Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -7789,6 +7789,11 @@
   "definition or redeclaration of %0 not allowed inside a block">;
 def err_not_tag_in_scope : Error<
   "no %select{struct|interface|union|class|enum}0 named %1 in %2">;
+def err_export_for_non_namespace_entities : Error <
+    "We couldn't export %0 which is not in namespace scopes.">;
+def err_export_entites_which_is_exported : Error <
+    "We couldn't export %0 which is exported already. "
+    "It was exported already at %0.">;
 
 def err_no_typeid_with_fno_rtti : Error<
   "use of typeid requires -frtti">;
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -5745,7 +5745,9 @@
     else if (isa<BlockDecl>(Cur))
       Diag(Loc, diag::err_invalid_declarator_in_block)
         << Name << SS.getRange();
-    else
+    else if (isa<ExportDecl>(Cur)) {
+
+    } else
       Diag(Loc, diag::err_invalid_declarator_scope)
       << Name << cast<NamedDecl>(Cur) << cast<NamedDecl>(DC) << SS.getRange();
 
@@ -5829,6 +5831,22 @@
         << D.getCXXScopeSpec().getRange();
       return nullptr;
     }
+
+    if (auto *ED = dyn_cast<ExportDecl>(CurContext)) {
+      if (!isa<NamespaceDecl>(DC)) {
+        Diag(ED->getExportLoc(), diag::err_export_for_non_namespace_entities)
+          << Name;
+      } else {
+        auto *TmpDC = DC;
+        while (TmpDC && !isa<ExportDecl>(TmpDC))
+          TmpDC = TmpDC->getParent();
+        if (TmpDC && isa<ExportDecl>(TmpDC)) {
+          Diag(ED->getExportLoc(), diag::err_export_entites_which_is_exported)
+            << Name << NameInfo.getLoc();;
+        }
+      }
+    }
+
     bool IsDependentContext = DC->isDependentContext();
 
     if (!IsDependentContext &&
@@ -16370,6 +16388,23 @@
     Invalid = true;
   }
 
+  if (isa<ExportDecl>(CurContext) && PrevDecl) {
+    auto *PrevDC = PrevDecl->getDeclContext();
+    if (!isa<NamespaceDecl>(PrevDC)) {
+      Diag(New->getLocation(), diag::err_export_for_non_namespace_entities)
+        << OrigName;
+      Invalid = true;
+    } else {
+      while (PrevDC && !isa<ExportDecl>(PrevDC))
+        PrevDC = PrevDC->getParent();
+      if (PrevDC && isa<ExportDecl>(PrevDC)) {
+        Diag(New->getLocation(), diag::err_export_entites_which_is_exported)
+          << OrigName << PrevDecl->getLocation();
+        Invalid = true;
+      }
+    }
+  }
+
   // Maybe add qualifier info.
   if (SS.isNotEmpty()) {
     if (SS.isSet()) {
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -3400,11 +3400,11 @@
       // class X {
       //   int X::member;
       // };
-      if (DeclContext *DC = computeDeclContext(SS, false))
+      if (DeclContext *DC = computeDeclContext(SS, false)) {
         diagnoseQualifiedDeclaration(SS, DC, Name, D.getIdentifierLoc(),
                                      D.getName().getKind() ==
                                          UnqualifiedIdKind::IK_TemplateId);
-      else
+      } else
         Diag(D.getIdentifierLoc(), diag::err_member_qualification)
           << Name << SS.getRange();
 
Index: clang/test/CXX/module/module.interface/tmp6.cpp
===================================================================
--- /dev/null
+++ clang/test/CXX/module/module.interface/tmp6.cpp
@@ -0,0 +1,25 @@
+
+// RUN: %clang_cc1 -std=c++20 %s -verify
+
+export module X;
+
+export template <typename T>
+struct X {
+  struct iterator {
+    T node;
+  };
+};
+
+export template <typename T> X<T>::iterator; // expected-error {{We couldn't export 'iterator' which is not in namespace scopes.}}
+export template <typename T> typename X<T>::iterator; //expected-error {{declaration does not declare anything}}
+
+export struct Y {
+  struct iterator { int Node; };
+};
+
+export struct Y::iterator; // expected-error {{We couldn't export 'iterator' which is not in namespace scopes.}}
+
+struct S { int n; };
+typedef S S;
+export typedef S S;             // OK, does not redeclare an entity
+export struct S; // expected-error {{We couldn't export 'S' which is not in namespace scopes.}}