diff --git a/crates/ra_hir/src/code_model_api.rs b/crates/ra_hir/src/code_model_api.rs
index d00d3246f0..09b532f746 100644
--- a/crates/ra_hir/src/code_model_api.rs
+++ b/crates/ra_hir/src/code_model_api.rs
@@ -1,7 +1,8 @@
+use relative_path::RelativePathBuf;
 use ra_db::{CrateId, Cancelable, FileId};
 use ra_syntax::{ast, SyntaxNode};
 
-use crate::{Name, db::HirDatabase, DefId, Path, PerNs, module::{Problem, ModuleScope}};
+use crate::{Name, db::HirDatabase, DefId, Path, PerNs, nameres::ModuleScope};
 
 /// hir::Crate describes a single crate. It's the main inteface with which
 /// crate's dependencies interact. Mostly, it should be just a proxy for the
@@ -39,6 +40,17 @@ pub enum ModuleSource {
     Module(ast::ModuleNode),
 }
 
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+pub enum Problem {
+    UnresolvedModule {
+        candidate: RelativePathBuf,
+    },
+    NotDirOwner {
+        move_to: RelativePathBuf,
+        candidate: RelativePathBuf,
+    },
+}
+
 impl Module {
     /// Name of this module.
     pub fn name(&self, db: &impl HirDatabase) -> Cancelable<Option<Name>> {
diff --git a/crates/ra_hir/src/code_model_impl.rs b/crates/ra_hir/src/code_model_impl.rs
index 4f4b506dd9..d602a439df 100644
--- a/crates/ra_hir/src/code_model_impl.rs
+++ b/crates/ra_hir/src/code_model_impl.rs
@@ -1,194 +1,2 @@
-use ra_db::{CrateId, Cancelable, SourceRootId, FileId};
-use ra_syntax::{ast, SyntaxNode, AstNode};
-
-use crate::{
-    HirFileId, Crate, CrateDependency, AsName, DefId, DefLoc, DefKind, Name, Path, PathKind, PerNs, Def, ModuleId,
-    module::{ModuleScope, Problem},
-    db::HirDatabase,
-};
-
-use crate::code_model_api::{Module, ModuleSource};
-
-impl Crate {
-    pub(crate) fn new(crate_id: CrateId) -> Crate {
-        Crate { crate_id }
-    }
-    pub(crate) fn dependencies_impl(&self, db: &impl HirDatabase) -> Vec<CrateDependency> {
-        let crate_graph = db.crate_graph();
-        crate_graph
-            .dependencies(self.crate_id)
-            .map(|dep| {
-                let krate = Crate::new(dep.crate_id());
-                let name = dep.as_name();
-                CrateDependency { krate, name }
-            })
-            .collect()
-    }
-    pub(crate) fn root_module_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Module>> {
-        let crate_graph = db.crate_graph();
-        let file_id = crate_graph.crate_root(self.crate_id);
-        let source_root_id = db.file_source_root(file_id);
-        let file_id = HirFileId::from(file_id);
-        let module_tree = db.module_tree(source_root_id)?;
-        // FIXME: teach module tree about crate roots instead of guessing
-        let (module_id, _) = ctry!(module_tree
-            .modules_with_sources()
-            .find(|(_, src)| src.file_id() == file_id));
-
-        let def_loc = DefLoc {
-            kind: DefKind::Module,
-            source_root_id,
-            module_id,
-            source_item_id: module_id.source(&module_tree).0,
-        };
-        let def_id = def_loc.id(db);
-
-        let module = Module::new(def_id);
-        Ok(Some(module))
-    }
-}
-
-impl Module {
-    pub(crate) fn new(def_id: DefId) -> Self {
-        crate::code_model_api::Module { def_id }
-    }
-    pub(crate) fn from_module_id(
-        db: &impl HirDatabase,
-        source_root_id: SourceRootId,
-        module_id: ModuleId,
-    ) -> Cancelable<Self> {
-        let module_tree = db.module_tree(source_root_id)?;
-        let def_loc = DefLoc {
-            kind: DefKind::Module,
-            source_root_id,
-            module_id,
-            source_item_id: module_id.source(&module_tree).0,
-        };
-        let def_id = def_loc.id(db);
-        let module = Module::new(def_id);
-        Ok(module)
-    }
-
-    pub(crate) fn name_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Name>> {
-        let loc = self.def_id.loc(db);
-        let module_tree = db.module_tree(loc.source_root_id)?;
-        let link = ctry!(loc.module_id.parent_link(&module_tree));
-        Ok(Some(link.name(&module_tree).clone()))
-    }
-
-    pub fn defenition_source_impl(
-        &self,
-        db: &impl HirDatabase,
-    ) -> Cancelable<(FileId, ModuleSource)> {
-        let loc = self.def_id.loc(db);
-        let file_id = loc.source_item_id.file_id.as_original_file();
-        let syntax_node = db.file_item(loc.source_item_id);
-        let syntax_node = syntax_node.borrowed();
-        let module_source = if let Some(source_file) = ast::SourceFile::cast(syntax_node) {
-            ModuleSource::SourceFile(source_file.owned())
-        } else {
-            let module = ast::Module::cast(syntax_node).unwrap();
-            ModuleSource::Module(module.owned())
-        };
-        Ok((file_id, module_source))
-    }
-
-    pub fn declaration_source_impl(
-        &self,
-        db: &impl HirDatabase,
-    ) -> Cancelable<Option<(FileId, ast::ModuleNode)>> {
-        let loc = self.def_id.loc(db);
-        let module_tree = db.module_tree(loc.source_root_id)?;
-        let link = ctry!(loc.module_id.parent_link(&module_tree));
-        let file_id = link
-            .owner(&module_tree)
-            .source(&module_tree)
-            .file_id()
-            .as_original_file();
-        let src = link.bind_source(&module_tree, db);
-        Ok(Some((file_id, src)))
-    }
-
-    pub(crate) fn krate_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Crate>> {
-        let root = self.crate_root(db)?;
-        let loc = root.def_id.loc(db);
-        let file_id = loc.source_item_id.file_id.as_original_file();
-
-        let crate_graph = db.crate_graph();
-        let crate_id = ctry!(crate_graph.crate_id_for_crate_root(file_id));
-        Ok(Some(Crate::new(crate_id)))
-    }
-
-    pub(crate) fn crate_root_impl(&self, db: &impl HirDatabase) -> Cancelable<Module> {
-        let loc = self.def_id.loc(db);
-        let module_tree = db.module_tree(loc.source_root_id)?;
-        let module_id = loc.module_id.crate_root(&module_tree);
-        Module::from_module_id(db, loc.source_root_id, module_id)
-    }
-    /// Finds a child module with the specified name.
-    pub fn child_impl(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
-        let loc = self.def_id.loc(db);
-        let module_tree = db.module_tree(loc.source_root_id)?;
-        let child_id = ctry!(loc.module_id.child(&module_tree, name));
-        Module::from_module_id(db, loc.source_root_id, child_id).map(Some)
-    }
-    pub fn parent_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Module>> {
-        let loc = self.def_id.loc(db);
-        let module_tree = db.module_tree(loc.source_root_id)?;
-        let parent_id = ctry!(loc.module_id.parent(&module_tree));
-        Module::from_module_id(db, loc.source_root_id, parent_id).map(Some)
-    }
-    /// Returns a `ModuleScope`: a set of items, visible in this module.
-    pub fn scope_impl(&self, db: &impl HirDatabase) -> Cancelable<ModuleScope> {
-        let loc = self.def_id.loc(db);
-        let item_map = db.item_map(loc.source_root_id)?;
-        let res = item_map.per_module[&loc.module_id].clone();
-        Ok(res)
-    }
-    pub fn resolve_path_impl(
-        &self,
-        db: &impl HirDatabase,
-        path: &Path,
-    ) -> Cancelable<PerNs<DefId>> {
-        let mut curr_per_ns = PerNs::types(
-            match path.kind {
-                PathKind::Crate => self.crate_root(db)?,
-                PathKind::Self_ | PathKind::Plain => self.clone(),
-                PathKind::Super => {
-                    if let Some(p) = self.parent(db)? {
-                        p
-                    } else {
-                        return Ok(PerNs::none());
-                    }
-                }
-            }
-            .def_id,
-        );
-
-        let segments = &path.segments;
-        for name in segments.iter() {
-            let curr = if let Some(r) = curr_per_ns.as_ref().take_types() {
-                r
-            } else {
-                return Ok(PerNs::none());
-            };
-            let module = match curr.resolve(db)? {
-                Def::Module(it) => it,
-                // TODO here would be the place to handle enum variants...
-                _ => return Ok(PerNs::none()),
-            };
-            let scope = module.scope(db)?;
-            curr_per_ns = if let Some(r) = scope.get(&name) {
-                r.def_id
-            } else {
-                return Ok(PerNs::none());
-            };
-        }
-        Ok(curr_per_ns)
-    }
-    pub fn problems_impl(&self, db: &impl HirDatabase) -> Cancelable<Vec<(SyntaxNode, Problem)>> {
-        let loc = self.def_id.loc(db);
-        let module_tree = db.module_tree(loc.source_root_id)?;
-        Ok(loc.module_id.problems(&module_tree, db))
-    }
-}
+mod krate; // `crate` is invalid ident :(
+pub(crate) mod module;
diff --git a/crates/ra_hir/src/code_model_impl/krate.rs b/crates/ra_hir/src/code_model_impl/krate.rs
new file mode 100644
index 0000000000..591a81597d
--- /dev/null
+++ b/crates/ra_hir/src/code_model_impl/krate.rs
@@ -0,0 +1,45 @@
+use ra_db::{CrateId, Cancelable};
+
+use crate::{
+    HirFileId, Crate, CrateDependency, AsName, DefLoc, DefKind, Module,
+    db::HirDatabase,
+};
+
+impl Crate {
+    pub(crate) fn new(crate_id: CrateId) -> Crate {
+        Crate { crate_id }
+    }
+    pub(crate) fn dependencies_impl(&self, db: &impl HirDatabase) -> Vec<CrateDependency> {
+        let crate_graph = db.crate_graph();
+        crate_graph
+            .dependencies(self.crate_id)
+            .map(|dep| {
+                let krate = Crate::new(dep.crate_id());
+                let name = dep.as_name();
+                CrateDependency { krate, name }
+            })
+            .collect()
+    }
+    pub(crate) fn root_module_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Module>> {
+        let crate_graph = db.crate_graph();
+        let file_id = crate_graph.crate_root(self.crate_id);
+        let source_root_id = db.file_source_root(file_id);
+        let file_id = HirFileId::from(file_id);
+        let module_tree = db.module_tree(source_root_id)?;
+        // FIXME: teach module tree about crate roots instead of guessing
+        let (module_id, _) = ctry!(module_tree
+            .modules_with_sources()
+            .find(|(_, src)| src.file_id() == file_id));
+
+        let def_loc = DefLoc {
+            kind: DefKind::Module,
+            source_root_id,
+            module_id,
+            source_item_id: module_id.source(&module_tree).0,
+        };
+        let def_id = def_loc.id(db);
+
+        let module = Module::new(def_id);
+        Ok(Some(module))
+    }
+}
diff --git a/crates/ra_hir/src/code_model_impl/module.rs b/crates/ra_hir/src/code_model_impl/module.rs
new file mode 100644
index 0000000000..02078f188d
--- /dev/null
+++ b/crates/ra_hir/src/code_model_impl/module.rs
@@ -0,0 +1,154 @@
+use ra_db::{Cancelable, SourceRootId, FileId};
+use ra_syntax::{ast, SyntaxNode, AstNode};
+
+use crate::{
+    Module, ModuleSource, Problem,
+    Crate, DefId, DefLoc, DefKind, Name, Path, PathKind, PerNs, Def, ModuleId,
+    nameres::ModuleScope,
+    db::HirDatabase,
+};
+
+impl Module {
+    pub(crate) fn new(def_id: DefId) -> Self {
+        crate::code_model_api::Module { def_id }
+    }
+    pub(crate) fn from_module_id(
+        db: &impl HirDatabase,
+        source_root_id: SourceRootId,
+        module_id: ModuleId,
+    ) -> Cancelable<Self> {
+        let module_tree = db.module_tree(source_root_id)?;
+        let def_loc = DefLoc {
+            kind: DefKind::Module,
+            source_root_id,
+            module_id,
+            source_item_id: module_id.source(&module_tree).0,
+        };
+        let def_id = def_loc.id(db);
+        let module = Module::new(def_id);
+        Ok(module)
+    }
+
+    pub(crate) fn name_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Name>> {
+        let loc = self.def_id.loc(db);
+        let module_tree = db.module_tree(loc.source_root_id)?;
+        let link = ctry!(loc.module_id.parent_link(&module_tree));
+        Ok(Some(link.name(&module_tree).clone()))
+    }
+
+    pub fn defenition_source_impl(
+        &self,
+        db: &impl HirDatabase,
+    ) -> Cancelable<(FileId, ModuleSource)> {
+        let loc = self.def_id.loc(db);
+        let file_id = loc.source_item_id.file_id.as_original_file();
+        let syntax_node = db.file_item(loc.source_item_id);
+        let syntax_node = syntax_node.borrowed();
+        let module_source = if let Some(source_file) = ast::SourceFile::cast(syntax_node) {
+            ModuleSource::SourceFile(source_file.owned())
+        } else {
+            let module = ast::Module::cast(syntax_node).unwrap();
+            ModuleSource::Module(module.owned())
+        };
+        Ok((file_id, module_source))
+    }
+
+    pub fn declaration_source_impl(
+        &self,
+        db: &impl HirDatabase,
+    ) -> Cancelable<Option<(FileId, ast::ModuleNode)>> {
+        let loc = self.def_id.loc(db);
+        let module_tree = db.module_tree(loc.source_root_id)?;
+        let link = ctry!(loc.module_id.parent_link(&module_tree));
+        let file_id = link
+            .owner(&module_tree)
+            .source(&module_tree)
+            .file_id()
+            .as_original_file();
+        let src = link.bind_source(&module_tree, db);
+        Ok(Some((file_id, src)))
+    }
+
+    pub(crate) fn krate_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Crate>> {
+        let root = self.crate_root(db)?;
+        let loc = root.def_id.loc(db);
+        let file_id = loc.source_item_id.file_id.as_original_file();
+
+        let crate_graph = db.crate_graph();
+        let crate_id = ctry!(crate_graph.crate_id_for_crate_root(file_id));
+        Ok(Some(Crate::new(crate_id)))
+    }
+
+    pub(crate) fn crate_root_impl(&self, db: &impl HirDatabase) -> Cancelable<Module> {
+        let loc = self.def_id.loc(db);
+        let module_tree = db.module_tree(loc.source_root_id)?;
+        let module_id = loc.module_id.crate_root(&module_tree);
+        Module::from_module_id(db, loc.source_root_id, module_id)
+    }
+    /// Finds a child module with the specified name.
+    pub fn child_impl(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+        let loc = self.def_id.loc(db);
+        let module_tree = db.module_tree(loc.source_root_id)?;
+        let child_id = ctry!(loc.module_id.child(&module_tree, name));
+        Module::from_module_id(db, loc.source_root_id, child_id).map(Some)
+    }
+    pub fn parent_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Module>> {
+        let loc = self.def_id.loc(db);
+        let module_tree = db.module_tree(loc.source_root_id)?;
+        let parent_id = ctry!(loc.module_id.parent(&module_tree));
+        Module::from_module_id(db, loc.source_root_id, parent_id).map(Some)
+    }
+    /// Returns a `ModuleScope`: a set of items, visible in this module.
+    pub fn scope_impl(&self, db: &impl HirDatabase) -> Cancelable<ModuleScope> {
+        let loc = self.def_id.loc(db);
+        let item_map = db.item_map(loc.source_root_id)?;
+        let res = item_map.per_module[&loc.module_id].clone();
+        Ok(res)
+    }
+    pub fn resolve_path_impl(
+        &self,
+        db: &impl HirDatabase,
+        path: &Path,
+    ) -> Cancelable<PerNs<DefId>> {
+        let mut curr_per_ns = PerNs::types(
+            match path.kind {
+                PathKind::Crate => self.crate_root(db)?,
+                PathKind::Self_ | PathKind::Plain => self.clone(),
+                PathKind::Super => {
+                    if let Some(p) = self.parent(db)? {
+                        p
+                    } else {
+                        return Ok(PerNs::none());
+                    }
+                }
+            }
+            .def_id,
+        );
+
+        let segments = &path.segments;
+        for name in segments.iter() {
+            let curr = if let Some(r) = curr_per_ns.as_ref().take_types() {
+                r
+            } else {
+                return Ok(PerNs::none());
+            };
+            let module = match curr.resolve(db)? {
+                Def::Module(it) => it,
+                // TODO here would be the place to handle enum variants...
+                _ => return Ok(PerNs::none()),
+            };
+            let scope = module.scope(db)?;
+            curr_per_ns = if let Some(r) = scope.get(&name) {
+                r.def_id
+            } else {
+                return Ok(PerNs::none());
+            };
+        }
+        Ok(curr_per_ns)
+    }
+    pub fn problems_impl(&self, db: &impl HirDatabase) -> Cancelable<Vec<(SyntaxNode, Problem)>> {
+        let loc = self.def_id.loc(db);
+        let module_tree = db.module_tree(loc.source_root_id)?;
+        Ok(loc.module_id.problems(&module_tree, db))
+    }
+}
diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index 96a3c60b9e..2702961ba7 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -9,8 +9,8 @@ use crate::{
     query_definitions,
     FnSignature, FnScopes,
     macros::MacroExpansion,
-    module::{ModuleId, ModuleTree, ModuleSource,
-    nameres::{ItemMap, InputModuleItems}},
+    module_tree::{ModuleId, ModuleTree, ModuleSource},
+    nameres::{ItemMap, InputModuleItems},
     ty::{InferenceResult, Ty},
     adt::{StructData, EnumData},
     impl_block::ModuleImplBlocks,
@@ -71,7 +71,7 @@ pub trait HirDatabase: SyntaxDatabase
         use fn query_definitions::file_item;
     }
 
-    fn submodules(source: ModuleSource) -> Cancelable<Arc<Vec<crate::module::imp::Submodule>>> {
+    fn submodules(source: ModuleSource) -> Cancelable<Arc<Vec<crate::module_tree::Submodule>>> {
         type SubmodulesQuery;
         use fn query_definitions::submodules;
     }
@@ -86,7 +86,7 @@ pub trait HirDatabase: SyntaxDatabase
     }
     fn module_tree(source_root_id: SourceRootId) -> Cancelable<Arc<ModuleTree>> {
         type ModuleTreeQuery;
-        use fn crate::module::imp::module_tree;
+        use fn crate::module_tree::ModuleTree::module_tree_query;
     }
 
     fn impls_in_module(source_root_id: SourceRootId, module_id: ModuleId) -> Cancelable<Arc<ModuleImplBlocks>> {
diff --git a/crates/ra_hir/src/impl_block.rs b/crates/ra_hir/src/impl_block.rs
index 0d1b94c425..7ce8d17e66 100644
--- a/crates/ra_hir/src/impl_block.rs
+++ b/crates/ra_hir/src/impl_block.rs
@@ -10,7 +10,7 @@ use crate::{
     Function,
     db::HirDatabase,
     type_ref::TypeRef,
-    module::ModuleId,
+    module_tree::ModuleId,
 };
 
 use crate::code_model_api::{Module, ModuleSource};
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 2fa357fecf..7e74f2eaf8 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -24,7 +24,8 @@ pub mod source_binder;
 mod ids;
 mod macros;
 mod name;
-mod module;
+mod module_tree;
+mod nameres;
 mod function;
 mod adt;
 mod type_ref;
@@ -32,14 +33,13 @@ mod ty;
 mod impl_block;
 mod expr;
 
-pub mod code_model_api;
+mod code_model_api;
 mod code_model_impl;
 
 use crate::{
     db::HirDatabase,
     name::{AsName, KnownName},
     ids::{DefKind, SourceItemId, SourceFileItemId, SourceFileItems},
-    code_model_api::{Crate, CrateDependency}
 };
 
 pub use self::{
@@ -56,7 +56,10 @@ pub use self::{
 
 pub use self::function::FnSignatureInfo;
 
-pub use self::code_model_api::Module;
+pub use self::code_model_api::{
+    Crate, CrateDependency,
+    Module, ModuleSource, Problem,
+};
 
 pub enum Def {
     Module(Module),
diff --git a/crates/ra_hir/src/module/imp.rs b/crates/ra_hir/src/module/imp.rs
deleted file mode 100644
index 3849026dbd..0000000000
--- a/crates/ra_hir/src/module/imp.rs
+++ /dev/null
@@ -1,190 +0,0 @@
-use std::sync::Arc;
-
-use ra_syntax::ast::{self, NameOwner};
-use relative_path::RelativePathBuf;
-use rustc_hash::{FxHashMap, FxHashSet};
-use arrayvec::ArrayVec;
-use ra_db::{SourceRoot, SourceRootId, Cancelable, FileId};
-
-use crate::{
-    HirDatabase, Name, AsName,
-};
-
-use super::{
-    LinkData, LinkId, ModuleData, ModuleId, ModuleSource,
-    ModuleTree, Problem,
-};
-
-#[derive(Clone, Hash, PartialEq, Eq, Debug)]
-pub enum Submodule {
-    Declaration(Name),
-    Definition(Name, ModuleSource),
-}
-
-impl Submodule {
-    fn name(&self) -> &Name {
-        match self {
-            Submodule::Declaration(name) => name,
-            Submodule::Definition(name, _) => name,
-        }
-    }
-}
-
-pub(crate) fn modules<'a>(
-    root: impl ast::ModuleItemOwner<'a>,
-) -> impl Iterator<Item = (Name, ast::Module<'a>)> {
-    root.items()
-        .filter_map(|item| match item {
-            ast::ModuleItem::Module(m) => Some(m),
-            _ => None,
-        })
-        .filter_map(|module| {
-            let name = module.name()?.as_name();
-            Some((name, module))
-        })
-}
-
-pub(crate) fn module_tree(
-    db: &impl HirDatabase,
-    source_root: SourceRootId,
-) -> Cancelable<Arc<ModuleTree>> {
-    db.check_canceled()?;
-    let res = create_module_tree(db, source_root)?;
-    Ok(Arc::new(res))
-}
-
-fn create_module_tree<'a>(
-    db: &impl HirDatabase,
-    source_root: SourceRootId,
-) -> Cancelable<ModuleTree> {
-    let mut tree = ModuleTree::default();
-
-    let mut roots = FxHashMap::default();
-    let mut visited = FxHashSet::default();
-
-    let source_root = db.source_root(source_root);
-    for &file_id in source_root.files.values() {
-        let source = ModuleSource::new_file(file_id.into());
-        if visited.contains(&source) {
-            continue; // TODO: use explicit crate_roots here
-        }
-        assert!(!roots.contains_key(&file_id));
-        let module_id = build_subtree(
-            db,
-            &source_root,
-            &mut tree,
-            &mut visited,
-            &mut roots,
-            None,
-            source,
-        )?;
-        roots.insert(file_id, module_id);
-    }
-    Ok(tree)
-}
-
-fn build_subtree(
-    db: &impl HirDatabase,
-    source_root: &SourceRoot,
-    tree: &mut ModuleTree,
-    visited: &mut FxHashSet<ModuleSource>,
-    roots: &mut FxHashMap<FileId, ModuleId>,
-    parent: Option<LinkId>,
-    source: ModuleSource,
-) -> Cancelable<ModuleId> {
-    visited.insert(source);
-    let id = tree.push_mod(ModuleData {
-        source,
-        parent,
-        children: Vec::new(),
-    });
-    for sub in db.submodules(source)?.iter() {
-        let link = tree.push_link(LinkData {
-            name: sub.name().clone(),
-            owner: id,
-            points_to: Vec::new(),
-            problem: None,
-        });
-
-        let (points_to, problem) = match sub {
-            Submodule::Declaration(name) => {
-                let (points_to, problem) = resolve_submodule(db, source, &name);
-                let points_to = points_to
-                    .into_iter()
-                    .map(|file_id| match roots.remove(&file_id) {
-                        Some(module_id) => {
-                            tree.mods[module_id].parent = Some(link);
-                            Ok(module_id)
-                        }
-                        None => build_subtree(
-                            db,
-                            source_root,
-                            tree,
-                            visited,
-                            roots,
-                            Some(link),
-                            ModuleSource::new_file(file_id.into()),
-                        ),
-                    })
-                    .collect::<Cancelable<Vec<_>>>()?;
-                (points_to, problem)
-            }
-            Submodule::Definition(_name, submodule_source) => {
-                let points_to = build_subtree(
-                    db,
-                    source_root,
-                    tree,
-                    visited,
-                    roots,
-                    Some(link),
-                    *submodule_source,
-                )?;
-                (vec![points_to], None)
-            }
-        };
-
-        tree.links[link].points_to = points_to;
-        tree.links[link].problem = problem;
-    }
-    Ok(id)
-}
-
-fn resolve_submodule(
-    db: &impl HirDatabase,
-    source: ModuleSource,
-    name: &Name,
-) -> (Vec<FileId>, Option<Problem>) {
-    // FIXME: handle submodules of inline modules properly
-    let file_id = source.file_id().original_file(db);
-    let source_root_id = db.file_source_root(file_id);
-    let path = db.file_relative_path(file_id);
-    let root = RelativePathBuf::default();
-    let dir_path = path.parent().unwrap_or(&root);
-    let mod_name = path.file_stem().unwrap_or("unknown");
-    let is_dir_owner = mod_name == "mod" || mod_name == "lib" || mod_name == "main";
-
-    let file_mod = dir_path.join(format!("{}.rs", name));
-    let dir_mod = dir_path.join(format!("{}/mod.rs", name));
-    let file_dir_mod = dir_path.join(format!("{}/{}.rs", mod_name, name));
-    let mut candidates = ArrayVec::<[_; 2]>::new();
-    if is_dir_owner {
-        candidates.push(file_mod.clone());
-        candidates.push(dir_mod);
-    } else {
-        candidates.push(file_dir_mod.clone());
-    };
-    let sr = db.source_root(source_root_id);
-    let points_to = candidates
-        .into_iter()
-        .filter_map(|path| sr.files.get(&path))
-        .map(|&it| it)
-        .collect::<Vec<_>>();
-    let problem = if points_to.is_empty() {
-        Some(Problem::UnresolvedModule {
-            candidate: if is_dir_owner { file_mod } else { file_dir_mod },
-        })
-    } else {
-        None
-    };
-    (points_to, problem)
-}
diff --git a/crates/ra_hir/src/module.rs b/crates/ra_hir/src/module_tree.rs
similarity index 50%
rename from crates/ra_hir/src/module.rs
rename to crates/ra_hir/src/module_tree.rs
index ebaf5f47a5..cd82f25dbe 100644
--- a/crates/ra_hir/src/module.rs
+++ b/crates/ra_hir/src/module_tree.rs
@@ -1,17 +1,32 @@
-pub(super) mod imp;
-pub(super) mod nameres;
+use std::sync::Arc;
 
+use rustc_hash::{FxHashMap, FxHashSet};
+use arrayvec::ArrayVec;
+use relative_path::RelativePathBuf;
+use ra_db::{FileId, SourceRootId, Cancelable, SourceRoot};
 use ra_syntax::{
     algo::generate,
     ast::{self, AstNode, NameOwner},
     SyntaxNode,
 };
 use ra_arena::{Arena, RawId, impl_arena_id};
-use relative_path::RelativePathBuf;
 
-use crate::{Name, HirDatabase, SourceItemId, SourceFileItemId, HirFileId};
+use crate::{Name, AsName, HirDatabase, SourceItemId, SourceFileItemId, HirFileId, Problem};
 
-pub use self::nameres::{ModuleScope, Resolution, Namespace, PerNs};
+#[derive(Clone, Hash, PartialEq, Eq, Debug)]
+pub enum Submodule {
+    Declaration(Name),
+    Definition(Name, ModuleSource),
+}
+
+impl Submodule {
+    fn name(&self) -> &Name {
+        match self {
+            Submodule::Declaration(name) => name,
+            Submodule::Definition(name, _) => name,
+        }
+    }
+}
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct ModuleId(RawId);
@@ -34,7 +49,31 @@ pub struct ModuleTree {
     links: Arena<LinkId, LinkData>,
 }
 
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub struct ModuleData {
+    source: ModuleSource,
+    parent: Option<LinkId>,
+    children: Vec<LinkId>,
+}
+
+#[derive(Hash, Debug, PartialEq, Eq)]
+struct LinkData {
+    owner: ModuleId,
+    name: Name,
+    points_to: Vec<ModuleId>,
+    problem: Option<Problem>,
+}
+
 impl ModuleTree {
+    pub(crate) fn module_tree_query(
+        db: &impl HirDatabase,
+        source_root: SourceRootId,
+    ) -> Cancelable<Arc<ModuleTree>> {
+        db.check_canceled()?;
+        let res = create_module_tree(db, source_root)?;
+        Ok(Arc::new(res))
+    }
+
     pub(crate) fn modules<'a>(&'a self) -> impl Iterator<Item = ModuleId> + 'a {
         self.mods.iter().map(|(id, _)| id)
     }
@@ -58,17 +97,6 @@ pub(crate) enum ModuleSourceNode {
     Module(ast::ModuleNode),
 }
 
-#[derive(Clone, Debug, Hash, PartialEq, Eq)]
-pub enum Problem {
-    UnresolvedModule {
-        candidate: RelativePathBuf,
-    },
-    NotDirOwner {
-        move_to: RelativePathBuf,
-        candidate: RelativePathBuf,
-    },
-}
-
 impl ModuleId {
     pub(crate) fn source(self, tree: &ModuleTree) -> ModuleSource {
         tree.mods[self].source
@@ -93,7 +121,10 @@ impl ModuleId {
             .find(|it| it.name == *name)?;
         Some(*link.points_to.first()?)
     }
-    fn children<'a>(self, tree: &'a ModuleTree) -> impl Iterator<Item = (Name, ModuleId)> + 'a {
+    pub(crate) fn children<'a>(
+        self,
+        tree: &'a ModuleTree,
+    ) -> impl Iterator<Item = (Name, ModuleId)> + 'a {
         tree.mods[self].children.iter().filter_map(move |&it| {
             let link = &tree.links[it];
             let module = *link.points_to.first()?;
@@ -133,7 +164,7 @@ impl LinkId {
         let owner = self.owner(tree);
         match owner.source(tree).resolve(db) {
             ModuleSourceNode::SourceFile(root) => {
-                let ast = imp::modules(root.borrowed())
+                let ast = modules(root.borrowed())
                     .find(|(name, _)| name == &tree.links[self].name)
                     .unwrap()
                     .1;
@@ -144,13 +175,6 @@ impl LinkId {
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Hash)]
-pub struct ModuleData {
-    source: ModuleSource,
-    parent: Option<LinkId>,
-    children: Vec<LinkId>,
-}
-
 impl ModuleSource {
     // precondition: item_id **must** point to module
     fn new(file_id: HirFileId, item_id: Option<SourceFileItemId>) -> ModuleSource {
@@ -188,14 +212,6 @@ impl ModuleSource {
     }
 }
 
-#[derive(Hash, Debug, PartialEq, Eq)]
-struct LinkData {
-    owner: ModuleId,
-    name: Name,
-    points_to: Vec<ModuleId>,
-    problem: Option<Problem>,
-}
-
 impl ModuleTree {
     fn push_mod(&mut self, data: ModuleData) -> ModuleId {
         self.mods.alloc(data)
@@ -207,3 +223,153 @@ impl ModuleTree {
         id
     }
 }
+
+fn modules<'a>(
+    root: impl ast::ModuleItemOwner<'a>,
+) -> impl Iterator<Item = (Name, ast::Module<'a>)> {
+    root.items()
+        .filter_map(|item| match item {
+            ast::ModuleItem::Module(m) => Some(m),
+            _ => None,
+        })
+        .filter_map(|module| {
+            let name = module.name()?.as_name();
+            Some((name, module))
+        })
+}
+
+fn create_module_tree<'a>(
+    db: &impl HirDatabase,
+    source_root: SourceRootId,
+) -> Cancelable<ModuleTree> {
+    let mut tree = ModuleTree::default();
+
+    let mut roots = FxHashMap::default();
+    let mut visited = FxHashSet::default();
+
+    let source_root = db.source_root(source_root);
+    for &file_id in source_root.files.values() {
+        let source = ModuleSource::new_file(file_id.into());
+        if visited.contains(&source) {
+            continue; // TODO: use explicit crate_roots here
+        }
+        assert!(!roots.contains_key(&file_id));
+        let module_id = build_subtree(
+            db,
+            &source_root,
+            &mut tree,
+            &mut visited,
+            &mut roots,
+            None,
+            source,
+        )?;
+        roots.insert(file_id, module_id);
+    }
+    Ok(tree)
+}
+
+fn build_subtree(
+    db: &impl HirDatabase,
+    source_root: &SourceRoot,
+    tree: &mut ModuleTree,
+    visited: &mut FxHashSet<ModuleSource>,
+    roots: &mut FxHashMap<FileId, ModuleId>,
+    parent: Option<LinkId>,
+    source: ModuleSource,
+) -> Cancelable<ModuleId> {
+    visited.insert(source);
+    let id = tree.push_mod(ModuleData {
+        source,
+        parent,
+        children: Vec::new(),
+    });
+    for sub in db.submodules(source)?.iter() {
+        let link = tree.push_link(LinkData {
+            name: sub.name().clone(),
+            owner: id,
+            points_to: Vec::new(),
+            problem: None,
+        });
+
+        let (points_to, problem) = match sub {
+            Submodule::Declaration(name) => {
+                let (points_to, problem) = resolve_submodule(db, source, &name);
+                let points_to = points_to
+                    .into_iter()
+                    .map(|file_id| match roots.remove(&file_id) {
+                        Some(module_id) => {
+                            tree.mods[module_id].parent = Some(link);
+                            Ok(module_id)
+                        }
+                        None => build_subtree(
+                            db,
+                            source_root,
+                            tree,
+                            visited,
+                            roots,
+                            Some(link),
+                            ModuleSource::new_file(file_id.into()),
+                        ),
+                    })
+                    .collect::<Cancelable<Vec<_>>>()?;
+                (points_to, problem)
+            }
+            Submodule::Definition(_name, submodule_source) => {
+                let points_to = build_subtree(
+                    db,
+                    source_root,
+                    tree,
+                    visited,
+                    roots,
+                    Some(link),
+                    *submodule_source,
+                )?;
+                (vec![points_to], None)
+            }
+        };
+
+        tree.links[link].points_to = points_to;
+        tree.links[link].problem = problem;
+    }
+    Ok(id)
+}
+
+fn resolve_submodule(
+    db: &impl HirDatabase,
+    source: ModuleSource,
+    name: &Name,
+) -> (Vec<FileId>, Option<Problem>) {
+    // FIXME: handle submodules of inline modules properly
+    let file_id = source.file_id().original_file(db);
+    let source_root_id = db.file_source_root(file_id);
+    let path = db.file_relative_path(file_id);
+    let root = RelativePathBuf::default();
+    let dir_path = path.parent().unwrap_or(&root);
+    let mod_name = path.file_stem().unwrap_or("unknown");
+    let is_dir_owner = mod_name == "mod" || mod_name == "lib" || mod_name == "main";
+
+    let file_mod = dir_path.join(format!("{}.rs", name));
+    let dir_mod = dir_path.join(format!("{}/mod.rs", name));
+    let file_dir_mod = dir_path.join(format!("{}/{}.rs", mod_name, name));
+    let mut candidates = ArrayVec::<[_; 2]>::new();
+    if is_dir_owner {
+        candidates.push(file_mod.clone());
+        candidates.push(dir_mod);
+    } else {
+        candidates.push(file_dir_mod.clone());
+    };
+    let sr = db.source_root(source_root_id);
+    let points_to = candidates
+        .into_iter()
+        .filter_map(|path| sr.files.get(&path))
+        .map(|&it| it)
+        .collect::<Vec<_>>();
+    let problem = if points_to.is_empty() {
+        Some(Problem::UnresolvedModule {
+            candidate: if is_dir_owner { file_mod } else { file_dir_mod },
+        })
+    } else {
+        None
+    };
+    (points_to, problem)
+}
diff --git a/crates/ra_hir/src/module/nameres.rs b/crates/ra_hir/src/nameres.rs
similarity index 99%
rename from crates/ra_hir/src/module/nameres.rs
rename to crates/ra_hir/src/nameres.rs
index 7d5e86c89b..e65cbcb270 100644
--- a/crates/ra_hir/src/module/nameres.rs
+++ b/crates/ra_hir/src/nameres.rs
@@ -31,7 +31,7 @@ use crate::{
     Path, PathKind,
     HirDatabase, Crate,
     Name, AsName,
-    module::{ModuleId, ModuleTree},
+    module_tree::{ModuleId, ModuleTree},
 };
 
 /// Item map is the result of the name resolution. Item map contains, for each
diff --git a/crates/ra_hir/src/module/nameres/tests.rs b/crates/ra_hir/src/nameres/tests.rs
similarity index 98%
rename from crates/ra_hir/src/module/nameres/tests.rs
rename to crates/ra_hir/src/nameres/tests.rs
index dcbe65aec3..a6a0bea316 100644
--- a/crates/ra_hir/src/module/nameres/tests.rs
+++ b/crates/ra_hir/src/nameres/tests.rs
@@ -17,7 +17,7 @@ fn item_map(fixture: &str) -> (Arc<hir::ItemMap>, hir::ModuleId) {
     let module = hir::source_binder::module_from_position(&db, pos)
         .unwrap()
         .unwrap();
-    let module_id = module.def_id.loc(&db).module_id;
+    let module_id = module.module_id;
     (db.item_map(source_root).unwrap(), module_id)
 }
 
@@ -155,7 +155,7 @@ fn item_map_across_crates() {
     let module = hir::source_binder::module_from_file_id(&db, main_id)
         .unwrap()
         .unwrap();
-    let module_id = module.def_id.loc(&db).module_id;
+    let module_id = module.module_id;
     let item_map = db.item_map(source_root).unwrap();
 
     check_module_item_map(
diff --git a/crates/ra_hir/src/query_definitions.rs b/crates/ra_hir/src/query_definitions.rs
index d9ee9d37f0..b17c00e26f 100644
--- a/crates/ra_hir/src/query_definitions.rs
+++ b/crates/ra_hir/src/query_definitions.rs
@@ -15,11 +15,8 @@ use crate::{
     MacroCallLoc,
     db::HirDatabase,
     function::FnScopes,
-    module::{
-        ModuleSource, ModuleSourceNode, ModuleId,
-        imp::Submodule,
-        nameres::{InputModuleItems, ItemMap, Resolver},
-    },
+    module_tree::{ModuleId, Submodule, ModuleSource, ModuleSourceNode},
+    nameres::{InputModuleItems, ItemMap, Resolver},
     adt::{StructData, EnumData},
 };
 
diff --git a/crates/ra_hir/src/source_binder.rs b/crates/ra_hir/src/source_binder.rs
index ac097e81a8..b7e3ff9b0c 100644
--- a/crates/ra_hir/src/source_binder.rs
+++ b/crates/ra_hir/src/source_binder.rs
@@ -14,7 +14,7 @@ use ra_syntax::{
 
 use crate::{
     HirDatabase, Function, SourceItemId,
-    module::ModuleSource,
+    module_tree::ModuleSource,
     DefKind, DefLoc, AsName,
 };