19 files changed, 244 insertions, 156 deletions

diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index c72649c41..6513daec8 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -196,7 +196,7 @@ impl Attrs {
     pub(crate) fn attrs_query(db: &dyn DefDatabase, def: AttrDefId) -> Attrs {
         let raw_attrs = match def {
             AttrDefId::ModuleId(module) => {
-                let def_map = db.crate_def_map(module.krate);
+                let def_map = module.def_map(db);
                 let mod_data = &def_map[module.local_id];
                 match mod_data.declaration_source(db) {
                     Some(it) => {
diff --git a/crates/hir_def/src/body.rs b/crates/hir_def/src/body.rs
index 2c2c999dd..d0c84ab0b 100644
--- a/crates/hir_def/src/body.rs
+++ b/crates/hir_def/src/body.rs
@@ -86,7 +86,7 @@ impl Expander {
         module: ModuleId,
     ) -> Expander {
         let cfg_expander = CfgExpander::new(db, current_file_id, module.krate);
-        let crate_def_map = db.crate_def_map(module.krate);
+        let crate_def_map = module.def_map(db);
         let ast_id_map = db.ast_id_map(current_file_id);
         Expander {
             cfg_expander,
diff --git a/crates/hir_def/src/child_by_source.rs b/crates/hir_def/src/child_by_source.rs
index dcb00a1d9..65d85c86a 100644
--- a/crates/hir_def/src/child_by_source.rs
+++ b/crates/hir_def/src/child_by_source.rs
@@ -74,7 +74,7 @@ impl ChildBySource for ImplId {
 
 impl ChildBySource for ModuleId {
     fn child_by_source(&self, db: &dyn DefDatabase) -> DynMap {
-        let crate_def_map = db.crate_def_map(self.krate);
+        let crate_def_map = self.def_map(db);
         let module_data = &crate_def_map[self.local_id];
         module_data.scope.child_by_source(db)
     }
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 db2d125ae..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
@@ -110,7 +106,7 @@ fn find_path_inner(
     // Base cases:
 
     // - if the item is already in scope, return the name under which it is
-    let def_map = db.crate_def_map(from.krate);
+    let def_map = from.def_map(db);
     let from_scope: &crate::item_scope::ItemScope = &def_map[from.local_id].scope;
     let scope_name =
         if let Some((name, _)) = from_scope.name_of(item) { Some(name.clone()) } 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()));
     }
 
@@ -145,7 +137,7 @@ fn find_path_inner(
 
     // - if the item is in the prelude, return the name from there
     if let Some(prelude_module) = def_map.prelude() {
-        let prelude_def_map = db.crate_def_map(prelude_module.krate);
+        let prelude_def_map = prelude_module.def_map(db);
         let prelude_scope: &crate::item_scope::ItemScope =
             &prelude_def_map[prelude_module.local_id].scope;
         if let Some((name, vis)) = prelude_scope.name_of(item) {
@@ -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;
@@ -283,19 +275,16 @@ fn find_local_import_locations(
     // above `from` with any visibility. That means we do not need to descend into private siblings
     // of `from` (and similar).
 
-    let def_map = db.crate_def_map(from.krate);
+    let def_map = from.def_map(db);
 
     // 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;
     }
 
@@ -312,7 +301,7 @@ fn find_local_import_locations(
             &def_map[module.local_id]
         } else {
             // The crate might reexport a module defined in another crate.
-            ext_def_map = db.crate_def_map(module.krate);
+            ext_def_map = module.def_map(db);
             &ext_def_map[module.local_id]
         };
 
@@ -375,7 +364,7 @@ mod tests {
             parsed_path_file.syntax_node().descendants().find_map(syntax::ast::Path::cast).unwrap();
         let mod_path = ModPath::from_src(ast_path, &Hygiene::new_unhygienic()).unwrap();
 
-        let crate_def_map = db.crate_def_map(module.krate);
+        let crate_def_map = module.def_map(&db);
         let resolved = crate_def_map
             .resolve_path(
                 &db,
diff --git a/crates/hir_def/src/import_map.rs b/crates/hir_def/src/import_map.rs
index 0251d016b..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;
@@ -83,7 +83,7 @@ impl ImportMap {
                 &def_map[module.local_id]
             } else {
                 // The crate might reexport a module defined in another crate.
-                ext_def_map = db.crate_def_map(module.krate);
+                ext_def_map = module.def_map(db);
                 &ext_def_map[module.local_id]
             };
 
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 08ed920c6..42b50b5b7 100644
--- a/crates/hir_def/src/lib.rs
+++ b/crates/hir_def/src/lib.rs
@@ -50,7 +50,10 @@ pub mod import_map;
 #[cfg(test)]
 mod test_db;
 
-use std::hash::{Hash, Hasher};
+use std::{
+    hash::{Hash, Hasher},
+    sync::Arc,
+};
 
 use base_db::{impl_intern_key, salsa, CrateId};
 use hir_expand::{
@@ -58,6 +61,7 @@ use hir_expand::{
     MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
 };
 use la_arena::Idx;
+use nameres::DefMap;
 use syntax::ast;
 
 use crate::builtin_type::BuiltinType;
@@ -69,10 +73,24 @@ use stdx::impl_from;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ModuleId {
-    pub krate: CrateId,
+    krate: CrateId,
+    block: Option<BlockId>,
     pub local_id: LocalModuleId,
 }
 
+impl ModuleId {
+    pub fn def_map(&self, db: &dyn db::DefDatabase) -> Arc<DefMap> {
+        match self.block {
+            Some(block) => db.block_def_map(block),
+            None => db.crate_def_map(self.krate),
+        }
+    }
+
+    pub fn krate(&self) -> CrateId {
+        self.krate
+    }
+}
+
 /// An ID of a module, **local** to a specific crate
 pub type LocalModuleId = Idx<nameres::ModuleData>;
 
@@ -216,6 +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 cd68efbe6..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);
         }
     }
 
@@ -578,7 +575,7 @@ impl DefCollector<'_> {
                     } else if m.krate != self.def_map.krate {
                         mark::hit!(glob_across_crates);
                         // glob import from other crate => we can just import everything once
-                        let item_map = self.db.crate_def_map(m.krate);
+                        let item_map = m.def_map(self.db);
                         let scope = &item_map[m.local_id].scope;
 
                         // Module scoped macros is included
@@ -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 ec90f4e65..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
@@ -243,7 +258,7 @@ impl DefMap {
                             kind: PathKind::Super(0),
                         };
                         log::debug!("resolving {:?} in other crate", path);
-                        let defp_map = db.crate_def_map(module.krate);
+                        let defp_map = module.def_map(db);
                         let (def, s) = defp_map.resolve_path(db, module.local_id, &path, shadow);
                         return ResolvePathResult::with(
                             def,
@@ -356,7 +371,7 @@ impl DefMap {
                 self
             } else {
                 // Extend lifetime
-                keep = db.crate_def_map(prelude.krate);
+                keep = prelude.def_map(db);
                 &keep
             };
             def_map[prelude.local_id].scope.get(name)
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 b2f577649..9021ea712 100644
--- a/crates/hir_def/src/resolver.rs
+++ b/crates/hir_def/src/resolver.rs
@@ -430,7 +430,7 @@ impl Resolver {
         for scope in &self.scopes {
             if let Scope::ModuleScope(m) = scope {
                 if let Some(prelude) = m.crate_def_map.prelude() {
-                    let prelude_def_map = db.crate_def_map(prelude.krate);
+                    let prelude_def_map = prelude.def_map(db);
                     traits.extend(prelude_def_map[prelude.local_id].scope.traits());
                 }
                 traits.extend(m.crate_def_map[m.module_id].scope.traits());
@@ -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> {
@@ -529,7 +529,7 @@ impl Scope {
                     f(name.clone(), ScopeDef::PerNs(def));
                 });
                 if let Some(prelude) = m.crate_def_map.prelude() {
-                    let prelude_def_map = db.crate_def_map(prelude.krate);
+                    let prelude_def_map = prelude.def_map(db);
                     prelude_def_map[prelude.local_id].scope.entries().for_each(|(name, def)| {
                         let seen_tuple = (name.clone(), def);
                         if !seen.contains(&seen_tuple) {
@@ -633,7 +633,7 @@ pub trait HasResolver: Copy {
 
 impl HasResolver for ModuleId {
     fn resolver(self, db: &dyn DefDatabase) -> Resolver {
-        let def_map = db.crate_def_map(self.krate);
+        let def_map = self.def_map(db);
         Resolver::default().push_module_scope(def_map, self.local_id)
     }
 }
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_def/src/visibility.rs b/crates/hir_def/src/visibility.rs
index 3134fa43d..e79a91102 100644
--- a/crates/hir_def/src/visibility.rs
+++ b/crates/hir_def/src/visibility.rs
@@ -103,7 +103,7 @@ impl Visibility {
         if from_module.krate != to_module.krate {
             return false;
         }
-        let def_map = db.crate_def_map(from_module.krate);
+        let def_map = from_module.def_map(db);
         self.is_visible_from_def_map(&def_map, from_module.local_id)
     }