diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index e6ff31842953c..c15b1c111ba50 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -114,16 +114,12 @@ impl<'a> Resolver<'a> {
     }
 
     pub fn get_module(&mut self, def_id: DefId) -> Module<'a> {
-        // If this is a local module, it will be in `module_map`, no need to recalculate it.
-        if let Some(def_id) = def_id.as_local() {
-            return self.module_map[&def_id];
-        }
-
         // Cache module resolution
-        if let Some(&module) = self.extern_module_map.get(&def_id) {
-            return module;
+        if let Some(module) = self.module_map.get(&def_id) {
+            return *module;
         }
 
+        assert!(!def_id.is_local());
         let (name, parent) = if def_id.index == CRATE_DEF_INDEX {
             // This is the crate root
             (self.cstore().crate_name(def_id.krate), None)
@@ -148,7 +144,7 @@ impl<'a> Resolver<'a> {
             // FIXME: Account for `#[no_implicit_prelude]` attributes.
             parent.map_or(false, |module| module.no_implicit_prelude),
         );
-        self.extern_module_map.insert(def_id, module);
+        self.module_map.insert(def_id, module);
         module
     }
 
@@ -772,7 +768,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                         || self.r.session.contains_name(&item.attrs, sym::no_implicit_prelude),
                 );
                 self.r.define(parent, ident, TypeNS, (module, vis, sp, expansion));
-                self.r.module_map.insert(local_def_id, module);
+                self.r.module_map.insert(def_id, module);
 
                 // Descend into the module.
                 self.parent_scope.module = module;
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index c92353ab7c008..b4d29684e790a 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -799,9 +799,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
     }
 
     fn with_scope<T>(&mut self, id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
-        let id = self.r.local_def_id(id);
-        let module = self.r.module_map.get(&id).cloned(); // clones a reference
-        if let Some(module) = module {
+        if let Some(module) = self.r.module_map.get(&self.r.local_def_id(id).to_def_id()).copied() {
             // Move down in the graph.
             let orig_module = replace(&mut self.parent_scope.module, module);
             self.with_rib(ValueNS, ModuleRibKind(module), |this| {
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index e53be0ee005c4..11ed7ded30483 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -943,8 +943,7 @@ pub struct Resolver<'a> {
     /// some AST passes can generate identifiers that only resolve to local or
     /// language items.
     empty_module: Module<'a>,
-    module_map: FxHashMap<LocalDefId, Module<'a>>,
-    extern_module_map: FxHashMap<DefId, Module<'a>>,
+    module_map: FxHashMap<DefId, Module<'a>>,
     binding_parent_modules: FxHashMap<PtrKey<'a, NameBinding<'a>>, Module<'a>>,
     underscore_disambiguator: u32,
 
@@ -1288,7 +1287,7 @@ impl<'a> Resolver<'a> {
             true,
         );
         let mut module_map = FxHashMap::default();
-        module_map.insert(CRATE_DEF_ID, graph_root);
+        module_map.insert(root_def_id, graph_root);
 
         let definitions = Definitions::new(session.local_stable_crate_id(), krate.span);
         let root = definitions.get_root_def();
@@ -1355,7 +1354,6 @@ impl<'a> Resolver<'a> {
             empty_module,
             module_map,
             block_map: Default::default(),
-            extern_module_map: FxHashMap::default(),
             binding_parent_modules: FxHashMap::default(),
             ast_transform_scopes: FxHashMap::default(),
 
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index ba7999e49eb93..a9778a28cb584 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -225,7 +225,8 @@ impl<'a> ResolverExpand for Resolver<'a> {
         features: &[Symbol],
         parent_module_id: Option<NodeId>,
     ) -> LocalExpnId {
-        let parent_module = parent_module_id.map(|module_id| self.local_def_id(module_id));
+        let parent_module =
+            parent_module_id.map(|module_id| self.local_def_id(module_id).to_def_id());
         let expn_id = LocalExpnId::fresh(
             ExpnData::allow_unstable(
                 ExpnKind::AstPass(pass),
@@ -233,13 +234,13 @@ impl<'a> ResolverExpand for Resolver<'a> {
                 self.session.edition(),
                 features.into(),
                 None,
-                parent_module.map(LocalDefId::to_def_id),
+                parent_module,
             ),
             self.create_stable_hashing_context(),
         );
 
-        let parent_scope = parent_module
-            .map_or(self.empty_module, |parent_def_id| self.module_map[&parent_def_id]);
+        let parent_scope =
+            parent_module.map_or(self.empty_module, |def_id| self.get_module(def_id));
         self.ast_transform_scopes.insert(expn_id, parent_scope);
 
         expn_id