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

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<

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 {

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;
   

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 {
 

lib/Basic/LangOptions.cpp

@@ -36,5 +36,6 @@ void LangOptions::resetNonModularOptions() {
   Sanitize = SanitizerOptions::Disabled;
 
   CurrentModule.clear();
+  ImplementationOfModule.clear();
 }
 

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.

lib/Frontend/CompilerInvocation.cpp

@@ -1495,6 +1495,14 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   Opts.DebuggerObjCLiteral = Args.hasArg(OPT_fdebugger_objc_literal);
   Opts.ApplePragmaPack = Args.hasArg(OPT_fapple_pragma_pack);
   Opts.CurrentModule = Args.getLastArgValue(OPT_fmodule_name);
+  Opts.ImplementationOfModule =
+      Args.getLastArgValue(OPT_fmodule_implementation_of);
+
+  if (!Opts.CurrentModule.empty() && !Opts.ImplementationOfModule.empty() &&
+      Opts.CurrentModule != Opts.ImplementationOfModule) {
+    Diags.Report(diag::err_conflicting_module_names)
+        << Opts.CurrentModule << Opts.ImplementationOfModule;
+  }
 
   if (Arg *A = Args.getLastArg(OPT_faddress_space_map_mangling_EQ)) {
     switch (llvm::StringSwitch<unsigned>(A->getValue())

lib/Lex/PPDirectives.cpp

@@ -1539,7 +1539,9 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
 
   // If we are supposed to import a module rather than including the header,
   // do so now.
-  if (SuggestedModule && getLangOpts().Modules) {
+  if (SuggestedModule && getLangOpts().Modules &&
+      SuggestedModule.getModule()->getTopLevelModuleName() !=
+      getLangOpts().ImplementationOfModule) {
     // Compute the module access path corresponding to this module.
     // FIXME: Should we have a second loadModule() overload to avoid this
     // extra lookup step?

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;

test/Modules/implementation-of-module.m

@@ -0,0 +1,29 @@
+// RUN: not %clang_cc1 -fmodule-implementation-of Foo -fmodule-name=Bar %s 2>&1 \
+// RUN:     | FileCheck -check-prefix=CHECK-IMPL-OF-ERR %s
+// CHECK-IMPL-OF-ERR: conflicting module names specified: '-fmodule-name=Bar' and '-fmodule-implementation-of Foo'
+
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -w -Werror=auto-import %s -I %S/Inputs \
+// RUN:     -fmodule-implementation-of category_right -fsyntax-only
+
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -w -Werror=auto-import %s -I %S/Inputs \
+// RUN:     -fmodule-implementation-of category_right -dM -E -o - 2>&1 | FileCheck %s
+// CHECK-NOT: __building_module
+
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -w -Werror=auto-import %s -I %S/Inputs \
+// RUN:     -fmodule-implementation-of category_left -verify
+
+// RUN: %clang_cc1 -x objective-c-header -fmodules -fmodules-cache-path=%t -w -Werror=auto-import %s -I %S/Inputs \
+// RUN:     -fmodule-implementation-of category_right -emit-pch -o %t.pch
+// RUN: %clang_cc1 -x objective-c-header -fmodules -fmodules-cache-path=%t -w -Werror=auto-import %s -I %S/Inputs \
+// RUN:     -DWITH_PREFIX -include-pch %t.pch -fmodule-implementation-of category_right
+
+#ifndef WITH_PREFIX
+
+@import category_left; // expected-error{{@import of module 'category_left' in implementation of 'category_left'; use #import}}
+@import category_left.sub; // expected-error{{@import of module 'category_left.sub' in implementation of 'category_left'; use #import}}
+#import "category_right.h" // expected-error{{treating}}
+#import "category_right_sub.h" // expected-error{{treating}}
+
+#endif
+