1 files changed, 11 insertions, 0 deletions
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 62692519674..548f336c3b4 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -930,6 +930,17 @@ void Sema::ActOnEndOfTranslationUnit() {
   }
 
   if (TUKind == TU_Module) {
+    // If we are building a module interface unit, we need to have seen the
+    // module declaration by now.
+    if (getLangOpts().getCompilingModule() ==
+            LangOptions::CMK_ModuleInterface &&
+        ModuleScopes.back().Module->Kind != Module::ModuleInterfaceUnit) {
+      // FIXME: Make a better guess as to where to put the module declaration.
+      Diag(getSourceManager().getLocForStartOfFile(
+               getSourceManager().getMainFileID()),
+           diag::err_module_declaration_missing);
+    }
+
     // If we are building a module, resolve all of the exported declarations
     // now.
     if (Module *CurrentModule = PP.getCurrentModule()) {