Test3

lib/DependencyScan/ModuleDependencyScanner.cpp

@@ -620,6 +620,23 @@ ModuleDependencyScanner::getMainModuleDependencyInfo(ModuleDecl *mainModule) {
       break;
     }
 
+    if (ScanASTContext.LangOpts.EnableCXXInterop) {
+      StringRef mainModuleName = mainModule->getName().str();
+      if (mainModuleName != CXX_MODULE_NAME)
+        mainDependencies.addModuleImport(CXX_MODULE_NAME, /* isExported */ false,
+                                         AccessLevel::Public,
+                                         &alreadyAddedModules);
+      if (llvm::none_of(llvm::ArrayRef<StringRef>{CXX_MODULE_NAME,
+                            ScanASTContext.Id_CxxStdlib.str(), "std"},
+                        [mainModuleName](StringRef Name) {
+                          return mainModuleName == Name;
+                        }))
+          mainDependencies.addModuleImport(ScanASTContext.Id_CxxStdlib.str(),
+                                           /* isExported */ false,
+                                           AccessLevel::Public,
+                                           &alreadyAddedModules);
+    }
+
     // Add any implicit module names.
     for (const auto &import : importInfo.AdditionalUnloadedImports) {
       mainDependencies.addModuleImport(
@@ -1583,60 +1600,6 @@ void ModuleDependencyScanner::resolveSwiftOverlayDependenciesForModule(
   for (const auto &clangDep : visibleClangDependencies)
     recordResult(clangDep.getKey().str());
 
-  // C++ Interop requires additional handling
-  bool lookupCxxStdLibOverlay =
-      ScanCompilerInvocation.getLangOptions().EnableCXXInterop;
-  if (lookupCxxStdLibOverlay &&
-      moduleID.Kind == ModuleDependencyKind::SwiftInterface) {
-    const auto &moduleInfo = DependencyCache.findKnownDependency(moduleID);
-    const auto commandLine = moduleInfo.getCommandline();
-    // If the textual interface was built without C++ interop, do not query
-    // the C++ Standard Library Swift overlay for its compilation.
-    if (llvm::find(commandLine, "-formal-cxx-interoperability-mode=off") !=
-        commandLine.end())
-      lookupCxxStdLibOverlay = false;
-  } else if (lookupCxxStdLibOverlay &&
-             moduleID.Kind == ModuleDependencyKind::SwiftBinary) {
-    const auto &moduleDetails =
-      DependencyCache.findKnownDependency(moduleID).getAsSwiftBinaryModule();
-    // If the binary module was built without C++ interop, do not query
-    // the C++ Standard Library Swift overlay.
-    if (!moduleDetails->isBuiltWithCxxInterop)
-      lookupCxxStdLibOverlay = false;
-  }
-
-  // FIXME: We always declare the 'Darwin' module as formally having been built
-  // without C++Interop, for compatibility with prior versions. Once we are certain
-  // that we are only building against modules built with support of
-  // '-formal-cxx-interoperability-mode', this hard-coded check should be removed.
-  if (lookupCxxStdLibOverlay && moduleID.ModuleName == "Darwin")
-    lookupCxxStdLibOverlay = false;
-
-  if (lookupCxxStdLibOverlay) {
-    for (const auto &clangDepNameEntry : visibleClangDependencies) {
-      auto clangDepName = clangDepNameEntry.getKey().str();
-
-      // If this Clang module is a part of the C++ stdlib, and we haven't
-      // loaded the overlay for it so far, it is a split libc++ module (e.g.
-      // std_vector). Load the CxxStdlib overlay explicitly.
-      const auto &clangDepInfo =
-        DependencyCache.findDependency(clangDepName,
-                                       ModuleDependencyKind::Clang)
-              .value()
-              ->getAsClangModule();
-      if (importer::isCxxStdModule(clangDepName, clangDepInfo->IsSystem) &&
-          !swiftOverlayDependencies.contains(
-              {clangDepName, ModuleDependencyKind::SwiftInterface}) &&
-          !swiftOverlayDependencies.contains(
-              {clangDepName, ModuleDependencyKind::SwiftBinary})) {
-        scanForSwiftDependency(
-            getModuleImportIdentifier(ScanASTContext.Id_CxxStdlib.str()));
-        recordResult(ScanASTContext.Id_CxxStdlib.str().str());
-        break;
-      }
-    }
-  }
-
   // Resolve the dependency info with Swift overlay dependency module
   // information.
   DependencyCache.setSwiftOverlayDependencies(

test/ScanDependencies/win-explicit-cxx-interop-cxxstdlib.swift

@@ -0,0 +1,43 @@
+// REQUIRES: OS=windows-msvc
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+// RUN: %target-swift-frontend -scan-dependencies -module-name NoCpp \
+// RUN:   -module-cache-path %t/clang-module-cache -disable-objc-interop \
+// RUN:   -cxx-interoperability-mode=default \
+// RUN:   %t/NoCpp.swift -o %t/NoCpp-deps.json -I %t 2>&1
+// RUN: %target-swift-frontend -scan-dependencies -module-name Cpp \
+// RUN:   -module-cache-path %t/clang-module-cache -disable-objc-interop \
+// RUN:   -cxx-interoperability-mode=default \
+// RUN:   %t/Cpp.swift -o %t/Cpp-deps.json -I %t 2>&1
+// RUN: %target-swift-frontend -scan-dependencies -module-name Crt \
+// RUN:   -module-cache-path %t/clang-module-cache -disable-objc-interop \
+// RUN:   -cxx-interoperability-mode=default \
+// RUN:   %t/Crt.swift -o %t/Crt-deps.json -I %t 2>&1
+// RUN: %FileCheck %s --check-prefix=NOCPP < %t/NoCpp-deps.json
+// RUN: %FileCheck %s --check-prefix=CPP < %t/Cpp-deps.json
+// RUN: %FileCheck %s --check-prefix=CRT < %t/Crt-deps.json
+
+// NOCPP:      "mainModuleName": "NoCpp"
+// NOCPP:      "linkName": "swiftCxxStdlib",
+// NOCPP-NEXT: "isStatic": true,
+
+// CPP:        "mainModuleName": "Cpp"
+// CPP:        "linkName": "swiftCxxStdlib",
+// CPP-NEXT:   "isStatic": true,
+
+// CRT:        "mainModuleName": "Crt"
+// CRT:        "linkName": "swiftCxxStdlib",
+// CRT-NEXT:   "isStatic": true,
+
+//--- NoCpp.swift
+// Empty
+
+//--- Cpp.swift
+import CxxStdlib
+
+//--- Crt.swift
+import CRT
+
+
+