[C++20] [Modules] Disambuguous Clang module and C++20 Named module further

This patch tries to make the boundary of clang module and C++20 named
module more clear.

The changes included:

- Rename `TranslationUnitKind::TU_Module` to
  `TranslationUnitKind::TU_ClangModule`.
- Rename `Sema::ActOnModuleInclude` to `Sema::ActOnAnnotModuleInclude`.
- Rename `ActOnModuleBegin` to `Sema::ActOnAnnotModuleBegin`.
- Rename `Sema::ActOnModuleEnd` to `Sema::ActOnAnnotModuleEnd`.
- Removes a warning if we're trying to compile a non-module unit as
  C++20 module unit. This is not actually useful and makes (the future)
  implementation unnecessarily complex.

This patch meant to be a NFC fix. But it shows that it fixed a bug
suprisingly that previously we would surppress the unused-value warning
in named modules. Because it shares the same logic with clang modules,
which has headers semantics. This shows the change is meaningful.

Author: ChuanqiXu9

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -11516,8 +11516,6 @@ def err_module_not_defined : Error<
 def err_module_redeclaration : Error<
   "translation unit contains multiple module declarations">;
 def note_prev_module_declaration : Note<"previous module declaration is here">;
-def err_module_declaration_missing : Error<
-  "missing 'export module' declaration in module interface unit">;
 def err_module_declaration_missing_after_global_module_introducer : Error<
   "missing 'module' declaration at end of global module fragment "
   "introduced here">;

clang/include/clang/Basic/LangOptions.h

@@ -560,11 +560,6 @@ class LangOptions : public LangOptionsBase {
     return getCompilingModule() != CMK_None;
   }
 
-  /// Are we compiling a standard c++ module interface?
-  bool isCompilingModuleInterface() const {
-    return getCompilingModule() == CMK_ModuleInterface;
-  }
-
   /// Are we compiling a module implementation?
   bool isCompilingModuleImplementation() const {
     return !isCompilingModule() && !ModuleName.empty();
@@ -993,8 +988,8 @@ enum TranslationUnitKind {
   /// not complete.
   TU_Prefix,
 
-  /// The translation unit is a module.
-  TU_Module,
+  /// The translation unit is a clang module.
+  TU_ClangModule,
 
   /// The translation unit is a is a complete translation unit that we might
   /// incrementally extend later.

clang/include/clang/Frontend/FrontendActions.h

@@ -125,7 +125,7 @@ class GenerateModuleAction : public ASTFrontendAction {
                                                  StringRef InFile) override;
 
   TranslationUnitKind getTranslationUnitKind() override {
-    return TU_Module;
+    return TU_ClangModule;
   }
 
   bool hasASTFileSupport() const override { return false; }
@@ -138,7 +138,9 @@ class GenerateInterfaceStubsAction : public ASTFrontendAction {
   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                  StringRef InFile) override;
 
-  TranslationUnitKind getTranslationUnitKind() override { return TU_Module; }
+  TranslationUnitKind getTranslationUnitKind() override {
+    return TU_ClangModule;
+  }
   bool hasASTFileSupport() const override { return false; }
 };
 
@@ -159,6 +161,8 @@ class GenerateModuleInterfaceAction : public GenerateModuleAction {
   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                  StringRef InFile) override;
 
+  TranslationUnitKind getTranslationUnitKind() override { return TU_Complete; }
+
   std::unique_ptr<raw_pwrite_stream>
   CreateOutputFile(CompilerInstance &CI, StringRef InFile) override;
 };

clang/include/clang/Sema/Sema.h

@@ -8064,13 +8064,13 @@ class Sema final {
 
   /// The parser has processed a module import translated from a
   /// #include or similar preprocessing directive.
-  void ActOnModuleInclude(SourceLocation DirectiveLoc, Module *Mod);
+  void ActOnAnnotModuleInclude(SourceLocation DirectiveLoc, Module *Mod);
   void BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod);
 
   /// The parsed has entered a submodule.
-  void ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod);
+  void ActOnAnnotModuleBegin(SourceLocation DirectiveLoc, Module *Mod);
   /// The parser has left a submodule.
-  void ActOnModuleEnd(SourceLocation DirectiveLoc, Module *Mod);
+  void ActOnAnnotModuleEnd(SourceLocation DirectiveLoc, Module *Mod);
 
   /// Create an implicit import of the given module at the given
   /// source location, for error recovery, if possible.

clang/lib/Parse/Parser.cpp

@@ -685,7 +685,7 @@ bool Parser::ParseTopLevelDecl(DeclGroupPtrTy &Result,
     // FIXME: We need a better way to disambiguate C++ clang modules and
     // standard C++ modules.
     if (!getLangOpts().CPlusPlusModules || !Mod->isHeaderUnit())
-      Actions.ActOnModuleInclude(Loc, Mod);
+      Actions.ActOnAnnotModuleInclude(Loc, Mod);
     else {
       DeclResult Import =
           Actions.ActOnModuleImport(Loc, SourceLocation(), Loc, Mod);
@@ -697,15 +697,17 @@ bool Parser::ParseTopLevelDecl(DeclGroupPtrTy &Result,
   }
 
   case tok::annot_module_begin:
-    Actions.ActOnModuleBegin(Tok.getLocation(), reinterpret_cast<Module *>(
-                                                    Tok.getAnnotationValue()));
+    Actions.ActOnAnnotModuleBegin(
+        Tok.getLocation(),
+        reinterpret_cast<Module *>(Tok.getAnnotationValue()));
     ConsumeAnnotationToken();
     ImportState = Sema::ModuleImportState::NotACXX20Module;
     return false;
 
   case tok::annot_module_end:
-    Actions.ActOnModuleEnd(Tok.getLocation(), reinterpret_cast<Module *>(
-                                                  Tok.getAnnotationValue()));
+    Actions.ActOnAnnotModuleEnd(
+        Tok.getLocation(),
+        reinterpret_cast<Module *>(Tok.getAnnotationValue()));
     ConsumeAnnotationToken();
     ImportState = Sema::ModuleImportState::NotACXX20Module;
     return false;
@@ -2708,9 +2710,9 @@ bool Parser::parseMisplacedModuleImport() {
       // happens.
       if (MisplacedModuleBeginCount) {
         --MisplacedModuleBeginCount;
-        Actions.ActOnModuleEnd(Tok.getLocation(),
-                               reinterpret_cast<Module *>(
-                                   Tok.getAnnotationValue()));
+        Actions.ActOnAnnotModuleEnd(
+            Tok.getLocation(),
+            reinterpret_cast<Module *>(Tok.getAnnotationValue()));
         ConsumeAnnotationToken();
         continue;
       }
@@ -2720,18 +2722,18 @@ bool Parser::parseMisplacedModuleImport() {
       return true;
     case tok::annot_module_begin:
       // Recover by entering the module (Sema will diagnose).
-      Actions.ActOnModuleBegin(Tok.getLocation(),
-                               reinterpret_cast<Module *>(
-                                   Tok.getAnnotationValue()));
+      Actions.ActOnAnnotModuleBegin(
+          Tok.getLocation(),
+          reinterpret_cast<Module *>(Tok.getAnnotationValue()));
       ConsumeAnnotationToken();
       ++MisplacedModuleBeginCount;
       continue;
     case tok::annot_module_include:
       // Module import found where it should not be, for instance, inside a
       // namespace. Recover by importing the module.
-      Actions.ActOnModuleInclude(Tok.getLocation(),
-                                 reinterpret_cast<Module *>(
-                                     Tok.getAnnotationValue()));
+      Actions.ActOnAnnotModuleInclude(
+          Tok.getLocation(),
+          reinterpret_cast<Module *>(Tok.getAnnotationValue()));
       ConsumeAnnotationToken();
       // If there is another module import, process it.
       continue;

clang/lib/Sema/Sema.cpp

@@ -1207,26 +1207,35 @@ void Sema::ActOnEndOfTranslationUnit() {
   }
 
   // A global-module-fragment is only permitted within a module unit.
-  bool DiagnosedMissingModuleDeclaration = false;
   if (!ModuleScopes.empty() && ModuleScopes.back().Module->Kind ==
                                    Module::ExplicitGlobalModuleFragment) {
     Diag(ModuleScopes.back().BeginLoc,
          diag::err_module_declaration_missing_after_global_module_introducer);
-    DiagnosedMissingModuleDeclaration = true;
-  }
-
-  if (TUKind == TU_Module) {
-    // If we are building a module interface unit, we need to have seen the
-    // module declaration by now.
-    if (getLangOpts().getCompilingModule() ==
-            LangOptions::CMK_ModuleInterface &&
-        !isCurrentModulePurview() && !DiagnosedMissingModuleDeclaration) {
-      // FIXME: Make a better guess as to where to put the module declaration.
-      Diag(getSourceManager().getLocForStartOfFile(
-               getSourceManager().getMainFileID()),
-           diag::err_module_declaration_missing);
-    }
+  }
+
+  // Now we can decide whether the modules we're building need an initializer.
+  if (Module *CurrentModule = getCurrentModule();
+      CurrentModule && CurrentModule->isInterfaceOrPartition()) {
+    auto DoesModNeedInit = [this](Module *M) {
+      if (!getASTContext().getModuleInitializers(M).empty())
+        return true;
+      for (auto [Exported, _] : M->Exports)
+        if (Exported->isNamedModuleInterfaceHasInit())
+          return true;
+      for (Module *I : M->Imports)
+        if (I->isNamedModuleInterfaceHasInit())
+          return true;
+
+      return false;
+    };
 
+    CurrentModule->NamedModuleHasInit =
+        DoesModNeedInit(CurrentModule) ||
+        llvm::any_of(CurrentModule->submodules(),
+                     [&](auto *SubM) { return DoesModNeedInit(SubM); });
+  }
+
+  if (TUKind == TU_ClangModule) {
     // If we are building a module, resolve all of the exported declarations
     // now.
     if (Module *CurrentModule = PP.getCurrentModule()) {
@@ -1251,28 +1260,6 @@ void Sema::ActOnEndOfTranslationUnit() {
       }
     }
 
-    // Now we can decide whether the modules we're building need an initializer.
-    if (Module *CurrentModule = getCurrentModule();
-        CurrentModule && CurrentModule->isInterfaceOrPartition()) {
-      auto DoesModNeedInit = [this](Module *M) {
-        if (!getASTContext().getModuleInitializers(M).empty())
-          return true;
-        for (auto [Exported, _] : M->Exports)
-          if (Exported->isNamedModuleInterfaceHasInit())
-            return true;
-        for (Module *I : M->Imports)
-          if (I->isNamedModuleInterfaceHasInit())
-            return true;
-
-        return false;
-      };
-
-      CurrentModule->NamedModuleHasInit =
-          DoesModNeedInit(CurrentModule) ||
-          llvm::any_of(CurrentModule->submodules(),
-                       [&](auto *SubM) { return DoesModNeedInit(SubM); });
-    }
-
     // Warnings emitted in ActOnEndOfTranslationUnit() should be emitted for
     // modules when they are built, not every time they are used.
     emitAndClearUnusedLocalTypedefWarnings();
@@ -1358,7 +1345,7 @@ void Sema::ActOnEndOfTranslationUnit() {
   // noise. Don't warn for a use from a module: either we should warn on all
   // file-scope declarations in modules or not at all, but whether the
   // declaration is used is immaterial.
-  if (!Diags.hasErrorOccurred() && TUKind != TU_Module) {
+  if (!Diags.hasErrorOccurred() && TUKind != TU_ClangModule) {
     // Output warning for unused file scoped decls.
     for (UnusedFileScopedDeclsType::iterator
              I = UnusedFileScopedDecls.begin(ExternalSource.get()),

clang/lib/Sema/SemaModule.cpp

@@ -713,7 +713,7 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
   return Import;
 }
 
-void Sema::ActOnModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
+void Sema::ActOnAnnotModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
   checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
   BuildModuleInclude(DirectiveLoc, Mod);
 }
@@ -723,9 +723,9 @@ void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
   // 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?
+  // FIXME: Should we even get ActOnAnnotModuleInclude calls for those?
   bool IsInModuleIncludes =
-      TUKind == TU_Module &&
+      TUKind == TU_ClangModule &&
       getSourceManager().isWrittenInMainFile(DirectiveLoc);
 
   // If we are really importing a module (not just checking layering) due to an
@@ -752,7 +752,7 @@ void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
   }
 }
 
-void Sema::ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
+void Sema::ActOnAnnotModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
   checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
 
   ModuleScopes.push_back({});
@@ -776,7 +776,7 @@ void Sema::ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
   }
 }
 
-void Sema::ActOnModuleEnd(SourceLocation EomLoc, Module *Mod) {
+void Sema::ActOnAnnotModuleEnd(SourceLocation EomLoc, Module *Mod) {
   if (getLangOpts().ModulesLocalVisibility) {
     VisibleModules = std::move(ModuleScopes.back().OuterVisibleModules);
     // Leaving a module hides namespace names, so our visible namespace cache

clang/test/CXX/module/dcl.dcl/dcl.module/dcl.module.interface/p1.cppm

@@ -15,10 +15,6 @@ module A; // #module-decl
   // expected-error@-2 {{missing 'export' specifier in module declaration while building module interface}}
   #define INTERFACE
  #endif
-#else
- #ifdef BUILT_AS_INTERFACE
-  // expected-error@1 {{missing 'export module' declaration in module interface unit}}
- #endif
 #endif
 
 #ifndef INTERFACE

clang/test/Modules/missing-module-declaration.cppm

@@ -17,7 +17,7 @@ struct s {
 
 void f() {
 	auto [x] = s();
-	[x] {};
+	(void) [x] {};
 }
 
 // Check that we can generate the LLVM IR expectedly.