Merge remote-tracking branch 'origin/main' into rebranch

include/swift/AST/ModuleDependencies.h

@@ -1097,13 +1097,8 @@ public:
     return SwiftDependencyTracker(CAS, Mapper.get(), CI);
   }
 
-  llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> getClangScanningFS() const {
-    if (CAS)
-      return llvm::cas::createCASProvidingFileSystem(
-          CAS, llvm::vfs::createPhysicalFileSystem());
-
-    return llvm::vfs::createPhysicalFileSystem();
-  }
+  llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>
+  getClangScanningFS(ASTContext &ctx) const;
 
   bool hasPathMapping() const {
     return Mapper && !Mapper->getMappings().empty();

include/swift/ClangImporter/ClangImporter.h

@@ -873,10 +873,19 @@ struct ClangInvocationFileMapping {
 /// `suppressDiagnostic` prevents us from emitting warning messages when we
 /// are unable to find headers.
 ClangInvocationFileMapping getClangInvocationFileMapping(
-    ASTContext &ctx,
+    const ASTContext &ctx,
     llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> vfs = nullptr,
     bool suppressDiagnostic = false);
 
+/// Apply the given file mapping to the specified 'fileSystem', used
+/// primarily to inject modulemaps on platforms with non-modularized
+/// platform libraries.
+ClangInvocationFileMapping applyClangInvocationMapping(
+    const ASTContext &ctx,
+    llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> baseVFS,
+    llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> &fileSystem,
+    bool suppressDiagnostics = false);
+
 /// Information used to compute the access level of inherited C++ members.
 class ClangInheritanceInfo {
   /// The cumulative inheritance access specifier, that is used to compute the