Ninja: generate scanning and build rules for C++20 module synthetic targets

5 files changed, 322 insertions, 24 deletions

diff --git a/Source/cmGlobalNinjaGenerator.cxx b/Source/cmGlobalNinjaGenerator.cxx
index 9ca1b2e..54c3737 100644
--- a/Source/cmGlobalNinjaGenerator.cxx
+++ b/Source/cmGlobalNinjaGenerator.cxx
@@ -2643,7 +2643,9 @@ bool cmGlobalNinjaGenerator::WriteDyndepFile(
   for (cmScanDepInfo const& object : objects) {
     for (auto const& p : object.Provides) {
       std::string mod;
-      if (!p.CompiledModulePath.empty()) {
+      if (cmDyndepCollation::IsBmiOnly(export_info, object.PrimaryOutput)) {
+        mod = object.PrimaryOutput;
+      } else if (!p.CompiledModulePath.empty()) {
         // The scanner provided the path to the module file.
         mod = p.CompiledModulePath;
         if (!cmSystemTools::FileIsFullPath(mod)) {
@@ -2714,8 +2716,12 @@ bool cmGlobalNinjaGenerator::WriteDyndepFile(
       build.Outputs[0] = this->ConvertToNinjaPath(object.PrimaryOutput);
       build.ImplicitOuts.clear();
       for (auto const& p : object.Provides) {
-        build.ImplicitOuts.push_back(
-          this->ConvertToNinjaPath(mod_files[p.LogicalName].BmiPath));
+        auto const implicitOut =
+          this->ConvertToNinjaPath(mod_files[p.LogicalName].BmiPath);
+        // Ignore the `provides` when the BMI is the output.
+        if (implicitOut != build.Outputs[0]) {
+          build.ImplicitOuts.emplace_back(implicitOut);
+        }
       }
       build.ImplicitDeps.clear();
       for (auto const& r : object.Requires) {
diff --git a/Source/cmNinjaNormalTargetGenerator.cxx b/Source/cmNinjaNormalTargetGenerator.cxx
index 089498b..48c30b6 100644
--- a/Source/cmNinjaNormalTargetGenerator.cxx
+++ b/Source/cmNinjaNormalTargetGenerator.cxx
@@ -62,12 +62,15 @@ cmNinjaNormalTargetGenerator::~cmNinjaNormalTargetGenerator() = default;
 
 void cmNinjaNormalTargetGenerator::Generate(const std::string& config)
 {
-  std::string lang = this->GeneratorTarget->GetLinkerLanguage(config);
-  if (this->TargetLinkLanguage(config).empty()) {
-    cmSystemTools::Error(
-      cmStrCat("CMake can not determine linker language for target: ",
-               this->GetGeneratorTarget()->GetName()));
-    return;
+  if (this->GetGeneratorTarget()->GetType() !=
+      cmStateEnums::INTERFACE_LIBRARY) {
+    std::string lang = this->GeneratorTarget->GetLinkerLanguage(config);
+    if (this->TargetLinkLanguage(config).empty()) {
+      cmSystemTools::Error(
+        cmStrCat("CMake can not determine linker language for target: ",
+                 this->GetGeneratorTarget()->GetName()));
+      return;
+    }
   }
 
   // Write the rules for each language.
@@ -87,6 +90,34 @@ void cmNinjaNormalTargetGenerator::Generate(const std::string& config)
 
   if (this->GetGeneratorTarget()->GetType() == cmStateEnums::OBJECT_LIBRARY) {
     this->WriteObjectLibStatement(config);
+  } else if (this->GetGeneratorTarget()->GetType() ==
+             cmStateEnums::INTERFACE_LIBRARY) {
+    bool haveCxxModuleSources = false;
+    if (this->GetGeneratorTarget()->HaveCxx20ModuleSources()) {
+      haveCxxModuleSources = true;
+    }
+
+    if (!haveCxxModuleSources) {
+      cmSystemTools::Error(cmStrCat(
+        "Ninja does not support INTERFACE libraries without C++ module "
+        "sources as a normal target: ",
+        this->GetGeneratorTarget()->GetName()));
+      return;
+    }
+
+    firstForConfig = true;
+    for (auto const& fileConfig : this->GetConfigNames()) {
+      if (!this->GetGlobalGenerator()
+             ->GetCrossConfigs(fileConfig)
+             .count(config)) {
+        continue;
+      }
+      if (haveCxxModuleSources) {
+        this->WriteCxxModuleLibraryStatement(config, fileConfig,
+                                             firstForConfig);
+      }
+      firstForConfig = false;
+    }
   } else {
     firstForConfig = true;
     for (auto const& fileConfig : this->GetConfigNames()) {
@@ -123,12 +154,26 @@ void cmNinjaNormalTargetGenerator::WriteLanguagesRules(
 #endif
 
   // Write rules for languages compiled in this target.
-  std::set<std::string> languages;
-  std::vector<cmSourceFile const*> sourceFiles;
-  this->GetGeneratorTarget()->GetObjectSources(sourceFiles, config);
-  if (this->HaveRequiredLanguages(sourceFiles, languages)) {
-    for (std::string const& language : languages) {
-      this->WriteLanguageRules(language, config);
+  {
+    std::set<std::string> languages;
+    std::vector<cmSourceFile const*> sourceFiles;
+    this->GetGeneratorTarget()->GetObjectSources(sourceFiles, config);
+    if (this->HaveRequiredLanguages(sourceFiles, languages)) {
+      for (std::string const& language : languages) {
+        this->WriteLanguageRules(language, config);
+      }
+    }
+  }
+
+  // Write rules for languages in BMI-only rules.
+  {
+    std::set<std::string> languages;
+    std::vector<cmSourceFile const*> sourceFiles;
+    this->GetGeneratorTarget()->GetCxxModuleSources(sourceFiles, config);
+    if (this->HaveRequiredLanguages(sourceFiles, languages)) {
+      for (std::string const& language : languages) {
+        this->WriteLanguageRules(language, config);
+      }
     }
   }
 }
@@ -1637,6 +1682,34 @@ void cmNinjaNormalTargetGenerator::WriteObjectLibStatement(
     this->GetTargetName(), this->GetGeneratorTarget(), config);
 }
 
+void cmNinjaNormalTargetGenerator::WriteCxxModuleLibraryStatement(
+  const std::string& config, const std::string& /*fileConfig*/,
+  bool firstForConfig)
+{
+  // TODO: How to use `fileConfig` properly?
+
+  // Write a phony output that depends on the scanning output.
+  {
+    cmNinjaBuild build("phony");
+    build.Comment =
+      cmStrCat("Imported C++ module library ", this->GetTargetName());
+    this->GetLocalGenerator()->AppendTargetOutputs(this->GetGeneratorTarget(),
+                                                   build.Outputs, config);
+    if (firstForConfig) {
+      this->GetLocalGenerator()->AppendTargetOutputs(
+        this->GetGeneratorTarget(),
+        this->GetGlobalGenerator()->GetByproductsForCleanTarget(config),
+        config);
+    }
+    build.ExplicitDeps.emplace_back(this->GetDyndepFilePath("CXX", config));
+    this->GetGlobalGenerator()->WriteBuild(this->GetCommonFileStream(), build);
+  }
+
+  // Add aliases for the target name.
+  this->GetGlobalGenerator()->AddTargetAlias(
+    this->GetTargetName(), this->GetGeneratorTarget(), config);
+}
+
 cmGeneratorTarget::Names cmNinjaNormalTargetGenerator::TargetNames(
   const std::string& config) const
 {
diff --git a/Source/cmNinjaNormalTargetGenerator.h b/Source/cmNinjaNormalTargetGenerator.h
index 187ea46..3ef0230 100644
--- a/Source/cmNinjaNormalTargetGenerator.h
+++ b/Source/cmNinjaNormalTargetGenerator.h
@@ -49,6 +49,9 @@ private:
                                       const std::string& output);
 
   void WriteObjectLibStatement(const std::string& config);
+  void WriteCxxModuleLibraryStatement(const std::string& config,
+                                      const std::string& fileConfig,
+                                      bool firstForConfig);
 
   std::vector<std::string> ComputeLinkCmd(const std::string& config);
   std::vector<std::string> ComputeDeviceLinkCmd();
diff --git a/Source/cmNinjaTargetGenerator.cxx b/Source/cmNinjaTargetGenerator.cxx
index 6792cd7..09f8495 100644
--- a/Source/cmNinjaTargetGenerator.cxx
+++ b/Source/cmNinjaTargetGenerator.cxx
@@ -28,6 +28,7 @@
 #include "cmGeneratedFileStream.h"
 #include "cmGeneratorExpression.h"
 #include "cmGeneratorTarget.h"
+#include "cmGlobalCommonGenerator.h"
 #include "cmGlobalNinjaGenerator.h"
 #include "cmList.h"
 #include "cmLocalGenerator.h"
@@ -59,8 +60,13 @@ std::unique_ptr<cmNinjaTargetGenerator> cmNinjaTargetGenerator::New(
     case cmStateEnums::OBJECT_LIBRARY:
       return cm::make_unique<cmNinjaNormalTargetGenerator>(target);
 
-    case cmStateEnums::UTILITY:
     case cmStateEnums::INTERFACE_LIBRARY:
+      if (target->HaveCxx20ModuleSources()) {
+        return cm::make_unique<cmNinjaNormalTargetGenerator>(target);
+      }
+      CM_FALLTHROUGH;
+
+    case cmStateEnums::UTILITY:
     case cmStateEnums::GLOBAL_TARGET:
       return cm::make_unique<cmNinjaUtilityTargetGenerator>(target);
 
@@ -167,7 +173,7 @@ std::string cmNinjaTargetGenerator::OrderDependsTargetForTarget(
 // Refactor it.
 std::string cmNinjaTargetGenerator::ComputeFlagsForObject(
   cmSourceFile const* source, const std::string& language,
-  const std::string& config)
+  const std::string& config, const std::string& objectFileName)
 {
   std::unordered_map<std::string, std::string> pchSources;
   std::vector<std::string> architectures =
@@ -247,6 +253,18 @@ std::string cmNinjaTargetGenerator::ComputeFlagsForObject(
                  "\nin a file set of type \"", fs->GetType(),
                  R"(" but the source is not classified as a "CXX" source.)"));
     }
+
+    if (!this->GeneratorTarget->Target->IsNormal()) {
+      auto flag = this->GetMakefile()->GetSafeDefinition(
+        "CMAKE_EXPERIMENTAL_CXX_MODULE_BMI_ONLY_FLAG");
+      cmRulePlaceholderExpander::RuleVariables compileObjectVars;
+      compileObjectVars.Object = objectFileName.c_str();
+      auto rulePlaceholderExpander =
+        this->GetLocalGenerator()->CreateRulePlaceholderExpander();
+      rulePlaceholderExpander->ExpandRuleVariables(this->GetLocalGenerator(),
+                                                   flag, compileObjectVars);
+      this->LocalGenerator->AppendCompileOptions(flags, flag);
+    }
   }
 
   return flags;
@@ -394,6 +412,31 @@ std::string cmNinjaTargetGenerator::GetObjectFilePath(
   return path;
 }
 
+std::string cmNinjaTargetGenerator::GetBmiFilePath(
+  cmSourceFile const* source, const std::string& config) const
+{
+  std::string path = this->LocalGenerator->GetHomeRelativeOutputPath();
+  if (!path.empty()) {
+    path += '/';
+  }
+
+  auto& importedConfigInfo = this->Configs.at(config).ImportedCxxModules;
+  if (!importedConfigInfo.Initialized()) {
+    std::string configUpper = cmSystemTools::UpperCase(config);
+    std::string propName = cmStrCat("IMPORTED_CXX_MODULES_", configUpper);
+    auto value = this->GeneratorTarget->GetSafeProperty(propName);
+    importedConfigInfo.Initialize(value);
+  }
+
+  std::string bmiName =
+    importedConfigInfo.BmiNameForSource(source->GetFullPath());
+
+  path += cmStrCat(
+    this->LocalGenerator->GetTargetDirectory(this->GeneratorTarget),
+    this->GetGlobalGenerator()->ConfigDirectory(config), '/', bmiName);
+  return path;
+}
+
 std::string cmNinjaTargetGenerator::GetClangTidyReplacementsFilePath(
   std::string const& directory, cmSourceFile const& source,
   std::string const& config) const
@@ -1027,6 +1070,16 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatements(
     }
   }
 
+  {
+    std::vector<cmSourceFile const*> bmiOnlySources;
+    this->GeneratorTarget->GetCxxModuleSources(bmiOnlySources, config);
+
+    for (cmSourceFile const* sf : bmiOnlySources) {
+      this->WriteCxxModuleBmiBuildStatement(sf, config, fileConfig,
+                                            firstForConfig);
+    }
+  }
+
   for (auto const& langScanningFiles : this->Configs[config].ScanningInfo) {
     std::string const& language = langScanningFiles.first;
     std::vector<ScanningFiles> const& scanningFiles = langScanningFiles.second;
@@ -1149,22 +1202,22 @@ cmNinjaBuild GetScanBuildStatement(const std::string& ruleName,
   scanBuild.Variables["OBJ_FILE"] = objectFileName;
 
   // Tell dependency scanner where to store dyndep intermediate results.
-  std::string const& ddiFile = cmStrCat(objectFileName, ".ddi");
-  scanBuild.Variables["DYNDEP_INTERMEDIATE_FILE"] = ddiFile;
+  std::string ddiFileName = cmStrCat(objectFileName, ".ddi");
+  scanBuild.Variables["DYNDEP_INTERMEDIATE_FILE"] = ddiFileName;
 
   // Outputs of the scan/preprocessor build statement.
   if (compilePP) {
     scanBuild.Outputs.push_back(ppFileName);
-    scanBuild.ImplicitOuts.push_back(ddiFile);
+    scanBuild.ImplicitOuts.push_back(ddiFileName);
   } else {
-    scanBuild.Outputs.push_back(ddiFile);
+    scanBuild.Outputs.push_back(ddiFileName);
     scanBuild.Variables["PREPROCESSED_OUTPUT_FILE"] = ppFileName;
     if (!compilationPreprocesses) {
       // Compilation does not preprocess and we are not compiling an
       // already-preprocessed source.  Make compilation depend on the scan
       // results to honor implicit dependencies discovered during scanning
       // (such as Fortran INCLUDE directives).
-      objBuild.ImplicitDeps.emplace_back(ddiFile);
+      objBuild.ImplicitDeps.emplace_back(ddiFileName);
     }
   }
 
@@ -1214,7 +1267,8 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatement(
   cmNinjaBuild objBuild(this->LanguageCompilerRule(
     language, config, needDyndep ? WithScanning::Yes : WithScanning::No));
   cmNinjaVars& vars = objBuild.Variables;
-  vars["FLAGS"] = this->ComputeFlagsForObject(source, language, config);
+  vars["FLAGS"] =
+    this->ComputeFlagsForObject(source, language, config, objectFileName);
   vars["DEFINES"] = this->ComputeDefines(source, language, config);
   vars["INCLUDES"] = this->ComputeIncludes(source, language, config);
 
@@ -1545,6 +1599,155 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatement(
   }
 }
 
+void cmNinjaTargetGenerator::WriteCxxModuleBmiBuildStatement(
+  cmSourceFile const* source, const std::string& config,
+  const std::string& fileConfig, bool firstForConfig)
+{
+  std::string const language = source->GetLanguage();
+  if (language != "CXX"_s) {
+    this->GetMakefile()->IssueMessage(
+      MessageType::FATAL_ERROR,
+      cmStrCat("Source file '", source->GetFullPath(), "' of target '",
+               this->GetTargetName(), "' is a '", language,
+               "' source but must be 'CXX' in order to have a BMI build "
+               "statement generated."));
+    return;
+  }
+
+  std::string const sourceFilePath = this->GetCompiledSourceNinjaPath(source);
+  std::string const bmiDir = this->ConvertToNinjaPath(
+    cmStrCat(this->GeneratorTarget->GetSupportDirectory(),
+             this->GetGlobalGenerator()->ConfigDirectory(config)));
+  std::string const bmiFileName =
+    this->ConvertToNinjaPath(this->GetBmiFilePath(source, config));
+  std::string const bmiFileDir = cmSystemTools::GetFilenamePath(bmiFileName);
+
+  int const commandLineLengthLimit = this->ForceResponseFile() ? -1 : 0;
+
+  cmNinjaBuild bmiBuild(
+    this->LanguageCompilerRule(language, config, WithScanning::Yes));
+  cmNinjaVars& vars = bmiBuild.Variables;
+  vars["FLAGS"] =
+    this->ComputeFlagsForObject(source, language, config, bmiFileName);
+  vars["DEFINES"] = this->ComputeDefines(source, language, config);
+  vars["INCLUDES"] = this->ComputeIncludes(source, language, config);
+
+  if (this->GetMakefile()->GetSafeDefinition(
+        cmStrCat("CMAKE_", language, "_DEPFILE_FORMAT")) != "msvc"_s) {
+    bool replaceExt(false);
+    if (!language.empty()) {
+      std::string repVar =
+        cmStrCat("CMAKE_", language, "_DEPFILE_EXTENSION_REPLACE");
+      replaceExt = this->Makefile->IsOn(repVar);
+    }
+    if (!replaceExt) {
+      // use original code
+      vars["DEP_FILE"] = this->GetLocalGenerator()->ConvertToOutputFormat(
+        cmStrCat(bmiFileName, ".d"), cmOutputConverter::SHELL);
+    } else {
+      // Replace the original source file extension with the
+      // depend file extension.
+      std::string dependFileName = cmStrCat(
+        cmSystemTools::GetFilenameWithoutLastExtension(bmiFileName), ".d");
+      vars["DEP_FILE"] = this->GetLocalGenerator()->ConvertToOutputFormat(
+        cmStrCat(bmiFileDir, '/', dependFileName), cmOutputConverter::SHELL);
+    }
+  }
+
+  std::string d =
+    this->GeneratorTarget->GetClangTidyExportFixesDirectory(language);
+  if (!d.empty()) {
+    this->GlobalCommonGenerator->AddClangTidyExportFixesDir(d);
+    std::string fixesFile =
+      this->GetClangTidyReplacementsFilePath(d, *source, config);
+    this->GlobalCommonGenerator->AddClangTidyExportFixesFile(fixesFile);
+    cmSystemTools::MakeDirectory(cmSystemTools::GetFilenamePath(fixesFile));
+    fixesFile = this->ConvertToNinjaPath(fixesFile);
+    vars["CLANG_TIDY_EXPORT_FIXES"] = fixesFile;
+  }
+
+  if (firstForConfig) {
+    this->ExportObjectCompileCommand(
+      language, sourceFilePath, bmiDir, bmiFileName, bmiFileDir, vars["FLAGS"],
+      vars["DEFINES"], vars["INCLUDES"], config);
+  }
+
+  bmiBuild.Outputs.push_back(bmiFileName);
+  bmiBuild.ExplicitDeps.push_back(sourceFilePath);
+
+  std::vector<std::string> depList;
+
+  std::vector<std::string> architectures =
+    this->GeneratorTarget->GetAppleArchs(config, language);
+  if (architectures.empty()) {
+    architectures.emplace_back();
+  }
+
+  bmiBuild.OrderOnlyDeps.push_back(this->OrderDependsTargetForTarget(config));
+
+  // For some cases we scan to dynamically discover dependencies.
+  std::string modmapFormat;
+  if (true) {
+    std::string const modmapFormatVar =
+      cmStrCat("CMAKE_EXPERIMENTAL_", language, "_MODULE_MAP_FORMAT");
+    modmapFormat = this->Makefile->GetSafeDefinition(modmapFormatVar);
+  }
+
+  {
+    bool const compilePPWithDefines = this->CompileWithDefines(language);
+
+    std::string scanRuleName = this->LanguageScanRule(language, config);
+    std::string ppFileName = cmStrCat(bmiFileName, ".ddi.i");
+
+    cmNinjaBuild ppBuild = GetScanBuildStatement(
+      scanRuleName, ppFileName, false, compilePPWithDefines, true, bmiBuild,
+      vars, bmiFileName, this->LocalGenerator);
+
+    ScanningFiles scanningFiles;
+
+    if (firstForConfig) {
+      scanningFiles.ScanningOutput = cmStrCat(bmiFileName, ".ddi");
+    }
+
+    this->addPoolNinjaVariable("JOB_POOL_COMPILE", this->GetGeneratorTarget(),
+                               ppBuild.Variables);
+
+    this->GetGlobalGenerator()->WriteBuild(this->GetImplFileStream(fileConfig),
+                                           ppBuild, commandLineLengthLimit);
+
+    std::string const dyndep = this->GetDyndepFilePath(language, config);
+    bmiBuild.OrderOnlyDeps.push_back(dyndep);
+    vars["dyndep"] = dyndep;
+
+    if (!modmapFormat.empty()) {
+      std::string ddModmapFile = cmStrCat(bmiFileName, ".modmap");
+      vars["DYNDEP_MODULE_MAP_FILE"] = ddModmapFile;
+      scanningFiles.ModuleMapFile = std::move(ddModmapFile);
+    }
+
+    if (!scanningFiles.IsEmpty()) {
+      this->Configs[config].ScanningInfo[language].emplace_back(scanningFiles);
+    }
+  }
+
+  this->EnsureParentDirectoryExists(bmiFileName);
+
+  vars["OBJECT_DIR"] = this->GetLocalGenerator()->ConvertToOutputFormat(
+    bmiDir, cmOutputConverter::SHELL);
+  vars["OBJECT_FILE_DIR"] = this->GetLocalGenerator()->ConvertToOutputFormat(
+    bmiFileDir, cmOutputConverter::SHELL);
+
+  this->addPoolNinjaVariable("JOB_POOL_COMPILE", this->GetGeneratorTarget(),
+                             vars);
+
+  this->SetMsvcTargetPdbVariable(vars, config);
+
+  bmiBuild.RspFile = cmStrCat(bmiFileName, ".rsp");
+
+  this->GetGlobalGenerator()->WriteBuild(this->GetImplFileStream(fileConfig),
+                                         bmiBuild, commandLineLengthLimit);
+}
+
 void cmNinjaTargetGenerator::WriteTargetDependInfo(std::string const& lang,
                                                    const std::string& config)
 {
@@ -1605,6 +1808,9 @@ void cmNinjaTargetGenerator::WriteTargetDependInfo(std::string const& lang,
   cb.ObjectFilePath = [this](cmSourceFile const* sf, std::string const& cnf) {
     return this->GetObjectFilePath(sf, cnf);
   };
+  cb.BmiFilePath = [this](cmSourceFile const* sf, std::string const& cnf) {
+    return this->GetBmiFilePath(sf, cnf);
+  };
 
 #if !defined(CMAKE_BOOTSTRAP)
   cmDyndepCollation::AddCollationInformation(tdi, this->GeneratorTarget,
diff --git a/Source/cmNinjaTargetGenerator.h b/Source/cmNinjaTargetGenerator.h
index 8c38499..49e7018 100644
--- a/Source/cmNinjaTargetGenerator.h
+++ b/Source/cmNinjaTargetGenerator.h
@@ -15,6 +15,7 @@
 
 #include "cmCommonTargetGenerator.h"
 #include "cmGlobalNinjaGenerator.h"
+#include "cmImportedCxxModuleInfo.h"
 #include "cmNinjaTypes.h"
 #include "cmOSXBundleGenerator.h"
 
@@ -91,7 +92,8 @@ protected:
    */
   std::string ComputeFlagsForObject(cmSourceFile const* source,
                                     const std::string& language,
-                                    const std::string& config);
+                                    const std::string& config,
+                                    const std::string& objectFileName);
 
   void AddIncludeFlags(std::string& flags, std::string const& lang,
                        const std::string& config) override;
@@ -129,6 +131,8 @@ protected:
   /// @return the object file path for the given @a source.
   std::string GetObjectFilePath(cmSourceFile const* source,
                                 const std::string& config) const;
+  std::string GetBmiFilePath(cmSourceFile const* source,
+                             const std::string& config) const;
 
   /// @return the preprocessed source file path for the given @a source.
   std::string GetPreprocessedFilePath(cmSourceFile const* source,
@@ -163,6 +167,10 @@ protected:
   void WriteObjectBuildStatements(const std::string& config,
                                   const std::string& fileConfig,
                                   bool firstForConfig);
+  void WriteCxxModuleBmiBuildStatement(cmSourceFile const* source,
+                                       const std::string& config,
+                                       const std::string& fileConfig,
+                                       bool firstForConfig);
   void WriteObjectBuildStatement(cmSourceFile const* source,
                                  const std::string& config,
                                  const std::string& fileConfig,
@@ -239,6 +247,8 @@ private:
     cmNinjaDeps Objects;
     // Dyndep Support
     std::map<std::string, std::vector<ScanningFiles>> ScanningInfo;
+    // Imported C++ module info.
+    mutable ImportedCxxModuleLookup ImportedCxxModules;
     // Swift Support
     Json::Value SwiftOutputMap;
     std::vector<cmCustomCommand const*> CustomCommands;