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.

llvm-svn: 213767

1 files changed, 8 insertions, 2 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 6af920d9fd7..4a75058e6af 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1265,7 +1265,8 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
   // when both the preprocessor and parser see the same import declaration.
   if (!ImportLoc.isInvalid() && LastModuleImportLoc == ImportLoc) {
     // Make the named module visible.
-    if (LastModuleImportResult && ModuleName != getLangOpts().CurrentModule)
+    if (LastModuleImportResult && ModuleName != getLangOpts().CurrentModule &&
+        ModuleName != getLangOpts().ImplementationOfModule)
       ModuleManager->makeModuleVisible(LastModuleImportResult, Visibility,
                                        ImportLoc, /*Complain=*/false);
     return LastModuleImportResult;
@@ -1279,7 +1280,8 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
   if (Known != KnownModules.end()) {
     // Retrieve the cached top-level module.
     Module = Known->second;    
-  } else if (ModuleName == getLangOpts().CurrentModule) {
+  } else if (ModuleName == getLangOpts().CurrentModule ||
+             ModuleName == getLangOpts().ImplementationOfModule) {
     // This is the module we're building. 
     Module = PP->getHeaderSearchInfo().lookupModule(ModuleName);
     Known = KnownModules.insert(std::make_pair(Path[0].first, Module)).first;
@@ -1448,6 +1450,10 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
       Module = Sub;
     }
   }
+
+  // Don't make the module visible if we are in the implementation.
+  if (ModuleName == getLangOpts().ImplementationOfModule)
+    return ModuleLoadResult(Module, false);
   
   // Make the named module visible, if it's not already part of the module
   // we are parsing.