47 files changed, 619 insertions, 305 deletions

diff --git a/Cargo.lock b/Cargo.lock
index bf1b9e417..efd1c6d33 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -275,9 +275,9 @@ checksum = "28b9d6de7f49e22cf97ad17fc4036ece69300032f45f78f30b4a4482cdc3f4a6"
 
 [[package]]
 name = "countme"
-version = "2.0.0-pre.2"
+version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c5716604cba7c02a846ecad3f4a3fd2d2b641faccc2a24a51efb21aff0d01f35"
+checksum = "4f8038ded86523aa26c1321dfe8bb432707d0a3e2608f9d0108803727546e089"
 dependencies = [
  "dashmap",
  "once_cell",
@@ -1400,9 +1400,9 @@ checksum = "b5eb417147ba9860a96cfe72a0b93bf88fee1744b5636ec99ab20c1aa9376581"
 
 [[package]]
 name = "rowan"
-version = "0.12.1"
+version = "0.12.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "24c2d78254049413f9d73495f883e7fa0b7a7d4b88468cd72a3bbbd0ad585cd1"
+checksum = "5e05df24c035422fb2b845d66ef3542d6c4f8572eafe077175a30787b0254207"
 dependencies = [
  "countme",
  "hashbrown",
@@ -1663,9 +1663,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.58"
+version = "1.0.59"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cc60a3d73ea6594cd712d830cc1f0390fd71542d8c8cd24e70cc54cdfd5e05d5"
+checksum = "07cb8b1b4ebf86a89ee88cbd201b022b94138c623644d035185c84d3f41b7e66"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1742,11 +1742,11 @@ dependencies = [
 
 [[package]]
 name = "thread_local"
-version = "1.1.0"
+version = "1.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bb9bc092d0d51e76b2b19d9d85534ffc9ec2db959a2523cdae0697e2972cd447"
+checksum = "301bdd13d23c49672926be451130892d274d3ba0b410c18e00daa7990ff38d99"
 dependencies = [
- "lazy_static",
+ "once_cell",
 ]
 
 [[package]]
@@ -1897,9 +1897,9 @@ checksum = "56dee185309b50d1f11bfedef0fe6d036842e3fb77413abef29f8f8d1c5d4c1c"
 
 [[package]]
 name = "ungrammar"
-version = "1.9.3"
+version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f5901372c0f3a6a1a9d880aef134c8eaf5e54409343637508c0a344270b42d7b"
+checksum = "ce24866975a8858d3a35eba845efc6b42962c5067afd2bc1a07b9ce0108d335c"
 
 [[package]]
 name = "unicase"
diff --git a/crates/completion/src/render.rs b/crates/completion/src/render.rs
index 6eb20df2b..e11b881ca 100644
--- a/crates/completion/src/render.rs
+++ b/crates/completion/src/render.rs
@@ -201,8 +201,7 @@ impl<'a> Render<'a> {
             ScopeDef::ModuleDef(Module(..)) => CompletionItemKind::SymbolKind(SymbolKind::Module),
             ScopeDef::ModuleDef(Adt(adt)) => CompletionItemKind::SymbolKind(match adt {
                 hir::Adt::Struct(_) => SymbolKind::Struct,
-                // FIXME: add CompletionItemKind::Union
-                hir::Adt::Union(_) => SymbolKind::Struct,
+                hir::Adt::Union(_) => SymbolKind::Union,
                 hir::Adt::Enum(_) => SymbolKind::Enum,
             }),
             ScopeDef::ModuleDef(Const(..)) => CompletionItemKind::SymbolKind(SymbolKind::Const),
diff --git a/crates/hir/src/code_model.rs b/crates/hir/src/code_model.rs
index d9b4cdfce..e9bb4f541 100644
--- a/crates/hir/src/code_model.rs
+++ b/crates/hir/src/code_model.rs
@@ -18,8 +18,8 @@ use hir_def::{
     type_ref::{Mutability, TypeRef},
     AdtId, AssocContainerId, AssocItemId, AssocItemLoc, AttrDefId, ConstId, ConstParamId,
     DefWithBodyId, EnumId, FunctionId, GenericDefId, HasModule, ImplId, LifetimeParamId,
-    LocalEnumVariantId, LocalFieldId, LocalModuleId, Lookup, ModuleId, StaticId, StructId, TraitId,
-    TypeAliasId, TypeParamId, UnionId,
+    LocalEnumVariantId, LocalFieldId, Lookup, ModuleId, StaticId, StructId, TraitId, TypeAliasId,
+    TypeParamId, UnionId,
 };
 use hir_def::{find_path::PrefixKind, item_scope::ItemInNs, visibility::Visibility};
 use hir_expand::{
@@ -90,8 +90,8 @@ impl Crate {
     }
 
     pub fn root_module(self, db: &dyn HirDatabase) -> Module {
-        let module_id = db.crate_def_map(self.id).root();
-        Module::new(self, module_id)
+        let def_map = db.crate_def_map(self.id);
+        Module { id: def_map.module_id(def_map.root()) }
     }
 
     pub fn root_file(self, db: &dyn HirDatabase) -> FileId {
@@ -275,10 +275,6 @@ impl ModuleDef {
 }
 
 impl Module {
-    pub(crate) fn new(krate: Crate, crate_module_id: LocalModuleId) -> Module {
-        Module { id: ModuleId::top_level(krate.id, crate_module_id) }
-    }
-
     /// Name of this module.
     pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
         let def_map = self.id.def_map(db.upcast());
@@ -302,7 +298,7 @@ impl Module {
     /// in the module tree of any target in `Cargo.toml`.
     pub fn crate_root(self, db: &dyn HirDatabase) -> Module {
         let def_map = db.crate_def_map(self.id.krate());
-        self.with_module_id(def_map.root())
+        Module { id: def_map.module_id(def_map.root()) }
     }
 
     /// Iterates over all child modules.
@@ -311,7 +307,7 @@ impl Module {
         let children = def_map[self.id.local_id]
             .children
             .iter()
-            .map(|(_, module_id)| self.with_module_id(*module_id))
+            .map(|(_, module_id)| Module { id: def_map.module_id(*module_id) })
             .collect::<Vec<_>>();
         children.into_iter()
     }
@@ -321,7 +317,7 @@ impl Module {
         // FIXME: handle block expressions as modules (their parent is in a different DefMap)
         let def_map = self.id.def_map(db.upcast());
         let parent_id = def_map[self.id.local_id].parent?;
-        Some(self.with_module_id(parent_id))
+        Some(Module { id: def_map.module_id(parent_id) })
     }
 
     pub fn path_to_root(self, db: &dyn HirDatabase) -> Vec<Module> {
@@ -406,10 +402,6 @@ impl Module {
         def_map[self.id.local_id].scope.impls().map(Impl::from).collect()
     }
 
-    pub(crate) fn with_module_id(self, module_id: LocalModuleId) -> Module {
-        Module::new(self.krate(), module_id)
-    }
-
     /// Finds a path that can be used to refer to the given item from within
     /// this module, if possible.
     pub fn find_use_path(self, db: &dyn DefDatabase, item: impl Into<ItemInNs>) -> Option<ModPath> {
@@ -1013,8 +1005,9 @@ impl MacroDef {
     /// early, in `hir_expand`, where modules simply do not exist yet.
     pub fn module(self, db: &dyn HirDatabase) -> Option<Module> {
         let krate = self.id.krate;
-        let module_id = db.crate_def_map(krate).root();
-        Some(Module::new(Crate { id: krate }, module_id))
+        let def_map = db.crate_def_map(krate);
+        let module_id = def_map.root();
+        Some(Module { id: def_map.module_id(module_id) })
     }
 
     /// XXX: this parses the file
diff --git a/crates/hir/src/diagnostics.rs b/crates/hir/src/diagnostics.rs
index 447faa04f..5343a036c 100644
--- a/crates/hir/src/diagnostics.rs
+++ b/crates/hir/src/diagnostics.rs
@@ -5,5 +5,5 @@ pub use hir_expand::diagnostics::{
 };
 pub use hir_ty::diagnostics::{
     IncorrectCase, MismatchedArgCount, MissingFields, MissingMatchArms, MissingOkOrSomeInTailExpr,
-    NoSuchField, RemoveThisSemicolon,
+    NoSuchField, RemoveThisSemicolon, ReplaceFilterMapNextWithFindMap,
 };
diff --git a/crates/hir/src/semantics/source_to_def.rs b/crates/hir/src/semantics/source_to_def.rs
index faede3269..6c612ee86 100644
--- a/crates/hir/src/semantics/source_to_def.rs
+++ b/crates/hir/src/semantics/source_to_def.rs
@@ -30,13 +30,12 @@ pub(super) struct SourceToDefCtx<'a, 'b> {
 impl SourceToDefCtx<'_, '_> {
     pub(super) fn file_to_def(&mut self, file: FileId) -> Option<ModuleId> {
         let _p = profile::span("SourceBinder::to_module_def");
-        let (krate, local_id) = self.db.relevant_crates(file).iter().find_map(|&crate_id| {
+        self.db.relevant_crates(file).iter().find_map(|&crate_id| {
             // FIXME: inner items
             let crate_def_map = self.db.crate_def_map(crate_id);
             let local_id = crate_def_map.modules_for_file(file).next()?;
-            Some((crate_id, local_id))
-        })?;
-        Some(ModuleId::top_level(krate, local_id))
+            Some(crate_def_map.module_id(local_id))
+        })
     }
 
     pub(super) fn module_to_def(&mut self, src: InFile<ast::Module>) -> Option<ModuleId> {
@@ -63,8 +62,7 @@ impl SourceToDefCtx<'_, '_> {
         let child_name = src.value.name()?.as_name();
         let def_map = parent_module.def_map(self.db.upcast());
         let child_id = *def_map[parent_module.local_id].children.get(&child_name)?;
-        // FIXME: handle block expression modules
-        Some(ModuleId::top_level(parent_module.krate(), child_id))
+        Some(def_map.module_id(child_id))
     }
 
     pub(super) fn trait_to_def(&mut self, src: InFile<ast::Trait>) -> Option<TraitId> {
diff --git a/crates/hir_def/src/db.rs b/crates/hir_def/src/db.rs
index a87c80b8a..aef7e1f6c 100644
--- a/crates/hir_def/src/db.rs
+++ b/crates/hir_def/src/db.rs
@@ -2,9 +2,9 @@
 use std::sync::Arc;
 
 use base_db::{salsa, CrateId, SourceDatabase, Upcast};
-use hir_expand::{db::AstDatabase, AstId, HirFileId};
+use hir_expand::{db::AstDatabase, HirFileId};
 use la_arena::ArenaMap;
-use syntax::{ast, SmolStr};
+use syntax::SmolStr;
 
 use crate::{
     adt::{EnumData, StructData},
@@ -16,9 +16,10 @@ use crate::{
     item_tree::ItemTree,
     lang_item::{LangItemTarget, LangItems},
     nameres::DefMap,
-    AttrDefId, ConstId, ConstLoc, DefWithBodyId, EnumId, EnumLoc, FunctionId, FunctionLoc,
-    GenericDefId, ImplId, ImplLoc, LocalEnumVariantId, LocalFieldId, StaticId, StaticLoc, StructId,
-    StructLoc, TraitId, TraitLoc, TypeAliasId, TypeAliasLoc, UnionId, UnionLoc, VariantId,
+    AttrDefId, BlockId, BlockLoc, ConstId, ConstLoc, DefWithBodyId, EnumId, EnumLoc, FunctionId,
+    FunctionLoc, GenericDefId, ImplId, ImplLoc, LocalEnumVariantId, LocalFieldId, StaticId,
+    StaticLoc, StructId, StructLoc, TraitId, TraitLoc, TypeAliasId, TypeAliasLoc, UnionId,
+    UnionLoc, VariantId,
 };
 
 #[salsa::query_group(InternDatabaseStorage)]
@@ -41,6 +42,8 @@ pub trait InternDatabase: SourceDatabase {
     fn intern_type_alias(&self, loc: TypeAliasLoc) -> TypeAliasId;
     #[salsa::interned]
     fn intern_impl(&self, loc: ImplLoc) -> ImplId;
+    #[salsa::interned]
+    fn intern_block(&self, loc: BlockLoc) -> BlockId;
 }
 
 #[salsa::query_group(DefDatabaseStorage)]
@@ -56,7 +59,7 @@ pub trait DefDatabase: InternDatabase + AstDatabase + Upcast<dyn AstDatabase> {
     fn crate_def_map_query(&self, krate: CrateId) -> Arc<DefMap>;
 
     #[salsa::invoke(DefMap::block_def_map_query)]
-    fn block_def_map(&self, krate: CrateId, block: AstId<ast::BlockExpr>) -> Arc<DefMap>;
+    fn block_def_map(&self, block: BlockId) -> Arc<DefMap>;
 
     #[salsa::invoke(StructData::struct_data_query)]
     fn struct_data(&self, id: StructId) -> Arc<StructData>;
diff --git a/crates/hir_def/src/find_path.rs b/crates/hir_def/src/find_path.rs
index c01b6daf2..94a1d567d 100644
--- a/crates/hir_def/src/find_path.rs
+++ b/crates/hir_def/src/find_path.rs
@@ -53,12 +53,8 @@ fn check_self_super(def_map: &DefMap, item: ItemInNs, from: ModuleId) -> Option<
         Some(ModPath::from_segments(PathKind::Super(0), Vec::new()))
     } else if let Some(parent_id) = def_map[from.local_id].parent {
         // - if the item is the parent module, use `super` (this is not used recursively, since `super::super` is ugly)
-        if item
-            == ItemInNs::Types(ModuleDefId::ModuleId(ModuleId {
-                krate: from.krate,
-                local_id: parent_id,
-            }))
-        {
+        let parent_id = def_map.module_id(parent_id);
+        if item == ItemInNs::Types(ModuleDefId::ModuleId(parent_id)) {
             Some(ModPath::from_segments(PathKind::Super(1), Vec::new()))
         } else {
             None
@@ -120,12 +116,8 @@ fn find_path_inner(
     }
 
     // - if the item is the crate root, return `crate`
-    if item
-        == ItemInNs::Types(ModuleDefId::ModuleId(ModuleId {
-            krate: from.krate,
-            local_id: def_map.root(),
-        }))
-    {
+    let root = def_map.module_id(def_map.root());
+    if item == ItemInNs::Types(ModuleDefId::ModuleId(root)) {
         return Some(ModPath::from_segments(PathKind::Crate, Vec::new()));
     }
 
@@ -175,7 +167,7 @@ fn find_path_inner(
 
     // - otherwise, look for modules containing (reexporting) it and import it from one of those
 
-    let crate_root = ModuleId { local_id: def_map.root(), krate: from.krate };
+    let crate_root = def_map.module_id(def_map.root());
     let crate_attrs = db.attrs(crate_root.into());
     let prefer_no_std = crate_attrs.by_key("no_std").exists();
     let mut best_path = None;
@@ -288,14 +280,11 @@ fn find_local_import_locations(
     // Compute the initial worklist. We start with all direct child modules of `from` as well as all
     // of its (recursive) parent modules.
     let data = &def_map[from.local_id];
-    let mut worklist = data
-        .children
-        .values()
-        .map(|child| ModuleId { krate: from.krate, local_id: *child })
-        .collect::<Vec<_>>();
+    let mut worklist =
+        data.children.values().map(|child| def_map.module_id(*child)).collect::<Vec<_>>();
     let mut parent = data.parent;
     while let Some(p) = parent {
-        worklist.push(ModuleId { krate: from.krate, local_id: p });
+        worklist.push(def_map.module_id(p));
         parent = def_map[p].parent;
     }
 
diff --git a/crates/hir_def/src/import_map.rs b/crates/hir_def/src/import_map.rs
index 0b7830445..0a3dc7956 100644
--- a/crates/hir_def/src/import_map.rs
+++ b/crates/hir_def/src/import_map.rs
@@ -75,7 +75,7 @@ impl ImportMap {
 
         // We look only into modules that are public(ly reexported), starting with the crate root.
         let empty = ImportPath { segments: vec![] };
-        let root = ModuleId { krate, local_id: def_map.root() };
+        let root = def_map.module_id(def_map.root());
         let mut worklist = vec![(root, empty)];
         while let Some((module, mod_path)) = worklist.pop() {
             let ext_def_map;
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index b8d7608e7..1e5c94660 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -66,7 +66,7 @@ impl GenericParamsId {
 }
 
 /// The item tree of a source file.
-#[derive(Debug, Eq, PartialEq)]
+#[derive(Debug, Default, Eq, PartialEq)]
 pub struct ItemTree {
     _c: Count<Self>,
 
@@ -82,7 +82,7 @@ impl ItemTree {
         let syntax = if let Some(node) = db.parse_or_expand(file_id) {
             node
         } else {
-            return Arc::new(Self::empty());
+            return Default::default();
         };
 
         let hygiene = Hygiene::new(db.upcast(), file_id);
@@ -118,15 +118,6 @@ impl ItemTree {
         Arc::new(item_tree)
     }
 
-    fn empty() -> Self {
-        Self {
-            _c: Count::new(),
-            top_level: Default::default(),
-            attrs: Default::default(),
-            data: Default::default(),
-        }
-    }
-
     fn shrink_to_fit(&mut self) {
         if let Some(data) = &mut self.data {
             let ItemTreeData {
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index ce470fc3b..8a71376b9 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -43,7 +43,7 @@ pub(super) struct Ctx {
 impl Ctx {
     pub(super) fn new(db: &dyn DefDatabase, hygiene: Hygiene, file: HirFileId) -> Self {
         Self {
-            tree: ItemTree::empty(),
+            tree: ItemTree::default(),
             hygiene,
             file,
             source_ast_id_map: db.ast_id_map(file),
diff --git a/crates/hir_def/src/lib.rs b/crates/hir_def/src/lib.rs
index c8dbb2aeb..42b50b5b7 100644
--- a/crates/hir_def/src/lib.rs
+++ b/crates/hir_def/src/lib.rs
@@ -74,16 +74,16 @@ use stdx::impl_from;
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ModuleId {
     krate: CrateId,
+    block: Option<BlockId>,
     pub local_id: LocalModuleId,
 }
 
 impl ModuleId {
-    pub fn top_level(krate: CrateId, local_id: LocalModuleId) -> Self {
-        Self { krate, local_id }
-    }
-
     pub fn def_map(&self, db: &dyn db::DefDatabase) -> Arc<DefMap> {
-        db.crate_def_map(self.krate)
+        match self.block {
+            Some(block) => db.block_def_map(block),
+            None => db.crate_def_map(self.krate),
+        }
     }
 
     pub fn krate(&self) -> CrateId {
@@ -234,6 +234,15 @@ pub struct ImplId(salsa::InternId);
 type ImplLoc = ItemLoc<Impl>;
 impl_intern!(ImplId, ImplLoc, intern_impl, lookup_intern_impl);
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub struct BlockId(salsa::InternId);
+#[derive(Debug, Hash, PartialEq, Eq, Clone)]
+pub struct BlockLoc {
+    ast_id: AstId<ast::BlockExpr>,
+    module: ModuleId,
+}
+impl_intern!(BlockId, BlockLoc, intern_block, lookup_intern_block);
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct TypeParamId {
     pub parent: GenericDefId,
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index bd3ea9b8b..199771e9a 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -62,7 +62,7 @@ use la_arena::Arena;
 use profile::Count;
 use rustc_hash::FxHashMap;
 use stdx::format_to;
-use syntax::{ast, AstNode};
+use syntax::ast;
 
 use crate::{
     db::DefDatabase,
@@ -70,14 +70,14 @@ use crate::{
     nameres::{diagnostics::DefDiagnostic, path_resolution::ResolveMode},
     path::ModPath,
     per_ns::PerNs,
-    AstId, LocalModuleId, ModuleDefId, ModuleId,
+    AstId, BlockId, BlockLoc, LocalModuleId, ModuleDefId, ModuleId,
 };
 
 /// Contains all top-level defs from a macro-expanded crate
 #[derive(Debug, PartialEq, Eq)]
 pub struct DefMap {
     _c: Count<Self>,
-    parent: Option<Arc<DefMap>>,
+    block: Option<BlockInfo>,
     root: LocalModuleId,
     modules: Arena<ModuleData>,
     krate: CrateId,
@@ -91,6 +91,13 @@ pub struct DefMap {
     diagnostics: Vec<DefDiagnostic>,
 }
 
+#[derive(Debug, PartialEq, Eq)]
+struct BlockInfo {
+    block: BlockId,
+    parent: Arc<DefMap>,
+    parent_module: LocalModuleId,
+}
+
 impl std::ops::Index<LocalModuleId> for DefMap {
     type Output = ModuleData;
     fn index(&self, id: LocalModuleId) -> &ModuleData {
@@ -190,15 +197,12 @@ impl DefMap {
         Arc::new(def_map)
     }
 
-    pub(crate) fn block_def_map_query(
-        db: &dyn DefDatabase,
-        krate: CrateId,
-        block: AstId<ast::BlockExpr>,
-    ) -> Arc<DefMap> {
-        let item_tree = db.item_tree(block.file_id);
-        let block_items = item_tree.inner_items_of_block(block.value);
+    pub(crate) fn block_def_map_query(db: &dyn DefDatabase, block_id: BlockId) -> Arc<DefMap> {
+        let block: BlockLoc = db.lookup_intern_block(block_id);
+        let item_tree = db.item_tree(block.ast_id.file_id);
+        let block_items = item_tree.inner_items_of_block(block.ast_id.value);
 
-        let parent = parent_def_map(db, krate, block);
+        let parent = block.module.def_map(db);
 
         if block_items.is_empty() {
             // If there are no inner items, nothing new is brought into scope, so we can just return
@@ -206,10 +210,13 @@ impl DefMap {
             return parent;
         }
 
-        let mut def_map = DefMap::empty(krate, parent.edition);
-        def_map.parent = Some(parent);
+        let block_info =
+            BlockInfo { block: block_id, parent, parent_module: block.module.local_id };
+
+        let mut def_map = DefMap::empty(block.module.krate, block_info.parent.edition);
+        def_map.block = Some(block_info);
 
-        let def_map = collector::collect_defs(db, def_map, Some(block.value));
+        let def_map = collector::collect_defs(db, def_map, Some(block.ast_id.value));
         Arc::new(def_map)
     }
 
@@ -218,7 +225,7 @@ impl DefMap {
         let root = modules.alloc(ModuleData::default());
         DefMap {
             _c: Count::new(),
-            parent: None,
+            block: None,
             krate,
             edition,
             extern_prelude: FxHashMap::default(),
@@ -265,6 +272,11 @@ impl DefMap {
         self.extern_prelude.iter()
     }
 
+    pub fn module_id(&self, local_id: LocalModuleId) -> ModuleId {
+        let block = self.block.as_ref().map(|b| b.block);
+        ModuleId { krate: self.krate, local_id, block }
+    }
+
     pub(crate) fn resolve_path(
         &self,
         db: &dyn DefDatabase,
@@ -282,9 +294,9 @@ impl DefMap {
     pub fn dump(&self) -> String {
         let mut buf = String::new();
         let mut current_map = self;
-        while let Some(parent) = &current_map.parent {
+        while let Some(block) = &current_map.block {
             go(&mut buf, current_map, "block scope", current_map.root);
-            current_map = &**parent;
+            current_map = &*block.parent;
         }
         go(&mut buf, current_map, "crate", current_map.root);
         return buf;
@@ -338,35 +350,6 @@ impl ModuleData {
     }
 }
 
-fn parent_def_map(
-    db: &dyn DefDatabase,
-    krate: CrateId,
-    block: AstId<ast::BlockExpr>,
-) -> Arc<DefMap> {
-    // FIXME: store this info in the item tree instead of reparsing here
-    let ast_id_map = db.ast_id_map(block.file_id);
-    let block_ptr = ast_id_map.get(block.value);
-    let root = match db.parse_or_expand(block.file_id) {
-        Some(it) => it,
-        None => {
-            return Arc::new(DefMap::empty(krate, Edition::Edition2018));
-        }
-    };
-    let ast = block_ptr.to_node(&root);
-
-    for ancestor in ast.syntax().ancestors().skip(1) {
-        if let Some(block_expr) = ast::BlockExpr::cast(ancestor) {
-            let ancestor_id = ast_id_map.ast_id(&block_expr);
-            let ast_id = InFile::new(block.file_id, ancestor_id);
-            let parent_map = db.block_def_map(krate, ast_id);
-            return parent_map;
-        }
-    }
-
-    // No enclosing block scope, so the parent is the crate-level DefMap.
-    db.crate_def_map(krate)
-}
-
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum ModuleSource {
     SourceFile(ast::SourceFile),
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index adfcf879a..393170b32 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -37,8 +37,8 @@ use crate::{
     per_ns::PerNs,
     visibility::{RawVisibility, Visibility},
     AdtId, AsMacroCall, AstId, AstIdWithPath, ConstLoc, ContainerId, EnumLoc, EnumVariantId,
-    FunctionLoc, ImplLoc, Intern, LocalModuleId, ModuleDefId, ModuleId, StaticLoc, StructLoc,
-    TraitLoc, TypeAliasLoc, UnionLoc,
+    FunctionLoc, ImplLoc, Intern, LocalModuleId, ModuleDefId, StaticLoc, StructLoc, TraitLoc,
+    TypeAliasLoc, UnionLoc,
 };
 
 const GLOB_RECURSION_LIMIT: usize = 100;
@@ -56,10 +56,9 @@ pub(super) fn collect_defs(
     for dep in &crate_graph[def_map.krate].dependencies {
         log::debug!("crate dep {:?} -> {:?}", dep.name, dep.crate_id);
         let dep_def_map = db.crate_def_map(dep.crate_id);
-        def_map.extern_prelude.insert(
-            dep.as_name(),
-            ModuleId { krate: dep.crate_id, local_id: dep_def_map.root }.into(),
-        );
+        def_map
+            .extern_prelude
+            .insert(dep.as_name(), dep_def_map.module_id(dep_def_map.root).into());
 
         // look for the prelude
         // If the dependency defines a prelude, we overwrite an already defined
@@ -332,11 +331,9 @@ impl DefCollector<'_> {
             // exported in type/value namespace. This function reduces the visibility of all items
             // in the crate root that aren't proc macros.
             let root = self.def_map.root;
+            let module_id = self.def_map.module_id(root);
             let root = &mut self.def_map.modules[root];
-            root.scope.censor_non_proc_macros(ModuleId {
-                krate: self.def_map.krate,
-                local_id: self.def_map.root,
-            });
+            root.scope.censor_non_proc_macros(module_id);
         }
     }
 
@@ -1029,8 +1026,7 @@ impl ModCollector<'_, '_> {
                     continue;
                 }
             }
-            let module =
-                ModuleId { krate: self.def_collector.def_map.krate, local_id: self.module_id };
+            let module = self.def_collector.def_map.module_id(self.module_id);
             let container = ContainerId::ModuleId(module);
 
             let mut def = None;
@@ -1097,10 +1093,7 @@ impl ModCollector<'_, '_> {
                     }
                 }
                 ModItem::Impl(imp) => {
-                    let module = ModuleId {
-                        krate: self.def_collector.def_map.krate,
-                        local_id: self.module_id,
-                    };
+                    let module = self.def_collector.def_map.module_id(self.module_id);
                     let container = ContainerId::ModuleId(module);
                     let impl_id = ImplLoc { container, id: ItemTreeId::new(self.file_id, imp) }
                         .intern(self.def_collector.db);
@@ -1343,7 +1336,7 @@ impl ModCollector<'_, '_> {
             modules[res].scope.define_legacy_macro(name, mac)
         }
         modules[self.module_id].children.insert(name.clone(), res);
-        let module = ModuleId { krate: self.def_collector.def_map.krate, local_id: res };
+        let module = self.def_collector.def_map.module_id(res);
         let def: ModuleDefId = module.into();
         self.def_collector.def_map.modules[self.module_id].scope.define_def(def);
         self.def_collector.update(
diff --git a/crates/hir_def/src/nameres/path_resolution.rs b/crates/hir_def/src/nameres/path_resolution.rs
index 82528b792..419e465ed 100644
--- a/crates/hir_def/src/nameres/path_resolution.rs
+++ b/crates/hir_def/src/nameres/path_resolution.rs
@@ -10,9 +10,8 @@
 //!
 //! `ReachedFixedPoint` signals about this.
 
-use std::iter::successors;
-
 use base_db::Edition;
+use hir_expand::name;
 use hir_expand::name::Name;
 use test_utils::mark;
 
@@ -23,7 +22,7 @@ use crate::{
     path::{ModPath, PathKind},
     per_ns::PerNs,
     visibility::{RawVisibility, Visibility},
-    AdtId, CrateId, EnumVariantId, LocalModuleId, ModuleDefId, ModuleId,
+    AdtId, CrateId, EnumVariantId, LocalModuleId, ModuleDefId,
 };
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -63,6 +62,10 @@ impl ResolvePathResult {
 
 impl DefMap {
     pub(super) fn resolve_name_in_extern_prelude(&self, name: &Name) -> PerNs {
+        if name == &name!(self) {
+            mark::hit!(extern_crate_self_as);
+            return PerNs::types(self.module_id(self.root).into(), Visibility::Public);
+        }
         self.extern_prelude
             .get(name)
             .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public))
@@ -126,8 +129,8 @@ impl DefMap {
             result.krate = result.krate.or(new.krate);
             result.segment_index = result.segment_index.min(new.segment_index);
 
-            match &current_map.parent {
-                Some(map) => current_map = map,
+            match &current_map.block {
+                Some(block) => current_map = &block.parent,
                 None => return result,
             }
         }
@@ -146,21 +149,15 @@ impl DefMap {
             PathKind::DollarCrate(krate) => {
                 if krate == self.krate {
                     mark::hit!(macro_dollar_crate_self);
-                    PerNs::types(
-                        ModuleId { krate: self.krate, local_id: self.root }.into(),
-                        Visibility::Public,
-                    )
+                    PerNs::types(self.module_id(self.root).into(), Visibility::Public)
                 } else {
                     let def_map = db.crate_def_map(krate);
-                    let module = ModuleId { krate, local_id: def_map.root };
+                    let module = def_map.module_id(def_map.root);
                     mark::hit!(macro_dollar_crate_other);
                     PerNs::types(module.into(), Visibility::Public)
                 }
             }
-            PathKind::Crate => PerNs::types(
-                ModuleId { krate: self.krate, local_id: self.root }.into(),
-                Visibility::Public,
-            ),
+            PathKind::Crate => PerNs::types(self.module_id(self.root).into(), Visibility::Public),
             // plain import or absolute path in 2015: crate-relative with
             // fallback to extern prelude (with the simplification in
             // rust-lang/rust#57745)
@@ -194,17 +191,35 @@ impl DefMap {
                 self.resolve_name_in_module(db, original_module, &segment, prefer_module)
             }
             PathKind::Super(lvl) => {
-                let m = successors(Some(original_module), |m| self.modules[*m].parent)
-                    .nth(lvl as usize);
-                if let Some(local_id) = m {
-                    PerNs::types(
-                        ModuleId { krate: self.krate, local_id }.into(),
-                        Visibility::Public,
-                    )
-                } else {
-                    log::debug!("super path in root module");
-                    return ResolvePathResult::empty(ReachedFixedPoint::Yes);
+                let mut module = original_module;
+                for i in 0..lvl {
+                    match self.modules[module].parent {
+                        Some(it) => module = it,
+                        None => match &self.block {
+                            Some(block) => {
+                                // Look up remaining path in parent `DefMap`
+                                let new_path = ModPath {
+                                    kind: PathKind::Super(lvl - i),
+                                    segments: path.segments.clone(),
+                                };
+                                log::debug!("`super` path: {} -> {} in parent map", path, new_path);
+                                return block.parent.resolve_path_fp_with_macro(
+                                    db,
+                                    mode,
+                                    block.parent_module,
+                                    &new_path,
+                                    shadow,
+                                );
+                            }
+                            None => {
+                                log::debug!("super path in root module");
+                                return ResolvePathResult::empty(ReachedFixedPoint::Yes);
+                            }
+                        },
+                    }
                 }
+
+                PerNs::types(self.module_id(module).into(), Visibility::Public)
             }
             PathKind::Abs => {
                 // 2018-style absolute path -- only extern prelude
diff --git a/crates/hir_def/src/nameres/tests.rs b/crates/hir_def/src/nameres/tests.rs
index 73e3a4702..b36d0b59b 100644
--- a/crates/hir_def/src/nameres/tests.rs
+++ b/crates/hir_def/src/nameres/tests.rs
@@ -8,12 +8,12 @@ mod block;
 
 use std::sync::Arc;
 
-use base_db::{fixture::WithFixture, SourceDatabase};
+use base_db::{fixture::WithFixture, FilePosition, SourceDatabase};
 use expect_test::{expect, Expect};
-use hir_expand::db::AstDatabase;
+use syntax::AstNode;
 use test_utils::mark;
 
-use crate::{db::DefDatabase, nameres::*, test_db::TestDB};
+use crate::{db::DefDatabase, nameres::*, test_db::TestDB, Lookup};
 
 fn compute_crate_def_map(ra_fixture: &str) -> Arc<DefMap> {
     let db = TestDB::with_files(ra_fixture);
@@ -23,14 +23,58 @@ fn compute_crate_def_map(ra_fixture: &str) -> Arc<DefMap> {
 
 fn compute_block_def_map(ra_fixture: &str) -> Arc<DefMap> {
     let (db, position) = TestDB::with_position(ra_fixture);
+
+    // FIXME: perhaps we should make this use body lowering tests instead?
+
     let module = db.module_for_file(position.file_id);
-    let ast_map = db.ast_id_map(position.file_id.into());
-    let ast = db.parse(position.file_id);
-    let block: ast::BlockExpr =
-        syntax::algo::find_node_at_offset(&ast.syntax_node(), position.offset).unwrap();
-    let block_id = ast_map.ast_id(&block);
+    let mut def_map = db.crate_def_map(module.krate);
+    while let Some(new_def_map) = descend_def_map_at_position(&db, position, def_map.clone()) {
+        def_map = new_def_map;
+    }
+
+    // FIXME: select the right module, not the root
+
+    def_map
+}
+
+fn descend_def_map_at_position(
+    db: &dyn DefDatabase,
+    position: FilePosition,
+    def_map: Arc<DefMap>,
+) -> Option<Arc<DefMap>> {
+    for (local_id, module_data) in def_map.modules() {
+        let mod_def = module_data.origin.definition_source(db);
+        let ast_map = db.ast_id_map(mod_def.file_id);
+        let item_tree = db.item_tree(mod_def.file_id);
+        let root = db.parse_or_expand(mod_def.file_id).unwrap();
+        for item in module_data.scope.declarations() {
+            match item {
+                ModuleDefId::FunctionId(it) => {
+                    // Technically blocks can be inside any type (due to arrays and const generics),
+                    // and also in const/static initializers. For tests we only really care about
+                    // functions though.
+
+                    let ast = ast_map.get(item_tree[it.lookup(db).id.value].ast_id).to_node(&root);
+
+                    if ast.syntax().text_range().contains(position.offset) {
+                        // Cursor inside function, descend into its body's DefMap.
+                        // Note that we don't handle block *expressions* inside function bodies.
+                        let ast_map = db.ast_id_map(position.file_id.into());
+                        let ast_id = ast_map.ast_id(&ast.body().unwrap());
+                        let block = BlockLoc {
+                            ast_id: InFile::new(position.file_id.into(), ast_id),
+                            module: def_map.module_id(local_id),
+                        };
+                        let block_id = db.intern_block(block);
+                        return Some(db.block_def_map(block_id));
+                    }
+                }
+                _ => continue,
+            }
+        }
+    }
 
-    db.block_def_map(module.krate, InFile::new(position.file_id.into(), block_id))
+    None
 }
 
 fn check(ra_fixture: &str, expect: Expect) {
diff --git a/crates/hir_def/src/nameres/tests/block.rs b/crates/hir_def/src/nameres/tests/block.rs
index 01d6326a7..470ca593e 100644
--- a/crates/hir_def/src/nameres/tests/block.rs
+++ b/crates/hir_def/src/nameres/tests/block.rs
@@ -95,3 +95,29 @@ fn outer() {
         "#]],
     );
 }
+
+#[test]
+fn super_imports() {
+    check_at(
+        r#"
+mod module {
+    fn f() {
+        use super::Struct;
+        $0
+    }
+}
+
+struct Struct {}
+"#,
+        expect![[r#"
+            block scope
+            Struct: t
+            crate
+            Struct: t
+            module: t
+
+            crate::module
+            f: v
+        "#]],
+    );
+}
diff --git a/crates/hir_def/src/nameres/tests/diagnostics.rs b/crates/hir_def/src/nameres/tests/diagnostics.rs
index 58d69d3c6..e8e72e5ef 100644
--- a/crates/hir_def/src/nameres/tests/diagnostics.rs
+++ b/crates/hir_def/src/nameres/tests/diagnostics.rs
@@ -62,6 +62,22 @@ fn unresolved_extern_crate() {
 }
 
 #[test]
+fn extern_crate_self_as() {
+    mark::check!(extern_crate_self_as);
+    check_diagnostics(
+        r"
+        //- /lib.rs
+          extern crate doesnotexist;
+        //^^^^^^^^^^^^^^^^^^^^^^^^^^ unresolved extern crate
+        // Should not error.
+        extern crate self as foo;
+        struct Foo;
+        use foo::Foo as Bar;
+        ",
+    );
+}
+
+#[test]
 fn dedup_unresolved_import_from_unresolved_crate() {
     check_diagnostics(
         r"
diff --git a/crates/hir_def/src/path.rs b/crates/hir_def/src/path.rs
index e34cd7f2f..84ea09b53 100644
--- a/crates/hir_def/src/path.rs
+++ b/crates/hir_def/src/path.rs
@@ -304,6 +304,7 @@ pub use hir_expand::name as __name;
 #[macro_export]
 macro_rules! __known_path {
     (core::iter::IntoIterator) => {};
+    (core::iter::Iterator) => {};
     (core::result::Result) => {};
     (core::option::Option) => {};
     (core::ops::Range) => {};
diff --git a/crates/hir_def/src/resolver.rs b/crates/hir_def/src/resolver.rs
index 130c074f0..9021ea712 100644
--- a/crates/hir_def/src/resolver.rs
+++ b/crates/hir_def/src/resolver.rs
@@ -459,7 +459,7 @@ impl Resolver {
 
     pub fn module(&self) -> Option<ModuleId> {
         let (def_map, local_id) = self.module_scope()?;
-        Some(ModuleId { krate: def_map.krate(), local_id })
+        Some(def_map.module_id(local_id))
     }
 
     pub fn krate(&self) -> Option<CrateId> {
diff --git a/crates/hir_def/src/test_db.rs b/crates/hir_def/src/test_db.rs
index 4ff219fb7..c4e36eda5 100644
--- a/crates/hir_def/src/test_db.rs
+++ b/crates/hir_def/src/test_db.rs
@@ -15,7 +15,7 @@ use rustc_hash::FxHashSet;
 use syntax::{TextRange, TextSize};
 use test_utils::extract_annotations;
 
-use crate::{db::DefDatabase, ModuleDefId};
+use crate::{db::DefDatabase, ModuleDefId, ModuleId};
 
 #[salsa::database(
     base_db::SourceDatabaseExtStorage,
@@ -72,12 +72,12 @@ impl FileLoader for TestDB {
 }
 
 impl TestDB {
-    pub(crate) fn module_for_file(&self, file_id: FileId) -> crate::ModuleId {
+    pub(crate) fn module_for_file(&self, file_id: FileId) -> ModuleId {
         for &krate in self.relevant_crates(file_id).iter() {
             let crate_def_map = self.crate_def_map(krate);
             for (local_id, data) in crate_def_map.modules() {
                 if data.origin.file_id() == Some(file_id) {
-                    return crate::ModuleId { krate, local_id };
+                    return crate_def_map.module_id(local_id);
                 }
             }
         }
diff --git a/crates/hir_expand/src/builtin_macro.rs b/crates/hir_expand/src/builtin_macro.rs
index 80b60d59f..57bc6fbd7 100644
--- a/crates/hir_expand/src/builtin_macro.rs
+++ b/crates/hir_expand/src/builtin_macro.rs
@@ -327,17 +327,14 @@ fn concat_expand(
                 // concat works with string and char literals, so remove any quotes.
                 // It also works with integer, float and boolean literals, so just use the rest
                 // as-is.
-
-                text += it
-                    .text
-                    .trim_start_matches(|c| match c {
-                        'r' | '#' | '\'' | '"' => true,
-                        _ => false,
-                    })
-                    .trim_end_matches(|c| match c {
-                        '#' | '\'' | '"' => true,
-                        _ => false,
-                    });
+                let component = unquote_str(&it).unwrap_or_else(|| it.text.to_string());
+                text.push_str(&component);
+            }
+            // handle boolean literals
+            tt::TokenTree::Leaf(tt::Leaf::Ident(id))
+                if i % 2 == 0 && (id.text == "true" || id.text == "false") =>
+            {
+                text.push_str(id.text.as_str());
             }
             tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) if i % 2 == 1 && punct.char == ',' => (),
             _ => {
@@ -345,7 +342,6 @@ fn concat_expand(
             }
         }
     }
-
     ExpandResult { value: Some((quote!(#text), FragmentKind::Expr)), err }
 }
 
@@ -745,12 +741,10 @@ mod tests {
             r##"
             #[rustc_builtin_macro]
             macro_rules! concat {}
-            concat!("foo", 0, r#"bar"#);
+            concat!("foo", "r", 0, r#"bar"#, false);
             "##,
         );
 
-        assert_eq!(expanded, r#""foo0bar""#);
-
-        // FIXME: `true`/`false` literals don't work.
+        assert_eq!(expanded, r#""foor0barfalse""#);
     }
 }
diff --git a/crates/hir_expand/src/name.rs b/crates/hir_expand/src/name.rs
index d692cec14..c7609e90d 100644
--- a/crates/hir_expand/src/name.rs
+++ b/crates/hir_expand/src/name.rs
@@ -186,6 +186,9 @@ pub mod known {
         Neg,
         Not,
         Index,
+        // Components of known path (function name)
+        filter_map,
+        next,
         // Builtin macros
         file,
         column,
diff --git a/crates/hir_ty/src/diagnostics.rs b/crates/hir_ty/src/diagnostics.rs
index 247da43f2..323c5f963 100644
--- a/crates/hir_ty/src/diagnostics.rs
+++ b/crates/hir_ty/src/diagnostics.rs
@@ -247,7 +247,7 @@ impl Diagnostic for RemoveThisSemicolon {
 
 // Diagnostic: break-outside-of-loop
 //
-// This diagnostic is triggered if `break` keyword is used outside of a loop.
+// This diagnostic is triggered if the `break` keyword is used outside of a loop.
 #[derive(Debug)]
 pub struct BreakOutsideOfLoop {
     pub file: HirFileId,
@@ -271,7 +271,7 @@ impl Diagnostic for BreakOutsideOfLoop {
 
 // Diagnostic: missing-unsafe
 //
-// This diagnostic is triggered if operation marked as `unsafe` is used outside of `unsafe` function or block.
+// This diagnostic is triggered if an operation marked as `unsafe` is used outside of an `unsafe` function or block.
 #[derive(Debug)]
 pub struct MissingUnsafe {
     pub file: HirFileId,
@@ -295,7 +295,7 @@ impl Diagnostic for MissingUnsafe {
 
 // Diagnostic: mismatched-arg-count
 //
-// This diagnostic is triggered if function is invoked with an incorrect amount of arguments.
+// This diagnostic is triggered if a function is invoked with an incorrect amount of arguments.
 #[derive(Debug)]
 pub struct MismatchedArgCount {
     pub file: HirFileId,
@@ -347,7 +347,7 @@ impl fmt::Display for CaseType {
 
 // Diagnostic: incorrect-ident-case
 //
-// This diagnostic is triggered if item name doesn't follow https://doc.rust-lang.org/1.0.0/style/style/naming/README.html[Rust naming convention].
+// This diagnostic is triggered if an item name doesn't follow https://doc.rust-lang.org/1.0.0/style/style/naming/README.html[Rust naming convention].
 #[derive(Debug)]
 pub struct IncorrectCase {
     pub file: HirFileId,
@@ -386,6 +386,31 @@ impl Diagnostic for IncorrectCase {
     }
 }
 
+// Diagnostic: replace-filter-map-next-with-find-map
+//
+// This diagnostic is triggered when `.filter_map(..).next()` is used, rather than the more concise `.find_map(..)`.
+#[derive(Debug)]
+pub struct ReplaceFilterMapNextWithFindMap {
+    pub file: HirFileId,
+    /// This expression is the whole method chain up to and including `.filter_map(..).next()`.
+    pub next_expr: AstPtr<ast::Expr>,
+}
+
+impl Diagnostic for ReplaceFilterMapNextWithFindMap {
+    fn code(&self) -> DiagnosticCode {
+        DiagnosticCode("replace-filter-map-next-with-find-map")
+    }
+    fn message(&self) -> String {
+        "replace filter_map(..).next() with find_map(..)".to_string()
+    }
+    fn display_source(&self) -> InFile<SyntaxNodePtr> {
+        InFile { file_id: self.file, value: self.next_expr.clone().into() }
+    }
+    fn as_any(&self) -> &(dyn Any + Send + 'static) {
+        self
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use base_db::{fixture::WithFixture, FileId, SourceDatabase, SourceDatabaseExt};
@@ -644,4 +669,87 @@ fn foo() { break; }
             "#,
         );
     }
+
+    // Register the required standard library types to make the tests work
+    fn add_filter_map_with_find_next_boilerplate(body: &str) -> String {
+        let prefix = r#"
+        //- /main.rs crate:main deps:core
+        use core::iter::Iterator;
+        use core::option::Option::{self, Some, None};
+        "#;
+        let suffix = r#"
+        //- /core/lib.rs crate:core
+        pub mod option {
+            pub enum Option<T> { Some(T), None }
+        }
+        pub mod iter {
+            pub trait Iterator {
+                type Item;
+                fn filter_map<B, F>(self, f: F) -> FilterMap where F: FnMut(Self::Item) -> Option<B> { FilterMap }
+                fn next(&mut self) -> Option<Self::Item>;
+            }
+            pub struct FilterMap {}
+            impl Iterator for FilterMap {
+                type Item = i32;
+                fn next(&mut self) -> i32 { 7 }
+            }
+        }
+        "#;
+        format!("{}{}{}", prefix, body, suffix)
+    }
+
+    #[test]
+    fn replace_filter_map_next_with_find_map2() {
+        check_diagnostics(&add_filter_map_with_find_next_boilerplate(
+            r#"
+            fn foo() {
+                let m = [1, 2, 3].iter().filter_map(|x| if *x == 2 { Some (4) } else { None }).next();
+                      //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ replace filter_map(..).next() with find_map(..)
+            }
+        "#,
+        ));
+    }
+
+    #[test]
+    fn replace_filter_map_next_with_find_map_no_diagnostic_without_next() {
+        check_diagnostics(&add_filter_map_with_find_next_boilerplate(
+            r#"
+            fn foo() {
+                let m = [1, 2, 3]
+                    .iter()
+                    .filter_map(|x| if *x == 2 { Some (4) } else { None })
+                    .len();
+            }
+            "#,
+        ));
+    }
+
+    #[test]
+    fn replace_filter_map_next_with_find_map_no_diagnostic_with_intervening_methods() {
+        check_diagnostics(&add_filter_map_with_find_next_boilerplate(
+            r#"
+            fn foo() {
+                let m = [1, 2, 3]
+                    .iter()
+                    .filter_map(|x| if *x == 2 { Some (4) } else { None })
+                    .map(|x| x + 2)
+                    .len();
+            }
+            "#,
+        ));
+    }
+
+    #[test]
+    fn replace_filter_map_next_with_find_map_no_diagnostic_if_not_in_chain() {
+        check_diagnostics(&add_filter_map_with_find_next_boilerplate(
+            r#"
+            fn foo() {
+                let m = [1, 2, 3]
+                    .iter()
+                    .filter_map(|x| if *x == 2 { Some (4) } else { None });
+                let n = m.next();
+            }
+            "#,
+        ));
+    }
 }
diff --git a/crates/hir_ty/src/diagnostics/expr.rs b/crates/hir_ty/src/diagnostics/expr.rs
index 107417c27..d740b7265 100644
--- a/crates/hir_ty/src/diagnostics/expr.rs
+++ b/crates/hir_ty/src/diagnostics/expr.rs
@@ -2,8 +2,10 @@
 
 use std::sync::Arc;
 
-use hir_def::{expr::Statement, path::path, resolver::HasResolver, AdtId, DefWithBodyId};
-use hir_expand::diagnostics::DiagnosticSink;
+use hir_def::{
+    expr::Statement, path::path, resolver::HasResolver, AdtId, AssocItemId, DefWithBodyId,
+};
+use hir_expand::{diagnostics::DiagnosticSink, name};
 use rustc_hash::FxHashSet;
 use syntax::{ast, AstPtr};
 
@@ -24,6 +26,8 @@ pub(crate) use hir_def::{
     LocalFieldId, VariantId,
 };
 
+use super::ReplaceFilterMapNextWithFindMap;
+
 pub(super) struct ExprValidator<'a, 'b: 'a> {
     owner: DefWithBodyId,
     infer: Arc<InferenceResult>,
@@ -40,6 +44,8 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
     }
 
     pub(super) fn validate_body(&mut self, db: &dyn HirDatabase) {
+        self.check_for_filter_map_next(db);
+
         let body = db.body(self.owner.into());
 
         for (id, expr) in body.exprs.iter() {
@@ -150,20 +156,76 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         }
     }
 
-    fn validate_call(&mut self, db: &dyn HirDatabase, call_id: ExprId, expr: &Expr) -> Option<()> {
+    fn check_for_filter_map_next(&mut self, db: &dyn HirDatabase) {
+        // Find the FunctionIds for Iterator::filter_map and Iterator::next
+        let iterator_path = path![core::iter::Iterator];
+        let resolver = self.owner.resolver(db.upcast());
+        let iterator_trait_id = match resolver.resolve_known_trait(db.upcast(), &iterator_path) {
+            Some(id) => id,
+            None => return,
+        };
+        let iterator_trait_items = &db.trait_data(iterator_trait_id).items;
+        let filter_map_function_id =
+            match iterator_trait_items.iter().find(|item| item.0 == name![filter_map]) {
+                Some((_, AssocItemId::FunctionId(id))) => id,
+                _ => return,
+            };
+        let next_function_id = match iterator_trait_items.iter().find(|item| item.0 == name![next])
+        {
+            Some((_, AssocItemId::FunctionId(id))) => id,
+            _ => return,
+        };
+
+        // Search function body for instances of .filter_map(..).next()
+        let body = db.body(self.owner.into());
+        let mut prev = None;
+        for (id, expr) in body.exprs.iter() {
+            if let Expr::MethodCall { receiver, .. } = expr {
+                let function_id = match self.infer.method_resolution(id) {
+                    Some(id) => id,
+                    None => continue,
+                };
+
+                if function_id == *filter_map_function_id {
+                    prev = Some(id);
+                    continue;
+                }
+
+                if function_id == *next_function_id {
+                    if let Some(filter_map_id) = prev {
+                        if *receiver == filter_map_id {
+                            let (_, source_map) = db.body_with_source_map(self.owner.into());
+                            if let Ok(next_source_ptr) = source_map.expr_syntax(id) {
+                                self.sink.push(ReplaceFilterMapNextWithFindMap {
+                                    file: next_source_ptr.file_id,
+                                    next_expr: next_source_ptr.value,
+                                });
+                            }
+                        }
+                    }
+                }
+            }
+            prev = None;
+        }
+    }
+
+    fn validate_call(&mut self, db: &dyn HirDatabase, call_id: ExprId, expr: &Expr) {
         // Check that the number of arguments matches the number of parameters.
 
         // FIXME: Due to shortcomings in the current type system implementation, only emit this
         // diagnostic if there are no type mismatches in the containing function.
         if self.infer.type_mismatches.iter().next().is_some() {
-            return None;
+            return;
         }
 
         let is_method_call = matches!(expr, Expr::MethodCall { .. });
         let (sig, args) = match expr {
             Expr::Call { callee, args } => {
                 let callee = &self.infer.type_of_expr[*callee];
-                let sig = callee.callable_sig(db)?;
+                let sig = match callee.callable_sig(db) {
+                    Some(sig) => sig,
+                    None => return,
+                };
                 (sig, args.clone())
             }
             Expr::MethodCall { receiver, args, .. } => {
@@ -175,22 +237,25 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
                     // if the receiver is of unknown type, it's very likely we
                     // don't know enough to correctly resolve the method call.
                     // This is kind of a band-aid for #6975.
-                    return None;
+                    return;
                 }
 
                 // FIXME: note that we erase information about substs here. This
                 // is not right, but, luckily, doesn't matter as we care only
                 // about the number of params
-                let callee = self.infer.method_resolution(call_id)?;
+                let callee = match self.infer.method_resolution(call_id) {
+                    Some(callee) => callee,
+                    None => return,
+                };
                 let sig = db.callable_item_signature(callee.into()).value;
 
                 (sig, args)
             }
-            _ => return None,
+            _ => return,
         };
 
         if sig.is_varargs {
-            return None;
+            return;
         }
 
         let params = sig.params();
@@ -213,8 +278,6 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
                 });
             }
         }
-
-        None
     }
 
     fn validate_match(
diff --git a/crates/hir_ty/src/test_db.rs b/crates/hir_ty/src/test_db.rs
index 09696fcf4..381b98ba8 100644
--- a/crates/hir_ty/src/test_db.rs
+++ b/crates/hir_ty/src/test_db.rs
@@ -83,7 +83,7 @@ impl TestDB {
             let crate_def_map = self.crate_def_map(krate);
             for (local_id, data) in crate_def_map.modules() {
                 if data.origin.file_id() == Some(file_id) {
-                    return ModuleId::top_level(krate, local_id);
+                    return crate_def_map.module_id(local_id);
                 }
             }
         }
diff --git a/crates/ide/src/diagnostics.rs b/crates/ide/src/diagnostics.rs
index b35bc2bae..8607139ba 100644
--- a/crates/ide/src/diagnostics.rs
+++ b/crates/ide/src/diagnostics.rs
@@ -136,6 +136,9 @@ pub(crate) fn diagnostics(
         .on::<hir::diagnostics::IncorrectCase, _>(|d| {
             res.borrow_mut().push(warning_with_fix(d, &sema));
         })
+        .on::<hir::diagnostics::ReplaceFilterMapNextWithFindMap, _>(|d| {
+            res.borrow_mut().push(warning_with_fix(d, &sema));
+        })
         .on::<hir::diagnostics::InactiveCode, _>(|d| {
             // If there's inactive code somewhere in a macro, don't propagate to the call-site.
             if d.display_source().file_id.expansion_info(db).is_some() {
diff --git a/crates/ide/src/diagnostics/fixes.rs b/crates/ide/src/diagnostics/fixes.rs
index 579d5a308..cbfc66ab3 100644
--- a/crates/ide/src/diagnostics/fixes.rs
+++ b/crates/ide/src/diagnostics/fixes.rs
@@ -4,7 +4,7 @@ use hir::{
     db::AstDatabase,
     diagnostics::{
         Diagnostic, IncorrectCase, MissingFields, MissingOkOrSomeInTailExpr, NoSuchField,
-        RemoveThisSemicolon, UnresolvedModule,
+        RemoveThisSemicolon, ReplaceFilterMapNextWithFindMap, UnresolvedModule,
     },
     HasSource, HirDisplay, InFile, Semantics, VariantDef,
 };
@@ -15,8 +15,8 @@ use ide_db::{
 };
 use syntax::{
     algo,
-    ast::{self, edit::IndentLevel, make},
-    AstNode,
+    ast::{self, edit::IndentLevel, make, ArgListOwner},
+    AstNode, TextRange,
 };
 use text_edit::TextEdit;
 
@@ -144,6 +144,33 @@ impl DiagnosticWithFix for IncorrectCase {
     }
 }
 
+impl DiagnosticWithFix for ReplaceFilterMapNextWithFindMap {
+    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix> {
+        let root = sema.db.parse_or_expand(self.file)?;
+        let next_expr = self.next_expr.to_node(&root);
+        let next_call = ast::MethodCallExpr::cast(next_expr.syntax().clone())?;
+
+        let filter_map_call = ast::MethodCallExpr::cast(next_call.receiver()?.syntax().clone())?;
+        let filter_map_name_range = filter_map_call.name_ref()?.ident_token()?.text_range();
+        let filter_map_args = filter_map_call.arg_list()?;
+
+        let range_to_replace =
+            TextRange::new(filter_map_name_range.start(), next_expr.syntax().text_range().end());
+        let replacement = format!("find_map{}", filter_map_args.syntax().text());
+        let trigger_range = next_expr.syntax().text_range();
+
+        let edit = TextEdit::replace(range_to_replace, replacement);
+
+        let source_change = SourceChange::from_text_edit(self.file.original_file(sema.db), edit);
+
+        Some(Fix::new(
+            "Replace filter_map(..).next() with find_map()",
+            source_change,
+            trigger_range,
+        ))
+    }
+}
+
 fn missing_record_expr_field_fix(
     sema: &Semantics<RootDatabase>,
     usage_file_id: FileId,
diff --git a/crates/ide/src/display/navigation_target.rs b/crates/ide/src/display/navigation_target.rs
index 16fa828ad..23d885218 100644
--- a/crates/ide/src/display/navigation_target.rs
+++ b/crates/ide/src/display/navigation_target.rs
@@ -173,6 +173,7 @@ impl ToNav for FileSymbol {
                 FileSymbolKind::Const => SymbolKind::Const,
                 FileSymbolKind::Static => SymbolKind::Static,
                 FileSymbolKind::Macro => SymbolKind::Macro,
+                FileSymbolKind::Union => SymbolKind::Union,
             }),
             full_range: self.range,
             focus_range: self.name_range,
@@ -434,13 +435,16 @@ impl TryToNav for hir::TypeParam {
     fn try_to_nav(&self, db: &RootDatabase) -> Option<NavigationTarget> {
         let src = self.source(db)?;
         let full_range = match &src.value {
-            Either::Left(it) => it.syntax().text_range(),
+            Either::Left(it) => it
+                .name()
+                .map_or_else(|| it.syntax().text_range(), |name| name.syntax().text_range()),
             Either::Right(it) => it.syntax().text_range(),
         };
         let focus_range = match &src.value {
-            Either::Left(_) => None,
-            Either::Right(it) => it.name().map(|it| it.syntax().text_range()),
-        };
+            Either::Left(it) => it.name(),
+            Either::Right(it) => it.name(),
+        }
+        .map(|it| it.syntax().text_range());
         Some(NavigationTarget {
             file_id: src.file_id.original_file(db),
             name: self.name(db).to_string().into(),
diff --git a/crates/ide/src/references.rs b/crates/ide/src/references.rs
index 3a4f4d80b..40d9487eb 100644
--- a/crates/ide/src/references.rs
+++ b/crates/ide/src/references.rs
@@ -1098,4 +1098,20 @@ fn foo<const FOO$0: usize>() -> usize {
             "#]],
         );
     }
+
+    #[test]
+    fn test_find_self_ty_in_trait_def() {
+        check(
+            r#"
+trait Foo {
+    fn f() -> Self$0;
+}
+"#,
+            expect![[r#"
+                Self TypeParam FileId(0) 6..9 6..9 Other
+
+                FileId(0) 26..30 Other
+            "#]],
+        );
+    }
 }
diff --git a/crates/ide_db/src/symbol_index.rs b/crates/ide_db/src/symbol_index.rs
index e954bd72e..9ed9568ce 100644
--- a/crates/ide_db/src/symbol_index.rs
+++ b/crates/ide_db/src/symbol_index.rs
@@ -356,15 +356,16 @@ pub struct FileSymbol {
 
 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
 pub enum FileSymbolKind {
+    Const,
+    Enum,
     Function,
+    Macro,
+    Module,
+    Static,
     Struct,
-    Enum,
     Trait,
-    Module,
     TypeAlias,
-    Const,
-    Static,
-    Macro,
+    Union,
 }
 
 impl FileSymbolKind {
@@ -375,6 +376,7 @@ impl FileSymbolKind {
                 | FileSymbolKind::Enum
                 | FileSymbolKind::Trait
                 | FileSymbolKind::TypeAlias
+                | FileSymbolKind::Union
         )
     }
 }
@@ -425,6 +427,7 @@ fn to_symbol(node: &SyntaxNode) -> Option<(SmolStr, SyntaxNodePtr, TextRange)> {
             ast::Const(it) => decl(it),
             ast::Static(it) => decl(it),
             ast::MacroRules(it) => decl(it),
+            ast::Union(it) => decl(it),
             _ => None,
         }
     }
@@ -443,6 +446,7 @@ fn to_file_symbol(node: &SyntaxNode, file_id: FileId) -> Option<FileSymbol> {
             CONST => FileSymbolKind::Const,
             STATIC => FileSymbolKind::Static,
             MACRO_RULES => FileSymbolKind::Macro,
+            UNION => FileSymbolKind::Union,
             kind => unreachable!("{:?}", kind),
         },
         range: node.text_range(),
diff --git a/crates/parser/src/grammar/items/consts.rs b/crates/parser/src/grammar/items/consts.rs
index eb7d1f828..12130df40 100644
--- a/crates/parser/src/grammar/items/consts.rs
+++ b/crates/parser/src/grammar/items/consts.rs
@@ -13,7 +13,7 @@ pub(super) fn konst(p: &mut Parser, m: Marker) {
 fn const_or_static(p: &mut Parser, m: Marker, kw: SyntaxKind, def: SyntaxKind) {
     assert!(p.at(kw));
     p.bump(kw);
-    p.eat(T![mut]); // FIXME: validator to forbid const mut
+    p.eat(T![mut]);
 
     // Allow `_` in place of an identifier in a `const`.
     let is_const_underscore = kw == T![const] && p.eat(T![_]);
diff --git a/crates/profile/Cargo.toml b/crates/profile/Cargo.toml
index cc7da27f7..4dd9acc98 100644
--- a/crates/profile/Cargo.toml
+++ b/crates/profile/Cargo.toml
@@ -14,7 +14,7 @@ once_cell = "1.3.1"
 cfg-if = "1"
 libc = "0.2.73"
 la-arena = { version = "0.2.0", path = "../../lib/arena" }
-countme = { version = "2.0.0-pre.2", features = ["enable"] }
+countme = { version = "2.0.0", features = ["enable"] }
 jemalloc-ctl = { version = "0.3.3", optional = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 3ddb9e19a..247bfe71e 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -147,6 +147,9 @@ config_data! {
         /// Whether to show `Method References` lens. Only applies when
         /// `#rust-analyzer.lens.enable#` is set.
         lens_methodReferences: bool = "false",
+        /// Whether to show `References` lens. Only applies when
+        /// `#rust-analyzer.lens.enable#` is set.
+        lens_references: bool = "false",
 
         /// Disable project auto-discovery in favor of explicitly specified set
         /// of projects.\n\nElements must be paths pointing to `Cargo.toml`,
@@ -221,6 +224,7 @@ pub struct LensConfig {
     pub debug: bool,
     pub implementations: bool,
     pub method_refs: bool,
+    pub refs: bool, // for Struct, Enum, Union and Trait
 }
 
 impl LensConfig {
@@ -237,7 +241,7 @@ impl LensConfig {
     }
 
     pub fn references(&self) -> bool {
-        self.method_refs
+        self.method_refs || self.refs
     }
 }
 
@@ -593,6 +597,7 @@ impl Config {
             debug: self.data.lens_enable && self.data.lens_debug,
             implementations: self.data.lens_enable && self.data.lens_implementations,
             method_refs: self.data.lens_enable && self.data.lens_methodReferences,
+            refs: self.data.lens_enable && self.data.lens_references,
         }
     }
     pub fn hover(&self) -> HoverConfig {
diff --git a/crates/rust-analyzer/src/handlers.rs b/crates/rust-analyzer/src/handlers.rs
index 809452e6d..07204436c 100644
--- a/crates/rust-analyzer/src/handlers.rs
+++ b/crates/rust-analyzer/src/handlers.rs
@@ -1112,42 +1112,48 @@ pub(crate) fn handle_code_lens(
         }
     }
 
-    if lens_config.implementations {
-        // Handle impls
-        lenses.extend(
-            snap.analysis
-                .file_structure(file_id)?
-                .into_iter()
-                .filter(|it| {
-                    matches!(
-                        it.kind,
-                        SymbolKind::Trait
-                            | SymbolKind::Struct
-                            | SymbolKind::Enum
-                            | SymbolKind::Union
-                    )
-                })
-                .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 {
+    if lens_config.implementations || lens_config.refs {
+        snap.analysis
+            .file_structure(file_id)?
+            .into_iter()
+            .filter(|it| {
+                matches!(
+                    it.kind,
+                    SymbolKind::Trait | SymbolKind::Struct | SymbolKind::Enum | SymbolKind::Union
+                )
+            })
+            .for_each(|it| {
+                let range = to_proto::range(&line_index, it.node_range);
+                let position = to_proto::position(&line_index, it.navigation_range.start());
+                let doc_pos = lsp_types::TextDocumentPositionParams::new(
+                    params.text_document.clone(),
+                    position,
+                );
+                let goto_params = lsp_types::request::GotoImplementationParams {
+                    text_document_position_params: doc_pos.clone(),
+                    work_done_progress_params: Default::default(),
+                    partial_result_params: Default::default(),
+                };
+
+                if lens_config.implementations {
+                    lenses.push(CodeLens {
                         range,
                         command: None,
-                        data: Some(to_value(CodeLensResolveData::Impls(lens_params)).unwrap()),
-                    }
-                }),
-        );
+                        data: Some(to_value(CodeLensResolveData::Impls(goto_params)).unwrap()),
+                    })
+                }
+
+                if lens_config.refs {
+                    lenses.push(CodeLens {
+                        range,
+                        command: None,
+                        data: Some(to_value(CodeLensResolveData::References(doc_pos)).unwrap()),
+                    })
+                }
+            });
     }
 
-    if lens_config.references() {
+    if lens_config.method_refs {
         lenses.extend(snap.analysis.find_all_methods(file_id)?.into_iter().map(|it| {
             let range = to_proto::range(&line_index, it.range);
             let position = to_proto::position(&line_index, it.range.start());
diff --git a/crates/syntax/Cargo.toml b/crates/syntax/Cargo.toml
index 24298fbfa..e70fbba9c 100644
--- a/crates/syntax/Cargo.toml
+++ b/crates/syntax/Cargo.toml
@@ -12,7 +12,7 @@ doctest = false
 
 [dependencies]
 itertools = "0.10.0"
-rowan = "0.12"
+rowan = "0.12.2"
 rustc_lexer = { version = "700.0.0", package = "rustc-ap-rustc_lexer" }
 rustc-hash = "1.1.0"
 arrayvec = "0.5.1"
diff --git a/crates/syntax/src/validation.rs b/crates/syntax/src/validation.rs
index 7694e8834..3e216fb70 100644
--- a/crates/syntax/src/validation.rs
+++ b/crates/syntax/src/validation.rs
@@ -1,4 +1,6 @@
-//! FIXME: write short doc here
+//! This module implements syntax validation that the parser doesn't handle.
+//!
+//! A failed validation emits a diagnostic.
 
 mod block;
 
@@ -92,6 +94,7 @@ pub(crate) fn validate(root: &SyntaxNode) -> Vec<SyntaxError> {
         match_ast! {
             match node {
                 ast::Literal(it) => validate_literal(it, &mut errors),
+                ast::Const(it) => validate_const(it, &mut errors),
                 ast::BlockExpr(it) => block::validate_block_expr(it, &mut errors),
                 ast::FieldExpr(it) => validate_numeric_name(it.name_ref(), &mut errors),
                 ast::RecordExprField(it) => validate_numeric_name(it.name_ref(), &mut errors),
@@ -362,3 +365,14 @@ fn validate_macro_rules(mac: ast::MacroRules, errors: &mut Vec<SyntaxError>) {
         ));
     }
 }
+
+fn validate_const(const_: ast::Const, errors: &mut Vec<SyntaxError>) {
+    if let Some(mut_token) = const_
+        .const_token()
+        .and_then(|t| t.next_token())
+        .and_then(|t| algo::skip_trivia_token(t, Direction::Next))
+        .filter(|t| t.kind() == T![mut])
+    {
+        errors.push(SyntaxError::new("const globals cannot be mutable", mut_token.text_range()));
+    }
+}
diff --git a/crates/syntax/test_data/parser/err/0047_mutable_const_item.rast b/crates/syntax/test_data/parser/err/0047_mutable_const_item.rast
new file mode 100644
index 000000000..c7eb312c9
--- /dev/null
+++ b/crates/syntax/test_data/parser/err/0047_mutable_const_item.rast
@@ -0,0 +1,22 @@
+[email protected]
+  [email protected]
+    [email protected] "const"
+    [email protected] " "
+    [email protected] "mut"
+    [email protected] " "
+    [email protected]
+      [email protected] "FOO"
+    [email protected] ":"
+    [email protected] " "
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+    [email protected] " "
+    [email protected] "="
+    [email protected] " "
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+    [email protected] ";"
+  [email protected] "\n"
+error 6..9: const globals cannot be mutable
diff --git a/crates/syntax/test_data/parser/err/0047_mutable_const_item.rs b/crates/syntax/test_data/parser/err/0047_mutable_const_item.rs
new file mode 100644
index 000000000..b34336f3f
--- /dev/null
+++ b/crates/syntax/test_data/parser/err/0047_mutable_const_item.rs
@@ -0,0 +1 @@
+const mut FOO: () = ();

diff --git a/crates/syntax/test_data/parser/ok/0024_const_item.rast b/crates/syntax/test_data/parser/ok/0024_const_item.rast
index dd1b9c9a0..b89ed6f98 100644
--- a/crates/syntax/test_data/parser/ok/0024_const_item.rast
+++ b/crates/syntax/test_data/parser/ok/0024_const_item.rast
@@ -1,4 +1,4 @@
-SOURCE_FILE@0..64
+SOURCE_FILE@0..39
   [email protected]
     [email protected] "const"
     [email protected] " "
@@ -36,24 +36,3 @@ [email protected]
       [email protected] "92"
     [email protected] ";"
   [email protected] "\n"
-  [email protected]
-    [email protected] "const"
-    [email protected] " "
-    [email protected] "mut"
-    [email protected] " "
-    [email protected]
-      [email protected] "BAR"
-    [email protected] ":"
-    [email protected] " "
-    [email protected]
-      [email protected]
-        [email protected]
-          [email protected]
-            [email protected] "u32"
-    [email protected] " "
-    [email protected] "="
-    [email protected] " "
-    [email protected]
-      [email protected] "62"
-    [email protected] ";"
-  [email protected] "\n"
diff --git a/crates/syntax/test_data/parser/ok/0024_const_item.rs b/crates/syntax/test_data/parser/ok/0024_const_item.rs
index a806a209d..1f2ffa0da 100644
--- a/crates/syntax/test_data/parser/ok/0024_const_item.rs
+++ b/crates/syntax/test_data/parser/ok/0024_const_item.rs
@@ -1,3 +1,2 @@
 const _: u32 = 0;
 const FOO: u32 = 92;
-const mut BAR: u32 = 62;
diff --git a/docs/dev/README.md b/docs/dev/README.md
index 24197b332..6bce38e56 100644
--- a/docs/dev/README.md
+++ b/docs/dev/README.md
@@ -43,6 +43,10 @@ https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Fwg-rls-2.2E0
   while unactionable ones are effectively wont-fix. Each triaged issue should have one of these labels.
 * [fun](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3Afun)
   is for cool, but probably hard stuff.
+* [Design](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%Design)
+  is for moderate/large scale architecture discussion.
+  Also a kind of fun.
+  These issues should generally include a link to a Zulip discussion thread.
 
 # CI
 
@@ -212,7 +216,7 @@ To log all communication between the server and the client, there are two choice
 
 * you can log on the server side, by running something like
   ```
-  env RA_LOG=gen_lsp_server=trace code .
+  env RA_LOG=lsp_server=debug code .
   ```
 
 * you can log on the client side, by enabling `"rust-analyzer.trace.server":
diff --git a/docs/dev/style.md b/docs/dev/style.md
index 428cee3ad..6dc6868c2 100644
--- a/docs/dev/style.md
+++ b/docs/dev/style.md
@@ -294,8 +294,9 @@ Prefer `Default` even it has to be implemented manually.
 
 **Rationale:** less typing in the common case, uniformity.
 
-Use `Vec::new` rather than `vec![]`. **Rationale:** uniformity, strength
-reduction.
+Use `Vec::new` rather than `vec![]`.
+
+**Rationale:** uniformity, strength reduction.
 
 ## Functions Over Objects
 
@@ -479,7 +480,7 @@ pub fn reachable_nodes(node: Node) -> FxHashSet<Node> {
 }
 ```
 
-**Rational:** re-use allocations, accumulator style is more concise for complex cases.
+**Rationale:** re-use allocations, accumulator style is more concise for complex cases.
 
 # Style
 
diff --git a/docs/user/generated_config.adoc b/docs/user/generated_config.adoc
index a76c99d1e..2f681b01a 100644
--- a/docs/user/generated_config.adoc
+++ b/docs/user/generated_config.adoc
@@ -86,6 +86,8 @@
  Whether to show `Run` lens. Only applies when  `#rust-analyzer.lens.enable#` is set.
 [[rust-analyzer.lens.methodReferences]]rust-analyzer.lens.methodReferences (default: `false`)::
  Whether to show `Method References` lens. Only applies when  `#rust-analyzer.lens.enable#` is set.
+[[rust-analyzer.lens.references]]rust-analyzer.lens.references (default: `false`)::
+ Whether to show `References` lens. Only applies when  `#rust-analyzer.lens.enable#` is set.
 [[rust-analyzer.linkedProjects]]rust-analyzer.linkedProjects (default: `[]`)::
  Disable project auto-discovery in favor of explicitly specified set  of projects.\n\nElements must be paths pointing to `Cargo.toml`,  `rust-project.json`, or JSON objects in `rust-project.json` format.
 [[rust-analyzer.lruCapacity]]rust-analyzer.lruCapacity (default: `null`)::
diff --git a/editors/code/package.json b/editors/code/package.json
index 3e6ebd7ed..2225cf1dd 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -633,6 +633,11 @@
                     "default": false,
                     "type": "boolean"
                 },
+                "rust-analyzer.lens.references": {
+                    "markdownDescription": "Whether to show `References` lens. Only applies when `#rust-analyzer.lens.enable#` is set.",
+                    "default": false,
+                    "type": "boolean"
+                },
                 "rust-analyzer.linkedProjects": {
                     "markdownDescription": "Disable project auto-discovery in favor of explicitly specified set of projects.\\n\\nElements must be paths pointing to `Cargo.toml`, `rust-project.json`, or JSON objects in `rust-project.json` format.",
                     "default": [],
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index ebe4de1ea..ddb5cfbd3 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -144,6 +144,7 @@ export class Config {
             debug: this.get<boolean>("lens.debug"),
             implementations: this.get<boolean>("lens.implementations"),
             methodReferences: this.get<boolean>("lens.methodReferences"),
+            references: this.get<boolean>("lens.references"),
         };
     }
 
diff --git a/editors/code/src/main.ts b/editors/code/src/main.ts
index 1edb7713d..1900d900a 100644
--- a/editors/code/src/main.ts
+++ b/editors/code/src/main.ts
@@ -208,7 +208,6 @@ async function bootstrapExtension(config: Config, state: PersistentState): Promi
             url: artifact.browser_download_url,
             dest,
             progressTitle: "Downloading rust-analyzer extension",
-            overwrite: true,
         });
     });
 
@@ -340,7 +339,6 @@ async function getServer(config: Config, state: PersistentState): Promise<string
             progressTitle: "Downloading rust-analyzer server",
             gunzip: true,
             mode: 0o755,
-            overwrite: true,
         });
     });
 
diff --git a/editors/code/src/net.ts b/editors/code/src/net.ts
index 1ab21e726..d39dc1baf 100644
--- a/editors/code/src/net.ts
+++ b/editors/code/src/net.ts
@@ -73,23 +73,16 @@ interface DownloadOpts {
     dest: string;
     mode?: number;
     gunzip?: boolean;
-    overwrite?: boolean;
 }
 
 export async function download(opts: DownloadOpts) {
     // Put artifact into a temporary file (in the same dir for simplicity)
     // to prevent partially downloaded files when user kills vscode
+    // This also avoids overwriting running executables
     const dest = path.parse(opts.dest);
     const randomHex = crypto.randomBytes(5).toString("hex");
     const tempFile = path.join(dest.dir, `${dest.name}${randomHex}`);
 
-    if (opts.overwrite) {
-        // Unlinking the exe file before moving new one on its place should prevent ETXTBSY error.
-        await fs.promises.unlink(opts.dest).catch(err => {
-            if (err.code !== "ENOENT") throw err;
-        });
-    }
-
     await vscode.window.withProgress(
         {
             location: vscode.ProgressLocation.Notification,
@@ -99,13 +92,15 @@ export async function download(opts: DownloadOpts) {
         async (progress, _cancellationToken) => {
             let lastPercentage = 0;
             await downloadFile(opts.url, tempFile, opts.mode, !!opts.gunzip, (readBytes, totalBytes) => {
-                const newPercentage = (readBytes / totalBytes) * 100;
-                progress.report({
-                    message: newPercentage.toFixed(0) + "%",
-                    increment: newPercentage - lastPercentage
-                });
-
-                lastPercentage = newPercentage;
+                const newPercentage = Math.round((readBytes / totalBytes) * 100);
+                if (newPercentage !== lastPercentage) {
+                    progress.report({
+                        message: `${newPercentage.toFixed(0)}%`,
+                        increment: newPercentage - lastPercentage
+                    });
+
+                    lastPercentage = newPercentage;
+                }
             });
         }
     );