[Modules TS] Module ownership semantics for redeclarations.

When declaring an entity in the "purview" of a module, it's never a
redeclaration of an entity in the purview of a default module or in no module
("in the global module"). Don't consider those other declarations as possible
redeclaration targets if they're not visible, and reject any cases where we
pick a prior visible declaration that violates this rule.

This reinstates r315251 and r315256, reverted in r315309 and r315308
respectively, tweaked to avoid triggering a linkage calculation when declaring
implicit special members (this exposed our pre-existing issue with typedef
names for linkage changing the linkage of types whose linkage has already been
computed and cached in more cases). A testcase for that regression has been
added in r315366.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@315379 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 118 insertions, 0 deletions

diff --git a/test/CXX/modules-ts/basic/basic.def.odr/p6/global-vs-module.cpp b/test/CXX/modules-ts/basic/basic.def.odr/p6/global-vs-module.cpp
new file mode 100644
index 0000000000..cceca5106c
--- /dev/null
+++ b/test/CXX/modules-ts/basic/basic.def.odr/p6/global-vs-module.cpp
@@ -0,0 +1,55 @@
+// RUN: %clang_cc1 -fmodules-ts -verify -std=c++17 %s 
+// RUN: %clang_cc1 -fmodules-ts -verify -std=c++17 %s -DEXPORT
+// RUN: %clang_cc1 -fmodules-ts -verify -std=c++17 %s -DUSING
+
+#ifndef NO_GLOBAL
+extern int var; // expected-note {{previous declaration is here}}
+int func(); // expected-note {{previous declaration is here}}
+struct str; // expected-note {{previous declaration is here}}
+using type = int;
+
+template<typename> extern int var_tpl; // expected-note {{previous declaration is here}}
+template<typename> int func_tpl(); // expected-note-re {{{{previous declaration is here|target of using declaration}}}}
+template<typename> struct str_tpl; // expected-note {{previous declaration is here}}
+template<typename> using type_tpl = int; // expected-note {{previous declaration is here}}
+
+typedef int type;
+namespace ns { using ::func; }
+namespace ns_alias = ns;
+#endif
+
+export module M;
+
+#ifdef USING
+using ::var;
+using ::func;
+using ::str;
+using ::type;
+using ::var_tpl;
+using ::func_tpl; // expected-note {{using declaration}}
+using ::str_tpl;
+using ::type_tpl;
+#endif
+
+#ifdef EXPORT
+export {
+#endif
+
+extern int var; // expected-error {{declaration of 'var' in module M follows declaration in the global module}}
+int func(); // expected-error {{declaration of 'func' in module M follows declaration in the global module}}
+struct str; // expected-error {{declaration of 'str' in module M follows declaration in the global module}}
+using type = int;
+
+template<typename> extern int var_tpl; // expected-error {{declaration of 'var_tpl' in module M follows declaration in the global module}}
+// FIXME: Is this the right diagnostic in the -DUSING case?
+template<typename> int func_tpl(); // expected-error-re {{{{declaration of 'func_tpl' in module M follows declaration in the global module|conflicts with target of using declaration}}}}
+template<typename> struct str_tpl; // expected-error {{declaration of 'str_tpl' in module M follows declaration in the global module}}
+template<typename> using type_tpl = int; // expected-error {{declaration of 'type_tpl' in module M follows declaration in the global module}}
+
+typedef int type;
+namespace ns { using ::func; }
+namespace ns_alias = ns;
+
+#ifdef EXPORT
+}
+#endif
diff --git a/test/CXX/modules-ts/basic/basic.def.odr/p6/module-vs-global.cpp b/test/CXX/modules-ts/basic/basic.def.odr/p6/module-vs-global.cpp
new file mode 100644
index 0000000000..f58506dd9c
--- /dev/null
+++ b/test/CXX/modules-ts/basic/basic.def.odr/p6/module-vs-global.cpp
@@ -0,0 +1,19 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules-ts -emit-module-interface -std=c++17 %S/global-vs-module.cpp -o %t -DNO_GLOBAL -DEXPORT
+// RUN: %clang_cc1 -fmodules-ts -verify -std=c++17 %s -fmodule-file=%t
+
+import M;
+
+extern int var; // expected-error {{declaration of 'var' in the global module follows declaration in module M}} expected-note@global-vs-module.cpp:38 {{previous}}
+int func(); // expected-error {{declaration of 'func' in the global module follows declaration in module M}} expected-note@global-vs-module.cpp:39 {{previous}}
+struct str; // expected-error {{declaration of 'str' in the global module follows declaration in module M}} expected-note@global-vs-module.cpp:40 {{previous}}
+using type = int;
+
+template<typename> extern int var_tpl; // expected-error {{declaration of 'var_tpl' in the global module follows declaration in module M}} expected-note@global-vs-module.cpp:43 {{previous}}
+template<typename> int func_tpl(); // expected-error {{declaration of 'func_tpl' in the global module follows declaration in module M}} expected-note@global-vs-module.cpp:45 {{previous}}
+template<typename> struct str_tpl; // expected-error {{declaration of 'str_tpl' in the global module follows declaration in module M}} expected-note@global-vs-module.cpp:46 {{previous}}
+template<typename> using type_tpl = int; // expected-error {{declaration of 'type_tpl' in the global module follows declaration in module M}} expected-note@global-vs-module.cpp:47 {{previous}}
+
+typedef int type;
+namespace ns { using ::func; }
+namespace ns_alias = ns;
diff --git a/test/CXX/modules-ts/basic/basic.def.odr/p6/module-vs-module.cpp b/test/CXX/modules-ts/basic/basic.def.odr/p6/module-vs-module.cpp
new file mode 100644
index 0000000000..39e210c4ad
--- /dev/null
+++ b/test/CXX/modules-ts/basic/basic.def.odr/p6/module-vs-module.cpp
@@ -0,0 +1,44 @@
+// RUN: rm -rf %t
+// RUN: mkdir %t
+//
+// Some of the following tests intentionally have no -verify in their RUN
+// lines; we are testing that those cases do not produce errors.
+//
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %S/global-vs-module.cpp -emit-module-interface -o %t/M.pcm -DNO_GLOBAL -DEXPORT
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %s -fmodule-file=%t/M.pcm -DMODULE_INTERFACE -verify
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %s -fmodule-file=%t/M.pcm -DMODULE_INTERFACE -DNO_IMPORT
+//
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %s -fmodule-file=%t/M.pcm -emit-module-interface -o %t/N.pcm -DMODULE_INTERFACE -DNO_ERRORS
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %s -fmodule-file=%t/N.pcm -verify
+// FIXME: Once we start importing "import" declarations properly, this should
+// be rejected (-verify should be added to the following line).
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %s -fmodule-file=%t/N.pcm -DNO_IMPORT
+//
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %s -fmodule-file=%t/M.pcm -emit-module-interface -o %t/N-no-M.pcm -DMODULE_INTERFACE -DNO_ERRORS -DNO_IMPORT
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %s -fmodule-file=%t/N-no-M.pcm -verify
+// RUN: %clang_cc1 -fmodules-ts -std=c++17 %s -fmodule-file=%t/N-no-M.pcm -DNO_IMPORT
+
+#ifdef MODULE_INTERFACE
+export
+#endif
+module N;
+
+#ifndef NO_IMPORT
+import M;
+#endif
+
+#ifndef NO_ERRORS
+extern int var; // expected-error {{declaration of 'var' in module N follows declaration in module M}} expected-note@global-vs-module.cpp:38 {{previous}}
+int func(); // expected-error {{declaration of 'func' in module N follows declaration in module M}} expected-note@global-vs-module.cpp:39 {{previous}}
+struct str; // expected-error {{declaration of 'str' in module N follows declaration in module M}} expected-note@global-vs-module.cpp:40 {{previous}}
+using type = int;
+
+template<typename> extern int var_tpl; // expected-error {{declaration of 'var_tpl' in module N follows declaration in module M}} expected-note@global-vs-module.cpp:43 {{previous}}
+template<typename> int func_tpl(); // expected-error {{declaration of 'func_tpl' in module N follows declaration in module M}} expected-note@global-vs-module.cpp:45 {{previous}}
+template<typename> struct str_tpl; // expected-error {{declaration of 'str_tpl' in module N follows declaration in module M}} expected-note@global-vs-module.cpp:46 {{previous}}
+template<typename> using type_tpl = int; // expected-error {{declaration of 'type_tpl' in module N follows declaration in module M}} expected-note@global-vs-module.cpp:47 {{previous}}
+
+typedef int type;
+namespace ns { using ::func; }
+namespace ns_alias = ns;
+#endif