21 files changed, 357 insertions, 156 deletions

diff --git a/crates/ra_hir_def/src/body.rs b/crates/ra_hir_def/src/body.rs
index d9ce6bcff..445d215b7 100644
--- a/crates/ra_hir_def/src/body.rs
+++ b/crates/ra_hir_def/src/body.rs
@@ -24,7 +24,7 @@ use crate::{
     DefWithBodyId, HasModule, Lookup, ModuleDefId, ModuleId,
 };
 
-struct Expander {
+pub(crate) struct Expander {
     crate_def_map: Arc<CrateDefMap>,
     current_file_id: HirFileId,
     hygiene: Hygiene,
@@ -33,18 +33,22 @@ struct Expander {
 }
 
 impl Expander {
-    fn new(db: &impl DefDatabase, current_file_id: HirFileId, module: ModuleId) -> Expander {
+    pub(crate) fn new(
+        db: &impl DefDatabase,
+        current_file_id: HirFileId,
+        module: ModuleId,
+    ) -> Expander {
         let crate_def_map = db.crate_def_map(module.krate);
         let hygiene = Hygiene::new(db, current_file_id);
         let ast_id_map = db.ast_id_map(current_file_id);
         Expander { crate_def_map, current_file_id, hygiene, ast_id_map, module }
     }
 
-    fn enter_expand(
+    pub(crate) fn enter_expand<T: ast::AstNode, DB: DefDatabase>(
         &mut self,
-        db: &impl DefDatabase,
+        db: &DB,
         macro_call: ast::MacroCall,
-    ) -> Option<(Mark, ast::Expr)> {
+    ) -> Option<(Mark, T)> {
         let ast_id = AstId::new(
             self.current_file_id,
             db.ast_id_map(self.current_file_id).ast_id(&macro_call),
@@ -55,7 +59,7 @@ impl Expander {
                 let call_id = def.as_call_id(db, MacroCallKind::FnLike(ast_id));
                 let file_id = call_id.as_file();
                 if let Some(node) = db.parse_or_expand(file_id) {
-                    if let Some(expr) = ast::Expr::cast(node) {
+                    if let Some(expr) = T::cast(node) {
                         log::debug!("macro expansion {:#?}", expr.syntax());
 
                         let mark = Mark {
@@ -78,14 +82,14 @@ impl Expander {
         None
     }
 
-    fn exit(&mut self, db: &impl DefDatabase, mut mark: Mark) {
+    pub(crate) fn exit(&mut self, db: &impl DefDatabase, mut mark: Mark) {
         self.hygiene = Hygiene::new(db, mark.file_id);
         self.current_file_id = mark.file_id;
         self.ast_id_map = mem::take(&mut mark.ast_id_map);
         mark.bomb.defuse();
     }
 
-    fn to_source<T>(&self, value: T) -> InFile<T> {
+    pub(crate) fn to_source<T>(&self, value: T) -> InFile<T> {
         InFile { file_id: self.current_file_id, value }
     }
 
@@ -110,7 +114,7 @@ impl Expander {
     }
 }
 
-struct Mark {
+pub(crate) struct Mark {
     file_id: HirFileId,
     ast_id_map: Arc<AstIdMap>,
     bomb: DropBomb,
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index 853e17bae..be5d17d85 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -372,8 +372,9 @@ where
                         arg_types.push(type_ref);
                     }
                 }
+                let ret_type = e.ret_type().and_then(|r| r.type_ref()).map(TypeRef::from_ast);
                 let body = self.collect_expr_opt(e.body());
-                self.alloc_expr(Expr::Lambda { args, arg_types, body }, syntax_ptr)
+                self.alloc_expr(Expr::Lambda { args, arg_types, ret_type, body }, syntax_ptr)
             }
             ast::Expr::BinExpr(e) => {
                 let lhs = self.collect_expr_opt(e.lhs());
diff --git a/crates/ra_hir_def/src/data.rs b/crates/ra_hir_def/src/data.rs
index 14e86936b..b0a3f1784 100644
--- a/crates/ra_hir_def/src/data.rs
+++ b/crates/ra_hir_def/src/data.rs
@@ -4,16 +4,16 @@ use std::sync::Arc;
 
 use hir_expand::{
     name::{name, AsName, Name},
-    AstId,
+    AstId, InFile,
 };
-use ra_syntax::ast::{self, NameOwner, TypeAscriptionOwner};
+use ra_syntax::ast::{self, AstNode, ImplItem, ModuleItemOwner, NameOwner, TypeAscriptionOwner};
 
 use crate::{
     db::DefDatabase,
     src::HasSource,
     type_ref::{Mutability, TypeRef},
-    AssocContainerId, AssocItemId, ConstId, ConstLoc, FunctionId, FunctionLoc, ImplId, Intern,
-    Lookup, StaticId, TraitId, TypeAliasId, TypeAliasLoc,
+    AssocContainerId, AssocItemId, ConstId, ConstLoc, Expander, FunctionId, FunctionLoc, HasModule,
+    ImplId, Intern, Lookup, ModuleId, StaticId, TraitId, TypeAliasId, TypeAliasLoc,
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -167,46 +167,24 @@ pub struct ImplData {
 
 impl ImplData {
     pub(crate) fn impl_data_query(db: &impl DefDatabase, id: ImplId) -> Arc<ImplData> {
-        let src = id.lookup(db).source(db);
-        let items = db.ast_id_map(src.file_id);
+        let impl_loc = id.lookup(db);
+        let src = impl_loc.source(db);
 
         let target_trait = src.value.target_trait().map(TypeRef::from_ast);
         let target_type = TypeRef::from_ast_opt(src.value.target_type());
         let is_negative = src.value.is_negative();
+        let module_id = impl_loc.container.module(db);
 
-        let items = if let Some(item_list) = src.value.item_list() {
-            item_list
-                .impl_items()
-                .map(|item_node| match item_node {
-                    ast::ImplItem::FnDef(it) => {
-                        let def = FunctionLoc {
-                            container: AssocContainerId::ImplId(id),
-                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
-                        }
-                        .intern(db);
-                        def.into()
-                    }
-                    ast::ImplItem::ConstDef(it) => {
-                        let def = ConstLoc {
-                            container: AssocContainerId::ImplId(id),
-                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
-                        }
-                        .intern(db);
-                        def.into()
-                    }
-                    ast::ImplItem::TypeAliasDef(it) => {
-                        let def = TypeAliasLoc {
-                            container: AssocContainerId::ImplId(id),
-                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
-                        }
-                        .intern(db);
-                        def.into()
-                    }
-                })
-                .collect()
-        } else {
-            Vec::new()
-        };
+        let mut items = Vec::new();
+        if let Some(item_list) = src.value.item_list() {
+            items.extend(collect_impl_items(db, item_list.impl_items(), src.file_id, id));
+            items.extend(collect_impl_items_in_macros(
+                db,
+                module_id,
+                &src.with_value(item_list),
+                id,
+            ));
+        }
 
         let res = ImplData { target_trait, target_type, items, is_negative };
         Arc::new(res)
@@ -237,3 +215,66 @@ impl ConstData {
         ConstData { name, type_ref }
     }
 }
+
+fn collect_impl_items_in_macros(
+    db: &impl DefDatabase,
+    module_id: ModuleId,
+    impl_block: &InFile<ast::ItemList>,
+    id: ImplId,
+) -> Vec<AssocItemId> {
+    let mut expander = Expander::new(db, impl_block.file_id, module_id);
+    let mut res = Vec::new();
+
+    for m in impl_block.value.syntax().children().filter_map(ast::MacroCall::cast) {
+        if let Some((mark, items)) = expander.enter_expand(db, m) {
+            let items: InFile<ast::MacroItems> = expander.to_source(items);
+            expander.exit(db, mark);
+            res.extend(collect_impl_items(
+                db,
+                items.value.items().filter_map(|it| ImplItem::cast(it.syntax().clone())),
+                items.file_id,
+                id,
+            ));
+        }
+    }
+
+    res
+}
+
+fn collect_impl_items(
+    db: &impl DefDatabase,
+    impl_items: impl Iterator<Item = ImplItem>,
+    file_id: crate::HirFileId,
+    id: ImplId,
+) -> Vec<AssocItemId> {
+    let items = db.ast_id_map(file_id);
+
+    impl_items
+        .map(|item_node| match item_node {
+            ast::ImplItem::FnDef(it) => {
+                let def = FunctionLoc {
+                    container: AssocContainerId::ImplId(id),
+                    ast_id: AstId::new(file_id, items.ast_id(&it)),
+                }
+                .intern(db);
+                def.into()
+            }
+            ast::ImplItem::ConstDef(it) => {
+                let def = ConstLoc {
+                    container: AssocContainerId::ImplId(id),
+                    ast_id: AstId::new(file_id, items.ast_id(&it)),
+                }
+                .intern(db);
+                def.into()
+            }
+            ast::ImplItem::TypeAliasDef(it) => {
+                let def = TypeAliasLoc {
+                    container: AssocContainerId::ImplId(id),
+                    ast_id: AstId::new(file_id, items.ast_id(&it)),
+                }
+                .intern(db);
+                def.into()
+            }
+        })
+        .collect()
+}
diff --git a/crates/ra_hir_def/src/expr.rs b/crates/ra_hir_def/src/expr.rs
index 6fad80a8d..a75ef9970 100644
--- a/crates/ra_hir_def/src/expr.rs
+++ b/crates/ra_hir_def/src/expr.rs
@@ -143,6 +143,7 @@ pub enum Expr {
     Lambda {
         args: Vec<PatId>,
         arg_types: Vec<Option<TypeRef>>,
+        ret_type: Option<TypeRef>,
         body: ExprId,
     },
     Tuple {
diff --git a/crates/ra_hir_def/src/lib.rs b/crates/ra_hir_def/src/lib.rs
index bf8d6d1d4..acd4f4af1 100644
--- a/crates/ra_hir_def/src/lib.rs
+++ b/crates/ra_hir_def/src/lib.rs
@@ -48,6 +48,7 @@ use ra_arena::{impl_arena_id, RawId};
 use ra_db::{impl_intern_key, salsa, CrateId};
 use ra_syntax::{ast, AstNode};
 
+use crate::body::Expander;
 use crate::builtin_type::BuiltinType;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
index 00325cd99..8e1294201 100644
--- a/crates/ra_hir_def/src/path.rs
+++ b/crates/ra_hir_def/src/path.rs
@@ -135,7 +135,7 @@ impl Path {
     }
 
     pub fn type_anchor(&self) -> Option<&TypeRef> {
-        self.type_anchor.as_ref().map(|it| &**it)
+        self.type_anchor.as_deref()
     }
 
     pub fn segments(&self) -> PathSegments<'_> {
diff --git a/crates/ra_hir_expand/src/db.rs b/crates/ra_hir_expand/src/db.rs
index f68aca789..d86445abf 100644
--- a/crates/ra_hir_expand/src/db.rs
+++ b/crates/ra_hir_expand/src/db.rs
@@ -188,6 +188,7 @@ fn to_fragment_kind(db: &dyn AstDatabase, macro_call_id: MacroCallId) -> Fragmen
         ARG_LIST => FragmentKind::Expr,
         TRY_EXPR => FragmentKind::Expr,
         TUPLE_EXPR => FragmentKind::Expr,
+        ITEM_LIST => FragmentKind::Items,
         _ => {
             // Unknown , Just guess it is `Items`
             FragmentKind::Items
diff --git a/crates/ra_hir_ty/src/infer.rs b/crates/ra_hir_ty/src/infer.rs
index bbbc391c4..e97b81473 100644
--- a/crates/ra_hir_ty/src/infer.rs
+++ b/crates/ra_hir_ty/src/infer.rs
@@ -196,7 +196,12 @@ struct InferenceContext<'a, D: HirDatabase> {
     trait_env: Arc<TraitEnvironment>,
     obligations: Vec<Obligation>,
     result: InferenceResult,
-    /// The return type of the function being inferred.
+    /// The return type of the function being inferred, or the closure if we're
+    /// currently within one.
+    ///
+    /// We might consider using a nested inference context for checking
+    /// closures, but currently this is the only field that will change there,
+    /// so it doesn't make sense.
     return_ty: Ty,
 
     /// Impls of `CoerceUnsized` used in coercion.
@@ -455,7 +460,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     }
 
     fn infer_body(&mut self) {
-        self.infer_expr(self.body.body_expr, &Expectation::has_type(self.return_ty.clone()));
+        self.infer_expr_coerce(self.body.body_expr, &Expectation::has_type(self.return_ty.clone()));
     }
 
     fn resolve_into_iter_item(&self) -> Option<TypeAliasId> {
diff --git a/crates/ra_hir_ty/src/infer/coerce.rs b/crates/ra_hir_ty/src/infer/coerce.rs
index 0f4dac45e..83c0c2c3f 100644
--- a/crates/ra_hir_ty/src/infer/coerce.rs
+++ b/crates/ra_hir_ty/src/infer/coerce.rs
@@ -134,6 +134,10 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 }
             }
 
+            (ty_app!(TypeCtor::Closure { .. }, params), ty_app!(TypeCtor::FnPtr { .. })) => {
+                from_ty = params[0].clone();
+            }
+
             _ => {}
         }
 
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index 8be567917..3af05394c 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -41,7 +41,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
     /// Infer type of expression with possibly implicit coerce to the expected type.
     /// Return the type after possible coercion.
-    fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
+    pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
         let ty = self.infer_expr_inner(expr, &expected);
         let ty = if !self.coerce(&ty, &expected.ty) {
             self.result
@@ -102,7 +102,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
                 Ty::unit()
             }
-            Expr::Lambda { body, args, arg_types } => {
+            Expr::Lambda { body, args, ret_type, arg_types } => {
                 assert_eq!(args.len(), arg_types.len());
 
                 let mut sig_tys = Vec::new();
@@ -118,7 +118,10 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 }
 
                 // add return type
-                let ret_ty = self.table.new_type_var();
+                let ret_ty = match ret_type {
+                    Some(type_ref) => self.make_ty(type_ref),
+                    None => self.table.new_type_var(),
+                };
                 sig_tys.push(ret_ty.clone());
                 let sig_ty = Ty::apply(
                     TypeCtor::FnPtr { num_args: sig_tys.len() as u16 - 1 },
@@ -134,7 +137,12 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 // infer the body.
                 self.coerce(&closure_ty, &expected.ty);
 
-                self.infer_expr(*body, &Expectation::has_type(ret_ty));
+                let prev_ret_ty = std::mem::replace(&mut self.return_ty, ret_ty.clone());
+
+                self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
+
+                self.return_ty = prev_ret_ty;
+
                 closure_ty
             }
             Expr::Call { callee, args } => {
@@ -192,6 +200,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Expr::Return { expr } => {
                 if let Some(expr) = expr {
                     self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
+                } else {
+                    let unit = Ty::unit();
+                    self.coerce(&unit, &self.return_ty.clone());
                 }
                 Ty::simple(TypeCtor::Never)
             }
diff --git a/crates/ra_hir_ty/src/tests/coercion.rs b/crates/ra_hir_ty/src/tests/coercion.rs
index ac9e3872a..7e99a42ed 100644
--- a/crates/ra_hir_ty/src/tests/coercion.rs
+++ b/crates/ra_hir_ty/src/tests/coercion.rs
@@ -370,6 +370,22 @@ fn test() {
 }
 
 #[test]
+fn return_coerce_unknown() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+fn foo() -> u32 {
+    return unknown;
+}
+"#, true),
+        @r###"
+    [17; 40) '{     ...own; }': !
+    [23; 37) 'return unknown': !
+    [30; 37) 'unknown': u32
+    "###
+    );
+}
+
+#[test]
 fn coerce_autoderef() {
     assert_snapshot!(
         infer_with_mismatches(r#"
@@ -440,3 +456,73 @@ fn test() {
     "###
     );
 }
+
+#[test]
+fn closure_return_coerce() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+fn foo() {
+    let x = || {
+        if true {
+            return &1u32;
+        }
+        &&1u32
+    };
+}
+"#, true),
+        @r###"
+    [10; 106) '{     ...  }; }': ()
+    [20; 21) 'x': || -> &u32
+    [24; 103) '|| {  ...     }': || -> &u32
+    [27; 103) '{     ...     }': &u32
+    [37; 82) 'if tru...     }': ()
+    [40; 44) 'true': bool
+    [45; 82) '{     ...     }': !
+    [59; 71) 'return &1u32': !
+    [66; 71) '&1u32': &u32
+    [67; 71) '1u32': u32
+    [91; 97) '&&1u32': &&u32
+    [92; 97) '&1u32': &u32
+    [93; 97) '1u32': u32
+    "###
+    );
+}
+
+#[test]
+fn coerce_fn_item_to_fn_ptr() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+fn foo(x: u32) -> isize { 1 }
+fn test() {
+    let f: fn(u32) -> isize = foo;
+}
+"#, true),
+        @r###"
+    [8; 9) 'x': u32
+    [25; 30) '{ 1 }': isize
+    [27; 28) '1': isize
+    [41; 79) '{     ...foo; }': ()
+    [51; 52) 'f': fn(u32) -> isize
+    [73; 76) 'foo': fn foo(u32) -> isize
+    "###
+    );
+}
+
+#[test]
+fn coerce_closure_to_fn_ptr() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+fn test() {
+    let f: fn(u32) -> isize = |x| { 1 };
+}
+"#, true),
+        @r###"
+    [11; 55) '{     ...1 }; }': ()
+    [21; 22) 'f': fn(u32) -> isize
+    [43; 52) '|x| { 1 }': |u32| -> isize
+    [44; 45) 'x': u32
+    [47; 52) '{ 1 }': isize
+    [49; 50) '1': isize
+    "###
+    );
+}
diff --git a/crates/ra_hir_ty/src/tests/macros.rs b/crates/ra_hir_ty/src/tests/macros.rs
index 812f171db..7fdbf996f 100644
--- a/crates/ra_hir_ty/src/tests/macros.rs
+++ b/crates/ra_hir_ty/src/tests/macros.rs
@@ -183,6 +183,25 @@ fn test() { S.foo()<|>; }
 }
 
 #[test]
+fn infer_impl_items_generated_by_macros() {
+    let t = type_at(
+        r#"
+//- /main.rs
+macro_rules! m {
+    () => (fn foo(&self) -> u128 {0})
+}
+struct S;
+impl S {
+    m!();
+}
+
+fn test() { S.foo()<|>; }
+"#,
+    );
+    assert_eq!(t, "u128");
+}
+
+#[test]
 fn infer_macro_with_dollar_crate_is_correct_in_expr() {
     let (db, pos) = TestDB::with_position(
         r#"
diff --git a/crates/ra_hir_ty/src/tests/simple.rs b/crates/ra_hir_ty/src/tests/simple.rs
index 18976c9ae..6fe647a5e 100644
--- a/crates/ra_hir_ty/src/tests/simple.rs
+++ b/crates/ra_hir_ty/src/tests/simple.rs
@@ -1606,3 +1606,58 @@ fn main() {
     );
     assert_eq!(t, "u32");
 }
+
+#[test]
+fn closure_return() {
+    assert_snapshot!(
+        infer(r#"
+fn foo() -> u32 {
+    let x = || -> usize { return 1; };
+}
+"#),
+        @r###"
+    [17; 59) '{     ...; }; }': ()
+    [27; 28) 'x': || -> usize
+    [31; 56) '|| -> ...n 1; }': || -> usize
+    [43; 56) '{ return 1; }': !
+    [45; 53) 'return 1': !
+    [52; 53) '1': usize
+    "###
+    );
+}
+
+#[test]
+fn closure_return_unit() {
+    assert_snapshot!(
+        infer(r#"
+fn foo() -> u32 {
+    let x = || { return; };
+}
+"#),
+        @r###"
+    [17; 48) '{     ...; }; }': ()
+    [27; 28) 'x': || -> ()
+    [31; 45) '|| { return; }': || -> ()
+    [34; 45) '{ return; }': !
+    [36; 42) 'return': !
+    "###
+    );
+}
+
+#[test]
+fn closure_return_inferred() {
+    assert_snapshot!(
+        infer(r#"
+fn foo() -> u32 {
+    let x = || { "test" };
+}
+"#),
+        @r###"
+    [17; 47) '{     ..." }; }': ()
+    [27; 28) 'x': || -> &str
+    [31; 44) '|| { "test" }': || -> &str
+    [34; 44) '{ "test" }': &str
+    [36; 42) '"test"': &str
+    "###
+    );
+}
diff --git a/crates/ra_hir_ty/src/tests/traits.rs b/crates/ra_hir_ty/src/tests/traits.rs
index 2d92a5eec..76e2198b6 100644
--- a/crates/ra_hir_ty/src/tests/traits.rs
+++ b/crates/ra_hir_ty/src/tests/traits.rs
@@ -393,11 +393,11 @@ fn test() -> u64 {
     [54; 55) 'a': S
     [58; 59) 'S': S(fn(u32) -> u64) -> S
     [58; 68) 'S(|i| 2*i)': S
-    [60; 67) '|i| 2*i': |i32| -> i32
-    [61; 62) 'i': i32
-    [64; 65) '2': i32
-    [64; 67) '2*i': i32
-    [66; 67) 'i': i32
+    [60; 67) '|i| 2*i': |u32| -> u64
+    [61; 62) 'i': u32
+    [64; 65) '2': u32
+    [64; 67) '2*i': u32
+    [66; 67) 'i': u32
     [78; 79) 'b': u64
     [82; 83) 'a': S
     [82; 85) 'a.0': fn(u32) -> u64
diff --git a/crates/ra_ide/src/display.rs b/crates/ra_ide/src/display.rs
index 30617412a..fbe89841b 100644
--- a/crates/ra_ide/src/display.rs
+++ b/crates/ra_ide/src/display.rs
@@ -15,7 +15,7 @@ pub use function_signature::FunctionSignature;
 pub use navigation_target::NavigationTarget;
 pub use structure::{file_structure, StructureNode};
 
-pub(crate) use navigation_target::{description_from_symbol, docs_from_symbol, ToNav};
+pub(crate) use navigation_target::ToNav;
 pub(crate) use short_label::ShortLabel;
 
 pub(crate) fn function_label(node: &ast::FnDef) -> String {
diff --git a/crates/ra_ide/src/hover.rs b/crates/ra_ide/src/hover.rs
index a227bf546..35e39f965 100644
--- a/crates/ra_ide/src/hover.rs
+++ b/crates/ra_ide/src/hover.rs
@@ -12,10 +12,7 @@ use ra_syntax::{
 
 use crate::{
     db::RootDatabase,
-    display::{
-        description_from_symbol, docs_from_symbol, macro_label, rust_code_markup,
-        rust_code_markup_with_doc, ShortLabel,
-    },
+    display::{macro_label, rust_code_markup, rust_code_markup_with_doc, ShortLabel},
     expand::descend_into_macros,
     references::{classify_name, classify_name_ref, NameKind, NameKind::*},
     FilePosition, FileRange, RangeInfo,
@@ -95,11 +92,7 @@ fn hover_text(docs: Option<String>, desc: Option<String>) -> Option<String> {
     }
 }
 
-fn hover_text_from_name_kind(
-    db: &RootDatabase,
-    name_kind: NameKind,
-    no_fallback: &mut bool,
-) -> Option<String> {
+fn hover_text_from_name_kind(db: &RootDatabase, name_kind: NameKind) -> Option<String> {
     return match name_kind {
         Macro(it) => {
             let src = it.source(db);
@@ -135,11 +128,7 @@ fn hover_text_from_name_kind(
             hir::ModuleDef::TypeAlias(it) => from_def_source(db, it),
             hir::ModuleDef::BuiltinType(it) => Some(it.to_string()),
         },
-        Local(_) => {
-            // Hover for these shows type names
-            *no_fallback = true;
-            None
-        }
+        Local(_) => None,
         TypeParam(_) | SelfType(_) => {
             // FIXME: Hover for generic param
             None
@@ -163,60 +152,35 @@ pub(crate) fn hover(db: &RootDatabase, position: FilePosition) -> Option<RangeIn
 
     let mut res = HoverResult::new();
 
-    let mut range = match_ast! {
+    if let Some((range, name_kind)) = match_ast! {
         match (token.value.parent()) {
             ast::NameRef(name_ref) => {
-                let mut no_fallback = false;
-                if let Some(name_kind) =
-                    classify_name_ref(db, token.with_value(&name_ref)).map(|d| d.kind)
-                {
-                    res.extend(hover_text_from_name_kind(db, name_kind, &mut no_fallback))
-                }
-
-                if res.is_empty() && !no_fallback {
-                    // Fallback index based approach:
-                    let symbols = crate::symbol_index::index_resolve(db, &name_ref);
-                    for sym in symbols {
-                        let docs = docs_from_symbol(db, &sym);
-                        let desc = description_from_symbol(db, &sym);
-                        res.extend(hover_text(docs, desc));
-                    }
-                }
-
-                if !res.is_empty() {
-                    Some(name_ref.syntax().text_range())
-                } else {
-                    None
-                }
+                classify_name_ref(db, token.with_value(&name_ref)).map(|d| (name_ref.syntax().text_range(), d.kind))
             },
             ast::Name(name) => {
-                if let Some(name_kind) = classify_name(db, token.with_value(&name)).map(|d| d.kind) {
-                    res.extend(hover_text_from_name_kind(db, name_kind, &mut true));
-                }
-
-                if !res.is_empty() {
-                    Some(name.syntax().text_range())
-                } else {
-                    None
-                }
+                classify_name(db, token.with_value(&name)).map(|d| (name.syntax().text_range(), d.kind))
             },
             _ => None,
         }
-    };
+    } {
+        res.extend(hover_text_from_name_kind(db, name_kind));
 
-    if range.is_none() {
-        let node = token.value.ancestors().find(|n| {
-            ast::Expr::cast(n.clone()).is_some() || ast::Pat::cast(n.clone()).is_some()
-        })?;
-        let frange = FileRange { file_id: position.file_id, range: node.text_range() };
-        res.extend(type_of(db, frange).map(rust_code_markup));
-        range = Some(node.text_range());
-    };
+        if !res.is_empty() {
+            return Some(RangeInfo::new(range, res));
+        }
+    }
 
-    let range = range?;
+    let node = token
+        .value
+        .ancestors()
+        .find(|n| ast::Expr::cast(n.clone()).is_some() || ast::Pat::cast(n.clone()).is_some())?;
+    let frange = FileRange { file_id: position.file_id, range: node.text_range() };
+    res.extend(type_of(db, frange).map(rust_code_markup));
     if res.is_empty() {
         return None;
     }
+    let range = node.text_range();
+
     Some(RangeInfo::new(range, res))
 }
 
@@ -314,7 +278,7 @@ mod tests {
             &["pub fn foo() -> u32"],
         );
 
-        // Multiple results
+        // Multiple candidates but results are ambiguous.
         check_hover_result(
             r#"
             //- /a.rs
@@ -335,7 +299,7 @@ mod tests {
                 let foo_test = fo<|>o();
             }
         "#,
-            &["pub fn foo() -> &str", "pub fn foo() -> u32", "pub fn foo(a: u32, b: u32)"],
+            &["{unknown}"],
         );
     }
 
diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index 9dd6bd3ea..8d65e2e08 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -1426,6 +1426,9 @@ impl LambdaExpr {
     pub fn param_list(&self) -> Option<ParamList> {
         AstChildren::new(&self.syntax).next()
     }
+    pub fn ret_type(&self) -> Option<RetType> {
+        AstChildren::new(&self.syntax).next()
+    }
     pub fn body(&self) -> Option<Expr> {
         AstChildren::new(&self.syntax).next()
     }
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 9ffa9095b..a228fa9d6 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -426,7 +426,7 @@ Grammar(
         "PathExpr": (options: ["Path"]),
         "LambdaExpr": (
             options: [
-                "ParamList",
+                "ParamList", "RetType",
                 ["body", "Expr"],
             ]
         ),
diff --git a/editors/code/package-lock.json b/editors/code/package-lock.json
index 127cdcfa1..4c5c13646 100644
--- a/editors/code/package-lock.json
+++ b/editors/code/package-lock.json
@@ -60,9 +60,9 @@
             "dev": true
         },
         "@types/node": {
-            "version": "10.17.6",
-            "resolved": "https://registry.npmjs.org/@types/node/-/node-10.17.6.tgz",
-            "integrity": "sha512-0a2X6cgN3RdPBL2MIlR6Lt0KlM7fOFsutuXcdglcOq6WvLnYXgPQSh0Mx6tO1KCAE8MxbHSOSTWDoUxRq+l3DA==",
+            "version": "12.12.21",
+            "resolved": "https://registry.npmjs.org/@types/node/-/node-12.12.21.tgz",
+            "integrity": "sha512-8sRGhbpU+ck1n0PGAUgVrWrWdjSW2aqNeyC15W88GRsMpSwzv6RJGlLhE7s2RhVSOdyDmxbqlWSeThq4/7xqlA==",
             "dev": true
         },
         "@types/resolve": {
@@ -81,9 +81,9 @@
             "dev": true
         },
         "@types/vscode": {
-            "version": "1.40.0",
-            "resolved": "https://registry.npmjs.org/@types/vscode/-/vscode-1.40.0.tgz",
-            "integrity": "sha512-5kEIxL3qVRkwhlMerxO7XuMffa+0LBl+iG2TcRa0NsdoeSFLkt/9hJ02jsi/Kvc6y8OVF2N2P2IHP5S4lWf/5w==",
+            "version": "1.41.0",
+            "resolved": "https://registry.npmjs.org/@types/vscode/-/vscode-1.41.0.tgz",
+            "integrity": "sha512-7SfeY5u9jgiELwxyLB3z7l6l/GbN9CqpCQGkcRlB7tKRFBxzbz2PoBfGrLxI1vRfUCIq5+hg5vtDHExwq5j3+A==",
             "dev": true
         },
         "acorn": {
@@ -791,9 +791,9 @@
             }
         },
         "lookpath": {
-            "version": "1.0.3",
-            "resolved": "https://registry.npmjs.org/lookpath/-/lookpath-1.0.3.tgz",
-            "integrity": "sha512-XIdgzlX26g10XnzyZdO/4obybEmfGnZyWQZ2DgmmEfVB79X+n3lhUoIzMe501C6s7RmCpAo66OPegWc+CsxYMg=="
+            "version": "1.0.4",
+            "resolved": "https://registry.npmjs.org/lookpath/-/lookpath-1.0.4.tgz",
+            "integrity": "sha512-xVFrWlfo7n8VZs1YjBWKkbSIJU7DKE/0Mep62KeT94V1Ui1IY9w5fXfgiCsDIDZkakIYSXSeaW2FLbCqfw9/Cw=="
         },
         "magic-string": {
             "version": "0.25.3",
@@ -1140,9 +1140,9 @@
             }
         },
         "rollup": {
-            "version": "1.27.9",
-            "resolved": "https://registry.npmjs.org/rollup/-/rollup-1.27.9.tgz",
-            "integrity": "sha512-8AfW4cJTPZfG6EXWwT/ujL4owUsDI1Xl8J1t+hvK4wDX81F5I4IbwP9gvGbHzxnV19fnU4rRABZQwZSX9J402Q==",
+            "version": "1.27.13",
+            "resolved": "https://registry.npmjs.org/rollup/-/rollup-1.27.13.tgz",
+            "integrity": "sha512-hDi7M07MpmNSDE8YVwGVFA8L7n8jTLJ4lG65nMAijAyqBe//rtu4JdxjUBE7JqXfdpqxqDTbCDys9WcqdpsQvw==",
             "dev": true,
             "requires": {
                 "@types/estree": "*",
@@ -1514,9 +1514,9 @@
             "dev": true
         },
         "vsce": {
-            "version": "1.70.0",
-            "resolved": "https://registry.npmjs.org/vsce/-/vsce-1.70.0.tgz",
-            "integrity": "sha512-mBTbVrWL348jODwfmaR+yXrlzb8EABGCT067C4shKOXriWiuMQi4/uCbFm6TUBcfnzTYLJv+DKa0VnKU8yEAjA==",
+            "version": "1.71.0",
+            "resolved": "https://registry.npmjs.org/vsce/-/vsce-1.71.0.tgz",
+            "integrity": "sha512-7k+LPC4oJYPyyxs0a5nh4A8CleQ6+2EMPiAiX/bDyN+PmwJFm2FFPqLRxdIsIWfFnkW4ZMQBf10+W62dCRd9kQ==",
             "dev": true,
             "requires": {
                 "azure-devops-node-api": "^7.2.0",
@@ -1547,12 +1547,12 @@
             "integrity": "sha512-k9akfglxWgr0dtLNscq2uBq48XJwnhf4EaDxn05KQowRwR0DkNML0zeYqFRLtXZe6x5vpL5ppyu4o6GqL+23YQ=="
         },
         "vscode-languageclient": {
-            "version": "6.0.0-next.8",
-            "resolved": "https://registry.npmjs.org/vscode-languageclient/-/vscode-languageclient-6.0.0-next.8.tgz",
-            "integrity": "sha512-452jskmuT7YKYnPd5uh7aELK4M25OITcnBq4ylPIyUtE5LQRgA9N9pR9NrviTTX/Hh6q6VGzm70OK9SpMO/zcA==",
+            "version": "6.0.0-next.9",
+            "resolved": "https://registry.npmjs.org/vscode-languageclient/-/vscode-languageclient-6.0.0-next.9.tgz",
+            "integrity": "sha512-NEpeeFM9FKrrRqlBHXGfwpkhtnjruDz3zfFBP+Cymr10qigAEtE/JsODJsIG/ErGqjh3/JXxu8SUOVTGu5oK+w==",
             "requires": {
                 "semver": "^6.3.0",
-                "vscode-languageserver-protocol": "^3.15.0-next.13"
+                "vscode-languageserver-protocol": "^3.15.0-next.14"
             },
             "dependencies": {
                 "semver": {
@@ -1563,9 +1563,9 @@
             }
         },
         "vscode-languageserver-protocol": {
-            "version": "3.15.0-next.13",
-            "resolved": "https://registry.npmjs.org/vscode-languageserver-protocol/-/vscode-languageserver-protocol-3.15.0-next.13.tgz",
-            "integrity": "sha512-2UGxOKc5VHav15n3zY5dtaOXGL/JuV0K2Mem/n6lhF8i3vaqIAnKv004SPU0flYHXIfCcQM7kCL+nwWVJ1K1qw==",
+            "version": "3.15.0-next.14",
+            "resolved": "https://registry.npmjs.org/vscode-languageserver-protocol/-/vscode-languageserver-protocol-3.15.0-next.14.tgz",
+            "integrity": "sha512-xUwwno6Q6RFd2Z2EWV9D3dQlsKPnHyiZMNWq+EC7JJdp2WH1gRlD+KPX4UGRCnJK0WI5omqHV313IESPwRY5xA==",
             "requires": {
                 "vscode-jsonrpc": "^5.0.0-next.5",
                 "vscode-languageserver-types": "^3.15.0-next.9"
@@ -1577,9 +1577,9 @@
             "integrity": "sha512-Rl/8qJ6932nrHCdPn+9y0x08uLVQaSLRG+U4JzhyKpWU4eJbVaDRoAcz1Llj7CErJGbPr6kdBvShPy5fRfR+Uw=="
         },
         "vscode-test": {
-            "version": "1.2.3",
-            "resolved": "https://registry.npmjs.org/vscode-test/-/vscode-test-1.2.3.tgz",
-            "integrity": "sha512-mKRTNso33NaUULiPBFg6zRjyntjcCpIgkrogyPQuKlvoQREQR8jLKN5UD4L5rkTSD+oBhcKtaLR2/g34FexURw==",
+            "version": "1.3.0",
+            "resolved": "https://registry.npmjs.org/vscode-test/-/vscode-test-1.3.0.tgz",
+            "integrity": "sha512-LddukcBiSU2FVTDr3c1D8lwkiOvwlJdDL2hqVbn6gIz+rpTqUCkMZSKYm94Y1v0WXlHSDQBsXyY+tchWQgGVsw==",
             "dev": true,
             "requires": {
                 "http-proxy-agent": "^2.1.0",
diff --git a/editors/code/package.json b/editors/code/package.json
index f2e8e647e..f75fafeb9 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -13,7 +13,7 @@
         "Other"
     ],
     "engines": {
-        "vscode": "^1.40.0"
+        "vscode": "^1.41.0"
     },
     "scripts": {
         "vscode:prepublish": "npm run compile",
@@ -32,20 +32,20 @@
         "trailingComma": "all"
     },
     "dependencies": {
-        "lookpath": "^1.0.3",
+        "lookpath": "^1.0.4",
         "seedrandom": "^3.0.5",
-        "vscode-languageclient": "^6.0.0-next.8"
+        "vscode-languageclient": "^6.0.0-next.9"
     },
     "devDependencies": {
         "@types/glob": "^7.1.1",
         "@types/mocha": "^5.2.7",
-        "@types/node": "^10.17.6",
+        "@types/node": "^12.12.21",
         "@types/seedrandom": "^2.4.28",
-        "@types/vscode": "^1.40.0",
+        "@types/vscode": "^1.41.0",
         "glob": "^7.1.6",
         "mocha": "^6.2.2",
         "prettier": "^1.19.1",
-        "rollup": "^1.27.9",
+        "rollup": "^1.27.13",
         "rollup-plugin-commonjs": "^10.1.0",
         "rollup-plugin-node-resolve": "^5.2.0",
         "rollup-plugin-sourcemaps": "^0.4.2",
@@ -55,8 +55,8 @@
         "tslint-config-prettier": "^1.18.0",
         "tslint-plugin-prettier": "^2.0.1",
         "typescript": "^3.7.3",
-        "vsce": "^1.70.0",
-        "vscode-test": "^1.2.3"
+        "vsce": "^1.71.0",
+        "vscode-test": "^1.3.0"
     },
     "activationEvents": [
         "onLanguage:rust",
diff --git a/editors/code/src/commands/cargo_watch.ts b/editors/code/src/commands/cargo_watch.ts
index 748be535c..ac62bdd48 100644
--- a/editors/code/src/commands/cargo_watch.ts
+++ b/editors/code/src/commands/cargo_watch.ts
@@ -111,8 +111,13 @@ export class CargoWatchProvider implements vscode.Disposable {
             },
         );
 
+        if (!this.cargoProcess) {
+            vscode.window.showErrorMessage('Cargo Watch failed to start');
+            return;
+        }
+
         const stdoutData = new LineBuffer();
-        this.cargoProcess.stdout.on('data', (s: string) => {
+        this.cargoProcess.stdout?.on('data', (s: string) => {
             stdoutData.processOutput(s, line => {
                 this.logInfo(line);
                 try {
@@ -124,7 +129,7 @@ export class CargoWatchProvider implements vscode.Disposable {
         });
 
         const stderrData = new LineBuffer();
-        this.cargoProcess.stderr.on('data', (s: string) => {
+        this.cargoProcess.stderr?.on('data', (s: string) => {
             stderrData.processOutput(s, line => {
                 this.logError('Error on cargo-watch : {\n' + line + '}\n');
             });