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, 3 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index bbe69306b64..9ce09288de1 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -13438,6 +13438,9 @@ DeclResult Sema::ActOnModuleImport(SourceLocation AtLoc,
   if (Mod->getTopLevelModuleName() == getLangOpts().CurrentModule)
     Diag(ImportLoc, diag::err_module_self_import)
         << Mod->getFullModuleName() << getLangOpts().CurrentModule;
+  else if (Mod->getTopLevelModuleName() == getLangOpts().ImplementationOfModule)
+    Diag(ImportLoc, diag::err_module_import_in_implementation)
+        << Mod->getFullModuleName() << getLangOpts().ImplementationOfModule;
 
   SmallVector<SourceLocation, 2> IdentifierLocs;
   Module *ModCheck = Mod;