[NFC] [C++20] [Modules] Add a test for no transitive changes

Author: ChuanqiXu9

clang/test/Modules/no-transitive-source-location-change-2.cppm

@@ -0,0 +1,66 @@
+// Testing that adding a new line in a module interface unit won't cause the BMI
+// of consuming module unit changes.
+//
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 %t/A.part.cppm -emit-reduced-module-interface -o %t/A-part.pcm
+//
+// RUN: %clang_cc1 -std=c++20 %t/A.cppm -emit-reduced-module-interface -o %t/A.v0.pcm \
+// RUN:     -fprebuilt-module-path=%t
+// RUN: %clang_cc1 -std=c++20 %t/A.v1.cppm -emit-reduced-module-interface -o %t/A.v1.pcm \
+// RUN:     -fprebuilt-module-path=%t
+//
+// The BMI may not be the same since the source location differs.
+// RUN: not diff %t/A.pcm %t/A.v1.pcm &> /dev/null
+//
+// The BMI of B shouldn't change since all the locations remain the same.
+// RUN: %clang_cc1 -std=c++20 %t/B.cppm -emit-reduced-module-interface -fmodule-file=A=%t/A.v0.pcm \
+// RUN:     -o %t/B.pcm -fprebuilt-module-path=%t
+// RUN: %clang_cc1 -std=c++20 %t/B.cppm -emit-reduced-module-interface -fmodule-file=A=%t/A.v1.pcm \
+// RUN:     -o %t/B.v1.pcm -fprebuilt-module-path=%t
+// RUN: diff %t/B.v1.pcm %t/B.pcm  &> /dev/null
+//
+// The BMI of C may change since the locations for instantiations changes.
+// RUN: %clang_cc1 -std=c++20 %t/C.cppm -emit-reduced-module-interface -fmodule-file=A=%t/A.v0.pcm \
+// RUN:     -o %t/C.pcm -fprebuilt-module-path=%t
+// RUN: %clang_cc1 -std=c++20 %t/C.cppm -emit-reduced-module-interface -fmodule-file=A=%t/A.v1.pcm \
+// RUN:     -o %t/C.v1.pcm -fprebuilt-module-path=%t
+// RUN: diff %t/C.v1.pcm %t/C.pcm  &> /dev/null
+
+//--- A.part.cppm
+export module A:part;
+export template <class T>
+struct C {
+    T func() {
+        return T(43);
+    }
+};
+export int funcA() {
+    return 43;
+}
+
+//--- A.cppm
+export module A;
+export import :part;
+
+//--- A.v1.cppm
+export module A;
+
+export import :part;
+
+//--- B.cppm
+export module B;
+import A;
+
+export int funcB() {
+    return funcA();
+}
+
+//--- C.cppm
+export module C;
+import A;
+export inline void testD() {
+    C<int> c;
+    c.func();
+}