6 files changed, 93 insertions, 20 deletions
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 030717b8bd5..8b5877934f6 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -1906,6 +1906,25 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
     }
   }
 
+  // The #included file will be considered to be a system header if either it is
+  // in a system include directory, or if the #includer is a system include
+  // header.
+  SrcMgr::CharacteristicKind FileCharacter =
+      SourceMgr.getFileCharacteristic(FilenameTok.getLocation());
+  if (File)
+    FileCharacter = std::max(HeaderInfo.getFileDirFlavor(File), FileCharacter);
+
+  // Ask HeaderInfo if we should enter this #include file.  If not, #including
+  // this file will have no effect.
+  bool SkipHeader = false;
+  if (ShouldEnter && File &&
+      !HeaderInfo.ShouldEnterIncludeFile(*this, File, isImport,
+                                         getLangOpts().Modules,
+                                         SuggestedModule.getModule())) {
+    ShouldEnter = false;
+    SkipHeader = true;
+  }
+
   if (Callbacks) {
     // Notify the callback object that we've seen an inclusion directive.
     Callbacks->InclusionDirective(
@@ -1913,18 +1932,13 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
         LangOpts.MSVCCompat ? NormalizedPath.c_str() : Filename, isAngled,
         FilenameRange, File, SearchPath, RelativePath,
         ShouldEnter ? nullptr : SuggestedModule.getModule());
+    if (SkipHeader && !SuggestedModule.getModule())
+      Callbacks->FileSkipped(*File, FilenameTok, FileCharacter);
   }
 
   if (!File)
     return;
 
-  // The #included file will be considered to be a system header if either it is
-  // in a system include directory, or if the #includer is a system include
-  // header.
-  SrcMgr::CharacteristicKind FileCharacter =
-    std::max(HeaderInfo.getFileDirFlavor(File),
-             SourceMgr.getFileCharacteristic(FilenameTok.getLocation()));
-
   // FIXME: If we have a suggested module, and we've already visited this file,
   // don't bother entering it again. We know it has no further effect.
 
@@ -1964,19 +1978,6 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
     }
   }
 
-  // Ask HeaderInfo if we should enter this #include file.  If not, #including
-  // this file will have no effect.
-  bool SkipHeader = false;
-  if (ShouldEnter &&
-      !HeaderInfo.ShouldEnterIncludeFile(*this, File, isImport,
-                                         getLangOpts().Modules,
-                                         SuggestedModule.getModule())) {
-    ShouldEnter = false;
-    SkipHeader = true;
-    if (Callbacks)
-      Callbacks->FileSkipped(*File, FilenameTok, FileCharacter);
-  }
-
   // If we don't need to enter the file, stop now.
   if (!ShouldEnter) {
     // If this is a module import, make it visible if needed.
diff --git a/clang/test/Modules/Inputs/preprocess/a.h b/clang/test/Modules/Inputs/preprocess/a.h
new file mode 100644
index 00000000000..1292e99b4b2
--- /dev/null
+++ b/clang/test/Modules/Inputs/preprocess/a.h
@@ -0,0 +1,2 @@
+#include "c.h"
+T a();
diff --git a/clang/test/Modules/Inputs/preprocess/b.h b/clang/test/Modules/Inputs/preprocess/b.h
new file mode 100644
index 00000000000..e8a9f55968f
--- /dev/null
+++ b/clang/test/Modules/Inputs/preprocess/b.h
@@ -0,0 +1,2 @@
+#include "c.h"
+T b();
diff --git a/clang/test/Modules/Inputs/preprocess/c.h b/clang/test/Modules/Inputs/preprocess/c.h
new file mode 100644
index 00000000000..718f5dc1829
--- /dev/null
+++ b/clang/test/Modules/Inputs/preprocess/c.h
@@ -0,0 +1,4 @@
+#ifndef C_H
+#define C_H
+using T = int;
+#endif
diff --git a/clang/test/Modules/Inputs/preprocess/module.modulemap b/clang/test/Modules/Inputs/preprocess/module.modulemap
index 943435a953d..f700db03bea 100644
--- a/clang/test/Modules/Inputs/preprocess/module.modulemap
+++ b/clang/test/Modules/Inputs/preprocess/module.modulemap
@@ -1,2 +1,7 @@
 module fwd { header "fwd.h" export * }
 module file { header "file.h" header "file2.h" export * }
+module nested {
+  module a { header "a.h" }
+  module b { header "b.h" }
+  module c { header "c.h" }
+}
diff --git a/clang/test/Modules/preprocess-nested.cpp b/clang/test/Modules/preprocess-nested.cpp
new file mode 100644
index 00000000000..8fccf137e94
--- /dev/null
+++ b/clang/test/Modules/preprocess-nested.cpp
@@ -0,0 +1,59 @@
+// RUN: rm -rf %t
+// RUN: mkdir %t
+
+// RUN: %clang_cc1 -fmodules -fmodules-local-submodule-visibility -fmodule-name=nested -I%S/Inputs/preprocess -x c++-module-map %S/Inputs/preprocess/module.modulemap -E -o %t/no-rewrite.ii
+// RUN: %clang_cc1 -fmodules -fmodules-local-submodule-visibility -fmodule-name=nested -I%S/Inputs/preprocess -x c++-module-map %S/Inputs/preprocess/module.modulemap -E -frewrite-includes -o %t/rewrite.ii
+
+// RUN: FileCheck %s --input-file %t/no-rewrite.ii --check-prefix=CHECK --check-prefix=NO-REWRITE
+// RUN: FileCheck %s --input-file %t/rewrite.ii    --check-prefix=CHECK --check-prefix=REWRITE
+
+// Check that we can build a module from the preprocessed output.
+// FIXME: For now, the files need to exist.
+// RUN: touch %t/a.h %t/b.h %t/c.h
+// RUN: %clang_cc1 -fmodules -fmodules-local-submodule-visibility -fmodule-name=nested -x c++-module-map-cpp-output %t/no-rewrite.ii -emit-module -o %t/no-rewrite.pcm
+// RUN: %clang_cc1 -fmodules -fmodules-local-submodule-visibility -fmodule-name=nested -x c++-module-map-cpp-output %t/rewrite.ii -emit-module -o %t/rewrite.pcm
+
+// Check the module we built works.
+// RUN: %clang_cc1 -fmodules -fmodule-file=%t/no-rewrite.pcm %s -I%t -verify -fno-modules-error-recovery
+// RUN: %clang_cc1 -fmodules -fmodule-file=%t/rewrite.pcm %s -I%t -verify -fno-modules-error-recovery -DREWRITE
+
+// == module map
+// CHECK: # 1 "{{.*}}module.modulemap"
+// CHECK: module nested {
+// CHECK:   module a {
+// CHECK:     header "a.h"
+// CHECK:   }
+// CHECK:   module b {
+// CHECK:     header "b.h"
+// CHECK:   }
+// CHECK:   module c {
+// CHECK:     header "c.h"
+// CHECK:   }
+// CHECK: }
+
+// CHECK: #pragma clang module begin nested.a
+// CHECK: #pragma clang module begin nested.c
+// CHECK: using T = int;
+// CHECK: #pragma clang module end
+// CHECK: T a();
+// CHECK: #pragma clang module end
+
+// CHECK: #pragma clang module begin nested.b
+// CHECK: #pragma clang module import nested.c
+// CHECK-NOT: #pragma clang module begin nested.c
+// CHECK-NOT: using T = int;
+// CHECK-NOT: #pragma clang module end
+// CHECK: T b();
+// CHECK: #pragma clang module end
+
+// CHECK: #pragma clang module import nested.c
+
+#pragma clang module import nested.b
+
+int n = b();
+T c; // expected-error {{must be imported}}
+#ifdef REWRITE
+// expected-note@rewrite.ii:* {{declar}}
+#else
+// expected-note@no-rewrite.ii:* {{declar}}
+#endif