Index: include/clang/Tooling/Tooling.h
===================================================================
--- include/clang/Tooling/Tooling.h
+++ include/clang/Tooling/Tooling.h
@@ -339,6 +339,10 @@
 
   llvm::ArrayRef<std::string> getSourcePaths() const { return SourcePaths; }
 
+  vfs::OverlayFileSystem &getOverlayFileSystem() const {
+    return *OverlayFileSystem;
+  }
+
 private:
   const CompilationDatabase &Compilations;
   std::vector<std::string> SourcePaths;