4 files changed, 123 insertions, 3 deletions

diff --git a/crates/ra_cli/Cargo.toml b/crates/ra_cli/Cargo.toml
index 17011e063..5e7bf3ed4 100644
--- a/crates/ra_cli/Cargo.toml
+++ b/crates/ra_cli/Cargo.toml
@@ -7,6 +7,7 @@ publish = false
 [dependencies]
 clap = "2.32.0"
 failure = "0.1.1"
+join_to_string = "0.1.1"
 ra_syntax = { path = "../ra_syntax" }
 ra_editor = { path = "../ra_editor" }
 tools = { path = "../tools" }
diff --git a/crates/ra_cli/src/main.rs b/crates/ra_cli/src/main.rs
index 96e5b718c..11605cfd8 100644
--- a/crates/ra_cli/src/main.rs
+++ b/crates/ra_cli/src/main.rs
@@ -1,6 +1,7 @@
 extern crate clap;
 #[macro_use]
 extern crate failure;
+extern crate join_to_string;
 extern crate ra_syntax;
 extern crate ra_editor;
 extern crate tools;
@@ -10,9 +11,10 @@ use std::{
     time::Instant
 };
 use clap::{App, Arg, SubCommand};
+use join_to_string::join;
 use tools::collect_tests;
-use ra_syntax::File;
-use ra_editor::{syntax_tree, file_structure};
+use ra_syntax::{TextRange, File};
+use ra_editor::{syntax_tree, file_structure, extend_selection};
 
 type Result<T> = ::std::result::Result<T, failure::Error>;
 
@@ -39,6 +41,10 @@ fn main() -> Result<()> {
                 .arg(Arg::with_name("no-dump").long("--no-dump"))
         )
         .subcommand(SubCommand::with_name("symbols"))
+        .subcommand(SubCommand::with_name("extend-selection")
+            .arg(Arg::with_name("start"))
+            .arg(Arg::with_name("end"))
+        )
         .get_matches();
     match matches.subcommand() {
         ("parse", Some(matches)) => {
@@ -65,6 +71,13 @@ fn main() -> Result<()> {
             let (test, tree) = render_test(file, line)?;
             println!("{}\n{}", test, tree);
         }
+        ("extend-selection", Some(matches)) => {
+            let start: u32 = matches.value_of("start").unwrap().parse()?;
+            let end: u32 = matches.value_of("end").unwrap().parse()?;
+            let file = file()?;
+            let sels = selections(&file, start, end);
+            println!("{}", sels)
+        }
         _ => unreachable!(),
     }
     Ok(())
@@ -95,3 +108,19 @@ fn render_test(file: &Path, line: usize) -> Result<(String, String)> {
     let tree = syntax_tree(&file);
     Ok((test.text, tree))
 }
+
+fn selections(file: &File, start: u32, end: u32) -> String {
+    let mut ranges = Vec::new();
+    let mut cur = Some(TextRange::from_to((start - 1).into(), (end - 1).into()));
+    while let Some(r) = cur {
+        ranges.push(r);
+        cur = extend_selection(&file, r);
+    }
+    let ranges = ranges.iter()
+        .map(|r| (1 + u32::from(r.start()), 1 + u32::from(r.end())))
+        .map(|(s, e)| format!("({} {})", s, e));
+    join(ranges)
+        .separator(" ")
+        .surround_with("(", ")")
+        .to_string()
+}
diff --git a/crates/ra_syntax/src/algo/mod.rs b/crates/ra_syntax/src/algo/mod.rs
index 7287f5bb2..8de44c586 100644
--- a/crates/ra_syntax/src/algo/mod.rs
+++ b/crates/ra_syntax/src/algo/mod.rs
@@ -78,7 +78,11 @@ impl<'f> Iterator for LeafAtOffset<'f> {
 }
 
 pub fn find_covering_node(root: SyntaxNodeRef, range: TextRange) -> SyntaxNodeRef {
-    assert!(is_subrange(root.range(), range));
+    assert!(
+        is_subrange(root.range(), range),
+        "node range: {:?}, target range: {:?}",
+        root.range(), range,
+    );
     let (left, right) = match (
         find_leaf_at_offset(root, range.start()).right_biased(),
         find_leaf_at_offset(root, range.end()).left_biased()
diff --git a/editors/emacs/ra.el b/editors/emacs/ra.el
new file mode 100644
index 000000000..6ff2ae742
--- /dev/null
+++ b/editors/emacs/ra.el
@@ -0,0 +1,86 @@
+;;; ra.el --- Rust analyzer emacs bindings -*- lexical-binding: t; -*-
+;;; Commentary:
+;;; Small utilities for interacting with Rust analyzer.
+;;; Run
+;;;   cargo install --git https://github.com/matklad/rust-analyzer/ --bin ra_cli
+;;; to install the binary, copy-paste the bellow code to your `.init.el` and use
+;;; `ra-extend-selection` and `ra-shrink-selection` functions
+;;; Code:
+
+
+(defvar ra--selections-cache '(0 0 ()))
+(defun ra--cache-tick ()
+  "Get buffer modification count for cache."
+  (nth 0 ra--selections-cache))
+(defun ra--cache-sel ()
+  "Get current selection for cache."
+  (nth 1 ra--selections-cache))
+(defun ra--cache-nth-sel (n)
+  "Get Nth selection."
+  (nth n (nth 2 ra--selections-cache)))
+(defun ra--cache-set-nth-sel (n)
+  "Get Nth selection."
+  (setf (nth 1 ra--selections-cache) n)
+  (nth n (nth 2 ra--selections-cache)))
+
+
+(defun ra-extend-selection ()
+  "Extend START END region to contain the encompassing syntactic construct."
+  (interactive)
+  (let* ((p (point))
+         (m (or (and mark-active (mark)) p))
+         (start (min p m))
+         (end (max p m)))
+    (ra--extend-selection start end)))
+
+
+(defun ra-shrink-selection (start end)
+  "Shrink START END region to contain previous selection."
+  (interactive "r")
+  (ra--freshen-cache start end)
+  (let ((sel-id (ra--cache-sel)))
+    (if (not (= 0 sel-id))
+        (let* ((r (ra--cache-set-nth-sel (- sel-id 1))))
+          (push-mark (nth 0 r) t t)
+          (goto-char (nth 1 r))
+          (setq deactivate-mark nil)))))
+
+; Add this to setup keybinding
+; (require 'rust-mode)
+; (define-key rust-mode-map (kbd "C-w") 'ra-extend-selection)
+; (define-key rust-mode-map (kbd "C-S-w") 'ra-shrink-selection)
+
+
+
+(defun ra--extend-selection (start end)
+  "Extend START END region to contain the encompassing syntactic construct."
+  (ra--freshen-cache start end)
+  (let* ((next-sel-idx (+ 1 (ra--cache-sel)))
+         (r (ra--cache-set-nth-sel next-sel-idx)))
+    (push-mark (nth 0 r) t t)
+    (goto-char (nth 1 r))
+    (setq deactivate-mark nil)))
+
+(defun ra--selections (start end)
+  "Get list of selections for START END from Rust analyzer."
+  (read (with-output-to-string
+          (call-process-region
+           (point-min) (point-max)
+           "ra_cli" nil standard-output nil
+           "extend-selection"
+           (number-to-string start)
+           (number-to-string end)))))
+
+(defun ra--freshen-cache (start end)
+  "Make selection cache up-to-date for current buffer state and START END."
+  (if (not (and
+            (= (buffer-modified-tick) (ra--cache-tick))
+            (equal `(,start ,end) (ra--cache-nth-sel (ra--cache-sel)))))
+      (ra--set-cache start end)))
+
+(defun ra--set-cache (start end)
+  "Set selections cache for current buffer state and START END."
+  (setq ra--selections-cache `(,(buffer-modified-tick) 0 ,(ra--selections start end))))
+
+(provide 'ra)
+;;; ra.el ends here