15 files changed, 514 insertions, 168 deletions

diff --git a/editors/code/src/client.ts b/editors/code/src/client.ts
index 1ff64a930..2e3d4aba2 100644
--- a/editors/code/src/client.ts
+++ b/editors/code/src/client.ts
@@ -1,25 +1,21 @@
-import { homedir } from 'os';
 import * as lc from 'vscode-languageclient';
-import { spawnSync } from 'child_process';
 
 import { window, workspace } from 'vscode';
 import { Config } from './config';
+import { ensureLanguageServerBinary } from './installation/language_server';
 
-export function createClient(config: Config): lc.LanguageClient {
+export async function createClient(config: Config): Promise<null | lc.LanguageClient> {
     // '.' Is the fallback if no folder is open
-    // TODO?: Workspace folders support Uri's (eg: file://test.txt). It might be a good idea to test if the uri points to a file.
-    let folder: string = '.';
-    if (workspace.workspaceFolders !== undefined) {
-        folder = workspace.workspaceFolders[0].uri.fsPath.toString();
-    }
+    // TODO?: Workspace folders support Uri's (eg: file://test.txt).
+    // It might be a good idea to test if the uri points to a file.
+    const workspaceFolderPath = workspace.workspaceFolders?.[0]?.uri.fsPath ?? '.';
+
+    const raLspServerPath = await ensureLanguageServerBinary(config.langServerSource);
+    if (!raLspServerPath) return null;
 
-    const command = expandPathResolving(config.raLspServerPath);
-    if (spawnSync(command, ["--version"]).status !== 0) {
-        window.showErrorMessage(`Unable to execute '${command} --version'`);
-    }
     const run: lc.Executable = {
-        command,
-        options: { cwd: folder },
+        command: raLspServerPath,
+        options: { cwd: workspaceFolderPath },
     };
     const serverOptions: lc.ServerOptions = {
         run,
@@ -37,8 +33,7 @@ export function createClient(config: Config): lc.LanguageClient {
             cargoWatchEnable: config.cargoWatchOptions.enable,
             cargoWatchArgs: config.cargoWatchOptions.arguments,
             cargoWatchCommand: config.cargoWatchOptions.command,
-            cargoWatchAllTargets:
-                config.cargoWatchOptions.allTargets,
+            cargoWatchAllTargets: config.cargoWatchOptions.allTargets,
             excludeGlobs: config.excludeGlobs,
             useClientWatching: config.useClientWatching,
             featureFlags: config.featureFlags,
@@ -62,7 +57,7 @@ export function createClient(config: Config): lc.LanguageClient {
     // This also requires considering our settings strategy, which is work which needs doing
     // @ts-ignore The tracer is private to vscode-languageclient, but we need access to it to not log publishDecorations requests
     res._tracer = {
-        log: (messageOrDataObject: string | any, data?: string) => {
+        log: (messageOrDataObject: string | unknown, data?: string) => {
             if (typeof messageOrDataObject === 'string') {
                 if (
                     messageOrDataObject.includes(
@@ -86,9 +81,3 @@ export function createClient(config: Config): lc.LanguageClient {
     res.registerProposedFeatures();
     return res;
 }
-function expandPathResolving(path: string) {
-    if (path.startsWith('~/')) {
-        return path.replace('~', homedir());
-    }
-    return path;
-}
diff --git a/editors/code/src/color_theme.ts b/editors/code/src/color_theme.ts
index cbad47f35..a6957a76e 100644
--- a/editors/code/src/color_theme.ts
+++ b/editors/code/src/color_theme.ts
@@ -28,9 +28,12 @@ export class ColorTheme {
     static fromRules(rules: TextMateRule[]): ColorTheme {
         const res = new ColorTheme();
         for (const rule of rules) {
-            const scopes = typeof rule.scope === 'string'
-                ? [rule.scope]
-                : rule.scope;
+            const scopes = typeof rule.scope === 'undefined'
+                ? []
+                : typeof rule.scope === 'string'
+                    ? [rule.scope]
+                    : rule.scope;
+
             for (const scope of scopes) {
                 res.rules.set(scope, rule.settings);
             }
@@ -59,7 +62,7 @@ export class ColorTheme {
 }
 
 function loadThemeNamed(themeName: string): ColorTheme {
-    function isTheme(extension: vscode.Extension<any>): boolean {
+    function isTheme(extension: vscode.Extension<unknown>): boolean {
         return (
             extension.extensionKind === vscode.ExtensionKind.UI &&
             extension.packageJSON.contributes &&
@@ -67,13 +70,13 @@ function loadThemeNamed(themeName: string): ColorTheme {
         );
     }
 
-    let themePaths = vscode.extensions.all
+    const themePaths: string[] = vscode.extensions.all
         .filter(isTheme)
-        .flatMap(ext => {
-            return ext.packageJSON.contributes.themes
+        .flatMap(
+            ext => ext.packageJSON.contributes.themes
                 .filter((it: any) => (it.id || it.label) === themeName)
-                .map((it: any) => path.join(ext.extensionPath, it.path));
-        });
+                .map((it: any) => path.join(ext.extensionPath, it.path))
+        );
 
     const res = new ColorTheme();
     for (const themePath of themePaths) {
@@ -94,13 +97,12 @@ function loadThemeFile(themePath: string): ColorTheme {
         return new ColorTheme();
     }
     const obj = jsonc.parse(text);
-    const tokenColors = obj?.tokenColors ?? [];
+    const tokenColors: TextMateRule[] = obj?.tokenColors ?? [];
     const res = ColorTheme.fromRules(tokenColors);
 
-    for (const include in obj?.include ?? []) {
+    for (const include of obj?.include ?? []) {
         const includePath = path.join(path.dirname(themePath), include);
-        const tmp = loadThemeFile(includePath);
-        res.mergeFrom(tmp);
+        res.mergeFrom(loadThemeFile(includePath));
     }
 
     return res;
diff --git a/editors/code/src/commands/index.ts b/editors/code/src/commands/index.ts
index dc075aa82..aee969432 100644
--- a/editors/code/src/commands/index.ts
+++ b/editors/code/src/commands/index.ts
@@ -4,24 +4,24 @@ import * as lc from 'vscode-languageclient';
 import { Ctx, Cmd } from '../ctx';
 import * as sourceChange from '../source_change';
 
-import { analyzerStatus } from './analyzer_status';
-import { matchingBrace } from './matching_brace';
-import { joinLines } from './join_lines';
-import { onEnter } from './on_enter';
-import { parentModule } from './parent_module';
-import { syntaxTree } from './syntax_tree';
-import { expandMacro } from './expand_macro';
-import { run, runSingle } from './runnables';
-
-function collectGarbage(ctx: Ctx): Cmd {
+export * from './analyzer_status';
+export * from './matching_brace';
+export * from './join_lines';
+export * from './on_enter';
+export * from './parent_module';
+export * from './syntax_tree';
+export * from './expand_macro';
+export * from './runnables';
+
+export function collectGarbage(ctx: Ctx): Cmd {
     return async () => {
         ctx.client?.sendRequest<null>('rust-analyzer/collectGarbage', null);
     };
 }
 
-function showReferences(ctx: Ctx): Cmd {
+export function showReferences(ctx: Ctx): Cmd {
     return (uri: string, position: lc.Position, locations: lc.Location[]) => {
-        let client = ctx.client;
+        const client = ctx.client;
         if (client) {
             vscode.commands.executeCommand(
                 'editor.action.showReferences',
@@ -33,13 +33,13 @@ function showReferences(ctx: Ctx): Cmd {
     };
 }
 
-function applySourceChange(ctx: Ctx): Cmd {
+export function applySourceChange(ctx: Ctx): Cmd {
     return async (change: sourceChange.SourceChange) => {
-        sourceChange.applySourceChange(ctx, change);
+        await sourceChange.applySourceChange(ctx, change);
     };
 }
 
-function selectAndApplySourceChange(ctx: Ctx): Cmd {
+export function selectAndApplySourceChange(ctx: Ctx): Cmd {
     return async (changes: sourceChange.SourceChange[]) => {
         if (changes.length === 1) {
             await sourceChange.applySourceChange(ctx, changes[0]);
@@ -51,26 +51,9 @@ function selectAndApplySourceChange(ctx: Ctx): Cmd {
     };
 }
 
-function reload(ctx: Ctx): Cmd {
+export function reload(ctx: Ctx): Cmd {
     return async () => {
         vscode.window.showInformationMessage('Reloading rust-analyzer...');
         await ctx.restartServer();
     };
 }
-
-export {
-    analyzerStatus,
-    expandMacro,
-    joinLines,
-    matchingBrace,
-    parentModule,
-    syntaxTree,
-    onEnter,
-    collectGarbage,
-    run,
-    runSingle,
-    showReferences,
-    applySourceChange,
-    selectAndApplySourceChange,
-    reload
-};
diff --git a/editors/code/src/commands/on_enter.ts b/editors/code/src/commands/on_enter.ts
index 6f61883cd..25eaebcbe 100644
--- a/editors/code/src/commands/on_enter.ts
+++ b/editors/code/src/commands/on_enter.ts
@@ -1,28 +1,35 @@
+import * as vscode from 'vscode';
 import * as lc from 'vscode-languageclient';
 
 import { applySourceChange, SourceChange } from '../source_change';
 import { Cmd, Ctx } from '../ctx';
 
-export function onEnter(ctx: Ctx): Cmd {
-    return async (event: { text: string }) => {
-        const editor = ctx.activeRustEditor;
-        const client = ctx.client;
-        if (!editor || event.text !== '\n') return false;
-        if (!client) return false;
+async function handleKeypress(ctx: Ctx) {
+    const editor = ctx.activeRustEditor;
+    const client = ctx.client;
+
+    if (!editor || !client) return false;
+
+    const request: lc.TextDocumentPositionParams = {
+        textDocument: { uri: editor.document.uri.toString() },
+        position: client.code2ProtocolConverter.asPosition(
+            editor.selection.active,
+        ),
+    };
+    const change = await client.sendRequest<undefined | SourceChange>(
+        'rust-analyzer/onEnter',
+        request,
+    );
+    if (!change) return false;
 
-        const request: lc.TextDocumentPositionParams = {
-            textDocument: { uri: editor.document.uri.toString() },
-            position: client.code2ProtocolConverter.asPosition(
-                editor.selection.active,
-            ),
-        };
-        const change = await client.sendRequest<undefined | SourceChange>(
-            'rust-analyzer/onEnter',
-            request,
-        );
-        if (!change) return false;
+    await applySourceChange(ctx, change);
+    return true;
+}
+
+export function onEnter(ctx: Ctx): Cmd {
+    return async () => {
+        if (await handleKeypress(ctx)) return;
 
-        await applySourceChange(ctx, change);
-        return true;
+        await vscode.commands.executeCommand('default:type', { text: '\n' });
     };
 }
diff --git a/editors/code/src/commands/syntax_tree.ts b/editors/code/src/commands/syntax_tree.ts
index 02ea9f166..7dde66ad1 100644
--- a/editors/code/src/commands/syntax_tree.ts
+++ b/editors/code/src/commands/syntax_tree.ts
@@ -22,6 +22,7 @@ export function syntaxTree(ctx: Ctx): Cmd {
             if (doc.languageId !== 'rust') return;
             afterLs(() => tdcp.eventEmitter.fire(tdcp.uri));
         },
+        null,
         ctx.subscriptions,
     );
 
@@ -30,6 +31,7 @@ export function syntaxTree(ctx: Ctx): Cmd {
             if (!editor || editor.document.languageId !== 'rust') return;
             tdcp.eventEmitter.fire(tdcp.uri);
         },
+        null,
         ctx.subscriptions,
     );
 
@@ -55,7 +57,7 @@ export function syntaxTree(ctx: Ctx): Cmd {
 
 // We need to order this after LS updates, but there's no API for that.
 // Hence, good old setTimeout.
-function afterLs(f: () => any) {
+function afterLs(f: () => void) {
     setTimeout(f, 10);
 }
 
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index fc21c8813..d5f3da2ed 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -1,4 +1,6 @@
+import * as os from "os";
 import * as vscode from 'vscode';
+import { BinarySource } from "./installation/interfaces";
 
 const RA_LSP_DEBUG = process.env.__RA_LSP_SERVER_DEBUG;
 
@@ -16,16 +18,17 @@ export interface CargoFeatures {
 }
 
 export class Config {
+    langServerSource!: null | BinarySource;
+
     highlightingOn = true;
     rainbowHighlightingOn = false;
     enableEnhancedTyping = true;
-    raLspServerPath = RA_LSP_DEBUG || 'ra_lsp_server';
     lruCapacity: null | number = null;
     displayInlayHints = true;
     maxInlayHintLength: null | number = null;
-    excludeGlobs = [];
+    excludeGlobs: string[] = [];
     useClientWatching = true;
-    featureFlags = {};
+    featureFlags: Record<string, boolean> = {};
     // for internal use
     withSysroot: null | boolean = null;
     cargoWatchOptions: CargoWatchOptions = {
@@ -45,11 +48,72 @@ export class Config {
     private prevCargoWatchOptions: null | CargoWatchOptions = null;
 
     constructor(ctx: vscode.ExtensionContext) {
-        vscode.workspace.onDidChangeConfiguration(_ => this.refresh(), ctx.subscriptions);
-        this.refresh();
+        vscode.workspace.onDidChangeConfiguration(_ => this.refresh(ctx), null, ctx.subscriptions);
+        this.refresh(ctx);
+    }
+
+    private static expandPathResolving(path: string) {
+        if (path.startsWith('~/')) {
+            return path.replace('~', os.homedir());
+        }
+        return path;
+    }
+
+    /**
+     * Name of the binary artifact for `ra_lsp_server` that is published for
+     * `platform` on GitHub releases. (It is also stored under the same name when
+     * downloaded by the extension).
+     */
+    private static prebuiltLangServerFileName(platform: NodeJS.Platform): null | string {
+        switch (platform) {
+            case "linux":  return "ra_lsp_server-linux";
+            case "darwin": return "ra_lsp_server-mac";
+            case "win32":  return "ra_lsp_server-windows.exe";
+
+            // Users on these platforms yet need to manually build from sources
+            case "aix":
+            case "android":
+            case "freebsd":
+            case "openbsd":
+            case "sunos":
+            case "cygwin":
+            case "netbsd": return null;
+            // The list of platforms is exhaustive (see `NodeJS.Platform` type definition)
+        }
+    }
+
+    private static langServerBinarySource(
+        ctx: vscode.ExtensionContext,
+        config: vscode.WorkspaceConfiguration
+    ): null | BinarySource {
+        const langServerPath = RA_LSP_DEBUG ?? config.get<null | string>("raLspServerPath");
+
+        if (langServerPath) {
+            return {
+                type: BinarySource.Type.ExplicitPath,
+                path: Config.expandPathResolving(langServerPath)
+            };
+        }
+
+        const prebuiltBinaryName = Config.prebuiltLangServerFileName(process.platform);
+
+        if (!prebuiltBinaryName) return null;
+
+        return {
+            type: BinarySource.Type.GithubRelease,
+            dir: ctx.globalStoragePath,
+            file: prebuiltBinaryName,
+            repo: {
+                name: "rust-analyzer",
+                owner: "rust-analyzer",
+            }
+        };
     }
 
-    private refresh() {
+
+    // FIXME: revisit the logic for `if (.has(...)) config.get(...)` set default
+    // values only in one place (i.e. remove default values from non-readonly members declarations)
+    private refresh(ctx: vscode.ExtensionContext) {
         const config = vscode.workspace.getConfiguration('rust-analyzer');
 
         let requireReloadMessage = null;
@@ -82,10 +146,7 @@ export class Config {
             this.prevEnhancedTyping = this.enableEnhancedTyping;
         }
 
-        if (config.has('raLspServerPath')) {
-            this.raLspServerPath =
-                RA_LSP_DEBUG || (config.get('raLspServerPath') as string);
-        }
+        this.langServerSource = Config.langServerBinarySource(ctx, config);
 
         if (config.has('cargo-watch.enable')) {
             this.cargoWatchOptions.enable = config.get<boolean>(
diff --git a/editors/code/src/ctx.ts b/editors/code/src/ctx.ts
index a2a4e42a9..70042a479 100644
--- a/editors/code/src/ctx.ts
+++ b/editors/code/src/ctx.ts
@@ -1,5 +1,6 @@
 import * as vscode from 'vscode';
 import * as lc from 'vscode-languageclient';
+
 import { Config } from './config';
 import { createClient } from './client';
 
@@ -10,6 +11,9 @@ export class Ctx {
     // deal with it.
     //
     // Ideally, this should be replaced with async getter though.
+    // FIXME: this actually needs syncronization of some kind (check how
+    // vscode deals with `deactivate()` call when extension has some work scheduled
+    // on the event loop to get a better picture of what we can do here)
     client: lc.LanguageClient | null = null;
     private extCtx: vscode.ExtensionContext;
     private onDidRestartHooks: Array<(client: lc.LanguageClient) => void> = [];
@@ -20,12 +24,19 @@ export class Ctx {
     }
 
     async restartServer() {
-        let old = this.client;
+        const old = this.client;
         if (old) {
             await old.stop();
         }
         this.client = null;
-        const client = createClient(this.config);
+        const client = await createClient(this.config);
+        if (!client) {
+            throw new Error(
+                "Rust Analyzer Language Server is not available. " +
+                "Please, ensure its [proper installation](https://github.com/rust-analyzer/rust-analyzer/tree/master/docs/user#vs-code)."
+            );
+        }
+
         this.pushCleanup(client.start());
         await client.onReady();
 
@@ -49,33 +60,11 @@ export class Ctx {
         this.pushCleanup(d);
     }
 
-    overrideCommand(name: string, factory: (ctx: Ctx) => Cmd) {
-        const defaultCmd = `default:${name}`;
-        const override = factory(this);
-        const original = (...args: any[]) =>
-            vscode.commands.executeCommand(defaultCmd, ...args);
-        try {
-            const d = vscode.commands.registerCommand(
-                name,
-                async (...args: any[]) => {
-                    if (!(await override(...args))) {
-                        return await original(...args);
-                    }
-                },
-            );
-            this.pushCleanup(d);
-        } catch (_) {
-            vscode.window.showWarningMessage(
-                'Enhanced typing feature is disabled because of incompatibility with VIM extension, consider turning off rust-analyzer.enableEnhancedTyping: https://github.com/rust-analyzer/rust-analyzer/blob/master/docs/user/README.md#settings',
-            );
-        }
-    }
-
-    get subscriptions(): { dispose(): any }[] {
+    get subscriptions(): Disposable[] {
         return this.extCtx.subscriptions;
     }
 
-    pushCleanup(d: { dispose(): any }) {
+    pushCleanup(d: Disposable) {
         this.extCtx.subscriptions.push(d);
     }
 
@@ -84,12 +73,15 @@ export class Ctx {
     }
 }
 
-export type Cmd = (...args: any[]) => any;
+export interface Disposable {
+    dispose(): void;
+}
+export type Cmd = (...args: any[]) => unknown;
 
 export async function sendRequestWithRetry<R>(
     client: lc.LanguageClient,
     method: string,
-    param: any,
+    param: unknown,
     token?: vscode.CancellationToken,
 ): Promise<R> {
     for (const delay of [2, 4, 6, 8, 10, null]) {
diff --git a/editors/code/src/highlighting.ts b/editors/code/src/highlighting.ts
index 014e96f75..4fbbe3ddc 100644
--- a/editors/code/src/highlighting.ts
+++ b/editors/code/src/highlighting.ts
@@ -1,7 +1,5 @@
 import * as vscode from 'vscode';
 import * as lc from 'vscode-languageclient';
-import * as seedrandom_ from 'seedrandom';
-const seedrandom = seedrandom_; // https://github.com/jvandemo/generator-angular2-library/issues/221#issuecomment-355945207
 
 import { ColorTheme, TextMateRuleSettings } from './color_theme';
 
@@ -34,6 +32,7 @@ export function activateHighlighting(ctx: Ctx) {
 
     vscode.workspace.onDidChangeConfiguration(
         _ => highlighter.removeHighlights(),
+        null,
         ctx.subscriptions,
     );
 
@@ -41,7 +40,7 @@ export function activateHighlighting(ctx: Ctx) {
         async (editor: vscode.TextEditor | undefined) => {
             if (!editor || editor.document.languageId !== 'rust') return;
             if (!ctx.config.highlightingOn) return;
-            let client = ctx.client;
+            const client = ctx.client;
             if (!client) return;
 
             const params: lc.TextDocumentIdentifier = {
@@ -54,6 +53,7 @@ export function activateHighlighting(ctx: Ctx) {
             );
             highlighter.setHighlights(editor, decorations);
         },
+        null,
         ctx.subscriptions,
     );
 }
@@ -71,9 +71,9 @@ interface Decoration {
 
 // Based on this HSL-based color generator: https://gist.github.com/bendc/76c48ce53299e6078a76
 function fancify(seed: string, shade: 'light' | 'dark') {
-    const random = seedrandom(seed);
+    const random = randomU32Numbers(hashString(seed));
     const randomInt = (min: number, max: number) => {
-        return Math.floor(random() * (max - min + 1)) + min;
+        return Math.abs(random()) % (max - min + 1) + min;
     };
 
     const h = randomInt(0, 360);
@@ -107,7 +107,7 @@ class Highlighter {
     }
 
     public setHighlights(editor: vscode.TextEditor, highlights: Decoration[]) {
-        let client = this.ctx.client;
+        const client = this.ctx.client;
         if (!client) return;
         // Initialize decorations if necessary
         //
@@ -176,7 +176,7 @@ function initDecorations(): Map<string, vscode.TextEditorDecorationType> {
     const res = new Map();
     TAG_TO_SCOPES.forEach((scopes, tag) => {
         if (!scopes) throw `unmapped tag: ${tag}`;
-        let rule = theme.lookup(scopes);
+        const rule = theme.lookup(scopes);
         const decor = createDecorationFromTextmate(rule);
         res.set(tag, decor);
     });
@@ -247,3 +247,23 @@ const TAG_TO_SCOPES = new Map<string, string[]>([
     ["keyword.unsafe", ["keyword.other.unsafe"]],
     ["keyword.control", ["keyword.control"]],
 ]);
+
+function randomU32Numbers(seed: number) {
+    let random = seed | 0;
+    return () => {
+        random ^= random << 13;
+        random ^= random >> 17;
+        random ^= random << 5;
+        random |= 0;
+        return random;
+    };
+}
+
+function hashString(str: string): number {
+    let res = 0;
+    for (let i = 0; i < str.length; ++i) {
+        const c = str.codePointAt(i)!;
+        res = (res * 31 + c) & ~0;
+    }
+    return res;
+}
diff --git a/editors/code/src/inlay_hints.ts b/editors/code/src/inlay_hints.ts
index 6357e44f1..1c019a51b 100644
--- a/editors/code/src/inlay_hints.ts
+++ b/editors/code/src/inlay_hints.ts
@@ -5,19 +5,27 @@ import { Ctx, sendRequestWithRetry } from './ctx';
 
 export function activateInlayHints(ctx: Ctx) {
     const hintsUpdater = new HintsUpdater(ctx);
-    vscode.window.onDidChangeVisibleTextEditors(async _ => {
-        await hintsUpdater.refresh();
-    }, ctx.subscriptions);
-
-    vscode.workspace.onDidChangeTextDocument(async e => {
-        if (e.contentChanges.length === 0) return;
-        if (e.document.languageId !== 'rust') return;
-        await hintsUpdater.refresh();
-    }, ctx.subscriptions);
-
-    vscode.workspace.onDidChangeConfiguration(_ => {
-        hintsUpdater.setEnabled(ctx.config.displayInlayHints);
-    }, ctx.subscriptions);
+    vscode.window.onDidChangeVisibleTextEditors(
+        async _ => hintsUpdater.refresh(),
+        null,
+        ctx.subscriptions
+    );
+
+    vscode.workspace.onDidChangeTextDocument(
+        async event => {
+            if (event.contentChanges.length !== 0) return;
+            if (event.document.languageId !== 'rust') return;
+            await hintsUpdater.refresh();
+        },
+        null,
+        ctx.subscriptions
+    );
+
+    vscode.workspace.onDidChangeConfiguration(
+        async _ => hintsUpdater.setEnabled(ctx.config.displayInlayHints),
+        null,
+        ctx.subscriptions
+    );
 
     ctx.onDidRestart(_ => hintsUpdater.setEnabled(ctx.config.displayInlayHints));
 }
@@ -127,13 +135,13 @@ class HintsUpdater {
     }
 
     private async queryHints(documentUri: string): Promise<InlayHint[] | null> {
-        let client = this.ctx.client;
+        const client = this.ctx.client;
         if (!client) return null;
         const request: InlayHintsParams = {
             textDocument: { uri: documentUri },
         };
-        let tokenSource = new vscode.CancellationTokenSource();
-        let prev = this.pending.get(documentUri);
+        const tokenSource = new vscode.CancellationTokenSource();
+        const prev = this.pending.get(documentUri);
         if (prev) prev.cancel();
         this.pending.set(documentUri, tokenSource);
         try {
diff --git a/editors/code/src/installation/download_file.ts b/editors/code/src/installation/download_file.ts
new file mode 100644
index 000000000..b51602ef9
--- /dev/null
+++ b/editors/code/src/installation/download_file.ts
@@ -0,0 +1,34 @@
+import fetch from "node-fetch";
+import * as fs from "fs";
+import { strict as assert } from "assert";
+
+/**
+ * Downloads file from `url` and stores it at `destFilePath`.
+ * `onProgress` callback is called on recieveing each chunk of bytes
+ * to track the progress of downloading, it gets the already read and total
+ * amount of bytes to read as its parameters.
+ */
+export async function downloadFile(
+    url: string,
+    destFilePath: fs.PathLike,
+    onProgress: (readBytes: number, totalBytes: number) => void
+): Promise<void> {
+    const response = await fetch(url);
+
+    const totalBytes = Number(response.headers.get('content-length'));
+    assert(!Number.isNaN(totalBytes), "Sanity check of content-length protocol");
+
+    let readBytes = 0;
+
+    console.log("Downloading file of", totalBytes, "bytes size from", url, "to", destFilePath);
+
+    return new Promise<void>((resolve, reject) => response.body
+        .on("data", (chunk: Buffer) => {
+            readBytes += chunk.length;
+            onProgress(readBytes, totalBytes);
+        })
+        .on("end", resolve)
+        .on("error", reject)
+        .pipe(fs.createWriteStream(destFilePath))
+    );
+}
diff --git a/editors/code/src/installation/fetch_latest_artifact_metadata.ts b/editors/code/src/installation/fetch_latest_artifact_metadata.ts
new file mode 100644
index 000000000..7e3700603
--- /dev/null
+++ b/editors/code/src/installation/fetch_latest_artifact_metadata.ts
@@ -0,0 +1,46 @@
+import fetch from "node-fetch";
+import { GithubRepo, ArtifactMetadata } from "./interfaces";
+
+const GITHUB_API_ENDPOINT_URL = "https://api.github.com";
+
+/**
+ * Fetches the latest release from GitHub `repo` and returns metadata about
+ * `artifactFileName` shipped with this release or `null` if no such artifact was published.
+ */
+export async function fetchLatestArtifactMetadata(
+    repo: GithubRepo, artifactFileName: string
+): Promise<null | ArtifactMetadata> {
+
+    const repoOwner = encodeURIComponent(repo.owner);
+    const repoName  = encodeURIComponent(repo.name);
+
+    const apiEndpointPath = `/repos/${repoOwner}/${repoName}/releases/latest`;
+    const requestUrl = GITHUB_API_ENDPOINT_URL + apiEndpointPath;
+
+    // We skip runtime type checks for simplicity (here we cast from `any` to `GithubRelease`)
+
+    console.log("Issuing request for released artifacts metadata to", requestUrl);
+
+    const response: GithubRelease = await fetch(requestUrl, {
+            headers: { Accept: "application/vnd.github.v3+json" }
+        })
+        .then(res => res.json());
+
+    const artifact = response.assets.find(artifact => artifact.name === artifactFileName);
+
+    if (!artifact) return null;
+
+    return {
+        releaseName: response.name,
+        downloadUrl: artifact.browser_download_url
+    };
+
+    // We omit declaration of tremendous amount of fields that we are not using here
+    interface GithubRelease {
+        name: string;
+        assets: Array<{
+            name: string;
+            browser_download_url: string;
+        }>;
+    }
+}
diff --git a/editors/code/src/installation/interfaces.ts b/editors/code/src/installation/interfaces.ts
new file mode 100644
index 000000000..8039d0b90
--- /dev/null
+++ b/editors/code/src/installation/interfaces.ts
@@ -0,0 +1,55 @@
+export interface GithubRepo {
+    name: string;
+    owner: string;
+}
+
+/**
+ * Metadata about particular artifact retrieved from GitHub releases.
+ */
+export interface ArtifactMetadata {
+    releaseName: string;
+    downloadUrl: string;
+}
+
+/**
+ * Represents the source of a binary artifact which is either specified by the user
+ * explicitly, or bundled by this extension from GitHub releases.
+ */
+export type BinarySource = BinarySource.ExplicitPath | BinarySource.GithubRelease;
+
+export namespace BinarySource {
+    /**
+     * Type tag for `BinarySource` discriminated union.
+     */
+    export const enum Type { ExplicitPath, GithubRelease }
+
+    export interface ExplicitPath {
+        type: Type.ExplicitPath;
+
+        /**
+         * Filesystem path to the binary specified by the user explicitly.
+         */
+        path: string;
+    }
+
+    export interface GithubRelease {
+        type: Type.GithubRelease;
+
+        /**
+         * Repository where the binary is stored.
+         */
+        repo: GithubRepo;
+
+        /**
+         * Directory on the filesystem where the bundled binary is stored.
+         */
+        dir: string;
+
+        /**
+         * Name of the binary file. It is stored under the same name on GitHub releases
+         * and in local `.dir`.
+         */
+        file: string;
+    }
+
+}
diff --git a/editors/code/src/installation/language_server.ts b/editors/code/src/installation/language_server.ts
new file mode 100644
index 000000000..1ce67b8b2
--- /dev/null
+++ b/editors/code/src/installation/language_server.ts
@@ -0,0 +1,141 @@
+import * as vscode from "vscode";
+import * as path from "path";
+import { strict as assert } from "assert";
+import { promises as fs } from "fs";
+import { promises as dns } from "dns";
+import { spawnSync } from "child_process";
+import { throttle } from "throttle-debounce";
+
+import { BinarySource } from "./interfaces";
+import { fetchLatestArtifactMetadata } from "./fetch_latest_artifact_metadata";
+import { downloadFile } from "./download_file";
+
+export async function downloadLatestLanguageServer(
+    {file: artifactFileName, dir: installationDir, repo}: BinarySource.GithubRelease
+) {
+    const { releaseName, downloadUrl } = (await fetchLatestArtifactMetadata(
+        repo, artifactFileName
+    ))!;
+
+    await fs.mkdir(installationDir).catch(err => assert.strictEqual(
+        err?.code,
+        "EEXIST",
+        `Couldn't create directory "${installationDir}" to download `+
+        `language server binary: ${err.message}`
+    ));
+
+    const installationPath = path.join(installationDir, artifactFileName);
+
+    console.time("Downloading ra_lsp_server");
+    await vscode.window.withProgress(
+        {
+            location: vscode.ProgressLocation.Notification,
+            cancellable: false, // FIXME: add support for canceling download?
+            title: `Downloading language server (${releaseName})`
+        },
+        async (progress, _cancellationToken) => {
+            let lastPrecentage = 0;
+            await downloadFile(downloadUrl, installationPath, throttle(
+                200,
+                /* noTrailing: */ true,
+                (readBytes, totalBytes) => {
+                    const newPercentage = (readBytes / totalBytes) * 100;
+                    progress.report({
+                        message: newPercentage.toFixed(0) + "%",
+                        increment: newPercentage - lastPrecentage
+                    });
+
+                    lastPrecentage = newPercentage;
+                })
+            );
+        }
+    );
+    console.timeEnd("Downloading ra_lsp_server");
+
+    await fs.chmod(installationPath, 0o755); // Set (rwx, r_x, r_x) permissions
+}
+export async function ensureLanguageServerBinary(
+    langServerSource: null | BinarySource
+): Promise<null | string> {
+
+    if (!langServerSource) {
+        vscode.window.showErrorMessage(
+            "Unfortunately we don't ship binaries for your platform yet. " +
+            "You need to manually clone rust-analyzer repository and " +
+            "run `cargo xtask install --server` to build the language server from sources. " +
+            "If you feel that your platform should be supported, please create an issue " +
+            "about that [here](https://github.com/rust-analyzer/rust-analyzer/issues) and we " +
+            "will consider it."
+        );
+        return null;
+    }
+
+    switch (langServerSource.type) {
+        case BinarySource.Type.ExplicitPath: {
+            if (isBinaryAvailable(langServerSource.path)) {
+                return langServerSource.path;
+            }
+
+            vscode.window.showErrorMessage(
+                `Unable to run ${langServerSource.path} binary. ` +
+                `To use the pre-built language server, set "rust-analyzer.raLspServerPath" ` +
+                "value to `null` or remove it from the settings to use it by default."
+            );
+            return null;
+        }
+        case BinarySource.Type.GithubRelease: {
+            const prebuiltBinaryPath = path.join(langServerSource.dir, langServerSource.file);
+
+            if (isBinaryAvailable(prebuiltBinaryPath)) {
+                return prebuiltBinaryPath;
+            }
+
+            const userResponse = await vscode.window.showInformationMessage(
+                "Language server binary for rust-analyzer was not found. " +
+                "Do you want to download it now?",
+                "Download now", "Cancel"
+            );
+            if (userResponse !== "Download now") return null;
+
+            try {
+                await downloadLatestLanguageServer(langServerSource);
+            } catch (err) {
+                await vscode.window.showErrorMessage(
+                    `Failed to download language server from ${langServerSource.repo.name} ` +
+                    `GitHub repository: ${err.message}`
+                );
+
+                await dns.resolve('www.google.com').catch(err => {
+                    console.error("DNS resolution failed, there might be an issue with Internet availability");
+                    console.error(err);
+                });
+
+                return null;
+            }
+
+            if (!isBinaryAvailable(prebuiltBinaryPath)) assert(false,
+                `Downloaded language server binary is not functional.` +
+                `Downloaded from: ${JSON.stringify(langServerSource)}`
+            );
+
+
+            vscode.window.showInformationMessage(
+                "Rust analyzer language server was successfully installed 🦀"
+            );
+
+            return prebuiltBinaryPath;
+        }
+    }
+
+    function isBinaryAvailable(binaryPath: string) {
+        const res = spawnSync(binaryPath, ["--version"]);
+
+        // ACHTUNG! `res` type declaration is inherently wrong, see
+        // https://github.com/DefinitelyTyped/DefinitelyTyped/issues/42221
+
+        console.log("Checked binary availablity via --version", res);
+        console.log(binaryPath, "--version output:", res.output?.map(String));
+
+        return res.status === 0;
+    }
+}
diff --git a/editors/code/src/main.ts b/editors/code/src/main.ts
index 0494ccf63..5efce41f4 100644
--- a/editors/code/src/main.ts
+++ b/editors/code/src/main.ts
@@ -6,12 +6,12 @@ import { activateStatusDisplay } from './status_display';
 import { Ctx } from './ctx';
 import { activateHighlighting } from './highlighting';
 
-let ctx!: Ctx;
+let ctx: Ctx | undefined;
 
 export async function activate(context: vscode.ExtensionContext) {
     ctx = new Ctx(context);
 
-    // Commands which invokes manually via command pallet, shortcut, etc.
+    // Commands which invokes manually via command palette, shortcut, etc.
     ctx.registerCommand('analyzerStatus', commands.analyzerStatus);
     ctx.registerCommand('collectGarbage', commands.collectGarbage);
     ctx.registerCommand('matchingBrace', commands.matchingBrace);
@@ -21,6 +21,7 @@ export async function activate(context: vscode.ExtensionContext) {
     ctx.registerCommand('expandMacro', commands.expandMacro);
     ctx.registerCommand('run', commands.run);
     ctx.registerCommand('reload', commands.reload);
+    ctx.registerCommand('onEnter', commands.onEnter);
 
     // Internal commands which are invoked by the server.
     ctx.registerCommand('runSingle', commands.runSingle);
@@ -28,9 +29,6 @@ export async function activate(context: vscode.ExtensionContext) {
     ctx.registerCommand('applySourceChange', commands.applySourceChange);
     ctx.registerCommand('selectAndApplySourceChange', commands.selectAndApplySourceChange);
 
-    if (ctx.config.enableEnhancedTyping) {
-        ctx.overrideCommand('type', commands.onEnter);
-    }
     activateStatusDisplay(ctx);
 
     activateHighlighting(ctx);
diff --git a/editors/code/src/status_display.ts b/editors/code/src/status_display.ts
index c75fddf9d..51dbf388b 100644
--- a/editors/code/src/status_display.ts
+++ b/editors/code/src/status_display.ts
@@ -1,6 +1,6 @@
 import * as vscode from 'vscode';
 
-import { WorkDoneProgress, WorkDoneProgressBegin, WorkDoneProgressReport, WorkDoneProgressEnd } from 'vscode-languageclient';
+import { WorkDoneProgress, WorkDoneProgressBegin, WorkDoneProgressReport, WorkDoneProgressEnd, Disposable } from 'vscode-languageclient';
 
 import { Ctx } from './ctx';
 
@@ -9,15 +9,17 @@ const spinnerFrames = ['⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '
 export function activateStatusDisplay(ctx: Ctx) {
     const statusDisplay = new StatusDisplay(ctx.config.cargoWatchOptions.command);
     ctx.pushCleanup(statusDisplay);
-    ctx.onDidRestart(client => {
-        client.onProgress(WorkDoneProgress.type, 'rustAnalyzer/cargoWatcher', params => statusDisplay.handleProgressNotification(params));
-    });
+    ctx.onDidRestart(client => ctx.pushCleanup(client.onProgress(
+        WorkDoneProgress.type,
+        'rustAnalyzer/cargoWatcher',
+        params => statusDisplay.handleProgressNotification(params)
+    )));
 }
 
-class StatusDisplay implements vscode.Disposable {
+class StatusDisplay implements Disposable {
     packageName?: string;
 
-    private i = 0;
+    private i: number = 0;
     private statusBarItem: vscode.StatusBarItem;
     private command: string;
     private timer?: NodeJS.Timeout;
@@ -37,11 +39,8 @@ class StatusDisplay implements vscode.Disposable {
         this.timer =
             this.timer ||
             setInterval(() => {
-                if (this.packageName) {
-                    this.statusBarItem!.text = `${this.frame()} cargo ${this.command} [${this.packageName}]`;
-                } else {
-                    this.statusBarItem!.text = `${this.frame()} cargo ${this.command}`;
-                }
+                this.tick();
+                this.refreshLabel();
             }, 300);
 
         this.statusBarItem.show();
@@ -65,6 +64,14 @@ class StatusDisplay implements vscode.Disposable {
         this.statusBarItem.dispose();
     }
 
+    refreshLabel() {
+        if (this.packageName) {
+            this.statusBarItem!.text = `${spinnerFrames[this.i]} cargo ${this.command} [${this.packageName}]`;
+        } else {
+            this.statusBarItem!.text = `${spinnerFrames[this.i]} cargo ${this.command}`;
+        }
+    }
+
     handleProgressNotification(params: WorkDoneProgressBegin | WorkDoneProgressReport | WorkDoneProgressEnd) {
         switch (params.kind) {
             case 'begin':
@@ -74,6 +81,7 @@ class StatusDisplay implements vscode.Disposable {
             case 'report':
                 if (params.message) {
                     this.packageName = params.message;
+                    this.refreshLabel();
                 }
                 break;
 
@@ -83,7 +91,7 @@ class StatusDisplay implements vscode.Disposable {
         }
     }
 
-    private frame() {
-        return spinnerFrames[(this.i = ++this.i % spinnerFrames.length)];
+    private tick() {
+        this.i = (this.i + 1) % spinnerFrames.length;
     }
 }