vendor/llvm-project/llvmorg-17-init-19304-gd0b54bb50e51

1 files changed, 140 insertions, 183 deletions

diff --git a/clang/lib/Sema/SemaModule.cpp b/clang/lib/Sema/SemaModule.cpp
index f52c0247f01c..cd38cd4cf69d 100644
--- a/clang/lib/Sema/SemaModule.cpp
+++ b/clang/lib/Sema/SemaModule.cpp
@@ -15,6 +15,7 @@
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/SemaInternal.h"
+#include "llvm/ADT/StringExtras.h"
 #include <optional>
 
 using namespace clang;
@@ -74,20 +75,9 @@ static std::string stringFromPath(ModuleIdPath Path) {
 
 Sema::DeclGroupPtrTy
 Sema::ActOnGlobalModuleFragmentDecl(SourceLocation ModuleLoc) {
-  if (!ModuleScopes.empty() &&
-      ModuleScopes.back().Module->Kind == Module::GlobalModuleFragment) {
-    // Under -std=c++2a -fmodules-ts, we can find an explicit 'module;' after
-    // already implicitly entering the global module fragment. That's OK.
-    assert(getLangOpts().CPlusPlusModules && getLangOpts().ModulesTS &&
-           "unexpectedly encountered multiple global module fragment decls");
-    ModuleScopes.back().BeginLoc = ModuleLoc;
-    return nullptr;
-  }
-
-  // We start in the global module; all those declarations are implicitly
-  // module-private (though they do not have module linkage).
+  // We start in the global module;
   Module *GlobalModule =
-      PushGlobalModuleFragment(ModuleLoc, /*IsImplicit=*/false);
+      PushGlobalModuleFragment(ModuleLoc);
 
   // All declarations created from now on are owned by the global module.
   auto *TU = Context.getTranslationUnitDecl();
@@ -135,7 +125,6 @@ void Sema::HandleStartOfHeaderUnit() {
   ModuleScopes.back().BeginLoc = StartOfTU;
   ModuleScopes.back().Module = Mod;
   ModuleScopes.back().ModuleInterface = true;
-  ModuleScopes.back().IsPartition = false;
   VisibleModules.setVisible(Mod, StartOfTU);
 
   // From now on, we have an owning module for all declarations we see.
@@ -168,19 +157,24 @@ static bool DiagReservedModuleName(Sema &S, const IdentifierInfo *II,
   if (Reason == Reserved && S.getSourceManager().isInSystemHeader(Loc))
     Reason = Valid;
 
-  if (Reason != Valid) {
-    S.Diag(Loc, diag::err_invalid_module_name) << II << (int)Reason;
-    return true;
+  switch (Reason) {
+  case Valid:
+    return false;
+  case Invalid:
+    return S.Diag(Loc, diag::err_invalid_module_name) << II;
+  case Reserved:
+    S.Diag(Loc, diag::warn_reserved_module_name) << II;
+    return false;
   }
-  return false;
+  llvm_unreachable("fell off a fully covered switch");
 }
 
 Sema::DeclGroupPtrTy
 Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
                       ModuleDeclKind MDK, ModuleIdPath Path,
                       ModuleIdPath Partition, ModuleImportState &ImportState) {
-  assert((getLangOpts().ModulesTS || getLangOpts().CPlusPlusModules) &&
-         "should only have module decl in Modules TS or C++20");
+  assert(getLangOpts().CPlusPlusModules &&
+         "should only have module decl in standard C++ modules");
 
   bool IsFirstDecl = ImportState == ModuleImportState::FirstDecl;
   bool SeenGMF = ImportState == ModuleImportState::GlobalFragment;
@@ -244,8 +238,8 @@ Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
     return nullptr;
   }
 
-  assert((!getLangOpts().CPlusPlusModules || getLangOpts().ModulesTS ||
-          SeenGMF == (bool)this->GlobalModuleFragment) &&
+  assert((!getLangOpts().CPlusPlusModules ||
+          SeenGMF == (bool)this->TheGlobalModuleFragment) &&
          "mismatched global module state");
 
   // In C++20, the module-declaration must be the first declaration if there
@@ -262,7 +256,7 @@ Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
     }
   }
 
-  // C++2b [module.unit]p1: ... The identifiers module and import shall not
+  // C++23 [module.unit]p1: ... The identifiers module and import shall not
   // appear as identifiers in a module-name or module-partition. All
   // module-names either beginning with an identifier consisting of std
   // followed by zero or more digits or containing a reserved identifier
@@ -275,11 +269,8 @@ Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
   if (!getSourceManager().isInSystemHeader(Path[0].second) &&
       (FirstComponentName == "std" ||
        (FirstComponentName.startswith("std") &&
-        llvm::all_of(FirstComponentName.drop_front(3), &llvm::isDigit)))) {
-    Diag(Path[0].second, diag::err_invalid_module_name)
-        << Path[0].first << /*reserved*/ 1;
-    return nullptr;
-  }
+        llvm::all_of(FirstComponentName.drop_front(3), &llvm::isDigit))))
+    Diag(Path[0].second, diag::warn_reserved_module_name) << Path[0].first;
 
   // Then test all of the components in the path to see if any of them are
   // using another kind of reserved or invalid identifier.
@@ -310,8 +301,8 @@ Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
   const_cast<LangOptions&>(getLangOpts()).CurrentModule = ModuleName;
 
   auto &Map = PP.getHeaderSearchInfo().getModuleMap();
-  Module *Mod;
-
+  Module *Mod;                 // The module we are creating.
+  Module *Interface = nullptr; // The interface for an implementation.
   switch (MDK) {
   case ModuleDeclKind::Interface:
   case ModuleDeclKind::PartitionInterface: {
@@ -337,19 +328,29 @@ Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
   }
 
   case ModuleDeclKind::Implementation: {
-    std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc(
-        PP.getIdentifierInfo(ModuleName), Path[0].second);
     // C++20 A module-declaration that contains neither an export-
     // keyword nor a module-partition implicitly imports the primary
     // module interface unit of the module as if by a module-import-
     // declaration.
-    Mod = getModuleLoader().loadModule(ModuleLoc, {ModuleNameLoc},
-                                       Module::AllVisible,
-                                       /*IsInclusionDirective=*/false);
-    if (!Mod) {
+    std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc(
+        PP.getIdentifierInfo(ModuleName), Path[0].second);
+
+    // The module loader will assume we're trying to import the module that
+    // we're building if `LangOpts.CurrentModule` equals to 'ModuleName'.
+    // Change the value for `LangOpts.CurrentModule` temporarily to make the
+    // module loader work properly.
+    const_cast<LangOptions &>(getLangOpts()).CurrentModule = "";
+    Interface = getModuleLoader().loadModule(ModuleLoc, {ModuleNameLoc},
+                                             Module::AllVisible,
+                                             /*IsInclusionDirective=*/false);
+    const_cast<LangOptions&>(getLangOpts()).CurrentModule = ModuleName;
+
+    if (!Interface) {
       Diag(ModuleLoc, diag::err_module_not_defined) << ModuleName;
       // Create an empty module interface unit for error recovery.
       Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName);
+    } else {
+      Mod = Map.createModuleForImplementationUnit(ModuleLoc, ModuleName);
     }
   } break;
 
@@ -361,7 +362,7 @@ Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
     break;
   }
 
-  if (!this->GlobalModuleFragment) {
+  if (!this->TheGlobalModuleFragment) {
     ModuleScopes.push_back({});
     if (getLangOpts().ModulesLocalVisibility)
       ModuleScopes.back().OuterVisibleModules = std::move(VisibleModules);
@@ -374,7 +375,6 @@ Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
   ModuleScopes.back().BeginLoc = StartLoc;
   ModuleScopes.back().Module = Mod;
   ModuleScopes.back().ModuleInterface = MDK != ModuleDeclKind::Implementation;
-  ModuleScopes.back().IsPartition = IsPartition;
   VisibleModules.setVisible(Mod, ModuleLoc);
 
   // From now on, we have an owning module for all declarations we see.
@@ -390,17 +390,32 @@ Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
   // statements, so imports are allowed.
   ImportState = ModuleImportState::ImportAllowed;
 
-  // For an implementation, We already made an implicit import (its interface).
-  // Make and return the import decl to be added to the current TU.
-  if (MDK == ModuleDeclKind::Implementation) {
-    // Make the import decl for the interface.
-    ImportDecl *Import =
-        ImportDecl::Create(Context, CurContext, ModuleLoc, Mod, Path[0].second);
-    // and return it to be added.
+  getASTContext().setCurrentNamedModule(Mod);
+
+  // We already potentially made an implicit import (in the case of a module
+  // implementation unit importing its interface).  Make this module visible
+  // and return the import decl to be added to the current TU.
+  if (Interface) {
+
+    VisibleModules.setVisible(Interface, ModuleLoc);
+    VisibleModules.makeTransitiveImportsVisible(Interface, ModuleLoc);
+
+    // Make the import decl for the interface in the impl module.
+    ImportDecl *Import = ImportDecl::Create(Context, CurContext, ModuleLoc,
+                                            Interface, Path[0].second);
+    CurContext->addDecl(Import);
+
+    // Sequence initialization of the imported module before that of the current
+    // module, if any.
+    Context.addModuleInitializer(ModuleScopes.back().Module, Import);
+    Mod->Imports.insert(Interface); // As if we imported it.
+    // Also save this as a shortcut to checking for decls in the interface
+    ThePrimaryInterface = Interface;
+    // If we made an implicit import of the module interface, then return the
+    // imported module decl.
     return ConvertDeclToDeclGroup(Import);
   }
 
-  // FIXME: Create a ModuleDecl.
   return nullptr;
 }
 
@@ -410,10 +425,11 @@ Sema::ActOnPrivateModuleFragmentDecl(SourceLocation ModuleLoc,
   // C++20 [basic.link]/2:
   //   A private-module-fragment shall appear only in a primary module
   //   interface unit.
-  switch (ModuleScopes.empty() ? Module::GlobalModuleFragment
+  switch (ModuleScopes.empty() ? Module::ExplicitGlobalModuleFragment
                                : ModuleScopes.back().Module->Kind) {
   case Module::ModuleMapModule:
-  case Module::GlobalModuleFragment:
+  case Module::ExplicitGlobalModuleFragment:
+  case Module::ImplicitGlobalModuleFragment:
   case Module::ModulePartitionImplementation:
   case Module::ModulePartitionInterface:
   case Module::ModuleHeaderUnit:
@@ -425,19 +441,17 @@ Sema::ActOnPrivateModuleFragmentDecl(SourceLocation ModuleLoc,
     Diag(ModuleScopes.back().BeginLoc, diag::note_previous_definition);
     return nullptr;
 
-  case Module::ModuleInterfaceUnit:
-    break;
-  }
-
-  if (!ModuleScopes.back().ModuleInterface) {
+  case Module::ModuleImplementationUnit:
     Diag(PrivateLoc, diag::err_private_module_fragment_not_module_interface);
     Diag(ModuleScopes.back().BeginLoc,
          diag::note_not_module_interface_add_export)
         << FixItHint::CreateInsertion(ModuleScopes.back().BeginLoc, "export ");
     return nullptr;
+
+  case Module::ModuleInterfaceUnit:
+    break;
   }
 
-  // FIXME: Check this isn't a module interface partition.
   // FIXME: Check that this translation unit does not import any partitions;
   // such imports would violate [basic.link]/2's "shall be the only module unit"
   // restriction.
@@ -473,9 +487,8 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
                                    SourceLocation ExportLoc,
                                    SourceLocation ImportLoc, ModuleIdPath Path,
                                    bool IsPartition) {
-
-  bool Cxx20Mode = getLangOpts().CPlusPlusModules || getLangOpts().ModulesTS;
-  assert((!IsPartition || Cxx20Mode) && "partition seen in non-C++20 code?");
+  assert((!IsPartition || getLangOpts().CPlusPlusModules) &&
+         "partition seen in non-C++20 code?");
 
   // For a C++20 module name, flatten into a single identifier with the source
   // location of the first component.
@@ -493,7 +506,7 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
     ModuleName += stringFromPath(Path);
     ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Path[0].second};
     Path = ModuleIdPath(ModuleNameLoc);
-  } else if (Cxx20Mode) {
+  } else if (getLangOpts().CPlusPlusModules) {
     ModuleName = stringFromPath(Path);
     ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Path[0].second};
     Path = ModuleIdPath(ModuleNameLoc);
@@ -533,6 +546,9 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
                                    SourceLocation ExportLoc,
                                    SourceLocation ImportLoc, Module *Mod,
                                    ModuleIdPath Path) {
+  if (Mod->isHeaderUnit())
+    Diag(ImportLoc, diag::warn_experimental_header_unit);
+
   VisibleModules.setVisible(Mod, ImportLoc);
 
   checkModuleImportContext(*this, Mod, ImportLoc, CurContext);
@@ -541,8 +557,7 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
   // of the same top-level module. Until we do, make it an error rather than
   // silently ignoring the import.
   // FIXME: Should we warn on a redundant import of the current module?
-  if (Mod->isForBuilding(getLangOpts()) &&
-      (getLangOpts().isCompilingModule() || !getLangOpts().ModulesTS)) {
+  if (Mod->isForBuilding(getLangOpts())) {
     Diag(ImportLoc, getLangOpts().isCompilingModule()
                         ? diag::err_module_self_import
                         : diag::err_module_import_in_implementation)
@@ -602,16 +617,9 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
     // [module.interface]p1:
     // An export-declaration shall inhabit a namespace scope and appear in the
     // purview of a module interface unit.
-    Diag(ExportLoc, diag::err_export_not_in_module_interface)
-        << (!ModuleScopes.empty() &&
-            !ModuleScopes.back().ImplicitGlobalModuleFragment);
+    Diag(ExportLoc, diag::err_export_not_in_module_interface);
   }
 
-  // In some cases we need to know if an entity was present in a directly-
-  // imported module (as opposed to a transitive import).  This avoids
-  // searching both Imports and Exports.
-  DirectModuleImports.insert(Mod);
-
   return Import;
 }
 
@@ -630,11 +638,9 @@ void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
       TUKind == TU_Module &&
       getSourceManager().isWrittenInMainFile(DirectiveLoc);
 
-  bool ShouldAddImport = !IsInModuleIncludes;
-
-  // If this module import was due to an inclusion directive, create an
-  // implicit import declaration to capture it in the AST.
-  if (ShouldAddImport) {
+  // If we are really importing a module (not just checking layering) due to an
+  // #include in the main file, synthesize an ImportDecl.
+  if (getLangOpts().Modules && !IsInModuleIncludes) {
     TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
     ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
                                                      DirectiveLoc, Mod,
@@ -810,76 +816,22 @@ Decl *Sema::ActOnStartExportDecl(Scope *S, SourceLocation ExportLoc,
   return D;
 }
 
-static bool checkExportedDeclContext(Sema &S, DeclContext *DC,
-                                     SourceLocation BlockStart);
-
-namespace {
-enum class UnnamedDeclKind {
-  Empty,
-  StaticAssert,
-  Asm,
-  UsingDirective,
-  Namespace,
-  Context
-};
-}
-
-static std::optional<UnnamedDeclKind> getUnnamedDeclKind(Decl *D) {
-  if (isa<EmptyDecl>(D))
-    return UnnamedDeclKind::Empty;
-  if (isa<StaticAssertDecl>(D))
-    return UnnamedDeclKind::StaticAssert;
-  if (isa<FileScopeAsmDecl>(D))
-    return UnnamedDeclKind::Asm;
-  if (isa<UsingDirectiveDecl>(D))
-    return UnnamedDeclKind::UsingDirective;
-  // Everything else either introduces one or more names or is ill-formed.
-  return std::nullopt;
-}
-
-unsigned getUnnamedDeclDiag(UnnamedDeclKind UDK, bool InBlock) {
-  switch (UDK) {
-  case UnnamedDeclKind::Empty:
-  case UnnamedDeclKind::StaticAssert:
-    // Allow empty-declarations and static_asserts in an export block as an
-    // extension.
-    return InBlock ? diag::ext_export_no_name_block : diag::err_export_no_name;
+static bool checkExportedDecl(Sema &, Decl *, SourceLocation);
 
-  case UnnamedDeclKind::UsingDirective:
-    // Allow exporting using-directives as an extension.
-    return diag::ext_export_using_directive;
-
-  case UnnamedDeclKind::Namespace:
-    // Anonymous namespace with no content.
-    return diag::introduces_no_names;
-
-  case UnnamedDeclKind::Context:
-    // Allow exporting DeclContexts that transitively contain no declarations
-    // as an extension.
-    return diag::ext_export_no_names;
-
-  case UnnamedDeclKind::Asm:
-    return diag::err_export_no_name;
-  }
-  llvm_unreachable("unknown kind");
-}
-
-static void diagExportedUnnamedDecl(Sema &S, UnnamedDeclKind UDK, Decl *D,
-                                    SourceLocation BlockStart) {
-  S.Diag(D->getLocation(), getUnnamedDeclDiag(UDK, BlockStart.isValid()))
-      << (unsigned)UDK;
-  if (BlockStart.isValid())
-    S.Diag(BlockStart, diag::note_export);
+/// Check that it's valid to export all the declarations in \p DC.
+static bool checkExportedDeclContext(Sema &S, DeclContext *DC,
+                                     SourceLocation BlockStart) {
+  bool AllUnnamed = true;
+  for (auto *D : DC->decls())
+    AllUnnamed &= checkExportedDecl(S, D, BlockStart);
+  return AllUnnamed;
 }
 
 /// Check that it's valid to export \p D.
 static bool checkExportedDecl(Sema &S, Decl *D, SourceLocation BlockStart) {
-  // C++2a [module.interface]p3:
-  //   An exported declaration shall declare at least one name
-  if (auto UDK = getUnnamedDeclKind(D))
-    diagExportedUnnamedDecl(S, *UDK, D, BlockStart);
 
-  //   [...] shall not declare a name with internal linkage.
+  //  C++20 [module.interface]p3:
+  //   [...] it shall not declare a name with internal linkage.
   bool HasName = false;
   if (auto *ND = dyn_cast<NamedDecl>(D)) {
     // Don't diagnose anonymous union objects; we'll diagnose their members
@@ -889,6 +841,7 @@ static bool checkExportedDecl(Sema &S, Decl *D, SourceLocation BlockStart) {
       S.Diag(ND->getLocation(), diag::err_export_internal) << ND;
       if (BlockStart.isValid())
         S.Diag(BlockStart, diag::note_export);
+      return false;
     }
   }
 
@@ -904,31 +857,29 @@ static bool checkExportedDecl(Sema &S, Decl *D, SourceLocation BlockStart) {
       S.Diag(Target->getLocation(), diag::note_using_decl_target);
       if (BlockStart.isValid())
         S.Diag(BlockStart, diag::note_export);
+      return false;
     }
   }
 
   // Recurse into namespace-scope DeclContexts. (Only namespace-scope
-  // declarations are exported.).
+  // declarations are exported).
   if (auto *DC = dyn_cast<DeclContext>(D)) {
-    if (isa<NamespaceDecl>(D) && DC->decls().empty()) {
-      if (!HasName)
-        // We don't allow an empty anonymous namespace (we don't allow decls
-        // in them either, but that's handled in the recursion).
-        diagExportedUnnamedDecl(S, UnnamedDeclKind::Namespace, D, BlockStart);
-      // We allow an empty named namespace decl.
-    } else if (DC->getRedeclContext()->isFileContext() && !isa<EnumDecl>(D))
-      return checkExportedDeclContext(S, DC, BlockStart);
-  }
-  return false;
-}
-
-/// Check that it's valid to export all the declarations in \p DC.
-static bool checkExportedDeclContext(Sema &S, DeclContext *DC,
-                                     SourceLocation BlockStart) {
-  bool AllUnnamed = true;
-  for (auto *D : DC->decls())
-    AllUnnamed &= checkExportedDecl(S, D, BlockStart);
-  return AllUnnamed;
+    if (!isa<NamespaceDecl>(D))
+      return true;
+
+    if (auto *ND = dyn_cast<NamedDecl>(D)) {
+      if (!ND->getDeclName()) {
+        S.Diag(ND->getLocation(), diag::err_export_anon_ns_internal);
+        if (BlockStart.isValid())
+          S.Diag(BlockStart, diag::note_export);
+        return false;
+      } else if (!DC->decls().empty() &&
+                 DC->getRedeclContext()->isFileContext()) {
+        return checkExportedDeclContext(S, DC, BlockStart);
+      }
+    }
+  }
+  return true;
 }
 
 /// Complete the definition of an export declaration.
@@ -943,12 +894,7 @@ Decl *Sema::ActOnFinishExportDecl(Scope *S, Decl *D, SourceLocation RBraceLoc) {
     SourceLocation BlockStart =
         ED->hasBraces() ? ED->getBeginLoc() : SourceLocation();
     for (auto *Child : ED->decls()) {
-      if (checkExportedDecl(*this, Child, BlockStart)) {
-        // If a top-level child is a linkage-spec declaration, it might contain
-        // no declarations (transitively), in which case it's ill-formed.
-        diagExportedUnnamedDecl(*this, UnnamedDeclKind::Context, Child,
-                                BlockStart);
-      }
+      checkExportedDecl(*this, Child, BlockStart);
       if (auto *FD = dyn_cast<FunctionDecl>(Child)) {
         // [dcl.inline]/7
         // If an inline function or variable that is attached to a named module
@@ -966,44 +912,55 @@ Decl *Sema::ActOnFinishExportDecl(Scope *S, Decl *D, SourceLocation RBraceLoc) {
   return D;
 }
 
-Module *Sema::PushGlobalModuleFragment(SourceLocation BeginLoc,
-                                       bool IsImplicit) {
+Module *Sema::PushGlobalModuleFragment(SourceLocation BeginLoc) {
   // We shouldn't create new global module fragment if there is already
   // one.
-  if (!GlobalModuleFragment) {
+  if (!TheGlobalModuleFragment) {
     ModuleMap &Map = PP.getHeaderSearchInfo().getModuleMap();
-    GlobalModuleFragment = Map.createGlobalModuleFragmentForModuleUnit(
+    TheGlobalModuleFragment = Map.createGlobalModuleFragmentForModuleUnit(
         BeginLoc, getCurrentModule());
   }
 
-  assert(GlobalModuleFragment && "module creation should not fail");
+  assert(TheGlobalModuleFragment && "module creation should not fail");
 
   // Enter the scope of the global module.
-  ModuleScopes.push_back({BeginLoc, GlobalModuleFragment,
+  ModuleScopes.push_back({BeginLoc, TheGlobalModuleFragment,
                           /*ModuleInterface=*/false,
-                          /*IsPartition=*/false,
-                          /*ImplicitGlobalModuleFragment=*/IsImplicit,
                           /*OuterVisibleModules=*/{}});
-  VisibleModules.setVisible(GlobalModuleFragment, BeginLoc);
+  VisibleModules.setVisible(TheGlobalModuleFragment, BeginLoc);
 
-  return GlobalModuleFragment;
+  return TheGlobalModuleFragment;
 }
 
 void Sema::PopGlobalModuleFragment() {
-  assert(!ModuleScopes.empty() && getCurrentModule()->isGlobalModule() &&
+  assert(!ModuleScopes.empty() &&
+         getCurrentModule()->isExplicitGlobalModule() &&
          "left the wrong module scope, which is not global module fragment");
   ModuleScopes.pop_back();
 }
 
-bool Sema::isModuleUnitOfCurrentTU(const Module *M) const {
-  assert(M);
-
-  Module *CurrentModuleUnit = getCurrentModule();
+Module *Sema::PushImplicitGlobalModuleFragment(SourceLocation BeginLoc,
+                                               bool IsExported) {
+  Module **M = IsExported ? &TheExportedImplicitGlobalModuleFragment
+                          : &TheImplicitGlobalModuleFragment;
+  if (!*M) {
+    ModuleMap &Map = PP.getHeaderSearchInfo().getModuleMap();
+    *M = Map.createImplicitGlobalModuleFragmentForModuleUnit(
+        BeginLoc, IsExported, getCurrentModule());
+  }
+  assert(*M && "module creation should not fail");
 
-  // If we are not in a module currently, M must not be the module unit of
-  // current TU.
-  if (!CurrentModuleUnit)
-    return false;
+  // Enter the scope of the global module.
+  ModuleScopes.push_back({BeginLoc, *M,
+                          /*ModuleInterface=*/false,
+                          /*OuterVisibleModules=*/{}});
+  VisibleModules.setVisible(*M, BeginLoc);
+  return *M;
+}
 
-  return M->isSubModuleOf(CurrentModuleUnit->getTopLevelModule());
+void Sema::PopImplicitGlobalModuleFragment() {
+  assert(!ModuleScopes.empty() &&
+         getCurrentModule()->isImplicitGlobalModule() &&
+         "left the wrong module scope, which is not global module fragment");
+  ModuleScopes.pop_back();
 }