--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/Modules/submodules-preprocess.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,61 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -x objective-c++ -Eonly -fmodules-cache-path=%t -I %S/Inputs/submodules %s -verify
+// FIXME: When we have a syntax for modules in C++, use that.
+
+@import std.vector;
+
+#ifndef HAVE_VECTOR
+#  error HAVE_VECTOR macro is not available (but should be)
+#endif
+
+#ifdef HAVE_TYPE_TRAITS
+#  error HAVE_TYPE_TRAITS_MAP macro is available (but shouldn't be)
+#endif
+
+#ifdef HAVE_HASH_MAP
+#  error HAVE_HASH_MAP macro is available (but shouldn't be)
+#endif
+
+@import std.typetraits; // expected-error{{no submodule named 'typetraits' in module 'std'; did you mean 'type_traits'?}}
+
+#ifndef HAVE_VECTOR
+#  error HAVE_VECTOR macro is not available (but should be)
+#endif
+
+#ifndef HAVE_TYPE_TRAITS
+#  error HAVE_TYPE_TRAITS_MAP macro is not available (but should be)
+#endif
+
+#ifdef HAVE_HASH_MAP
+#  error HAVE_HASH_MAP macro is available (but shouldn't be)
+#endif
+
+@import std.vector.compare; // expected-error{{no submodule named 'compare' in module 'std.vector'}}
+
+@import std; // import everything in 'std'
+
+#ifndef HAVE_VECTOR
+#  error HAVE_VECTOR macro is not available (but should be)
+#endif
+
+#ifndef HAVE_TYPE_TRAITS
+#  error HAVE_TYPE_TRAITS_MAP macro is not available (but should be)
+#endif
+
+#ifdef HAVE_HASH_MAP
+#  error HAVE_HASH_MAP macro is available (but shouldn't be)
+#endif
+
+@import std.hash_map;
+
+#ifndef HAVE_VECTOR
+#  error HAVE_VECTOR macro is not available (but should be)
+#endif
+
+#ifndef HAVE_TYPE_TRAITS
+#  error HAVE_TYPE_TRAITS_MAP macro is not available (but should be)
+#endif
+
+#ifndef HAVE_HASH_MAP
+#  error HAVE_HASH_MAP macro is not available (but should be)
+#endif