diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -11151,6 +11151,9 @@
 def err_export_not_in_module_interface : Error<
   "export declaration can only be used within a module interface unit"
   "%select{ after the module declaration|}0">;
+def err_export_inline_not_defined : Error<
+  "exported inline functions must be defined within the module purview"
+  " and before any private module fragment">;
 def err_export_partition_impl : Error<
   "module partition implementations cannot be exported">;
 def err_export_in_private_module_fragment : Error<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -2245,6 +2245,10 @@
   /// Namespace definitions that we will export when they finish.
   llvm::SmallPtrSet<const NamespaceDecl*, 8> DeferredExportedNamespaces;
 
+  /// Exported inlines that require a definition to be present at the end of
+  /// the TU (or before the PMF starts, if that is present).
+  llvm::SmallPtrSet<const Decl *, 8> PendingInlineExports;
+
   /// Get the module unit whose scope we are currently within.
   Module *getCurrentModule() const {
     return ModuleScopes.empty() ? nullptr : ModuleScopes.back().Module;
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -1095,6 +1095,15 @@
     PerformPendingInstantiations();
   }
 
+  if (Kind == TUFragmentKind::Normal && !PendingInlineExports.empty()) {
+    for (auto *D : PendingInlineExports)
+      if (auto *FD = dyn_cast<FunctionDecl>(D)) {
+        if (!FD->isDefined())
+          Diag(FD->getLocation(), diag::err_export_inline_not_defined);
+      }
+    PendingInlineExports.clear();
+  }
+
   emitDeferredDiags();
 
   assert(LateParsedInstantiations.empty() &&
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -5425,7 +5425,7 @@
   llvm::SmallVector<Module*, 8> UniqueModules;
   llvm::SmallDenseSet<Module*, 8> UniqueModuleSet;
   for (auto *M : Modules) {
-    if (M->Kind == Module::GlobalModuleFragment)
+    if (M->isGlobalModule() || M->isPrivateModule())
       continue;
     if (UniqueModuleSet.insert(M).second)
       UniqueModules.push_back(M);
diff --git a/clang/lib/Sema/SemaModule.cpp b/clang/lib/Sema/SemaModule.cpp
--- a/clang/lib/Sema/SemaModule.cpp
+++ b/clang/lib/Sema/SemaModule.cpp
@@ -892,6 +892,17 @@
         diagExportedUnnamedDecl(*this, UnnamedDeclKind::Context, Child,
                                 BlockStart);
       }
+      if (auto *FD = dyn_cast<FunctionDecl>(Child)) {
+        // [dcl.inline]/7
+        // If an inline function or variable that is attached to a named module
+        // is declared in a definition domain, it shall be defined in that
+        // domain.
+        // So, if the current declaration does not have a definition, we must
+        // check at the end of the TU (or when the PMF starts) to see that we
+        // have a definition at that point.
+        if (FD->isInlineSpecified() && !FD->isDefined())
+          PendingInlineExports.insert(FD);
+      }
     }
   }
 
diff --git a/clang/test/Modules/cxx20-10-5-ex1.cpp b/clang/test/Modules/cxx20-10-5-ex1.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Modules/cxx20-10-5-ex1.cpp
@@ -0,0 +1,50 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: cd %t
+
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface std-10-5-ex1-interface.cpp \
+// RUN: -DBAD_FWD_DECL  -fsyntax-only -verify
+
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface std-10-5-ex1-interface.cpp \
+// RUN: -o A.pcm
+
+// RUN: %clang_cc1 -std=c++20 std-10-5-ex1-use.cpp  -fmodule-file=A.pcm \
+// RUN:    -fsyntax-only -verify
+
+//--- std-10-5-ex1-interface.cpp
+
+export module A;
+#ifdef BAD_FWD_DECL
+export inline void fn_e(); // expected-error {{exported inline functions must be defined within the module purview and before any private module fragment}}
+#endif
+export inline void ok_fn() {}
+export inline void ok_fn2();
+inline void fn_m();
+static void fn_s();
+export struct X;
+export void g(X *x) {
+  fn_s();
+  fn_m();
+}
+export X *factory();
+void ok_fn2() {}
+
+module :private;
+struct X {};
+X *factory() {
+  return new X();
+}
+
+void fn_e() {}
+void fn_m() {}
+void fn_s() {}
+
+//--- std-10-5-ex1-use.cpp
+
+import A;
+
+void foo() {
+  X x; // expected-error 1+{{missing '#include'; 'X' must be defined before it is used}}
+       // expected-note@std-10-5-ex1-interface.cpp:19 1+{{definition here is not reachable}}
+  X *p = factory();
+}