13 files changed, 160 insertions, 171 deletions

diff --git a/README.md b/README.md
index 74c971c0d..979e4ef88 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,8 @@ $ cargo xtask install
 $ cargo xtask install --server
 ```
 
-For non-standard setup of VS Code and other editors, see [./docs/user](./docs/user).
+For non-standard setup of VS Code and other editors, or if the language server
+cannot start, see [./docs/user](./docs/user).
 
 ## Documentation
 
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index 71c08f024..cc068ff94 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -437,9 +437,7 @@ where
                     None => self.alloc_expr(Expr::Missing, syntax_ptr),
                 }
             }
-
-            // FIXME implement HIR for these:
-            ast::Expr::Label(_e) => self.alloc_expr(Expr::Missing, syntax_ptr),
+            // FIXME expand to statements in statement position
             ast::Expr::MacroCall(e) => match self.expander.enter_expand(self.db, e) {
                 Some((mark, expansion)) => {
                     let id = self.collect_expr(expansion);
@@ -448,6 +446,9 @@ where
                 }
                 None => self.alloc_expr(Expr::Missing, syntax_ptr),
             },
+
+            // FIXME implement HIR for these:
+            ast::Expr::Label(_e) => self.alloc_expr(Expr::Missing, syntax_ptr),
         }
     }
 
diff --git a/crates/ra_hir_def/src/nameres/collector.rs b/crates/ra_hir_def/src/nameres/collector.rs
index 3ff071f9e..a80067979 100644
--- a/crates/ra_hir_def/src/nameres/collector.rs
+++ b/crates/ra_hir_def/src/nameres/collector.rs
@@ -12,7 +12,7 @@ use hir_expand::{
 use ra_cfg::CfgOptions;
 use ra_db::{CrateId, FileId};
 use ra_syntax::ast;
-use rustc_hash::{FxHashMap, FxHashSet};
+use rustc_hash::FxHashMap;
 use test_utils::tested_by;
 
 use crate::{
@@ -63,42 +63,12 @@ pub(super) fn collect_defs(db: &impl DefDatabase, mut def_map: CrateDefMap) -> C
         unexpanded_macros: Vec::new(),
         unexpanded_attribute_macros: Vec::new(),
         mod_dirs: FxHashMap::default(),
-        macro_stack_monitor: MacroStackMonitor::default(),
-        poison_macros: FxHashSet::default(),
         cfg_options,
     };
     collector.collect();
     collector.finish()
 }
 
-#[derive(Default)]
-struct MacroStackMonitor {
-    counts: FxHashMap<MacroDefId, u32>,
-
-    /// Mainly use for test
-    validator: Option<Box<dyn Fn(u32) -> bool>>,
-}
-
-impl MacroStackMonitor {
-    fn increase(&mut self, macro_def_id: MacroDefId) {
-        *self.counts.entry(macro_def_id).or_default() += 1;
-    }
-
-    fn decrease(&mut self, macro_def_id: MacroDefId) {
-        *self.counts.entry(macro_def_id).or_default() -= 1;
-    }
-
-    fn is_poison(&self, macro_def_id: MacroDefId) -> bool {
-        let cur = *self.counts.get(&macro_def_id).unwrap_or(&0);
-
-        if let Some(validator) = &self.validator {
-            validator(cur)
-        } else {
-            cur > 100
-        }
-    }
-}
-
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 enum PartialResolvedImport {
     /// None of any namespaces is resolved
@@ -127,6 +97,14 @@ struct ImportDirective {
     status: PartialResolvedImport,
 }
 
+#[derive(Clone, Debug, Eq, PartialEq)]
+struct MacroDirective {
+    module_id: LocalModuleId,
+    ast_id: AstId<ast::MacroCall>,
+    path: Path,
+    legacy: Option<MacroCallId>,
+}
+
 /// Walks the tree of module recursively
 struct DefCollector<'a, DB> {
     db: &'a DB,
@@ -134,25 +112,9 @@ struct DefCollector<'a, DB> {
     glob_imports: FxHashMap<LocalModuleId, Vec<(LocalModuleId, LocalImportId)>>,
     unresolved_imports: Vec<ImportDirective>,
     resolved_imports: Vec<ImportDirective>,
-    unexpanded_macros: Vec<(LocalModuleId, AstId<ast::MacroCall>, Path)>,
+    unexpanded_macros: Vec<MacroDirective>,
     unexpanded_attribute_macros: Vec<(LocalModuleId, AstId<ast::ModuleItem>, Path)>,
     mod_dirs: FxHashMap<LocalModuleId, ModDir>,
-
-    /// Some macro use `$tt:tt which mean we have to handle the macro perfectly
-    /// To prevent stack overflow, we add a deep counter here for prevent that.
-    macro_stack_monitor: MacroStackMonitor,
-    /// Some macros are not well-behavior, which leads to infinite loop
-    /// e.g. macro_rules! foo { ($ty:ty) => { foo!($ty); } }
-    /// We mark it down and skip it in collector
-    ///
-    /// FIXME:
-    /// Right now it only handle a poison macro in a single crate,
-    /// such that if other crate try to call that macro,
-    /// the whole process will do again until it became poisoned in that crate.
-    /// We should handle this macro set globally
-    /// However, do we want to put it as a global variable?
-    poison_macros: FxHashSet<MacroDefId>,
-
     cfg_options: &'a CfgOptions,
 }
 
@@ -556,18 +518,24 @@ where
             std::mem::replace(&mut self.unexpanded_attribute_macros, Vec::new());
         let mut resolved = Vec::new();
         let mut res = ReachedFixedPoint::Yes;
-        macros.retain(|(module_id, ast_id, path)| {
+        macros.retain(|directive| {
+            if let Some(call_id) = directive.legacy {
+                res = ReachedFixedPoint::No;
+                resolved.push((directive.module_id, call_id));
+                return false;
+            }
+
             let resolved_res = self.def_map.resolve_path_fp_with_macro(
                 self.db,
                 ResolveMode::Other,
-                *module_id,
-                path,
+                directive.module_id,
+                &directive.path,
                 BuiltinShadowMode::Module,
             );
 
             if let Some(def) = resolved_res.resolved_def.take_macros() {
-                let call_id = def.as_call_id(self.db, MacroCallKind::FnLike(*ast_id));
-                resolved.push((*module_id, call_id, def));
+                let call_id = def.as_call_id(self.db, MacroCallKind::FnLike(directive.ast_id));
+                resolved.push((directive.module_id, call_id));
                 res = ReachedFixedPoint::No;
                 return false;
             }
@@ -579,7 +547,7 @@ where
 
             if let Some(def) = resolved_res {
                 let call_id = def.as_call_id(self.db, MacroCallKind::Attr(*ast_id));
-                resolved.push((*module_id, call_id, def));
+                resolved.push((*module_id, call_id));
                 res = ReachedFixedPoint::No;
                 return false;
             }
@@ -590,8 +558,8 @@ where
         self.unexpanded_macros = macros;
         self.unexpanded_attribute_macros = attribute_macros;
 
-        for (module_id, macro_call_id, macro_def_id) in resolved {
-            self.collect_macro_expansion(module_id, macro_call_id, macro_def_id);
+        for (module_id, macro_call_id) in resolved {
+            self.collect_macro_expansion(module_id, macro_call_id);
         }
 
         res
@@ -611,36 +579,18 @@ where
         None
     }
 
-    fn collect_macro_expansion(
-        &mut self,
-        module_id: LocalModuleId,
-        macro_call_id: MacroCallId,
-        macro_def_id: MacroDefId,
-    ) {
-        if self.poison_macros.contains(&macro_def_id) {
-            return;
-        }
-
-        self.macro_stack_monitor.increase(macro_def_id);
-
-        if !self.macro_stack_monitor.is_poison(macro_def_id) {
-            let file_id: HirFileId = macro_call_id.as_file();
-            let raw_items = self.db.raw_items(file_id);
-            let mod_dir = self.mod_dirs[&module_id].clone();
-            ModCollector {
-                def_collector: &mut *self,
-                file_id,
-                module_id,
-                raw_items: &raw_items,
-                mod_dir,
-            }
-            .collect(raw_items.items());
-        } else {
-            log::error!("Too deep macro expansion: {:?}", macro_call_id);
-            self.poison_macros.insert(macro_def_id);
+    fn collect_macro_expansion(&mut self, module_id: LocalModuleId, macro_call_id: MacroCallId) {
+        let file_id: HirFileId = macro_call_id.as_file();
+        let raw_items = self.db.raw_items(file_id);
+        let mod_dir = self.mod_dirs[&module_id].clone();
+        ModCollector {
+            def_collector: &mut *self,
+            file_id,
+            module_id,
+            raw_items: &raw_items,
+            mod_dir,
         }
-
-        self.macro_stack_monitor.decrease(macro_def_id);
+        .collect(raw_items.items());
     }
 
     fn finish(self) -> CrateDefMap {
@@ -908,15 +858,20 @@ where
             return;
         }
 
-        // Case 2: try to resolve in legacy scope and expand macro_rules, triggering
-        // recursive item collection.
+        // Case 2: try to resolve in legacy scope and expand macro_rules
         if let Some(macro_def) = mac.path.as_ident().and_then(|name| {
             self.def_collector.def_map[self.module_id].scope.get_legacy_macro(&name)
         }) {
             let macro_call_id =
                 macro_def.as_call_id(self.def_collector.db, MacroCallKind::FnLike(ast_id));
 
-            self.def_collector.collect_macro_expansion(self.module_id, macro_call_id, macro_def);
+            self.def_collector.unexpanded_macros.push(MacroDirective {
+                module_id: self.module_id,
+                path: mac.path.clone(),
+                ast_id,
+                legacy: Some(macro_call_id),
+            });
+
             return;
         }
 
@@ -926,7 +881,13 @@ where
         if path.is_ident() {
             path.kind = PathKind::Self_;
         }
-        self.def_collector.unexpanded_macros.push((self.module_id, ast_id, path));
+
+        self.def_collector.unexpanded_macros.push(MacroDirective {
+            module_id: self.module_id,
+            path,
+            ast_id,
+            legacy: None,
+        });
     }
 
     fn import_all_legacy_macros(&mut self, module_id: LocalModuleId) {
@@ -951,19 +912,13 @@ fn is_macro_rules(path: &Path) -> bool {
 
 #[cfg(test)]
 mod tests {
+    use crate::{db::DefDatabase, test_db::TestDB};
     use ra_arena::Arena;
     use ra_db::{fixture::WithFixture, SourceDatabase};
-    use rustc_hash::FxHashSet;
-
-    use crate::{db::DefDatabase, test_db::TestDB};
 
     use super::*;
 
-    fn do_collect_defs(
-        db: &impl DefDatabase,
-        def_map: CrateDefMap,
-        monitor: MacroStackMonitor,
-    ) -> (CrateDefMap, FxHashSet<MacroDefId>) {
+    fn do_collect_defs(db: &impl DefDatabase, def_map: CrateDefMap) -> CrateDefMap {
         let mut collector = DefCollector {
             db,
             def_map,
@@ -973,19 +928,13 @@ mod tests {
             unexpanded_macros: Vec::new(),
             unexpanded_attribute_macros: Vec::new(),
             mod_dirs: FxHashMap::default(),
-            macro_stack_monitor: monitor,
-            poison_macros: FxHashSet::default(),
             cfg_options: &CfgOptions::default(),
         };
         collector.collect();
-        (collector.def_map, collector.poison_macros)
+        collector.def_map
     }
 
-    fn do_limited_resolve(
-        code: &str,
-        limit: u32,
-        poison_limit: u32,
-    ) -> (CrateDefMap, FxHashSet<MacroDefId>) {
+    fn do_resolve(code: &str) -> CrateDefMap {
         let (db, _file_id) = TestDB::with_single_file(&code);
         let krate = db.test_crate();
 
@@ -1003,59 +952,18 @@ mod tests {
                 diagnostics: Vec::new(),
             }
         };
-
-        let mut monitor = MacroStackMonitor::default();
-        monitor.validator = Some(Box::new(move |count| {
-            assert!(count < limit);
-            count >= poison_limit
-        }));
-
-        do_collect_defs(&db, def_map, monitor)
+        do_collect_defs(&db, def_map)
     }
 
     #[test]
-    fn test_macro_expand_limit_width() {
-        do_limited_resolve(
+    fn test_macro_expand_will_stop() {
+        do_resolve(
             r#"
         macro_rules! foo {
             ($($ty:ty)*) => { foo!($($ty)*, $($ty)*); }
         }
 foo!(KABOOM);
         "#,
-            16,
-            1000,
         );
     }
-
-    #[test]
-    fn test_macro_expand_poisoned() {
-        let (_, poison_macros) = do_limited_resolve(
-            r#"
-        macro_rules! foo {
-            ($ty:ty) => { foo!($ty); }
-        }
-foo!(KABOOM);
-        "#,
-            100,
-            16,
-        );
-
-        assert_eq!(poison_macros.len(), 1);
-    }
-
-    #[test]
-    fn test_macro_expand_normal() {
-        let (_, poison_macros) = do_limited_resolve(
-            r#"
-        macro_rules! foo {
-            ($ident:ident) => { struct $ident {} }
-        }
-foo!(Bar);
-        "#,
-            16,
-            16,
-        );
-
-        assert_eq!(poison_macros.len(), 0);
-    }
 }
diff --git a/crates/ra_hir_expand/src/builtin_macro.rs b/crates/ra_hir_expand/src/builtin_macro.rs
index c7071fe85..ec5ace757 100644
--- a/crates/ra_hir_expand/src/builtin_macro.rs
+++ b/crates/ra_hir_expand/src/builtin_macro.rs
@@ -208,15 +208,20 @@ fn format_args_expand(
     _id: MacroCallId,
     tt: &tt::Subtree,
 ) -> Result<tt::Subtree, mbe::ExpandError> {
-    // We expand `format_args!("", arg1, arg2)` to
-    // `std::fmt::Arguments::new_v1(&[], &[&arg1, &arg2])`,
+    // We expand `format_args!("", a1, a2)` to
+    // ```
+    // std::fmt::Arguments::new_v1(&[], &[
+    //   std::fmt::ArgumentV1::new(&arg1,std::fmt::Display::fmt),
+    //   std::fmt::ArgumentV1::new(&arg2,std::fmt::Display::fmt),
+    // ])
+    // ```,
     // which is still not really correct, but close enough for now
     let mut args = Vec::new();
     let mut current = Vec::new();
     for tt in tt.token_trees.iter().cloned() {
         match tt {
             tt::TokenTree::Leaf(tt::Leaf::Punct(p)) if p.char == ',' => {
-                args.push(tt::Subtree { delimiter: tt::Delimiter::None, token_trees: current });
+                args.push(current);
                 current = Vec::new();
             }
             _ => {
@@ -225,13 +230,15 @@ fn format_args_expand(
         }
     }
     if !current.is_empty() {
-        args.push(tt::Subtree { delimiter: tt::Delimiter::None, token_trees: current });
+        args.push(current);
     }
     if args.is_empty() {
         return Err(mbe::ExpandError::NoMatchingRule);
     }
     let _format_string = args.remove(0);
-    let arg_tts = args.into_iter().flat_map(|arg| (quote! { & #arg , }).token_trees);
+    let arg_tts = args.into_iter().flat_map(|arg| {
+        quote! { std::fmt::ArgumentV1::new(&(##arg), std::fmt::Display::fmt), }
+    }.token_trees).collect::<Vec<_>>();
     let expanded = quote! {
         std::fmt::Arguments::new_v1(&[], &[##arg_tts])
     };
@@ -360,6 +367,6 @@ mod tests {
             BuiltinFnLikeExpander::FormatArgs,
         );
 
-        assert_eq!(expanded, r#"std::fmt::Arguments::new_v1(&[] ,&[&arg1(a,b,c),&arg2,])"#);
+        assert_eq!(expanded, r#"std::fmt::Arguments::new_v1(&[] ,&[std::fmt::ArgumentV1::new(&(arg1(a,b,c)),std::fmt::Display::fmt),std::fmt::ArgumentV1::new(&(arg2),std::fmt::Display::fmt),])"#);
     }
 }
diff --git a/crates/ra_hir_expand/src/db.rs b/crates/ra_hir_expand/src/db.rs
index 4bdb41619..f68aca789 100644
--- a/crates/ra_hir_expand/src/db.rs
+++ b/crates/ra_hir_expand/src/db.rs
@@ -183,8 +183,8 @@ fn to_fragment_kind(db: &dyn AstDatabase, macro_call_id: MacroCallId) -> Fragmen
             // FIXME: Handle Pattern
             FragmentKind::Expr
         }
-        EXPR_STMT => FragmentKind::Statements,
-        BLOCK => FragmentKind::Statements,
+        // FIXME: Expand to statements in appropriate positions; HIR lowering needs to handle that
+        EXPR_STMT | BLOCK => FragmentKind::Expr,
         ARG_LIST => FragmentKind::Expr,
         TRY_EXPR => FragmentKind::Expr,
         TUPLE_EXPR => FragmentKind::Expr,
diff --git a/crates/ra_hir_ty/src/infer/coerce.rs b/crates/ra_hir_ty/src/infer/coerce.rs
index 9daa77cfa..0f4dac45e 100644
--- a/crates/ra_hir_ty/src/infer/coerce.rs
+++ b/crates/ra_hir_ty/src/infer/coerce.rs
@@ -332,7 +332,11 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     // It will not recurse to `coerce`.
                     return self.table.unify_substs(st1, st2, 0);
                 }
-                _ => {}
+                _ => {
+                    if self.table.unify_inner_trivial(&derefed_ty, &to_ty) {
+                        return true;
+                    }
+                }
             }
         }
 
diff --git a/crates/ra_hir_ty/src/tests/coercion.rs b/crates/ra_hir_ty/src/tests/coercion.rs
index 58b22396f..ac9e3872a 100644
--- a/crates/ra_hir_ty/src/tests/coercion.rs
+++ b/crates/ra_hir_ty/src/tests/coercion.rs
@@ -403,3 +403,40 @@ fn test() {
     "###
     );
 }
+
+#[test]
+fn coerce_autoderef_generic() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+struct Foo;
+fn takes_ref<T>(x: &T) -> T { *x }
+fn test() {
+    takes_ref(&Foo);
+    takes_ref(&&Foo);
+    takes_ref(&&&Foo);
+}
+"#, true),
+        @r###"
+    [29; 30) 'x': &T
+    [41; 47) '{ *x }': T
+    [43; 45) '*x': T
+    [44; 45) 'x': &T
+    [58; 127) '{     ...oo); }': ()
+    [64; 73) 'takes_ref': fn takes_ref<Foo>(&T) -> T
+    [64; 79) 'takes_ref(&Foo)': Foo
+    [74; 78) '&Foo': &Foo
+    [75; 78) 'Foo': Foo
+    [85; 94) 'takes_ref': fn takes_ref<&Foo>(&T) -> T
+    [85; 101) 'takes_...&&Foo)': &Foo
+    [95; 100) '&&Foo': &&Foo
+    [96; 100) '&Foo': &Foo
+    [97; 100) 'Foo': Foo
+    [107; 116) 'takes_ref': fn takes_ref<&&Foo>(&T) -> T
+    [107; 124) 'takes_...&&Foo)': &&Foo
+    [117; 123) '&&&Foo': &&&Foo
+    [118; 123) '&&Foo': &&Foo
+    [119; 123) '&Foo': &Foo
+    [120; 123) 'Foo': Foo
+    "###
+    );
+}
diff --git a/crates/ra_ide/src/goto_definition.rs b/crates/ra_ide/src/goto_definition.rs
index 1b968134d..b93d6a931 100644
--- a/crates/ra_ide/src/goto_definition.rs
+++ b/crates/ra_ide/src/goto_definition.rs
@@ -693,7 +693,6 @@ mod tests {
         );
     }
 
-    #[should_panic] // currently failing because of expr mapping problems
     #[test]
     fn goto_through_format() {
         check_goto(
@@ -718,7 +717,7 @@ mod tests {
                 format!(\"{}\", fo<|>o())
             }
             ",
-            "foo FN_DEF FileId(1) [359; 376) [362; 365)",
+            "foo FN_DEF FileId(1) [398; 415) [401; 404)",
         );
     }
 
diff --git a/docs/user/README.md b/docs/user/README.md
index 5ec8fb25d..04c349342 100644
--- a/docs/user/README.md
+++ b/docs/user/README.md
@@ -204,4 +204,19 @@ Installation:
 
 * You can now invoke the command palette and type LSP enable to locally/globally enable the rust-analyzer LSP (type LSP enable, then choose either locally or globally, then select rust-analyzer)
 
-* Note that `ra_lsp_server` binary must be in `$PATH` for this to work. If it's not the case, you can specify full path to the binary, which is typically `.cargo/bin/ra_lsp_server`.
+### Setting up the `PATH` variable
+
+On Unix systems, `rustup` adds `~/.cargo/bin` to `PATH` by modifying the shell's
+startup file. Depending on your configuration, your Desktop Environment might not
+actually load it. If you find that `rust-analyzer` only runs when starting the
+editor from the terminal, you will have to set up your `PATH` variable manually.
+
+There are a couple of ways to do that:
+
+- for Code, set `rust-analyzer.raLspServerPath` to `~/.cargo/bin` (the `~` is
+  automatically resolved by the extension)
+- copy the binary to a location that is already in `PATH`, e.g. `/usr/local/bin`
+- on Linux, use PAM to configure the `PATH` variable, by e.g. putting
+  `PATH DEFAULT=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:@{HOME}/.cargo/bin:@{HOME}/.local/bin`
+  in your `~/.pam_environment` file; note that this might interfere with other
+  defaults set by the system administrator via `/etc/environment`.
diff --git a/editors/code/package-lock.json b/editors/code/package-lock.json
index 2ceac60a0..099aaaaa2 100644
--- a/editors/code/package-lock.json
+++ b/editors/code/package-lock.json
@@ -763,6 +763,11 @@
                 "chalk": "^2.0.1"
             }
         },
+        "lookpath": {
+            "version": "1.0.3",
+            "resolved": "https://registry.npmjs.org/lookpath/-/lookpath-1.0.3.tgz",
+            "integrity": "sha512-XIdgzlX26g10XnzyZdO/4obybEmfGnZyWQZ2DgmmEfVB79X+n3lhUoIzMe501C6s7RmCpAo66OPegWc+CsxYMg=="
+        },
         "magic-string": {
             "version": "0.25.3",
             "resolved": "https://registry.npmjs.org/magic-string/-/magic-string-0.25.3.tgz",
diff --git a/editors/code/package.json b/editors/code/package.json
index 94887674b..5dea8fac0 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -31,6 +31,7 @@
         "singleQuote": true
     },
     "dependencies": {
+        "lookpath": "^1.0.3",
         "seedrandom": "^3.0.1",
         "vscode-languageclient": "^5.3.0-next.4"
     },
diff --git a/editors/code/src/extension.ts b/editors/code/src/extension.ts
index 683497dfd..6637c3bf0 100644
--- a/editors/code/src/extension.ts
+++ b/editors/code/src/extension.ts
@@ -14,7 +14,7 @@ import * as events from './events';
 import * as notifications from './notifications';
 import { Server } from './server';
 
-export function activate(context: vscode.ExtensionContext) {
+export async function activate(context: vscode.ExtensionContext) {
     function disposeOnDeactivation(disposable: vscode.Disposable) {
         context.subscriptions.push(disposable);
     }
@@ -159,7 +159,11 @@ export function activate(context: vscode.ExtensionContext) {
     });
 
     // Start the language server, finally!
-    startServer();
+    try {
+        await startServer();
+    } catch (e) {
+        vscode.window.showErrorMessage(e.message);
+    }
 
     if (Server.config.displayInlayHints) {
         const hintsUpdater = new HintsUpdater();
@@ -204,10 +208,10 @@ export function deactivate(): Thenable<void> {
     return Server.client.stop();
 }
 
-async function reloadServer(startServer: () => void) {
+async function reloadServer(startServer: () => Promise<void>) {
     if (Server.client != null) {
         vscode.window.showInformationMessage('Reloading rust-analyzer...');
         await Server.client.stop();
-        startServer();
+        await startServer();
     }
 }
diff --git a/editors/code/src/server.ts b/editors/code/src/server.ts
index 7907b70bc..e717ab294 100644
--- a/editors/code/src/server.ts
+++ b/editors/code/src/server.ts
@@ -1,3 +1,4 @@
+import { lookpath } from 'lookpath';
 import { homedir } from 'os';
 import * as lc from 'vscode-languageclient';
 
@@ -17,7 +18,7 @@ export class Server {
     public static config = new Config();
     public static client: lc.LanguageClient;
 
-    public static start(
+    public static async start(
         notificationHandlers: Iterable<[string, lc.GenericNotificationHandler]>
     ) {
         // '.' Is the fallback if no folder is open
@@ -27,8 +28,14 @@ export class Server {
             folder = workspace.workspaceFolders[0].uri.fsPath.toString();
         }
 
+        const command = expandPathResolving(this.config.raLspServerPath);
+        if (!(await lookpath(command))) {
+            throw new Error(
+                `Cannot find rust-analyzer server \`${command}\` in PATH.`
+            );
+        }
         const run: lc.Executable = {
-            command: expandPathResolving(this.config.raLspServerPath),
+            command,
             options: { cwd: folder }
         };
         const serverOptions: lc.ServerOptions = {