Index: clang/test/Modules/Inputs/redundant-template-default-arg/foo.h
===================================================================
--- clang/test/Modules/Inputs/redundant-template-default-arg/foo.h
+++ /dev/null
@@ -1,37 +0,0 @@
-template <typename T>
-T u;
-
-template <typename T = int>
-T v;
-
-template <int T = 8>
-int v2;
-
-template <typename T>
-class my_array {};
-
-template <template <typename> typename C = my_array>
-int v3;
-
-template <typename T, int *i = nullptr>
-T v4;
-
-template <typename T, T *i = nullptr>
-T v5;
-
-inline int a = 43;
-template <typename T, int *i = &a>
-T v6;
-
-inline int b = 43;
-template <typename T, T *i = &b>
-T v7;
-
-template <int T = (3 > 2)>
-int v8;
-
-consteval int getInt() {
-  return 55;
-}
-template <int T = getInt()>
-int v9;
Index: clang/test/Modules/Inputs/redundant-template-default-arg/foo.cppm
===================================================================
--- clang/test/Modules/Inputs/redundant-template-default-arg/foo.cppm
+++ /dev/null
@@ -1,3 +0,0 @@
-module;
-#include "foo.h"
-export module foo;
Index: clang/test/Modules/Inputs/redundant-template-default-arg2/foo.cppm
===================================================================
--- clang/test/Modules/Inputs/redundant-template-default-arg2/foo.cppm
+++ /dev/null
@@ -1,12 +0,0 @@
-export module foo;
-export template <typename T = int>
-T v;
-
-export template <int T = 8>
-int v2;
-
-export template <typename T>
-class my_array {};
-
-export template <template <typename> typename C = my_array>
-int v3;
Index: clang/test/Modules/Inputs/redundant-template-default-arg3/foo.h
===================================================================
--- clang/test/Modules/Inputs/redundant-template-default-arg3/foo.h
+++ /dev/null
@@ -1,34 +0,0 @@
-template <typename T = int>
-T v;
-
-template <int T = 8>
-int v2;
-
-template <typename T>
-class my_array {};
-
-template <template <typename> typename C = my_array>
-int v3;
-
-template <typename T, int *i = nullptr>
-T v4;
-
-template <typename T, T *i = nullptr>
-T v5;
-
-inline int a = 43;
-template <typename T, int *i = &a>
-T v6;
-
-inline int b = 43;
-template <typename T, T *i = &b>
-T v7;
-
-template <int T = (3 > 2)>
-int v8;
-
-consteval int getInt() {
-  return 55;
-}
-template <int T = getInt()>
-int v9;
Index: clang/test/Modules/Inputs/redundant-template-default-arg3/foo.cppm
===================================================================
--- clang/test/Modules/Inputs/redundant-template-default-arg3/foo.cppm
+++ /dev/null
@@ -1,3 +0,0 @@
-module;
-#include "foo.h"
-export module foo;
Index: clang/test/Modules/Inputs/redundant-template-default-arg3/foo_bad.h
===================================================================
--- clang/test/Modules/Inputs/redundant-template-default-arg3/foo_bad.h
+++ /dev/null
@@ -1,41 +0,0 @@
-template <typename T = double>
-T v;
-
-template <int T = 9>
-int v2;
-
-template <typename T>
-class others_array {};
-
-template <template <typename> typename C = others_array>
-int v3;
-
-static int a;
-consteval int *getIntPtr() {
-  return &a;
-}
-template <typename T, int *i = getIntPtr()>
-T v4;
-
-consteval void *getVoidPtr() {
-  return &a;
-}
-template <typename T, T *i = getVoidPtr()>
-T v5;
-
-inline int a_ = 43;
-template <typename T, int *i = &a_>
-T v6;
-
-inline int b_ = 43;
-template <typename T, T *i = &b_>
-T v7;
-
-template <int T = -1>
-int v8;
-
-consteval int getInt2() {
-  return 55;
-}
-template <int T = getInt2()>
-int v9;
Index: clang/test/Modules/fwd-declaration.cppm
===================================================================
--- /dev/null
+++ clang/test/Modules/fwd-declaration.cppm
@@ -0,0 +1,49 @@
+// RUN: rm -rf %t
+// RUN: mkdir %t
+// RUN: split-file %s %t
+//
+// RUN: %clang -std=c++20 --precompile %t/A.cppm -o %t/M-A.pcm
+// RUN: %clang -std=c++20 --precompile %t/B.cppm -o %t/M-B.pcm
+// RUN: %clang -std=c++20 --precompile %t/M.cppm -o %t/M.pcm -fprebuilt-module-path=%t
+// RUN: %clang -std=c++20 -fprebuilt-module-path=%t %t/Use.cpp -S -o -
+//--- fwd.h
+template <class T>
+class A;
+
+//--- impl.h
+template <class T>
+class A;
+typedef A<int> a;
+template <class T>
+class A {};
+
+template <>
+class A<char> {
+public:
+    A() {}
+
+    A(int, double) {}
+};
+
+//--- A.cppm
+module;
+#include "fwd.h"
+export module M:A;
+export using ::A;
+
+//--- B.cppm
+module;
+#include "impl.h"
+export module M:B;
+export using ::A;
+
+//--- M.cppm
+export module M;
+export import :A;
+export import :B;
+
+//--- Use.cpp
+import M;
+void use() {
+    A<int> a;
+}
Index: clang/test/Modules/redundant-template-default-arg.cpp
===================================================================
--- clang/test/Modules/redundant-template-default-arg.cpp
+++ clang/test/Modules/redundant-template-default-arg.cpp
@@ -1,7 +1,56 @@
 // RUN: rm -rf %t
 // RUN: mkdir %t
-// RUN: %clang_cc1  -std=c++20 %S/Inputs/redundant-template-default-arg/foo.cppm -I%S/Inputs/redundant-template-default-arg/. -emit-module-interface -o %t/foo.pcm
-// RUN: %clang_cc1  -fprebuilt-module-path=%t -std=c++20 %s -I%S/Inputs/redundant-template-default-arg/. -fsyntax-only -verify
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1  -std=c++20 %t/foo.cppm -I%t -emit-module-interface -o %t/foo.pcm
+// RUN: %clang_cc1  -fprebuilt-module-path=%t -std=c++20 %t/use.cpp -I%t -fsyntax-only -verify
+
+//--- foo.h
+template <typename T>
+T u;
+
+template <typename T = int>
+T v;
+
+template <int T = 8>
+int v2;
+
+template <typename T>
+class my_array {};
+
+template <template <typename> typename C = my_array>
+int v3;
+
+template <typename T, int *i = nullptr>
+T v4;
+
+template <typename T, T *i = nullptr>
+T v5;
+
+inline int a = 43;
+template <typename T, int *i = &a>
+T v6;
+
+inline int b = 43;
+template <typename T, T *i = &b>
+T v7;
+
+template <int T = (3 > 2)>
+int v8;
+
+consteval int getInt() {
+  return 55;
+}
+template <int T = getInt()>
+int v9;
+
+//--- foo.cppm
+module;
+#include "foo.h"
+export module foo;
+
+
+//--- use.cpp
 // expected-no-diagnostics
 import foo;
 #include "foo.h"
Index: clang/test/Modules/redundant-template-default-arg2.cpp
===================================================================
--- clang/test/Modules/redundant-template-default-arg2.cpp
+++ clang/test/Modules/redundant-template-default-arg2.cpp
@@ -1,20 +1,38 @@
 // RUN: rm -rf %t
 // RUN: mkdir %t
-// RUN: %clang_cc1  -std=c++20 %S/Inputs/redundant-template-default-arg2/foo.cppm -I%S/Inputs/redundant-template-default-arg2/. -emit-module-interface -o %t/foo.pcm
-// RUN: %clang_cc1  -fprebuilt-module-path=%t -std=c++20 %s -fsyntax-only -verify
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 %t/foo.cppm -I%t -emit-module-interface -o %t/foo.pcm
+// RUN: %clang_cc1 -fprebuilt-module-path=%t -std=c++20 %t/use.cpp -fsyntax-only -verify
+
+//--- foo.cppm
+export module foo;
+export template <typename T = int>
+T v;
+
+export template <int T = 8>
+int v2;
+
+export template <typename T>
+class my_array {};
+
+export template <template <typename> typename C = my_array>
+int v3;
+
+//--- use.cpp
 import foo;
 template <typename T = int>
 T v; // expected-error {{declaration of 'v' in the global module follows declaration in module foo}}
-     // expected-note@Inputs/redundant-template-default-arg2/foo.cppm:3 {{previous declaration is here}}
+     // expected-note@foo.cppm:3 {{previous declaration is here}}
 
 template <int T = 8>
 int v2; // expected-error {{declaration of 'v2' in the global module follows declaration in module foo}}
-        // expected-note@Inputs/redundant-template-default-arg2/foo.cppm:6 {{previous declaration is here}}
+        // expected-note@foo.cppm:6 {{previous declaration is here}}
 
 template <typename T>
 class my_array {}; // expected-error {{redefinition of 'my_array'}}
-                   // expected-note@Inputs/redundant-template-default-arg2/foo.cppm:9 {{previous definition is here}}
+                   // expected-note@foo.cppm:9 {{previous definition is here}}
 
 template <template <typename> typename C = my_array>
 int v3; // expected-error {{declaration of 'v3' in the global module follows declaration in module foo}}
-        // expected-note@Inputs/redundant-template-default-arg2/foo.cppm:12 {{previous declaration is here}}
+        // expected-note@foo.cppm:12 {{previous declaration is here}}
Index: clang/test/Modules/redundant-template-default-arg3.cpp
===================================================================
--- clang/test/Modules/redundant-template-default-arg3.cpp
+++ clang/test/Modules/redundant-template-default-arg3.cpp
@@ -1,26 +1,113 @@
 // RUN: rm -rf %t
 // RUN: mkdir %t
-// RUN: %clang_cc1  -std=c++20 %S/Inputs/redundant-template-default-arg3/foo.cppm -I%S/Inputs/redundant-template-default-arg3/. -emit-module-interface -o %t/foo.pcm
-// RUN: %clang_cc1  -fprebuilt-module-path=%t -std=c++20 %s -I%S/Inputs/redundant-template-default-arg3/. -fsyntax-only -verify
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1  -std=c++20 %t/foo.cppm -I%t -emit-module-interface -o %t/foo.pcm
+// RUN: %clang_cc1  -fprebuilt-module-path=%t -std=c++20 %t/use.cpp -I%t/. -fsyntax-only -verify
 
+//--- foo.h
+template <typename T = int>
+T v;
+
+template <int T = 8>
+int v2;
+
+template <typename T>
+class my_array {};
+
+template <template <typename> typename C = my_array>
+int v3;
+
+template <typename T, int *i = nullptr>
+T v4;
+
+template <typename T, T *i = nullptr>
+T v5;
+
+inline int a = 43;
+template <typename T, int *i = &a>
+T v6;
+
+inline int b = 43;
+template <typename T, T *i = &b>
+T v7;
+
+template <int T = (3 > 2)>
+int v8;
+
+consteval int getInt() {
+  return 55;
+}
+template <int T = getInt()>
+int v9;
+
+//--- foo_bad.h
+template <typename T = double>
+T v;
+
+template <int T = 9>
+int v2;
+
+template <typename T>
+class others_array {};
+
+template <template <typename> typename C = others_array>
+int v3;
+
+static int a;
+consteval int *getIntPtr() {
+  return &a;
+}
+template <typename T, int *i = getIntPtr()>
+T v4;
+
+consteval void *getVoidPtr() {
+  return &a;
+}
+template <typename T, T *i = getVoidPtr()>
+T v5;
+
+inline int a_ = 43;
+template <typename T, int *i = &a_>
+T v6;
+
+inline int b_ = 43;
+template <typename T, T *i = &b_>
+T v7;
+
+template <int T = -1>
+int v8;
+
+consteval int getInt2() {
+  return 55;
+}
+template <int T = getInt2()>
+int v9;
+
+//--- foo.cppm
+module;
+#include "foo.h"
+export module foo;
+
+//--- use.cpp
 import foo;
 #include "foo_bad.h"
 
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:1 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:1 {{previous default template argument defined in module foo.<global>}}
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:4 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:4 {{previous default template argument defined in module foo.<global>}}
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:10 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:10 {{previous default template argument defined in module foo.<global>}}
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:17 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:13 {{previous default template argument defined in module foo.<global>}}
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:23 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:16 {{previous default template argument defined in module foo.<global>}}
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:27 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:20 {{previous default template argument defined in module foo.<global>}}
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:31 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:24 {{previous default template argument defined in module foo.<global>}}
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:34 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:27 {{previous default template argument defined in module foo.<global>}}
-// expected-error@Inputs/redundant-template-default-arg3/foo_bad.h:40 {{template parameter default argument is inconsistent with previous definition}}
-// expected-note@Inputs/redundant-template-default-arg3/foo.h:33 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:1 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:1 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:4 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:4 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:10 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:10 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:17 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:13 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:23 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:16 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:27 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:20 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:31 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:24 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:34 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:27 {{previous default template argument defined in module foo.<global>}}
+// expected-error@foo_bad.h:40 {{template parameter default argument is inconsistent with previous definition}}
+// expected-note@foo.h:33 {{previous default template argument defined in module foo.<global>}}