r358633 - Split out modules-specific declaration handling from SemaDecl.cpp into a

Richard Smith via cfe-commits cfe-commits at lists.llvm.org
Wed Apr 17 17:57:02 PDT 2019


Author: rsmith
Date: Wed Apr 17 17:57:02 2019
New Revision: 358633

URL: http://llvm.org/viewvc/llvm-project?rev=358633&view=rev
Log:
Split out modules-specific declaration handling from SemaDecl.cpp into a
new SemaModule.cpp.

Added:
    cfe/trunk/lib/Sema/SemaModule.cpp
Modified:
    cfe/trunk/lib/Sema/CMakeLists.txt
    cfe/trunk/lib/Sema/SemaDecl.cpp

Modified: cfe/trunk/lib/Sema/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/CMakeLists.txt?rev=358633&r1=358632&r2=358633&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/CMakeLists.txt (original)
+++ cfe/trunk/lib/Sema/CMakeLists.txt Wed Apr 17 17:57:02 2019
@@ -43,6 +43,7 @@ add_clang_library(clangSema
   SemaInit.cpp
   SemaLambda.cpp
   SemaLookup.cpp
+  SemaModule.cpp
   SemaObjCProperty.cpp
   SemaOpenMP.cpp
   SemaOverload.cpp

Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=358633&r1=358632&r2=358633&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
+++ cfe/trunk/lib/Sema/SemaDecl.cpp Wed Apr 17 17:57:02 2019
@@ -17007,471 +17007,6 @@ Decl *Sema::ActOnFileScopeAsmDecl(Expr *
   return New;
 }
 
-static void checkModuleImportContext(Sema &S, Module *M,
-                                     SourceLocation ImportLoc, DeclContext *DC,
-                                     bool FromInclude = false) {
-  SourceLocation ExternCLoc;
-
-  if (auto *LSD = dyn_cast<LinkageSpecDecl>(DC)) {
-    switch (LSD->getLanguage()) {
-    case LinkageSpecDecl::lang_c:
-      if (ExternCLoc.isInvalid())
-        ExternCLoc = LSD->getBeginLoc();
-      break;
-    case LinkageSpecDecl::lang_cxx:
-      break;
-    }
-    DC = LSD->getParent();
-  }
-
-  while (isa<LinkageSpecDecl>(DC) || isa<ExportDecl>(DC))
-    DC = DC->getParent();
-
-  if (!isa<TranslationUnitDecl>(DC)) {
-    S.Diag(ImportLoc, (FromInclude && S.isModuleVisible(M))
-                          ? diag::ext_module_import_not_at_top_level_noop
-                          : diag::err_module_import_not_at_top_level_fatal)
-        << M->getFullModuleName() << DC;
-    S.Diag(cast<Decl>(DC)->getBeginLoc(),
-           diag::note_module_import_not_at_top_level)
-        << DC;
-  } else if (!M->IsExternC && ExternCLoc.isValid()) {
-    S.Diag(ImportLoc, diag::ext_module_import_in_extern_c)
-      << M->getFullModuleName();
-    S.Diag(ExternCLoc, diag::note_extern_c_begins_here);
-  }
-}
-
-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).
-  auto &Map = PP.getHeaderSearchInfo().getModuleMap();
-  auto *GlobalModule = Map.createGlobalModuleForInterfaceUnit(ModuleLoc);
-  assert(GlobalModule && "module creation should not fail");
-
-  // Enter the scope of the global module.
-  ModuleScopes.push_back({});
-  ModuleScopes.back().BeginLoc = ModuleLoc;
-  ModuleScopes.back().Module = GlobalModule;
-  VisibleModules.setVisible(GlobalModule, ModuleLoc);
-
-  // All declarations created from now on are owned by the global module.
-  auto *TU = Context.getTranslationUnitDecl();
-  TU->setModuleOwnershipKind(Decl::ModuleOwnershipKind::Visible);
-  TU->setLocalOwningModule(GlobalModule);
-
-  // FIXME: Consider creating an explicit representation of this declaration.
-  return nullptr;
-}
-
-Sema::DeclGroupPtrTy
-Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
-                      ModuleDeclKind MDK, ModuleIdPath Path, bool IsFirstDecl) {
-  assert((getLangOpts().ModulesTS || getLangOpts().CPlusPlusModules) &&
-         "should only have module decl in Modules TS or C++20");
-
-  // A module implementation unit requires that we are not compiling a module
-  // of any kind. A module interface unit requires that we are not compiling a
-  // module map.
-  switch (getLangOpts().getCompilingModule()) {
-  case LangOptions::CMK_None:
-    // It's OK to compile a module interface as a normal translation unit.
-    break;
-
-  case LangOptions::CMK_ModuleInterface:
-    if (MDK != ModuleDeclKind::Implementation)
-      break;
-
-    // We were asked to compile a module interface unit but this is a module
-    // implementation unit. That indicates the 'export' is missing.
-    Diag(ModuleLoc, diag::err_module_interface_implementation_mismatch)
-      << FixItHint::CreateInsertion(ModuleLoc, "export ");
-    MDK = ModuleDeclKind::Interface;
-    break;
-
-  case LangOptions::CMK_ModuleMap:
-    Diag(ModuleLoc, diag::err_module_decl_in_module_map_module);
-    return nullptr;
-
-  case LangOptions::CMK_HeaderModule:
-    Diag(ModuleLoc, diag::err_module_decl_in_header_module);
-    return nullptr;
-  }
-
-  assert(ModuleScopes.size() <= 1 && "expected to be at global module scope");
-
-  // FIXME: Most of this work should be done by the preprocessor rather than
-  // here, in order to support macro import.
-
-  // Only one module-declaration is permitted per source file.
-  if (!ModuleScopes.empty() &&
-      ModuleScopes.back().Module->Kind == Module::ModuleInterfaceUnit) {
-    Diag(ModuleLoc, diag::err_module_redeclaration);
-    Diag(VisibleModules.getImportLoc(ModuleScopes.back().Module),
-         diag::note_prev_module_declaration);
-    return nullptr;
-  }
-
-  // Find the global module fragment we're adopting into this module, if any.
-  Module *GlobalModuleFragment = nullptr;
-  if (!ModuleScopes.empty() &&
-      ModuleScopes.back().Module->Kind == Module::GlobalModuleFragment)
-    GlobalModuleFragment = ModuleScopes.back().Module;
-
-  // In C++20, the module-declaration must be the first declaration if there
-  // is no global module fragment.
-  if (getLangOpts().CPlusPlusModules && !IsFirstDecl && !GlobalModuleFragment) {
-    Diag(ModuleLoc, diag::err_module_decl_not_at_start);
-    SourceLocation BeginLoc =
-        ModuleScopes.empty()
-            ? SourceMgr.getLocForStartOfFile(SourceMgr.getMainFileID())
-            : ModuleScopes.back().BeginLoc;
-    if (BeginLoc.isValid()) {
-      Diag(BeginLoc, diag::note_global_module_introducer_missing)
-          << FixItHint::CreateInsertion(BeginLoc, "module;\n");
-    }
-  }
-
-  // Flatten the dots in a module name. Unlike Clang's hierarchical module map
-  // modules, the dots here are just another character that can appear in a
-  // module name.
-  std::string ModuleName;
-  for (auto &Piece : Path) {
-    if (!ModuleName.empty())
-      ModuleName += ".";
-    ModuleName += Piece.first->getName();
-  }
-
-  // If a module name was explicitly specified on the command line, it must be
-  // correct.
-  if (!getLangOpts().CurrentModule.empty() &&
-      getLangOpts().CurrentModule != ModuleName) {
-    Diag(Path.front().second, diag::err_current_module_name_mismatch)
-        << SourceRange(Path.front().second, Path.back().second)
-        << getLangOpts().CurrentModule;
-    return nullptr;
-  }
-  const_cast<LangOptions&>(getLangOpts()).CurrentModule = ModuleName;
-
-  auto &Map = PP.getHeaderSearchInfo().getModuleMap();
-  Module *Mod;
-
-  switch (MDK) {
-  case ModuleDeclKind::Interface: {
-    // We can't have parsed or imported a definition of this module or parsed a
-    // module map defining it already.
-    if (auto *M = Map.findModule(ModuleName)) {
-      Diag(Path[0].second, diag::err_module_redefinition) << ModuleName;
-      if (M->DefinitionLoc.isValid())
-        Diag(M->DefinitionLoc, diag::note_prev_module_definition);
-      else if (const auto *FE = M->getASTFile())
-        Diag(M->DefinitionLoc, diag::note_prev_module_definition_from_ast_file)
-            << FE->getName();
-      Mod = M;
-      break;
-    }
-
-    // Create a Module for the module that we're defining.
-    Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
-                                           GlobalModuleFragment);
-    assert(Mod && "module creation should not fail");
-    break;
-  }
-
-  case ModuleDeclKind::Implementation:
-    std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc(
-        PP.getIdentifierInfo(ModuleName), Path[0].second);
-    Mod = getModuleLoader().loadModule(ModuleLoc, {ModuleNameLoc},
-                                       Module::AllVisible,
-                                       /*IsIncludeDirective=*/false);
-    if (!Mod) {
-      Diag(ModuleLoc, diag::err_module_not_defined) << ModuleName;
-      // Create an empty module interface unit for error recovery.
-      Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
-                                             GlobalModuleFragment);
-    }
-    break;
-  }
-
-  if (!GlobalModuleFragment) {
-    ModuleScopes.push_back({});
-    if (getLangOpts().ModulesLocalVisibility)
-      ModuleScopes.back().OuterVisibleModules = std::move(VisibleModules);
-  }
-
-  // Switch from the global module fragment (if any) to the named module.
-  ModuleScopes.back().BeginLoc = StartLoc;
-  ModuleScopes.back().Module = Mod;
-  ModuleScopes.back().ModuleInterface = MDK != ModuleDeclKind::Implementation;
-  VisibleModules.setVisible(Mod, ModuleLoc);
-
-  // From now on, we have an owning module for all declarations we see.
-  // However, those declarations are module-private unless explicitly
-  // exported.
-  auto *TU = Context.getTranslationUnitDecl();
-  TU->setModuleOwnershipKind(Decl::ModuleOwnershipKind::ModulePrivate);
-  TU->setLocalOwningModule(Mod);
-
-  // FIXME: Create a ModuleDecl.
-  return nullptr;
-}
-
-DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
-                                   SourceLocation ExportLoc,
-                                   SourceLocation ImportLoc,
-                                   ModuleIdPath Path) {
-  // Flatten the module path for a Modules TS module name.
-  std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc;
-  if (getLangOpts().ModulesTS) {
-    std::string ModuleName;
-    for (auto &Piece : Path) {
-      if (!ModuleName.empty())
-        ModuleName += ".";
-      ModuleName += Piece.first->getName();
-    }
-    ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Path[0].second};
-    Path = ModuleIdPath(ModuleNameLoc);
-  }
-
-  Module *Mod =
-      getModuleLoader().loadModule(ImportLoc, Path, Module::AllVisible,
-                                   /*IsIncludeDirective=*/false);
-  if (!Mod)
-    return true;
-
-  return ActOnModuleImport(StartLoc, ExportLoc, ImportLoc, Mod, Path);
-}
-
-DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
-                                   SourceLocation ExportLoc,
-                                   SourceLocation ImportLoc,
-                                   Module *Mod, ModuleIdPath Path) {
-  VisibleModules.setVisible(Mod, ImportLoc);
-
-  checkModuleImportContext(*this, Mod, ImportLoc, CurContext);
-
-  // FIXME: we should support importing a submodule within a different submodule
-  // of the same top-level module. Until we do, make it an error rather than
-  // silently ignoring the import.
-  // Import-from-implementation is valid in the Modules TS. FIXME: Should we
-  // warn on a redundant import of the current module?
-  // FIXME: Import of a module from an implementation partition of the same
-  // module is permitted.
-  if (Mod->getTopLevelModuleName() == getLangOpts().CurrentModule &&
-      (getLangOpts().isCompilingModule() || !getLangOpts().ModulesTS)) {
-    Diag(ImportLoc, getLangOpts().isCompilingModule()
-                        ? diag::err_module_self_import
-                        : diag::err_module_import_in_implementation)
-        << Mod->getFullModuleName() << getLangOpts().CurrentModule;
-  }
-
-  SmallVector<SourceLocation, 2> IdentifierLocs;
-  Module *ModCheck = Mod;
-  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
-    // If we've run out of module parents, just drop the remaining identifiers.
-    // We need the length to be consistent.
-    if (!ModCheck)
-      break;
-    ModCheck = ModCheck->Parent;
-
-    IdentifierLocs.push_back(Path[I].second);
-  }
-
-  // If this was a header import, pad out with dummy locations.
-  // FIXME: Pass in and use the location of the header-name token in this case.
-  if (Path.empty()) {
-    for (; ModCheck; ModCheck = ModCheck->Parent) {
-      IdentifierLocs.push_back(SourceLocation());
-    }
-  }
-
-  ImportDecl *Import = ImportDecl::Create(Context, CurContext, StartLoc,
-                                          Mod, IdentifierLocs);
-  CurContext->addDecl(Import);
-
-  // Sequence initialization of the imported module before that of the current
-  // module, if any.
-  if (!ModuleScopes.empty())
-    Context.addModuleInitializer(ModuleScopes.back().Module, Import);
-
-  // Re-export the module if needed.
-  if (!ModuleScopes.empty() && ModuleScopes.back().ModuleInterface) {
-    if (ExportLoc.isValid() || Import->isExported())
-      getCurrentModule()->Exports.emplace_back(Mod, false);
-  } else if (ExportLoc.isValid()) {
-    Diag(ExportLoc, diag::err_export_not_in_module_interface);
-  }
-
-  return Import;
-}
-
-void Sema::ActOnModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
-  checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
-  BuildModuleInclude(DirectiveLoc, Mod);
-}
-
-void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
-  // Determine whether we're in the #include buffer for a module. The #includes
-  // in that buffer do not qualify as module imports; they're just an
-  // implementation detail of us building the module.
-  //
-  // FIXME: Should we even get ActOnModuleInclude calls for those?
-  bool IsInModuleIncludes =
-      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) {
-    TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
-    ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
-                                                     DirectiveLoc, Mod,
-                                                     DirectiveLoc);
-    if (!ModuleScopes.empty())
-      Context.addModuleInitializer(ModuleScopes.back().Module, ImportD);
-    TU->addDecl(ImportD);
-    Consumer.HandleImplicitImportDecl(ImportD);
-  }
-
-  getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, DirectiveLoc);
-  VisibleModules.setVisible(Mod, DirectiveLoc);
-}
-
-void Sema::ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
-  checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
-
-  ModuleScopes.push_back({});
-  ModuleScopes.back().Module = Mod;
-  if (getLangOpts().ModulesLocalVisibility)
-    ModuleScopes.back().OuterVisibleModules = std::move(VisibleModules);
-
-  VisibleModules.setVisible(Mod, DirectiveLoc);
-
-  // The enclosing context is now part of this module.
-  // FIXME: Consider creating a child DeclContext to hold the entities
-  // lexically within the module.
-  if (getLangOpts().trackLocalOwningModule()) {
-    for (auto *DC = CurContext; DC; DC = DC->getLexicalParent()) {
-      cast<Decl>(DC)->setModuleOwnershipKind(
-          getLangOpts().ModulesLocalVisibility
-              ? Decl::ModuleOwnershipKind::VisibleWhenImported
-              : Decl::ModuleOwnershipKind::Visible);
-      cast<Decl>(DC)->setLocalOwningModule(Mod);
-    }
-  }
-}
-
-void Sema::ActOnModuleEnd(SourceLocation EomLoc, Module *Mod) {
-  if (getLangOpts().ModulesLocalVisibility) {
-    VisibleModules = std::move(ModuleScopes.back().OuterVisibleModules);
-    // Leaving a module hides namespace names, so our visible namespace cache
-    // is now out of date.
-    VisibleNamespaceCache.clear();
-  }
-
-  assert(!ModuleScopes.empty() && ModuleScopes.back().Module == Mod &&
-         "left the wrong module scope");
-  ModuleScopes.pop_back();
-
-  // We got to the end of processing a local module. Create an
-  // ImportDecl as we would for an imported module.
-  FileID File = getSourceManager().getFileID(EomLoc);
-  SourceLocation DirectiveLoc;
-  if (EomLoc == getSourceManager().getLocForEndOfFile(File)) {
-    // We reached the end of a #included module header. Use the #include loc.
-    assert(File != getSourceManager().getMainFileID() &&
-           "end of submodule in main source file");
-    DirectiveLoc = getSourceManager().getIncludeLoc(File);
-  } else {
-    // We reached an EOM pragma. Use the pragma location.
-    DirectiveLoc = EomLoc;
-  }
-  BuildModuleInclude(DirectiveLoc, Mod);
-
-  // Any further declarations are in whatever module we returned to.
-  if (getLangOpts().trackLocalOwningModule()) {
-    // The parser guarantees that this is the same context that we entered
-    // the module within.
-    for (auto *DC = CurContext; DC; DC = DC->getLexicalParent()) {
-      cast<Decl>(DC)->setLocalOwningModule(getCurrentModule());
-      if (!getCurrentModule())
-        cast<Decl>(DC)->setModuleOwnershipKind(
-            Decl::ModuleOwnershipKind::Unowned);
-    }
-  }
-}
-
-void Sema::createImplicitModuleImportForErrorRecovery(SourceLocation Loc,
-                                                      Module *Mod) {
-  // Bail if we're not allowed to implicitly import a module here.
-  if (isSFINAEContext() || !getLangOpts().ModulesErrorRecovery ||
-      VisibleModules.isVisible(Mod))
-    return;
-
-  // Create the implicit import declaration.
-  TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
-  ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
-                                                   Loc, Mod, Loc);
-  TU->addDecl(ImportD);
-  Consumer.HandleImplicitImportDecl(ImportD);
-
-  // Make the module visible.
-  getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, Loc);
-  VisibleModules.setVisible(Mod, Loc);
-}
-
-/// We have parsed the start of an export declaration, including the '{'
-/// (if present).
-Decl *Sema::ActOnStartExportDecl(Scope *S, SourceLocation ExportLoc,
-                                 SourceLocation LBraceLoc) {
-  ExportDecl *D = ExportDecl::Create(Context, CurContext, ExportLoc);
-
-  // C++ Modules TS draft:
-  //   An export-declaration shall appear in the purview of a module other than
-  //   the global module.
-  if (ModuleScopes.empty() || !ModuleScopes.back().ModuleInterface)
-    Diag(ExportLoc, diag::err_export_not_in_module_interface);
-
-  //   An export-declaration [...] shall not contain more than one
-  //   export keyword.
-  //
-  // The intent here is that an export-declaration cannot appear within another
-  // export-declaration.
-  if (D->isExported())
-    Diag(ExportLoc, diag::err_export_within_export);
-
-  CurContext->addDecl(D);
-  PushDeclContext(S, D);
-  D->setModuleOwnershipKind(Decl::ModuleOwnershipKind::VisibleWhenImported);
-  return D;
-}
-
-/// Complete the definition of an export declaration.
-Decl *Sema::ActOnFinishExportDecl(Scope *S, Decl *D, SourceLocation RBraceLoc) {
-  auto *ED = cast<ExportDecl>(D);
-  if (RBraceLoc.isValid())
-    ED->setRBraceLoc(RBraceLoc);
-
-  // FIXME: Diagnose export of internal-linkage declaration (including
-  // anonymous namespace).
-
-  PopDeclContext();
-  return D;
-}
-
 void Sema::ActOnPragmaRedefineExtname(IdentifierInfo* Name,
                                       IdentifierInfo* AliasName,
                                       SourceLocation PragmaLoc,

Added: cfe/trunk/lib/Sema/SemaModule.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaModule.cpp?rev=358633&view=auto
==============================================================================
--- cfe/trunk/lib/Sema/SemaModule.cpp (added)
+++ cfe/trunk/lib/Sema/SemaModule.cpp Wed Apr 17 17:57:02 2019
@@ -0,0 +1,485 @@
+//===--- SemaModule.cpp - Semantic Analysis for Modules -------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements semantic analysis for modules (C++ modules syntax,
+//  Objective-C modules syntax, and Clang header modules).
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/AST/ASTConsumer.h"
+#include "clang/Lex/HeaderSearch.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Sema/SemaInternal.h"
+
+using namespace clang;
+using namespace sema;
+
+static void checkModuleImportContext(Sema &S, Module *M,
+                                     SourceLocation ImportLoc, DeclContext *DC,
+                                     bool FromInclude = false) {
+  SourceLocation ExternCLoc;
+
+  if (auto *LSD = dyn_cast<LinkageSpecDecl>(DC)) {
+    switch (LSD->getLanguage()) {
+    case LinkageSpecDecl::lang_c:
+      if (ExternCLoc.isInvalid())
+        ExternCLoc = LSD->getBeginLoc();
+      break;
+    case LinkageSpecDecl::lang_cxx:
+      break;
+    }
+    DC = LSD->getParent();
+  }
+
+  while (isa<LinkageSpecDecl>(DC) || isa<ExportDecl>(DC))
+    DC = DC->getParent();
+
+  if (!isa<TranslationUnitDecl>(DC)) {
+    S.Diag(ImportLoc, (FromInclude && S.isModuleVisible(M))
+                          ? diag::ext_module_import_not_at_top_level_noop
+                          : diag::err_module_import_not_at_top_level_fatal)
+        << M->getFullModuleName() << DC;
+    S.Diag(cast<Decl>(DC)->getBeginLoc(),
+           diag::note_module_import_not_at_top_level)
+        << DC;
+  } else if (!M->IsExternC && ExternCLoc.isValid()) {
+    S.Diag(ImportLoc, diag::ext_module_import_in_extern_c)
+      << M->getFullModuleName();
+    S.Diag(ExternCLoc, diag::note_extern_c_begins_here);
+  }
+}
+
+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).
+  auto &Map = PP.getHeaderSearchInfo().getModuleMap();
+  auto *GlobalModule = Map.createGlobalModuleForInterfaceUnit(ModuleLoc);
+  assert(GlobalModule && "module creation should not fail");
+
+  // Enter the scope of the global module.
+  ModuleScopes.push_back({});
+  ModuleScopes.back().BeginLoc = ModuleLoc;
+  ModuleScopes.back().Module = GlobalModule;
+  VisibleModules.setVisible(GlobalModule, ModuleLoc);
+
+  // All declarations created from now on are owned by the global module.
+  auto *TU = Context.getTranslationUnitDecl();
+  TU->setModuleOwnershipKind(Decl::ModuleOwnershipKind::Visible);
+  TU->setLocalOwningModule(GlobalModule);
+
+  // FIXME: Consider creating an explicit representation of this declaration.
+  return nullptr;
+}
+
+Sema::DeclGroupPtrTy
+Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
+                      ModuleDeclKind MDK, ModuleIdPath Path, bool IsFirstDecl) {
+  assert((getLangOpts().ModulesTS || getLangOpts().CPlusPlusModules) &&
+         "should only have module decl in Modules TS or C++20");
+
+  // A module implementation unit requires that we are not compiling a module
+  // of any kind. A module interface unit requires that we are not compiling a
+  // module map.
+  switch (getLangOpts().getCompilingModule()) {
+  case LangOptions::CMK_None:
+    // It's OK to compile a module interface as a normal translation unit.
+    break;
+
+  case LangOptions::CMK_ModuleInterface:
+    if (MDK != ModuleDeclKind::Implementation)
+      break;
+
+    // We were asked to compile a module interface unit but this is a module
+    // implementation unit. That indicates the 'export' is missing.
+    Diag(ModuleLoc, diag::err_module_interface_implementation_mismatch)
+      << FixItHint::CreateInsertion(ModuleLoc, "export ");
+    MDK = ModuleDeclKind::Interface;
+    break;
+
+  case LangOptions::CMK_ModuleMap:
+    Diag(ModuleLoc, diag::err_module_decl_in_module_map_module);
+    return nullptr;
+
+  case LangOptions::CMK_HeaderModule:
+    Diag(ModuleLoc, diag::err_module_decl_in_header_module);
+    return nullptr;
+  }
+
+  assert(ModuleScopes.size() <= 1 && "expected to be at global module scope");
+
+  // FIXME: Most of this work should be done by the preprocessor rather than
+  // here, in order to support macro import.
+
+  // Only one module-declaration is permitted per source file.
+  if (!ModuleScopes.empty() &&
+      ModuleScopes.back().Module->Kind == Module::ModuleInterfaceUnit) {
+    Diag(ModuleLoc, diag::err_module_redeclaration);
+    Diag(VisibleModules.getImportLoc(ModuleScopes.back().Module),
+         diag::note_prev_module_declaration);
+    return nullptr;
+  }
+
+  // Find the global module fragment we're adopting into this module, if any.
+  Module *GlobalModuleFragment = nullptr;
+  if (!ModuleScopes.empty() &&
+      ModuleScopes.back().Module->Kind == Module::GlobalModuleFragment)
+    GlobalModuleFragment = ModuleScopes.back().Module;
+
+  // In C++20, the module-declaration must be the first declaration if there
+  // is no global module fragment.
+  if (getLangOpts().CPlusPlusModules && !IsFirstDecl && !GlobalModuleFragment) {
+    Diag(ModuleLoc, diag::err_module_decl_not_at_start);
+    SourceLocation BeginLoc =
+        ModuleScopes.empty()
+            ? SourceMgr.getLocForStartOfFile(SourceMgr.getMainFileID())
+            : ModuleScopes.back().BeginLoc;
+    if (BeginLoc.isValid()) {
+      Diag(BeginLoc, diag::note_global_module_introducer_missing)
+          << FixItHint::CreateInsertion(BeginLoc, "module;\n");
+    }
+  }
+
+  // Flatten the dots in a module name. Unlike Clang's hierarchical module map
+  // modules, the dots here are just another character that can appear in a
+  // module name.
+  std::string ModuleName;
+  for (auto &Piece : Path) {
+    if (!ModuleName.empty())
+      ModuleName += ".";
+    ModuleName += Piece.first->getName();
+  }
+
+  // If a module name was explicitly specified on the command line, it must be
+  // correct.
+  if (!getLangOpts().CurrentModule.empty() &&
+      getLangOpts().CurrentModule != ModuleName) {
+    Diag(Path.front().second, diag::err_current_module_name_mismatch)
+        << SourceRange(Path.front().second, Path.back().second)
+        << getLangOpts().CurrentModule;
+    return nullptr;
+  }
+  const_cast<LangOptions&>(getLangOpts()).CurrentModule = ModuleName;
+
+  auto &Map = PP.getHeaderSearchInfo().getModuleMap();
+  Module *Mod;
+
+  switch (MDK) {
+  case ModuleDeclKind::Interface: {
+    // We can't have parsed or imported a definition of this module or parsed a
+    // module map defining it already.
+    if (auto *M = Map.findModule(ModuleName)) {
+      Diag(Path[0].second, diag::err_module_redefinition) << ModuleName;
+      if (M->DefinitionLoc.isValid())
+        Diag(M->DefinitionLoc, diag::note_prev_module_definition);
+      else if (const auto *FE = M->getASTFile())
+        Diag(M->DefinitionLoc, diag::note_prev_module_definition_from_ast_file)
+            << FE->getName();
+      Mod = M;
+      break;
+    }
+
+    // Create a Module for the module that we're defining.
+    Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
+                                           GlobalModuleFragment);
+    assert(Mod && "module creation should not fail");
+    break;
+  }
+
+  case ModuleDeclKind::Implementation:
+    std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc(
+        PP.getIdentifierInfo(ModuleName), Path[0].second);
+    Mod = getModuleLoader().loadModule(ModuleLoc, {ModuleNameLoc},
+                                       Module::AllVisible,
+                                       /*IsIncludeDirective=*/false);
+    if (!Mod) {
+      Diag(ModuleLoc, diag::err_module_not_defined) << ModuleName;
+      // Create an empty module interface unit for error recovery.
+      Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
+                                             GlobalModuleFragment);
+    }
+    break;
+  }
+
+  if (!GlobalModuleFragment) {
+    ModuleScopes.push_back({});
+    if (getLangOpts().ModulesLocalVisibility)
+      ModuleScopes.back().OuterVisibleModules = std::move(VisibleModules);
+  }
+
+  // Switch from the global module fragment (if any) to the named module.
+  ModuleScopes.back().BeginLoc = StartLoc;
+  ModuleScopes.back().Module = Mod;
+  ModuleScopes.back().ModuleInterface = MDK != ModuleDeclKind::Implementation;
+  VisibleModules.setVisible(Mod, ModuleLoc);
+
+  // From now on, we have an owning module for all declarations we see.
+  // However, those declarations are module-private unless explicitly
+  // exported.
+  auto *TU = Context.getTranslationUnitDecl();
+  TU->setModuleOwnershipKind(Decl::ModuleOwnershipKind::ModulePrivate);
+  TU->setLocalOwningModule(Mod);
+
+  // FIXME: Create a ModuleDecl.
+  return nullptr;
+}
+
+DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
+                                   SourceLocation ExportLoc,
+                                   SourceLocation ImportLoc,
+                                   ModuleIdPath Path) {
+  // Flatten the module path for a Modules TS module name.
+  std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc;
+  if (getLangOpts().ModulesTS) {
+    std::string ModuleName;
+    for (auto &Piece : Path) {
+      if (!ModuleName.empty())
+        ModuleName += ".";
+      ModuleName += Piece.first->getName();
+    }
+    ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Path[0].second};
+    Path = ModuleIdPath(ModuleNameLoc);
+  }
+
+  Module *Mod =
+      getModuleLoader().loadModule(ImportLoc, Path, Module::AllVisible,
+                                   /*IsIncludeDirective=*/false);
+  if (!Mod)
+    return true;
+
+  return ActOnModuleImport(StartLoc, ExportLoc, ImportLoc, Mod, Path);
+}
+
+DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
+                                   SourceLocation ExportLoc,
+                                   SourceLocation ImportLoc,
+                                   Module *Mod, ModuleIdPath Path) {
+  VisibleModules.setVisible(Mod, ImportLoc);
+
+  checkModuleImportContext(*this, Mod, ImportLoc, CurContext);
+
+  // FIXME: we should support importing a submodule within a different submodule
+  // of the same top-level module. Until we do, make it an error rather than
+  // silently ignoring the import.
+  // Import-from-implementation is valid in the Modules TS. FIXME: Should we
+  // warn on a redundant import of the current module?
+  // FIXME: Import of a module from an implementation partition of the same
+  // module is permitted.
+  if (Mod->getTopLevelModuleName() == getLangOpts().CurrentModule &&
+      (getLangOpts().isCompilingModule() || !getLangOpts().ModulesTS)) {
+    Diag(ImportLoc, getLangOpts().isCompilingModule()
+                        ? diag::err_module_self_import
+                        : diag::err_module_import_in_implementation)
+        << Mod->getFullModuleName() << getLangOpts().CurrentModule;
+  }
+
+  SmallVector<SourceLocation, 2> IdentifierLocs;
+  Module *ModCheck = Mod;
+  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
+    // If we've run out of module parents, just drop the remaining identifiers.
+    // We need the length to be consistent.
+    if (!ModCheck)
+      break;
+    ModCheck = ModCheck->Parent;
+
+    IdentifierLocs.push_back(Path[I].second);
+  }
+
+  // If this was a header import, pad out with dummy locations.
+  // FIXME: Pass in and use the location of the header-name token in this case.
+  if (Path.empty()) {
+    for (; ModCheck; ModCheck = ModCheck->Parent) {
+      IdentifierLocs.push_back(SourceLocation());
+    }
+  }
+
+  ImportDecl *Import = ImportDecl::Create(Context, CurContext, StartLoc,
+                                          Mod, IdentifierLocs);
+  CurContext->addDecl(Import);
+
+  // Sequence initialization of the imported module before that of the current
+  // module, if any.
+  if (!ModuleScopes.empty())
+    Context.addModuleInitializer(ModuleScopes.back().Module, Import);
+
+  // Re-export the module if needed.
+  if (!ModuleScopes.empty() && ModuleScopes.back().ModuleInterface) {
+    if (ExportLoc.isValid() || Import->isExported())
+      getCurrentModule()->Exports.emplace_back(Mod, false);
+  } else if (ExportLoc.isValid()) {
+    Diag(ExportLoc, diag::err_export_not_in_module_interface);
+  }
+
+  return Import;
+}
+
+void Sema::ActOnModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
+  checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
+  BuildModuleInclude(DirectiveLoc, Mod);
+}
+
+void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
+  // Determine whether we're in the #include buffer for a module. The #includes
+  // in that buffer do not qualify as module imports; they're just an
+  // implementation detail of us building the module.
+  //
+  // FIXME: Should we even get ActOnModuleInclude calls for those?
+  bool IsInModuleIncludes =
+      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) {
+    TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
+    ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
+                                                     DirectiveLoc, Mod,
+                                                     DirectiveLoc);
+    if (!ModuleScopes.empty())
+      Context.addModuleInitializer(ModuleScopes.back().Module, ImportD);
+    TU->addDecl(ImportD);
+    Consumer.HandleImplicitImportDecl(ImportD);
+  }
+
+  getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, DirectiveLoc);
+  VisibleModules.setVisible(Mod, DirectiveLoc);
+}
+
+void Sema::ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
+  checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
+
+  ModuleScopes.push_back({});
+  ModuleScopes.back().Module = Mod;
+  if (getLangOpts().ModulesLocalVisibility)
+    ModuleScopes.back().OuterVisibleModules = std::move(VisibleModules);
+
+  VisibleModules.setVisible(Mod, DirectiveLoc);
+
+  // The enclosing context is now part of this module.
+  // FIXME: Consider creating a child DeclContext to hold the entities
+  // lexically within the module.
+  if (getLangOpts().trackLocalOwningModule()) {
+    for (auto *DC = CurContext; DC; DC = DC->getLexicalParent()) {
+      cast<Decl>(DC)->setModuleOwnershipKind(
+          getLangOpts().ModulesLocalVisibility
+              ? Decl::ModuleOwnershipKind::VisibleWhenImported
+              : Decl::ModuleOwnershipKind::Visible);
+      cast<Decl>(DC)->setLocalOwningModule(Mod);
+    }
+  }
+}
+
+void Sema::ActOnModuleEnd(SourceLocation EomLoc, Module *Mod) {
+  if (getLangOpts().ModulesLocalVisibility) {
+    VisibleModules = std::move(ModuleScopes.back().OuterVisibleModules);
+    // Leaving a module hides namespace names, so our visible namespace cache
+    // is now out of date.
+    VisibleNamespaceCache.clear();
+  }
+
+  assert(!ModuleScopes.empty() && ModuleScopes.back().Module == Mod &&
+         "left the wrong module scope");
+  ModuleScopes.pop_back();
+
+  // We got to the end of processing a local module. Create an
+  // ImportDecl as we would for an imported module.
+  FileID File = getSourceManager().getFileID(EomLoc);
+  SourceLocation DirectiveLoc;
+  if (EomLoc == getSourceManager().getLocForEndOfFile(File)) {
+    // We reached the end of a #included module header. Use the #include loc.
+    assert(File != getSourceManager().getMainFileID() &&
+           "end of submodule in main source file");
+    DirectiveLoc = getSourceManager().getIncludeLoc(File);
+  } else {
+    // We reached an EOM pragma. Use the pragma location.
+    DirectiveLoc = EomLoc;
+  }
+  BuildModuleInclude(DirectiveLoc, Mod);
+
+  // Any further declarations are in whatever module we returned to.
+  if (getLangOpts().trackLocalOwningModule()) {
+    // The parser guarantees that this is the same context that we entered
+    // the module within.
+    for (auto *DC = CurContext; DC; DC = DC->getLexicalParent()) {
+      cast<Decl>(DC)->setLocalOwningModule(getCurrentModule());
+      if (!getCurrentModule())
+        cast<Decl>(DC)->setModuleOwnershipKind(
+            Decl::ModuleOwnershipKind::Unowned);
+    }
+  }
+}
+
+void Sema::createImplicitModuleImportForErrorRecovery(SourceLocation Loc,
+                                                      Module *Mod) {
+  // Bail if we're not allowed to implicitly import a module here.
+  if (isSFINAEContext() || !getLangOpts().ModulesErrorRecovery ||
+      VisibleModules.isVisible(Mod))
+    return;
+
+  // Create the implicit import declaration.
+  TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
+  ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
+                                                   Loc, Mod, Loc);
+  TU->addDecl(ImportD);
+  Consumer.HandleImplicitImportDecl(ImportD);
+
+  // Make the module visible.
+  getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, Loc);
+  VisibleModules.setVisible(Mod, Loc);
+}
+
+/// We have parsed the start of an export declaration, including the '{'
+/// (if present).
+Decl *Sema::ActOnStartExportDecl(Scope *S, SourceLocation ExportLoc,
+                                 SourceLocation LBraceLoc) {
+  ExportDecl *D = ExportDecl::Create(Context, CurContext, ExportLoc);
+
+  // C++ Modules TS draft:
+  //   An export-declaration shall appear in the purview of a module other than
+  //   the global module.
+  if (ModuleScopes.empty() || !ModuleScopes.back().ModuleInterface)
+    Diag(ExportLoc, diag::err_export_not_in_module_interface);
+
+  //   An export-declaration [...] shall not contain more than one
+  //   export keyword.
+  //
+  // The intent here is that an export-declaration cannot appear within another
+  // export-declaration.
+  if (D->isExported())
+    Diag(ExportLoc, diag::err_export_within_export);
+
+  CurContext->addDecl(D);
+  PushDeclContext(S, D);
+  D->setModuleOwnershipKind(Decl::ModuleOwnershipKind::VisibleWhenImported);
+  return D;
+}
+
+/// Complete the definition of an export declaration.
+Decl *Sema::ActOnFinishExportDecl(Scope *S, Decl *D, SourceLocation RBraceLoc) {
+  auto *ED = cast<ExportDecl>(D);
+  if (RBraceLoc.isValid())
+    ED->setRBraceLoc(RBraceLoc);
+
+  // FIXME: Diagnose export of internal-linkage declaration (including
+  // anonymous namespace).
+
+  PopDeclContext();
+  return D;
+}




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