cmExperimental: remove the flag for C++ modules

All the major compilers now have scheduled releases with support for
scanning, so remove the experimental gate.

Fixes: #18355

8 files changed, 30 insertions, 90 deletions

diff --git a/Source/cmCoreTryCompile.cxx b/Source/cmCoreTryCompile.cxx
index ee40bd5..6ca0e14 100644
--- a/Source/cmCoreTryCompile.cxx
+++ b/Source/cmCoreTryCompile.cxx
@@ -235,25 +235,16 @@ ArgumentParser::Continue cmCoreTryCompile::Arguments::SetSourceType(
     this->SourceTypeContext = SourceType::Normal;
     matched = true;
   } else if (sourceType == "CXX_MODULE"_s) {
-    bool const supportCxxModuleSources = cmExperimental::HasSupportEnabled(
-      *this->Makefile, cmExperimental::Feature::CxxModuleCMakeApi);
-    if (supportCxxModuleSources) {
-      this->SourceTypeContext = SourceType::CxxModule;
-      matched = true;
-    }
+    this->SourceTypeContext = SourceType::CxxModule;
+    matched = true;
   }
 
   if (!matched && this->SourceTypeError.empty()) {
-    bool const supportCxxModuleSources = cmExperimental::HasSupportEnabled(
-      *this->Makefile, cmExperimental::Feature::CxxModuleCMakeApi);
-    auto const* message = "'SOURCE'";
-    if (supportCxxModuleSources) {
-      message = "one of 'SOURCE' or 'CXX_MODULE'";
-    }
     // Only remember one error at a time; all other errors related to argument
     // parsing are "indicate one error and return" anyways.
     this->SourceTypeError =
-      cmStrCat("Invalid 'SOURCE_TYPE' '", sourceType, "'; must be ", message);
+      cmStrCat("Invalid 'SOURCE_TYPE' '", sourceType,
+               "'; must be one of 'SOURCE' or 'CXX_MODULE'");
   }
   return ArgumentParser::Continue::Yes;
 }
diff --git a/Source/cmExperimental.cxx b/Source/cmExperimental.cxx
index 104ab81..d75879f 100644
--- a/Source/cmExperimental.cxx
+++ b/Source/cmExperimental.cxx
@@ -19,17 +19,6 @@ namespace {
  * up-to-date.
  */
 cmExperimental::FeatureData LookupTable[] = {
-  // CxxModuleCMakeApi
-  { "CxxModuleCMakeApi",
-    "ac01f462-0f5f-432a-86aa-acef252918a6",
-    "CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API",
-    "CMake's C++ module support is experimental. It is meant only for "
-    "experimentation and feedback to CMake developers.",
-    { "CMAKE_EXPERIMENTAL_CXX_SCANDEP_SOURCE",
-      "CMAKE_EXPERIMENTAL_CXX_MODULE_MAP_FORMAT",
-      "CMAKE_EXPERIMENTAL_CXX_MODULE_MAP_FLAG" },
-    cmExperimental::TryCompileCondition::SkipCompilerChecks,
-    false },
   // WindowsKernelModeDriver
   { "WindowsKernelModeDriver",
     "5c2d848d-4efa-4529-a768-efd57171bf68",
diff --git a/Source/cmExperimental.h b/Source/cmExperimental.h
index c958ab6..e4c1448 100644
--- a/Source/cmExperimental.h
+++ b/Source/cmExperimental.h
@@ -15,7 +15,6 @@ class cmExperimental
 public:
   enum class Feature
   {
-    CxxModuleCMakeApi,
     WindowsKernelModeDriver,
 
     Sentinel,
diff --git a/Source/cmExportCommand.cxx b/Source/cmExportCommand.cxx
index 273296d..e78b869 100644
--- a/Source/cmExportCommand.cxx
+++ b/Source/cmExportCommand.cxx
@@ -16,7 +16,6 @@
 #include "cmArgumentParserTypes.h"
 #include "cmCryptoHash.h"
 #include "cmExecutionStatus.h"
-#include "cmExperimental.h"
 #include "cmExportBuildAndroidMKGenerator.h"
 #include "cmExportBuildFileGenerator.h"
 #include "cmExportSet.h"
@@ -69,15 +68,11 @@ bool cmExportCommand(std::vector<std::string> const& args,
     bool ExportOld = false;
   };
 
-  auto parser = cmArgumentParser<Arguments>{}
-                  .Bind("NAMESPACE"_s, &Arguments::Namespace)
-                  .Bind("FILE"_s, &Arguments::Filename);
-
-  bool const supportCxx20FileSetTypes = cmExperimental::HasSupportEnabled(
-    status.GetMakefile(), cmExperimental::Feature::CxxModuleCMakeApi);
-  if (supportCxx20FileSetTypes) {
-    parser.Bind("CXX_MODULES_DIRECTORY"_s, &Arguments::CxxModulesDirectory);
-  }
+  auto parser =
+    cmArgumentParser<Arguments>{}
+      .Bind("NAMESPACE"_s, &Arguments::Namespace)
+      .Bind("FILE"_s, &Arguments::Filename)
+      .Bind("CXX_MODULES_DIRECTORY"_s, &Arguments::CxxModulesDirectory);
 
   if (args[0] == "EXPORT") {
     parser.Bind("EXPORT"_s, &Arguments::ExportSetName);
diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 04d7bb1..bbb47e4 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -31,7 +31,6 @@
 #include "cmCustomCommandGenerator.h"
 #include "cmCxxModuleUsageEffects.h"
 #include "cmEvaluatedTargetProperty.h"
-#include "cmExperimental.h"
 #include "cmFileSet.h"
 #include "cmFileTimes.h"
 #include "cmGeneratedFileStream.h"
@@ -9106,9 +9105,10 @@ cmGeneratorTarget::Cxx20SupportLevel cmGeneratorTarget::HaveCxxModuleSupport(
   // Else, an empty CMAKE_CXX_STANDARD_DEFAULT means CMake does not detect and
   // set a default standard level for this compiler, so assume all standards
   // are available.
-  if (!cmExperimental::HasSupportEnabled(
-        *this->Makefile, cmExperimental::Feature::CxxModuleCMakeApi)) {
-    return Cxx20SupportLevel::MissingExperimentalFlag;
+  cmValue scandepRule =
+    this->Target->GetMakefile()->GetDefinition("CMAKE_CXX_SCANDEP_SOURCE");
+  if (!scandepRule) {
+    return Cxx20SupportLevel::MissingRule;
   }
   return Cxx20SupportLevel::Supported;
 }
@@ -9125,13 +9125,6 @@ void cmGeneratorTarget::CheckCxxModuleStatus(std::string const& config) const
                    "\" has C++ sources that export modules but the \"CXX\" "
                    "language has not been enabled"));
         break;
-      case cmGeneratorTarget::Cxx20SupportLevel::MissingExperimentalFlag:
-        this->Makefile->IssueMessage(
-          MessageType::FATAL_ERROR,
-          cmStrCat("The target named \"", this->GetName(),
-                   "\" has C++ sources that export modules but its "
-                   "experimental support has not been requested"));
-        break;
       case cmGeneratorTarget::Cxx20SupportLevel::NoCxx20: {
         cmStandardLevelResolver standardResolver(this->Makefile);
         auto effStandard =
@@ -9149,6 +9142,7 @@ void cmGeneratorTarget::CheckCxxModuleStatus(std::string const& config) const
             "\"cxx_std_20\" (or newer) among its `target_compile_features`",
             effStandard));
       } break;
+      case cmGeneratorTarget::Cxx20SupportLevel::MissingRule:
       case cmGeneratorTarget::Cxx20SupportLevel::Supported:
         // All is well.
         break;
diff --git a/Source/cmGeneratorTarget.h b/Source/cmGeneratorTarget.h
index 751f907..72920d6 100644
--- a/Source/cmGeneratorTarget.h
+++ b/Source/cmGeneratorTarget.h
@@ -1288,10 +1288,10 @@ public:
   {
     // C++ is not available.
     MissingCxx,
-    // The experimental feature is not available.
-    MissingExperimentalFlag,
     // The target does not require at least C++20.
     NoCxx20,
+    // C++20 module scanning rules are not present.
+    MissingRule,
     // C++20 modules are available and working.
     Supported,
   };
diff --git a/Source/cmInstallCommand.cxx b/Source/cmInstallCommand.cxx
index 1b47ec4..0fc4011 100644
--- a/Source/cmInstallCommand.cxx
+++ b/Source/cmInstallCommand.cxx
@@ -21,7 +21,6 @@
 #include "cmArgumentParser.h"
 #include "cmArgumentParserTypes.h"
 #include "cmExecutionStatus.h"
-#include "cmExperimental.h"
 #include "cmExportSet.h"
 #include "cmFileSet.h"
 #include "cmGeneratorExpression.h"
@@ -491,6 +490,7 @@ bool HandleTargetsMode(std::vector<std::string> const& args,
   publicHeaderArgs.Parse(argVectors.PublicHeader, &unknownArgs);
   resourceArgs.Parse(argVectors.Resource, &unknownArgs);
   includesArgs.Parse(&argVectors.Includes, &unknownArgs);
+  cxxModuleBmiArgs.Parse(argVectors.CxxModulesBmi, &unknownArgs);
   for (std::size_t i = 0; i < argVectors.FileSets.size(); i++) {
     // We have to create a separate object for the parsing because
     // cmArgumentParser<void>::Bind() binds to a specific address, but the
@@ -501,15 +501,6 @@ bool HandleTargetsMode(std::vector<std::string> const& args,
     fileSetArgs[i] = std::move(fileSetArg);
   }
 
-  bool const supportCxx20FileSetTypes = cmExperimental::HasSupportEnabled(
-    *helper.Makefile, cmExperimental::Feature::CxxModuleCMakeApi);
-  if (!supportCxx20FileSetTypes) {
-    std::copy(argVectors.CxxModulesBmi.begin(), argVectors.CxxModulesBmi.end(),
-              std::back_inserter(unknownArgs));
-  } else {
-    cxxModuleBmiArgs.Parse(argVectors.CxxModulesBmi, &unknownArgs);
-  }
-
   if (!unknownArgs.empty()) {
     // Unknown argument.
     status.SetError(
@@ -541,12 +532,10 @@ bool HandleTargetsMode(std::vector<std::string> const& args,
   success = success && privateHeaderArgs.Finalize();
   success = success && publicHeaderArgs.Finalize();
   success = success && resourceArgs.Finalize();
+  success = success && cxxModuleBmiArgs.Finalize();
   for (auto& fileSetArg : fileSetArgs) {
     success = success && fileSetArg.Finalize();
   }
-  if (supportCxx20FileSetTypes) {
-    success = success && cxxModuleBmiArgs.Finalize();
-  }
 
   if (!success) {
     return false;
@@ -1173,8 +1162,7 @@ bool HandleTargetsMode(std::vector<std::string> const& args,
       }
     }
 
-    if (supportCxx20FileSetTypes &&
-        !cxxModuleBmiArgs.GetDestination().empty()) {
+    if (!cxxModuleBmiArgs.GetDestination().empty()) {
       cxxModuleBmiGenerator = cm::make_unique<cmInstallCxxModuleBmiGenerator>(
         target.GetName(),
         helper.GetCxxModulesBmiDestination(&cxxModuleBmiArgs),
@@ -2071,12 +2059,7 @@ bool HandleExportMode(std::vector<std::string> const& args,
   ica.Bind("NAMESPACE"_s, name_space);
   ica.Bind("EXPORT_LINK_INTERFACE_LIBRARIES"_s, exportOld);
   ica.Bind("FILE"_s, filename);
-
-  bool const supportCxx20FileSetTypes = cmExperimental::HasSupportEnabled(
-    *helper.Makefile, cmExperimental::Feature::CxxModuleCMakeApi);
-  if (supportCxx20FileSetTypes) {
-    ica.Bind("CXX_MODULES_DIRECTORY"_s, cxx_modules_directory);
-  }
+  ica.Bind("CXX_MODULES_DIRECTORY"_s, cxx_modules_directory);
 
   std::vector<std::string> unknownArgs;
   ica.Parse(args, &unknownArgs);
diff --git a/Source/cmTargetSourcesCommand.cxx b/Source/cmTargetSourcesCommand.cxx
index 3d484f5..babbaa5 100644
--- a/Source/cmTargetSourcesCommand.cxx
+++ b/Source/cmTargetSourcesCommand.cxx
@@ -10,7 +10,6 @@
 
 #include "cmArgumentParser.h"
 #include "cmArgumentParserTypes.h"
-#include "cmExperimental.h"
 #include "cmFileSet.h"
 #include "cmGeneratorExpression.h"
 #include "cmList.h"
@@ -260,28 +259,18 @@ bool TargetSourcesImpl::HandleOneFileSet(
       this->SetError("Must specify a TYPE when creating file set");
       return false;
     }
-    bool const supportCxx20FileSetTypes = cmExperimental::HasSupportEnabled(
-      *this->Makefile, cmExperimental::Feature::CxxModuleCMakeApi);
+    if (type != "HEADERS"_s && type != "CXX_MODULES"_s) {
+      this->SetError(
+        R"(File set TYPE may only be "HEADERS" or "CXX_MODULES")");
+      return false;
+    }
 
-    if (supportCxx20FileSetTypes) {
-      if (type != "HEADERS"_s && type != "CXX_MODULES"_s) {
+    if (cmFileSetVisibilityIsForInterface(visibility) &&
+        !cmFileSetVisibilityIsForSelf(visibility) &&
+        !this->Target->IsImported()) {
+      if (type == "CXX_MODULES"_s) {
         this->SetError(
-          R"(File set TYPE may only be "HEADERS" or "CXX_MODULES")");
-        return false;
-      }
-
-      if (cmFileSetVisibilityIsForInterface(visibility) &&
-          !cmFileSetVisibilityIsForSelf(visibility) &&
-          !this->Target->IsImported()) {
-        if (type == "CXX_MODULES"_s) {
-          this->SetError(
-            R"(File set TYPE "CXX_MODULES" may not have "INTERFACE" visibility)");
-          return false;
-        }
-      }
-    } else {
-      if (type != "HEADERS"_s) {
-        this->SetError("File set TYPE may only be \"HEADERS\"");
+          R"(File set TYPE "CXX_MODULES" may not have "INTERFACE" visibility)");
         return false;
       }
     }