8 files changed, 34 insertions, 1 deletions
diff --git a/clang/lib/Basic/Module.cpp b/clang/lib/Basic/Module.cpp
index baeeb9edbdd..e119c0535eb 100644
--- a/clang/lib/Basic/Module.cpp
+++ b/clang/lib/Basic/Module.cpp
@@ -492,6 +492,7 @@ LLVM_DUMP_METHOD void Module::dump() const {
 
 void VisibleModuleSet::setVisible(Module *M, SourceLocation Loc,
                                   VisibleCallback Vis, ConflictCallback Cb) {
+  assert(Loc.isValid() && "setVisible expects a valid import location");
   if (isVisible(M))
     return;
 
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 1c62b4e57b0..b2f59d1fa6c 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -4062,7 +4062,9 @@ void ASTReader::InitializeContext() {
     if (Module *Imported = getSubmodule(Import.ID)) {
       makeModuleVisible(Imported, Module::AllVisible,
                         /*ImportLoc=*/Import.ImportLoc);
-      PP.makeModuleVisible(Imported, Import.ImportLoc);
+      if (Import.ImportLoc.isValid())
+        PP.makeModuleVisible(Imported, Import.ImportLoc);
+      // FIXME: should we tell Sema to make the module visible too?
     }
   }
   ImportedModules.clear();
diff --git a/clang/test/Index/Inputs/module.map b/clang/test/Index/Inputs/module.map
index 4bfc109a8b1..10712accb1c 100644
--- a/clang/test/Index/Inputs/module.map
+++ b/clang/test/Index/Inputs/module.map
@@ -6,3 +6,17 @@ module ModuleNeedsVFS {
 framework module * { }
 
 module ModuleUndef { header "module-undef.h" }
+
+module PreambleWithImplicitImport {
+  module A {
+    header "preamble-with-implicit-import-A.h"
+  }
+  module B {
+    header "preamble-with-implicit-import-B.h"
+    export *
+  }
+  module C {
+    header "preamble-with-implicit-import-C.h"
+    export *
+  }
+}
diff --git a/clang/test/Index/Inputs/preamble-with-implicit-import-A.h b/clang/test/Index/Inputs/preamble-with-implicit-import-A.h
new file mode 100644
index 00000000000..c6839015909
--- /dev/null
+++ b/clang/test/Index/Inputs/preamble-with-implicit-import-A.h
@@ -0,0 +1 @@
+// preamble-with-implicit-import-A
diff --git a/clang/test/Index/Inputs/preamble-with-implicit-import-B.h b/clang/test/Index/Inputs/preamble-with-implicit-import-B.h
new file mode 100644
index 00000000000..17c138dfb5a
--- /dev/null
+++ b/clang/test/Index/Inputs/preamble-with-implicit-import-B.h
@@ -0,0 +1,3 @@
+#pragma once
+#include "preamble-with-implicit-import-C.h" // Circular
+typedef struct { char x; } Typo;
diff --git a/clang/test/Index/Inputs/preamble-with-implicit-import-C.h b/clang/test/Index/Inputs/preamble-with-implicit-import-C.h
new file mode 100644
index 00000000000..a3fc1d4fea0
--- /dev/null
+++ b/clang/test/Index/Inputs/preamble-with-implicit-import-C.h
@@ -0,0 +1,2 @@
+#pragma once
+#include "preamble-with-implicit-import-B.h" // Circular
diff --git a/clang/test/Index/Inputs/preamble-with-implicit-import.h b/clang/test/Index/Inputs/preamble-with-implicit-import.h
new file mode 100644
index 00000000000..1b429678f21
--- /dev/null
+++ b/clang/test/Index/Inputs/preamble-with-implicit-import.h
@@ -0,0 +1,4 @@
+#include "preamble-with-implicit-import-A.h"
+
+// Typo is defined in B, which is not imported.
+void useTypeFromB(Typo *);
diff --git a/clang/test/Index/preamble-with-implicit-import.m b/clang/test/Index/preamble-with-implicit-import.m
new file mode 100644
index 00000000000..e3d0e8b1a62
--- /dev/null
+++ b/clang/test/Index/preamble-with-implicit-import.m
@@ -0,0 +1,6 @@
+// RUN: rm -rf %t
+// RUN: env CINDEXTEST_EDITING=1 c-index-test -test-load-source-reparse 2 none %s -I %S/Inputs -fmodules -fmodules-cache-path=%t -fspell-checking 2>&1 | FileCheck %s
+// CHECK: error: declaration of 'Typo' must be imported
+// CHECK: error: declaration of 'Typo' must be imported
+
+#include "preamble-with-implicit-import.h"