme(theme);
277 }
278 }
279
280 pub fn set_language_server_download_dir(&mut self, path: impl Into<Arc<Path>>) {
281 self.language_server_download_dir = Some(path.into());
282 }
283
284 pub fn get_language(&self, name: &str) -> Option<Arc<Language>> {
285 self.languages
286 .read()
287 .iter()
288 .find(|language| language.name().to_lowercase() == name.to_lowercase())
289 .cloned()
290 }
291
292 pub fn to_vec(&self) -> Vec<Arc<Language>> {
293 self.languages.read().iter().cloned().collect()
294 }
295
296 pub fn language_names(&self) -> Vec<String> {
297 self.languages
298 .read()
299 .iter()
300 .map(|language| language.name().to_string())
301 .collect()
302 }
303
304 pub fn select_language(&self, path: impl AsRef<Path>) -> Option<Arc<Language>> {
305 let path = path.as_ref();
306 let filename = path.file_name().and_then(|name| name.to_str());
307 let extension = path.extension().and_then(|name| name.to_str());
308 let path_suffixes = [extension, filename];
309 self.languages
310 .read()
311 .iter()
312 .find(|language| {
313 language
314 .config
315 .path_suffixes
316 .iter()
317 .any(|suffix| dbg!(path_suffixes.contains(&Some(dbg!(suffix.as_str())))))
318 })
319 .cloned()
320 }
321
322 pub fn start_language_server(
323 self: &Arc<Self>,
324 server_id: usize,
325 language: Arc<Language>,
326 root_path: Arc<Path>,
327 http_client: Arc<dyn HttpClient>,
328 cx: &mut MutableAppContext,
329 ) -> Option<Task<Result<lsp::LanguageServer>>> {
330 #[cfg(any(test, feature = "test-support"))]
331 if language.fake_adapter.is_some() {
332 let language = language.clone();
333 return Some(cx.spawn(|cx| async move {
334 let (servers_tx, fake_adapter) = language.fake_adapter.as_ref().unwrap();
335 let (server, mut fake_server) = lsp::LanguageServer::fake(
336 fake_adapter.name.to_string(),
337 fake_adapter.capabilities.clone(),
338 cx.clone(),
339 );
340
341 if let Some(initializer) = &fake_adapter.initializer {
342 initializer(&mut fake_server);
343 }
344
345 let servers_tx = servers_tx.clone();
346 cx.background()
347 .spawn(async move {
348 if fake_server
349 .try_receive_notification::<lsp::notification::Initialized>()
350 .await
351 .is_some()
352 {
353 servers_tx.unbounded_send(fake_server).ok();
354 }
355 })
356 .detach();
357 Ok(server)
358 }));
359 }
360
361 let download_dir = self
362 .language_server_download_dir
363 .clone()
364 .ok_or_else(|| anyhow!("language server download directory has not been assigned"))
365 .log_err()?;
366
367 let this = self.clone();
368 let adapter = language.adapter.clone()?;
369 let lsp_binary_statuses = self.lsp_binary_statuses_tx.clone();
370 let login_shell_env_loaded = self.login_shell_env_loaded.clone();
371 Some(cx.spawn(|cx| async move {
372 login_shell_env_loaded.await;
373 let server_binary_path = this
374 .lsp_binary_paths
375 .lock()
376 .entry(adapter.name().await)
377 .or_insert_with(|| {
378 get_server_binary_path(
379 adapter.clone(),
380 language.clone(),
381 http_client,
382 download_dir,
383 lsp_binary_statuses,
384 )
385 .map_err(Arc::new)
386 .boxed()
387 .shared()
388 })
389 .clone()
390 .map_err(|e| anyhow!(e));
391
392 let server_binary_path = server_binary_path.await?;
393 let server_args = adapter.server_args().await;
394 let server = lsp::LanguageServer::new(
395 server_id,
396 &server_binary_path,
397 &server_args,
398 &root_path,
399 cx,
400 )?;
401 Ok(server)
402 }))
403 }
404
405 pub fn language_server_binary_statuses(
406 &self,
407 ) -> async_broadcast::Receiver<(Arc<Language>, LanguageServerBinaryStatus)> {
408 self.lsp_binary_statuses_rx.clone()
409 }
410}
411
412async fn get_server_binary_path(
413 adapter: Arc<dyn LspAdapter>,
414 language: Arc<Language>,
415 http_client: Arc<dyn HttpClient>,
416 download_dir: Arc<Path>,
417 statuses: async_broadcast::Sender<(Arc<Language>, LanguageServerBinaryStatus)>,
418) -> Result<PathBuf> {
419 let container_dir = download_dir.join(adapter.name().await.0.as_ref());
420 if !container_dir.exists() {
421 smol::fs::create_dir_all(&container_dir)
422 .await
423 .context("failed to create container directory")?;
424 }
425
426 let path = fetch_latest_server_binary_path(
427 adapter.clone(),
428 language.clone(),
429 http_client,
430 &container_dir,
431 statuses.clone(),
432 )
433 .await;
434 if let Err(error) = path.as_ref() {
435 if let Some(cached_path) = adapter.cached_server_binary(container_dir).await {
436 statuses
437 .broadcast((language.clone(), LanguageServerBinaryStatus::Cached))
438 .await?;
439 return Ok(cached_path);
440 } else {
441 statuses
442 .broadcast((
443 language.clone(),
444 LanguageServerBinaryStatus::Failed {
445 error: format!("{:?}", error),
446 },
447 ))
448 .await?;
449 }
450 }
451 path
452}
453
454async fn fetch_latest_server_binary_path(
455 adapter: Arc<dyn LspAdapter>,
456 language: Arc<Language>,
457 http_client: Arc<dyn HttpClient>,
458 container_dir: &Path,
459 lsp_binary_statuses_tx: async_broadcast::Sender<(Arc<Language>, LanguageServerBinaryStatus)>,
460) -> Result<PathBuf> {
461 let container_dir: Arc<Path> = container_dir.into();
462 lsp_binary_statuses_tx
463 .broadcast((
464 language.clone(),
465 LanguageServerBinaryStatus::CheckingForUpdate,
466 ))
467 .await?;
468 let version_info = adapter
469 .fetch_latest_server_version(http_client.clone())
470 .await?;
471 lsp_binary_statuses_tx
472 .broadcast((language.clone(), LanguageServerBinaryStatus::Downloading))
473 .await?;
474 let path = adapter
475 .fetch_server_binary(version_info, http_client, container_dir.clone())
476 .await?;
477 lsp_binary_statuses_tx
478 .broadcast((language.clone(), LanguageServerBinaryStatus::Downloaded))
479 .await?;
480 Ok(path)
481}
482
483impl Language {
484 pub fn new(config: LanguageConfig, ts_language: Option<tree_sitter::Language>) -> Self {
485 Self {
486 config,
487 grammar: ts_language.map(|ts_language| {
488 Arc::new(Grammar {
489 highlights_query: None,
490 brackets_query: None,
491 indents_query: None,
492 outline_query: None,
493 ts_language,
494 highlight_map: Default::default(),
495 })
496 }),
497 adapter: None,
498
499 #[cfg(any(test, feature = "test-support"))]
500 fake_adapter: None,
501 }
502 }
503
504 pub fn lsp_adapter(&self) -> Option<Arc<dyn LspAdapter>> {
505 self.adapter.clone()
506 }
507
508 pub fn with_highlights_query(mut self, source: &str) -> Result<Self> {
509 let grammar = self.grammar_mut();
510 grammar.highlights_query = Some(Query::new(grammar.ts_language, source)?);
511 Ok(self)
512 }
513
514 pub fn with_brackets_query(mut self, source: &str) -> Result<Self> {
515 let grammar = self.grammar_mut();
516 grammar.brackets_query = Some(Query::new(grammar.ts_language, source)?);
517 Ok(self)
518 }
519
520 pub fn with_indents_query(mut self, source: &str) -> Result<Self> {
521 let grammar = self.grammar_mut();
522 grammar.indents_query = Some(Query::new(grammar.ts_language, source)?);
523 Ok(self)
524 }
525
526 pub fn with_outline_query(mut self, source: &str) -> Result<Self> {
527 let grammar = self.grammar_mut();
528 grammar.outline_query = Some(Query::new(grammar.ts_language, source)?);
529 Ok(self)
530 }
531
532 fn grammar_mut(&mut self) -> &mut Grammar {
533 Arc::get_mut(self.grammar.as_mut().unwrap()).unwrap()
534 }
535
536 pub fn with_lsp_adapter(mut self, lsp_adapter: Arc<dyn LspAdapter>) -> Self {
537 self.adapter = Some(lsp_adapter);
538 self
539 }
540
541 #[cfg(any(test, feature = "test-support"))]
542 pub fn set_fake_lsp_adapter(
543 &mut self,
544 fake_lsp_adapter: FakeLspAdapter,
545 ) -> mpsc::UnboundedReceiver<lsp::FakeLanguageServer> {
546 let (servers_tx, servers_rx) = mpsc::unbounded();
547 let adapter = Arc::new(fake_lsp_adapter);
548 self.fake_adapter = Some((servers_tx, adapter.clone()));
549 self.adapter = Some(adapter);
550 servers_rx
551 }
552
553 pub fn name(&self) -> Arc<str> {
554 self.config.name.clone()
555 }
556
557 pub fn line_comment_prefix(&self) -> Option<&str> {
558 self.config.line_comment.as_deref()
559 }
560
561 pub async fn disk_based_diagnostic_sources(&self) -> Vec<String> {
562 match self.adapter.as_ref() {
563 Some(adapter) => adapter.disk_based_diagnostic_sources().await,
564 None => Vec::new(),
565 }
566 }
567
568 pub async fn disk_based_diagnostics_progress_token(&self) -> Option<String> {
569 if let Some(adapter) = self.adapter.as_ref() {
570 adapter.disk_based_diagnostics_progress_token().await
571 } else {
572 None
573 }
574 }
575
576 pub async fn process_diagnostics(&self, diagnostics: &mut lsp::PublishDiagnosticsParams) {
577 if let Some(processor) = self.adapter.as_ref() {
578 processor.process_diagnostics(diagnostics).await;
579 }
580 }
581
582 pub async fn label_for_completion(
583 &self,
584 completion: &lsp::CompletionItem,
585 ) -> Option<CodeLabel> {
586 self.adapter
587 .as_ref()?
588 .label_for_completion(completion, self)
589 .await
590 }
591
592 pub async fn label_for_symbol(&self, name: &str, kind: lsp::SymbolKind) -> Option<CodeLabel> {
593 self.adapter
594 .as_ref()?
595 .label_for_symbol(name, kind, self)
596 .await
597 }
598
599 pub fn highlight_text<'a>(
600 &'a self,
601 text: &'a Rope,
602 range: Range<usize>,
603 ) -> Vec<(Range<usize>, HighlightId)> {
604 let mut result = Vec::new();
605 if let Some(grammar) = &self.grammar {
606 let tree = grammar.parse_text(text, None);
607 let mut offset = 0;
608 for chunk in BufferChunks::new(text, range, Some(&tree), self.grammar.as_ref(), vec![])
609 {
610 let end_offset = offset + chunk.text.len();
611 if let Some(highlight_id) = chunk.syntax_highlight_id {
612 if !highlight_id.is_default() {
613 result.push((offset..end_offset, highlight_id));
614 }
615 }
616 offset = end_offset;
617 }
618 }
619 result
620 }
621
622 pub fn brackets(&self) -> &[BracketPair] {
623 &self.config.brackets
624 }
625
626 pub fn path_suffixes(&self) -> &[String] {
627 &self.config.path_suffixes
628 }
629
630 pub fn should_autoclose_before(&self, c: char) -> bool {
631 c.is_whitespace() || self.config.autoclose_before.contains(c)
632 }
633
634 pub fn set_theme(&self, theme: &SyntaxTheme) {
635 if let Some(grammar) = self.grammar.as_ref() {
636 if let Some(highlights_query) = &grammar.highlights_query {
637 *grammar.highlight_map.lock() =
638 HighlightMap::new(highlights_query.capture_names(), theme);
639 }
640 }
641 }
642
643 pub fn grammar(&self) -> Option<&Arc<Grammar>> {
644 self.grammar.as_ref()
645 }
646}
647
648impl Grammar {
649 fn parse_text(&self, text: &Rope, old_tree: Option<Tree>) -> Tree {
650 PARSER.with(|parser| {
651 let mut parser = parser.borrow_mut();
652 parser
653 .set_language(self.ts_language)
654 .expect("incompatible grammar");
655 let mut chunks = text.chunks_in_range(0..text.len());
656 parser
657 .parse_with(
658 &mut move |offset, _| {
659 chunks.seek(offset);
660 chunks.next().unwrap_or("").as_bytes()
661 },
662 old_tree.as_ref(),
663 )
664 .unwrap()
665 })
666 }
667
668 pub fn highlight_map(&self) -> HighlightMap {
669 self.highlight_map.lock().clone()
670 }
671
672 pub fn highlight_id_for_name(&self, name: &str) -> Option<HighlightId> {
673 let capture_id = self
674 .highlights_query
675 .as_ref()?
676 .capture_index_for_name(name)?;
677 Some(self.highlight_map.lock().get(capture_id))
678 }
679}
680
681impl CodeLabel {
682 pub fn plain(text: String, filter_text: Option<&str>) -> Self {
683 let mut result = Self {
684 runs: Vec::new(),
685 filter_range: 0..text.len(),
686 text,
687 };
688 if let Some(filter_text) = filter_text {
689 if let Some(ix) = result.text.find(filter_text) {
690 result.filter_range = ix..ix + filter_text.len();
691 }
692 }
693 result
694 }
695}
696
697#[cfg(any(test, feature = "test-support"))]
698impl Default for FakeLspAdapter {
699 fn default() -> Self {
700 Self {
701 name: "the-fake-language-server",
702 capabilities: lsp::LanguageServer::full_capabilities(),
703 initializer: None,
704 disk_based_diagnostics_progress_token: None,
705 disk_based_diagnostics_sources: Vec::new(),
706 }
707 }
708}
709
710#[cfg(any(test, feature = "test-support"))]
711#[async_trait]
712impl LspAdapter for FakeLspAdapter {
713 async fn name(&self) -> LanguageServerName {
714 LanguageServerName(self.name.into())
715 }
716
717 async fn fetch_latest_server_version(
718 &self,
719 _: Arc<dyn HttpClient>,
720 ) -> Result<Box<dyn 'static + Send + Any>> {
721 unreachable!();
722 }
723
724 async fn fetch_server_binary(
725 &self,
726 _: Box<dyn 'static + Send + Any>,
727 _: Arc<dyn HttpClient>,
728 _: PathBuf,
729 ) -> Result<PathBuf> {
730 unreachable!();
731 }
732
733 async fn cached_server_binary(&self, _: PathBuf) -> Option<PathBuf> {
734 unreachable!();
735 }
736
737 async fn process_diagnostics(&self, _: &mut lsp::PublishDiagnosticsParams) {}
738
739 async fn disk_based_diagnostic_sources(&self) -> Vec<String> {
740 self.disk_based_diagnostics_sources.clone()
741 }
742
743 async fn disk_based_diagnostics_progress_token(&self) -> Option<String> {
744 self.disk_based_diagnostics_progress_token.clone()
745 }
746}
747
748pub fn point_to_lsp(point: PointUtf16) -> lsp::Position {
749 lsp::Position::new(point.row, point.column)
750}
751
752pub fn point_from_lsp(point: lsp::Position) -> PointUtf16 {
753 PointUtf16::new(point.line, point.character)
754}
755
756pub fn range_to_lsp(range: Range<PointUtf16>) -> lsp::Range {
757 lsp::Range {
758 start: point_to_lsp(range.start),
759 end: point_to_lsp(range.end),
760 }
761}
762
763pub fn range_from_lsp(range: lsp::Range) -> Range<PointUtf16> {
764 let mut start = point_from_lsp(range.start);
765 let mut end = point_from_lsp(range.end);
766 if start > end {
767 mem::swap(&mut start, &mut end);
768 }
769 start..end
770}