--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/Modules/diag-pragma.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,47 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -emit-module -fmodules-cache-path=%t -fmodule-name=diag_pragma -x c++ %S/Inputs/module.map -fmodules-ts
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -verify -fmodules-cache-path=%t -I %S/Inputs %s -fmodules-ts
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -emit-module -fmodule-name=diag_pragma -x c++ %S/Inputs/module.map -fmodules-ts -o %t/explicit.pcm -Werror=string-plus-int
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -verify -fmodules-cache-path=%t -I %S/Inputs %s -fmodules-ts -DEXPLICIT_FLAG -fmodule-file=%t/explicit.pcm
+
+import diag_pragma;
+
+int foo(int x) {
+  // Diagnostics from templates in the module follow the diagnostic state from
+  // when the module was built.
+#ifdef EXPLICIT_FLAG
+  // expected-error@diag_pragma.h:7 {{adding 'int' to a string}}
+#else
+  // expected-warning@diag_pragma.h:7 {{adding 'int' to a string}}
+#endif
+  // expected-note@diag_pragma.h:7 {{use array indexing}}
+  f(0); // expected-note {{instantiation of}}
+
+  g(0); // ok, warning was ignored when building module
+
+  // Diagnostics from this source file ignore the diagnostic state from the
+  // module.
+  void("foo" + x); // expected-warning {{adding 'int' to a string}}
+  // expected-note@-1 {{use array indexing}}
+
+#pragma clang diagnostic ignored "-Wstring-plus-int"
+
+  // Diagnostics from the module ignore diagnostic state changes from this
+  // source file.
+#ifdef EXPLICIT_FLAG
+  // expected-error@diag_pragma.h:7 {{adding 'long' to a string}}
+#else
+  // expected-warning@diag_pragma.h:7 {{adding 'long' to a string}}
+#endif
+  // expected-note@diag_pragma.h:7 {{use array indexing}}
+  f(0L); // expected-note {{instantiation of}}
+
+  g(0L);
+
+  void("bar" + x);
+
+  if (x = DIAG_PRAGMA_MACRO) // expected-warning {{using the result of an assignment as a condition without parentheses}} \
+                             // expected-note {{place parentheses}} expected-note {{use '=='}}
+    return 0;
+  return 1;
+}