5 files changed, 144 insertions, 50 deletions

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"