Add stopgap option -fmodule-implementation-of <name>

This flag specifies that we are building an implementation file of the
module <name>, preventing importing <name> as a module. This does not
consider this to be the 'current module' for the purposes of doing
modular checks like decluse or non-modular-include warnings, unlike
-fmodule-name.

This is needed as a stopgap until:
1) we can resolve relative includes to a VFS-mapped module (or can
   safely import a header textually and as part of a module)

and ideally
2) we can safely do incremental rebuilding when implementation files
   import submodules.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213767 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 14 insertions, 0 deletions

diff --git a/include/clang/Basic/DiagnosticFrontendKinds.td b/include/clang/Basic/DiagnosticFrontendKinds.td
index ab0c6cfb1b..bbe0fa730e 100644
--- a/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -178,6 +178,10 @@ def note_module_def_undef_here : Note<
 def remark_module_build : Remark<"building module '%0' as '%1'">,
   InGroup<DiagGroup<"module-build">>, DefaultIgnore;
 
+def err_conflicting_module_names : Error<
+  "conflicting module names specified: '-fmodule-name=%0' and "
+  "'-fmodule-implementation-of %1'">;
+
 def err_missing_vfs_overlay_file : Error<
   "virtual filesystem overlay file '%0' not found">, DefaultFatal;
 def err_invalid_vfs_overlay : Error<
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 6d781f9714..85072f1d15 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -7212,6 +7212,8 @@ def err_module_import_not_at_top_level : Error<
 def note_module_import_not_at_top_level : Note<"%0 begins here">;
 def err_module_self_import : Error<
   "import of module '%0' appears within same top-level module '%1'">;
+def err_module_import_in_implementation : Error<
+  "@import of module '%0' in implementation of '%1'; use #import">;
 }
 
 let CategoryName = "Documentation Issue" in {
diff --git a/include/clang/Basic/LangOptions.h b/include/clang/Basic/LangOptions.h
index 9bffc7cb18..fb406a2ed3 100644
--- a/include/clang/Basic/LangOptions.h
+++ b/include/clang/Basic/LangOptions.h
@@ -88,6 +88,11 @@ public:
   /// \brief The name of the current module.
   std::string CurrentModule;
 
+  /// \brief The name of the module that the translation unit is an
+  /// implementation of. Prevents semantic imports, but does not otherwise
+  /// treat this as the CurrentModule.
+  std::string ImplementationOfModule;
+
   /// \brief Options for parsing comments.
   CommentOptions CommentOpts;
   
diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index d25560c9f3..c3685e0f30 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -327,6 +327,9 @@ def fno_modules_global_index : Flag<["-"], "fno-modules-global-index">,
   HelpText<"Do not automatically generate or update the global module index">;
 def fno_modules_error_recovery : Flag<["-"], "fno-modules-error-recovery">,
   HelpText<"Do not automatically import modules for error recovery">;
+def fmodule_implementation_of : Separate<["-"], "fmodule-implementation-of">,
+  MetaVarName<"<name>">,
+  HelpText<"Specify the name of the module whose implementation file this is">;
 
 let Group = Action_Group in {