15 files changed, 409 insertions, 135 deletions

diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index 443b057ab..c69e0efea 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -60,13 +60,10 @@ pub(super) fn lower(
     params: Option<ast::ParamList>,
     body: Option<ast::Expr>,
 ) -> (Body, BodySourceMap) {
-    let ctx = LowerCtx::new(db, expander.current_file_id.clone());
-
     ExprCollector {
         db,
         def,
         expander,
-        ctx,
         source_map: BodySourceMap::default(),
         body: Body {
             exprs: Arena::default(),
@@ -83,7 +80,6 @@ struct ExprCollector<'a> {
     db: &'a dyn DefDatabase,
     def: DefWithBodyId,
     expander: Expander,
-    ctx: LowerCtx,
     body: Body,
     source_map: BodySourceMap,
 }
@@ -122,6 +118,10 @@ impl ExprCollector<'_> {
         (self.body, self.source_map)
     }
 
+    fn ctx(&self) -> LowerCtx {
+        LowerCtx::new(self.db, self.expander.current_file_id)
+    }
+
     fn alloc_expr(&mut self, expr: Expr, ptr: AstPtr<ast::Expr>) -> ExprId {
         let src = self.expander.to_source(ptr);
         let id = self.make_expr(expr, Ok(src.clone()));
@@ -268,7 +268,7 @@ impl ExprCollector<'_> {
                 };
                 let method_name = e.name_ref().map(|nr| nr.as_name()).unwrap_or_else(Name::missing);
                 let generic_args =
-                    e.type_arg_list().and_then(|it| GenericArgs::from_ast(&self.ctx, it));
+                    e.type_arg_list().and_then(|it| GenericArgs::from_ast(&self.ctx(), it));
                 self.alloc_expr(
                     Expr::MethodCall { receiver, method_name, args, generic_args },
                     syntax_ptr,
@@ -373,7 +373,7 @@ impl ExprCollector<'_> {
             }
             ast::Expr::CastExpr(e) => {
                 let expr = self.collect_expr_opt(e.expr());
-                let type_ref = TypeRef::from_ast_opt(&self.ctx, e.type_ref());
+                let type_ref = TypeRef::from_ast_opt(&self.ctx(), e.type_ref());
                 self.alloc_expr(Expr::Cast { expr, type_ref }, syntax_ptr)
             }
             ast::Expr::RefExpr(e) => {
@@ -396,7 +396,7 @@ impl ExprCollector<'_> {
                     for param in pl.params() {
                         let pat = self.collect_pat_opt(param.pat());
                         let type_ref =
-                            param.ascribed_type().map(|it| TypeRef::from_ast(&self.ctx, it));
+                            param.ascribed_type().map(|it| TypeRef::from_ast(&self.ctx(), it));
                         args.push(pat);
                         arg_types.push(type_ref);
                     }
@@ -404,7 +404,7 @@ impl ExprCollector<'_> {
                 let ret_type = e
                     .ret_type()
                     .and_then(|r| r.type_ref())
-                    .map(|it| TypeRef::from_ast(&self.ctx, it));
+                    .map(|it| TypeRef::from_ast(&self.ctx(), it));
                 let body = self.collect_expr_opt(e.body());
                 self.alloc_expr(Expr::Lambda { args, arg_types, ret_type, body }, syntax_ptr)
             }
@@ -507,7 +507,8 @@ impl ExprCollector<'_> {
             .map(|s| match s {
                 ast::Stmt::LetStmt(stmt) => {
                     let pat = self.collect_pat_opt(stmt.pat());
-                    let type_ref = stmt.ascribed_type().map(|it| TypeRef::from_ast(&self.ctx, it));
+                    let type_ref =
+                        stmt.ascribed_type().map(|it| TypeRef::from_ast(&self.ctx(), it));
                     let initializer = stmt.initializer().map(|e| self.collect_expr(e));
                     Statement::Let { pat, type_ref, initializer }
                 }
diff --git a/crates/ra_hir_def/src/db.rs b/crates/ra_hir_def/src/db.rs
index e665ab45d..2f71511ba 100644
--- a/crates/ra_hir_def/src/db.rs
+++ b/crates/ra_hir_def/src/db.rs
@@ -1,7 +1,7 @@
 //! Defines database & queries for name resolution.
 use std::sync::Arc;
 
-use hir_expand::{db::AstDatabase, HirFileId};
+use hir_expand::{db::AstDatabase, name::Name, HirFileId};
 use ra_db::{salsa, CrateId, SourceDatabase, Upcast};
 use ra_prof::profile;
 use ra_syntax::SmolStr;
@@ -12,9 +12,12 @@ use crate::{
     body::{scope::ExprScopes, Body, BodySourceMap},
     data::{ConstData, FunctionData, ImplData, StaticData, TraitData, TypeAliasData},
     docs::Documentation,
+    find_path,
     generics::GenericParams,
+    item_scope::ItemInNs,
     lang_item::{LangItemTarget, LangItems},
     nameres::{raw::RawItems, CrateDefMap},
+    visibility::Visibility,
     AttrDefId, ConstId, ConstLoc, DefWithBodyId, EnumId, EnumLoc, FunctionId, FunctionLoc,
     GenericDefId, ImplId, ImplLoc, ModuleId, StaticId, StaticLoc, StructId, StructLoc, TraitId,
     TraitLoc, TypeAliasId, TypeAliasLoc, UnionId, UnionLoc,
@@ -108,6 +111,13 @@ pub trait DefDatabase: InternDatabase + AstDatabase + Upcast<dyn AstDatabase> {
     // Remove this query completely, in favor of `Attrs::docs` method
     #[salsa::invoke(Documentation::documentation_query)]
     fn documentation(&self, def: AttrDefId) -> Option<Documentation>;
+
+    #[salsa::invoke(find_path::importable_locations_of_query)]
+    fn importable_locations_of(
+        &self,
+        item: ItemInNs,
+        krate: CrateId,
+    ) -> Arc<[(ModuleId, Name, Visibility)]>;
 }
 
 fn crate_def_map_wait(db: &impl DefDatabase, krate: CrateId) -> Arc<CrateDefMap> {
diff --git a/crates/ra_hir_def/src/find_path.rs b/crates/ra_hir_def/src/find_path.rs
index 70dcb03e6..2eb12ec8f 100644
--- a/crates/ra_hir_def/src/find_path.rs
+++ b/crates/ra_hir_def/src/find_path.rs
@@ -1,5 +1,11 @@
 //! An algorithm to find a path to refer to a certain item.
 
+use std::sync::Arc;
+
+use hir_expand::name::{known, AsName, Name};
+use ra_prof::profile;
+use test_utils::tested_by;
+
 use crate::{
     db::DefDatabase,
     item_scope::ItemInNs,
@@ -7,25 +13,28 @@ use crate::{
     visibility::Visibility,
     CrateId, ModuleDefId, ModuleId,
 };
-use hir_expand::name::{known, AsName, Name};
-use test_utils::tested_by;
+
+// FIXME: handle local items
+
+/// Find a path that can be used to refer to a certain item. This can depend on
+/// *from where* you're referring to the item, hence the `from` parameter.
+pub fn find_path(db: &dyn DefDatabase, item: ItemInNs, from: ModuleId) -> Option<ModPath> {
+    let _p = profile("find_path");
+    find_path_inner(db, item, from, MAX_PATH_LEN)
+}
 
 const MAX_PATH_LEN: usize = 15;
 
 impl ModPath {
     fn starts_with_std(&self) -> bool {
-        self.segments.first().filter(|&first_segment| first_segment == &known::std).is_some()
+        self.segments.first() == Some(&known::std)
     }
 
     // When std library is present, paths starting with `std::`
     // should be preferred over paths starting with `core::` and `alloc::`
     fn can_start_with_std(&self) -> bool {
-        self.segments
-            .first()
-            .filter(|&first_segment| {
-                first_segment == &known::alloc || first_segment == &known::core
-            })
-            .is_some()
+        let first_segment = self.segments.first();
+        first_segment == Some(&known::alloc) || first_segment == Some(&known::core)
     }
 
     fn len(&self) -> usize {
@@ -40,14 +49,6 @@ impl ModPath {
     }
 }
 
-// FIXME: handle local items
-
-/// Find a path that can be used to refer to a certain item. This can depend on
-/// *from where* you're referring to the item, hence the `from` parameter.
-pub fn find_path(db: &dyn DefDatabase, item: ItemInNs, from: ModuleId) -> Option<ModPath> {
-    find_path_inner(db, item, from, MAX_PATH_LEN)
-}
-
 fn find_path_inner(
     db: &dyn DefDatabase,
     item: ItemInNs,
@@ -198,7 +199,7 @@ fn find_importable_locations(
         .chain(crate_graph[from.krate].dependencies.iter().map(|dep| dep.crate_id))
     {
         result.extend(
-            importable_locations_in_crate(db, item, krate)
+            db.importable_locations_of(item, krate)
                 .iter()
                 .filter(|(_, _, vis)| vis.is_visible_from(db, from))
                 .map(|(m, n, _)| (*m, n.clone())),
@@ -213,11 +214,12 @@ fn find_importable_locations(
 ///
 /// Note that the crate doesn't need to be the one in which the item is defined;
 /// it might be re-exported in other crates.
-fn importable_locations_in_crate(
+pub(crate) fn importable_locations_of_query(
     db: &dyn DefDatabase,
     item: ItemInNs,
     krate: CrateId,
-) -> Vec<(ModuleId, Name, Visibility)> {
+) -> Arc<[(ModuleId, Name, Visibility)]> {
+    let _p = profile("importable_locations_of_query");
     let def_map = db.crate_def_map(krate);
     let mut result = Vec::new();
     for (local_id, data) in def_map.modules.iter() {
@@ -243,7 +245,8 @@ fn importable_locations_in_crate(
             result.push((ModuleId { krate, local_id }, name.clone(), vis));
         }
     }
-    result
+
+    Arc::from(result)
 }
 
 #[cfg(test)]
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index ccc4348f4..daea02f88 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -808,15 +808,13 @@ impl Ty {
         }
     }
 
-    /// If this is an `impl Trait` or `dyn Trait`, returns that trait.
-    pub fn inherent_trait(&self) -> Option<TraitId> {
+    /// If this is a `dyn Trait`, returns that trait.
+    pub fn dyn_trait(&self) -> Option<TraitId> {
         match self {
-            Ty::Dyn(predicates) | Ty::Opaque(predicates) => {
-                predicates.iter().find_map(|pred| match pred {
-                    GenericPredicate::Implemented(tr) => Some(tr.trait_),
-                    _ => None,
-                })
-            }
+            Ty::Dyn(predicates) => predicates.iter().find_map(|pred| match pred {
+                GenericPredicate::Implemented(tr) => Some(tr.trait_),
+                _ => None,
+            }),
             _ => None,
         }
     }
diff --git a/crates/ra_hir_ty/src/method_resolution.rs b/crates/ra_hir_ty/src/method_resolution.rs
index 657284fd0..0851e16a8 100644
--- a/crates/ra_hir_ty/src/method_resolution.rs
+++ b/crates/ra_hir_ty/src/method_resolution.rs
@@ -408,8 +408,9 @@ fn iterate_trait_method_candidates<T>(
     receiver_ty: Option<&Canonical<Ty>>,
     mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>,
 ) -> Option<T> {
-    // if ty is `impl Trait` or `dyn Trait`, the trait doesn't need to be in scope
-    let inherent_trait = self_ty.value.inherent_trait().into_iter();
+    // if ty is `dyn Trait`, the trait doesn't need to be in scope
+    let inherent_trait =
+        self_ty.value.dyn_trait().into_iter().flat_map(|t| all_super_traits(db.upcast(), t));
     let env_traits = if let Ty::Placeholder(_) = self_ty.value {
         // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
         env.trait_predicates_for_self_ty(&self_ty.value)
@@ -601,11 +602,6 @@ pub fn implements_trait(
     krate: CrateId,
     trait_: TraitId,
 ) -> bool {
-    if ty.value.inherent_trait() == Some(trait_) {
-        // FIXME this is a bit of a hack, since Chalk should say the same thing
-        // anyway, but currently Chalk doesn't implement `dyn/impl Trait` yet
-        return true;
-    }
     let goal = generic_implements_goal(db, env, trait_, ty.clone());
     let solution = db.trait_solve(krate, goal);
 
diff --git a/crates/ra_hir_ty/src/tests/method_resolution.rs b/crates/ra_hir_ty/src/tests/method_resolution.rs
index 67f964ab5..9c2c9e1d2 100644
--- a/crates/ra_hir_ty/src/tests/method_resolution.rs
+++ b/crates/ra_hir_ty/src/tests/method_resolution.rs
@@ -1096,3 +1096,34 @@ fn test() { (S {}).method()<|>; }
     );
     assert_eq!(t, "()");
 }
+
+#[test]
+fn dyn_trait_super_trait_not_in_scope() {
+    assert_snapshot!(
+        infer(r#"
+mod m {
+    pub trait SuperTrait {
+        fn foo(&self) -> u32 { 0 }
+    }
+}
+trait Trait: m::SuperTrait {}
+
+struct S;
+impl m::SuperTrait for S {}
+impl Trait for S {}
+
+fn test(d: &dyn Trait) {
+    d.foo();
+}
+"#),
+        @r###"
+    52..56 'self': &Self
+    65..70 '{ 0 }': u32
+    67..68 '0': u32
+    177..178 'd': &dyn Trait
+    192..208 '{     ...o(); }': ()
+    198..199 'd': &dyn Trait
+    198..205 'd.foo()': u32
+    "###
+    );
+}
diff --git a/crates/ra_hir_ty/src/tests/regression.rs b/crates/ra_hir_ty/src/tests/regression.rs
index 115ad8328..c2168222e 100644
--- a/crates/ra_hir_ty/src/tests/regression.rs
+++ b/crates/ra_hir_ty/src/tests/regression.rs
@@ -564,6 +564,37 @@ fn main() {
 }
 
 #[test]
+fn issue_4465_dollar_crate_at_type() {
+    assert_snapshot!(
+        infer(r#"
+pub struct Foo {}
+pub fn anything<T>() -> T {
+    loop {}
+}
+macro_rules! foo {
+    () => {{
+        let r: $crate::Foo = anything();
+        r
+    }};
+}
+fn main() {
+    let _a = foo!();
+}
+"#), @r###"
+    45..60 '{     loop {} }': T
+    51..58 'loop {}': !
+    56..58 '{}': ()
+    !0..31 '{letr:...g();r}': Foo
+    !4..5 'r': Foo
+    !18..26 'anything': fn anything<Foo>() -> Foo
+    !18..28 'anything()': Foo
+    !29..30 'r': Foo
+    164..188 '{     ...!(); }': ()
+    174..176 '_a': Foo
+"###);
+}
+
+#[test]
 fn issue_4053_diesel_where_clauses() {
     assert_snapshot!(
         infer(r#"
diff --git a/crates/ra_hir_ty/src/tests/traits.rs b/crates/ra_hir_ty/src/tests/traits.rs
index 9d32cbc7a..c49aacf98 100644
--- a/crates/ra_hir_ty/src/tests/traits.rs
+++ b/crates/ra_hir_ty/src/tests/traits.rs
@@ -1617,6 +1617,138 @@ fn test<F: FnOnce(u32, u64) -> u128>(f: F) {
 }
 
 #[test]
+fn fn_ptr_and_item() {
+    assert_snapshot!(
+        infer(r#"
+#[lang="fn_once"]
+trait FnOnce<Args> {
+    type Output;
+
+    fn call_once(self, args: Args) -> Self::Output;
+}
+
+trait Foo<T> {
+    fn foo(&self) -> T;
+}
+
+struct Bar<T>(T);
+
+impl<A1, R, F: FnOnce(A1) -> R> Foo<(A1, R)> for Bar<F> {
+    fn foo(&self) -> (A1, R) {}
+}
+
+enum Opt<T> { None, Some(T) }
+impl<T> Opt<T> {
+    fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Opt<U> {}
+}
+
+fn test() {
+    let bar: Bar<fn(u8) -> u32>;
+    bar.foo();
+
+    let opt: Opt<u8>;
+    let f: fn(u8) -> u32;
+    opt.map(f);
+}
+"#),
+        @r###"
+75..79 'self': Self
+81..85 'args': Args
+140..144 'self': &Self
+244..248 'self': &Bar<F>
+261..263 '{}': ()
+347..351 'self': Opt<T>
+353..354 'f': F
+369..371 '{}': ()
+385..501 '{     ...(f); }': ()
+395..398 'bar': Bar<fn(u8) -> u32>
+424..427 'bar': Bar<fn(u8) -> u32>
+424..433 'bar.foo()': {unknown}
+444..447 'opt': Opt<u8>
+466..467 'f': fn(u8) -> u32
+488..491 'opt': Opt<u8>
+488..498 'opt.map(f)': Opt<FnOnce::Output<fn(u8) -> u32, (u8,)>>
+496..497 'f': fn(u8) -> u32
+"###
+    );
+}
+
+#[test]
+fn fn_trait_deref_with_ty_default() {
+    assert_snapshot!(
+        infer(r#"
+#[lang = "deref"]
+trait Deref {
+    type Target;
+
+    fn deref(&self) -> &Self::Target;
+}
+
+#[lang="fn_once"]
+trait FnOnce<Args> {
+    type Output;
+
+    fn call_once(self, args: Args) -> Self::Output;
+}
+
+struct Foo;
+
+impl Foo {
+    fn foo(&self) -> usize {}
+}
+
+struct Lazy<T, F = fn() -> T>(F);
+
+impl<T, F> Lazy<T, F> {
+    pub fn new(f: F) -> Lazy<T, F> {}
+}
+
+impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
+    type Target = T;
+}
+
+fn test() {
+    let lazy1: Lazy<Foo, _> = Lazy::new(|| Foo);
+    let r1 = lazy1.foo();
+
+    fn make_foo_fn() -> Foo {}
+    let make_foo_fn_ptr: fn() -> Foo = make_foo_fn;
+    let lazy2: Lazy<Foo, _> = Lazy::new(make_foo_fn_ptr);
+    let r2 = lazy2.foo();
+}
+"#),
+        @r###"
+65..69 'self': &Self
+166..170 'self': Self
+172..176 'args': Args
+240..244 'self': &Foo
+255..257 '{}': ()
+335..336 'f': F
+355..357 '{}': ()
+444..690 '{     ...o(); }': ()
+454..459 'lazy1': Lazy<Foo, fn() -> T>
+476..485 'Lazy::new': fn new<Foo, fn() -> T>(fn() -> T) -> Lazy<Foo, fn() -> T>
+476..493 'Lazy::...| Foo)': Lazy<Foo, fn() -> T>
+486..492 '|| Foo': || -> T
+489..492 'Foo': Foo
+503..505 'r1': {unknown}
+508..513 'lazy1': Lazy<Foo, fn() -> T>
+508..519 'lazy1.foo()': {unknown}
+561..576 'make_foo_fn_ptr': fn() -> Foo
+592..603 'make_foo_fn': fn make_foo_fn() -> Foo
+613..618 'lazy2': Lazy<Foo, fn() -> T>
+635..644 'Lazy::new': fn new<Foo, fn() -> T>(fn() -> T) -> Lazy<Foo, fn() -> T>
+635..661 'Lazy::...n_ptr)': Lazy<Foo, fn() -> T>
+645..660 'make_foo_fn_ptr': fn() -> Foo
+671..673 'r2': {unknown}
+676..681 'lazy2': Lazy<Foo, fn() -> T>
+676..687 'lazy2.foo()': {unknown}
+550..552 '{}': ()
+"###
+    );
+}
+
+#[test]
 fn closure_1() {
     assert_snapshot!(
         infer(r#"
diff --git a/crates/ra_mbe/src/mbe_expander/transcriber.rs b/crates/ra_mbe/src/mbe_expander/transcriber.rs
index 4b173edd3..7c9bb4d00 100644
--- a/crates/ra_mbe/src/mbe_expander/transcriber.rs
+++ b/crates/ra_mbe/src/mbe_expander/transcriber.rs
@@ -1,4 +1,4 @@
-//! Transcraber takes a template, like `fn $ident() {}`, a set of bindings like
+//! Transcriber takes a template, like `fn $ident() {}`, a set of bindings like
 //! `$ident => foo`, interpolates variables in the template, to get `fn foo() {}`
 
 use ra_syntax::SmolStr;
@@ -53,7 +53,8 @@ impl Bindings {
 pub(super) fn transcribe(template: &tt::Subtree, bindings: &Bindings) -> ExpandResult<tt::Subtree> {
     assert!(template.delimiter == None);
     let mut ctx = ExpandCtx { bindings: &bindings, nesting: Vec::new() };
-    expand_subtree(&mut ctx, template)
+    let mut arena: Vec<tt::TokenTree> = Vec::new();
+    expand_subtree(&mut ctx, template, &mut arena)
 }
 
 #[derive(Debug)]
@@ -73,8 +74,13 @@ struct ExpandCtx<'a> {
     nesting: Vec<NestingState>,
 }
 
-fn expand_subtree(ctx: &mut ExpandCtx, template: &tt::Subtree) -> ExpandResult<tt::Subtree> {
-    let mut buf: Vec<tt::TokenTree> = Vec::new();
+fn expand_subtree(
+    ctx: &mut ExpandCtx,
+    template: &tt::Subtree,
+    arena: &mut Vec<tt::TokenTree>,
+) -> ExpandResult<tt::Subtree> {
+    // remember how many elements are in the arena now - when returning, we want to drain exactly how many elements we added. This way, the recursive uses of the arena get their own "view" of the arena, but will reuse the allocation
+    let start_elements = arena.len();
     let mut err = None;
     for op in parse_template(template) {
         let op = match op {
@@ -85,25 +91,27 @@ fn expand_subtree(ctx: &mut ExpandCtx, template: &tt::Subtree) -> ExpandResult<t
             }
         };
         match op {
-            Op::TokenTree(tt @ tt::TokenTree::Leaf(..)) => buf.push(tt.clone()),
+            Op::TokenTree(tt @ tt::TokenTree::Leaf(..)) => arena.push(tt.clone()),
             Op::TokenTree(tt::TokenTree::Subtree(tt)) => {
-                let ExpandResult(tt, e) = expand_subtree(ctx, tt);
+                let ExpandResult(tt, e) = expand_subtree(ctx, tt, arena);
                 err = err.or(e);
-                buf.push(tt.into());
+                arena.push(tt.into());
             }
             Op::Var { name, kind: _ } => {
                 let ExpandResult(fragment, e) = expand_var(ctx, name);
                 err = err.or(e);
-                push_fragment(&mut buf, fragment);
+                push_fragment(arena, fragment);
             }
             Op::Repeat { subtree, kind, separator } => {
-                let ExpandResult(fragment, e) = expand_repeat(ctx, subtree, kind, separator);
+                let ExpandResult(fragment, e) = expand_repeat(ctx, subtree, kind, separator, arena);
                 err = err.or(e);
-                push_fragment(&mut buf, fragment)
+                push_fragment(arena, fragment)
             }
         }
     }
-    ExpandResult(tt::Subtree { delimiter: template.delimiter, token_trees: buf }, err)
+    // drain the elements added in this instance of expand_subtree
+    let tts = arena.drain(start_elements..arena.len()).collect();
+    ExpandResult(tt::Subtree { delimiter: template.delimiter, token_trees: tts }, err)
 }
 
 fn expand_var(ctx: &mut ExpandCtx, v: &SmolStr) -> ExpandResult<Fragment> {
@@ -155,6 +163,7 @@ fn expand_repeat(
     template: &tt::Subtree,
     kind: RepeatKind,
     separator: Option<Separator>,
+    arena: &mut Vec<tt::TokenTree>,
 ) -> ExpandResult<Fragment> {
     let mut buf: Vec<tt::TokenTree> = Vec::new();
     ctx.nesting.push(NestingState { idx: 0, at_end: false, hit: false });
@@ -165,7 +174,7 @@ fn expand_repeat(
     let mut counter = 0;
 
     loop {
-        let ExpandResult(mut t, e) = expand_subtree(ctx, template);
+        let ExpandResult(mut t, e) = expand_subtree(ctx, template, arena);
         let nesting_state = ctx.nesting.last_mut().unwrap();
         if nesting_state.at_end || !nesting_state.hit {
             break;
diff --git a/crates/ra_parser/src/lib.rs b/crates/ra_parser/src/lib.rs
index e08ad4dae..eeb8ad66b 100644
--- a/crates/ra_parser/src/lib.rs
+++ b/crates/ra_parser/src/lib.rs
@@ -25,7 +25,7 @@ pub(crate) use token_set::TokenSet;
 pub use syntax_kind::SyntaxKind;
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct ParseError(pub String);
+pub struct ParseError(pub Box<String>);
 
 /// `TokenSource` abstracts the source of the tokens parser operates on.
 ///
diff --git a/crates/ra_parser/src/parser.rs b/crates/ra_parser/src/parser.rs
index faa63d53f..4f59b0a23 100644
--- a/crates/ra_parser/src/parser.rs
+++ b/crates/ra_parser/src/parser.rs
@@ -192,7 +192,7 @@ impl<'t> Parser<'t> {
     /// structured errors with spans and notes, like rustc
     /// does.
     pub(crate) fn error<T: Into<String>>(&mut self, message: T) {
-        let msg = ParseError(message.into());
+        let msg = ParseError(Box::new(message.into()));
         self.push_event(Event::Error { msg })
     }
 
diff --git a/crates/ra_syntax/src/syntax_node.rs b/crates/ra_syntax/src/syntax_node.rs
index f9d379abf..e566af7e8 100644
--- a/crates/ra_syntax/src/syntax_node.rs
+++ b/crates/ra_syntax/src/syntax_node.rs
@@ -70,6 +70,6 @@ impl SyntaxTreeBuilder {
     }
 
     pub fn error(&mut self, error: ra_parser::ParseError, text_pos: TextSize) {
-        self.errors.push(SyntaxError::new_at_offset(error.0, text_pos))
+        self.errors.push(SyntaxError::new_at_offset(*error.0, text_pos))
     }
 }
diff --git a/crates/ra_tt/src/buffer.rs b/crates/ra_tt/src/buffer.rs
index 14b3f707d..5967f44cd 100644
--- a/crates/ra_tt/src/buffer.rs
+++ b/crates/ra_tt/src/buffer.rs
@@ -42,7 +42,9 @@ impl<'t> TokenBuffer<'t> {
         buffers: &mut Vec<Box<[Entry<'t>]>>,
         next: Option<EntryPtr>,
     ) -> usize {
-        let mut entries = vec![];
+        // Must contain everything in tokens and then the Entry::End
+        let start_capacity = tokens.len() + 1;
+        let mut entries = Vec::with_capacity(start_capacity);
         let mut children = vec![];
 
         for (idx, tt) in tokens.iter().enumerate() {
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 53aee833d..b5dc6f0fa 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -33,6 +33,36 @@ pub struct Config {
     pub inlay_hints: InlayHintsConfig,
     pub completion: CompletionConfig,
     pub call_info_full: bool,
+    pub lens: LensConfig,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct LensConfig {
+    pub run: bool,
+    pub debug: bool,
+    pub impementations: bool,
+}
+
+impl Default for LensConfig {
+    fn default() -> Self {
+        Self { run: true, debug: true, impementations: true }
+    }
+}
+
+impl LensConfig {
+    pub const NO_LENS: LensConfig = Self { run: false, debug: false, impementations: false };
+
+    pub fn any(&self) -> bool {
+        self.impementations || self.runnable()
+    }
+
+    pub fn none(&self) -> bool {
+        !self.any()
+    }
+
+    pub fn runnable(&self) -> bool {
+        self.run || self.debug
+    }
 }
 
 #[derive(Debug, Clone)]
@@ -107,6 +137,7 @@ impl Default for Config {
                 ..CompletionConfig::default()
             },
             call_info_full: true,
+            lens: LensConfig::default(),
         }
     }
 }
@@ -196,6 +227,16 @@ impl Config {
         set(value, "/completion/addCallArgumentSnippets", &mut self.completion.add_call_argument_snippets);
         set(value, "/callInfo/full", &mut self.call_info_full);
 
+        let mut lens_enabled = true;
+        set(value, "/lens/enable", &mut lens_enabled);
+        if lens_enabled {
+            set(value, "/lens/run", &mut self.lens.run);
+            set(value, "/lens/debug", &mut self.lens.debug);
+            set(value, "/lens/implementations", &mut self.lens.impementations);
+        } else {
+            self.lens = LensConfig::NO_LENS;
+        }
+
         log::info!("Config::update() = {:#?}", self);
 
         fn get<'a, T: Deserialize<'a>>(value: &'a serde_json::Value, pointer: &str) -> Option<T> {
diff --git a/crates/rust-analyzer/src/main_loop/handlers.rs b/crates/rust-analyzer/src/main_loop/handlers.rs
index 6b14830b6..e67556752 100644
--- a/crates/rust-analyzer/src/main_loop/handlers.rs
+++ b/crates/rust-analyzer/src/main_loop/handlers.rs
@@ -812,88 +812,108 @@ pub fn handle_code_lens(
     params: lsp_types::CodeLensParams,
 ) -> Result<Option<Vec<CodeLens>>> {
     let _p = profile("handle_code_lens");
-    let file_id = from_proto::file_id(&world, &params.text_document.uri)?;
-    let line_index = world.analysis().file_line_index(file_id)?;
-
     let mut lenses: Vec<CodeLens> = Default::default();
 
+    if world.config.lens.none() {
+        // early return before any db query!
+        return Ok(Some(lenses));
+    }
+
+    let file_id = from_proto::file_id(&world, &params.text_document.uri)?;
+    let line_index = world.analysis().file_line_index(file_id)?;
     let cargo_spec = CargoTargetSpec::for_file(&world, file_id)?;
-    // Gather runnables
-    for runnable in world.analysis().runnables(file_id)? {
-        let title = match &runnable.kind {
-            RunnableKind::Test { .. } | RunnableKind::TestMod { .. } => "▶\u{fe0e} Run Test",
-            RunnableKind::DocTest { .. } => "▶\u{fe0e} Run Doctest",
-            RunnableKind::Bench { .. } => "Run Bench",
-            RunnableKind::Bin => {
-                // Do not suggest binary run on other target than binary
-                match &cargo_spec {
-                    Some(spec) => match spec.target_kind {
-                        TargetKind::Bin => "Run",
-                        _ => continue,
-                    },
-                    None => continue,
+
+    if world.config.lens.runnable() {
+        // Gather runnables
+        for runnable in world.analysis().runnables(file_id)? {
+            let (run_title, debugee) = match &runnable.kind {
+                RunnableKind::Test { .. } | RunnableKind::TestMod { .. } => {
+                    ("▶️\u{fe0e}Run Test", true)
                 }
+                RunnableKind::DocTest { .. } => {
+                    // cargo does not support -no-run for doctests
+                    ("▶️\u{fe0e}Run Doctest", false)
+                }
+                RunnableKind::Bench { .. } => {
+                    // Nothing wrong with bench debugging
+                    ("Run Bench", true)
+                }
+                RunnableKind::Bin => {
+                    // Do not suggest binary run on other target than binary
+                    match &cargo_spec {
+                        Some(spec) => match spec.target_kind {
+                            TargetKind::Bin => ("Run", true),
+                            _ => continue,
+                        },
+                        None => continue,
+                    }
+                }
+            };
+
+            let mut r = to_lsp_runnable(&world, file_id, runnable)?;
+            if world.config.lens.run {
+                let lens = CodeLens {
+                    range: r.range,
+                    command: Some(Command {
+                        title: run_title.to_string(),
+                        command: "rust-analyzer.runSingle".into(),
+                        arguments: Some(vec![to_value(&r).unwrap()]),
+                    }),
+                    data: None,
+                };
+                lenses.push(lens);
             }
-        }
-        .to_string();
-        let mut r = to_lsp_runnable(&world, file_id, runnable)?;
-        let lens = CodeLens {
-            range: r.range,
-            command: Some(Command {
-                title,
-                command: "rust-analyzer.runSingle".into(),
-                arguments: Some(vec![to_value(&r).unwrap()]),
-            }),
-            data: None,
-        };
-        lenses.push(lens);
 
-        if r.args[0] == "run" {
-            r.args[0] = "build".into();
-        } else {
-            r.args.push("--no-run".into());
+            if debugee && world.config.lens.debug {
+                if r.args[0] == "run" {
+                    r.args[0] = "build".into();
+                } else {
+                    r.args.push("--no-run".into());
+                }
+                let debug_lens = CodeLens {
+                    range: r.range,
+                    command: Some(Command {
+                        title: "Debug".into(),
+                        command: "rust-analyzer.debugSingle".into(),
+                        arguments: Some(vec![to_value(r).unwrap()]),
+                    }),
+                    data: None,
+                };
+                lenses.push(debug_lens);
+            }
         }
-        let debug_lens = CodeLens {
-            range: r.range,
-            command: Some(Command {
-                title: "Debug".into(),
-                command: "rust-analyzer.debugSingle".into(),
-                arguments: Some(vec![to_value(r).unwrap()]),
-            }),
-            data: None,
-        };
-        lenses.push(debug_lens);
     }
 
-    // Handle impls
-    lenses.extend(
-        world
-            .analysis()
-            .file_structure(file_id)?
-            .into_iter()
-            .filter(|it| match it.kind {
-                SyntaxKind::TRAIT_DEF | SyntaxKind::STRUCT_DEF | SyntaxKind::ENUM_DEF => true,
-                _ => false,
-            })
-            .map(|it| {
-                let range = to_proto::range(&line_index, it.node_range);
-                let pos = range.start;
-                let lens_params = lsp_types::request::GotoImplementationParams {
-                    text_document_position_params: lsp_types::TextDocumentPositionParams::new(
-                        params.text_document.clone(),
-                        pos,
-                    ),
-                    work_done_progress_params: Default::default(),
-                    partial_result_params: Default::default(),
-                };
-                CodeLens {
-                    range,
-                    command: None,
-                    data: Some(to_value(CodeLensResolveData::Impls(lens_params)).unwrap()),
-                }
-            }),
-    );
-
+    if world.config.lens.impementations {
+        // Handle impls
+        lenses.extend(
+            world
+                .analysis()
+                .file_structure(file_id)?
+                .into_iter()
+                .filter(|it| match it.kind {
+                    SyntaxKind::TRAIT_DEF | SyntaxKind::STRUCT_DEF | SyntaxKind::ENUM_DEF => true,
+                    _ => false,
+                })
+                .map(|it| {
+                    let range = to_proto::range(&line_index, it.node_range);
+                    let pos = range.start;
+                    let lens_params = lsp_types::request::GotoImplementationParams {
+                        text_document_position_params: lsp_types::TextDocumentPositionParams::new(
+                            params.text_document.clone(),
+                            pos,
+                        ),
+                        work_done_progress_params: Default::default(),
+                        partial_result_params: Default::default(),
+                    };
+                    CodeLens {
+                        range,
+                        command: None,
+                        data: Some(to_value(CodeLensResolveData::Impls(lens_params)).unwrap()),
+                    }
+                }),
+        );
+    }
     Ok(Some(lenses))
 }