Fix an assert failure for CAS with include tree and vfs overlay

clang/test/ClangScanDeps/include-tree-vfs-overlay.c

@@ -0,0 +1,37 @@
+// REQUIRES: ondisk_cas
+
+// This is a reduced test for https://github.com/swiftlang/llvm-project/issues/11616
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s|DIR|%/t|g" %t/vfs-overlay.yaml.template > %t/vfs-overlay.yaml
+
+// RUN: %clang -I%t -fdepscan=inline -fdepscan-include-tree -Xclang -fcas-path -Xclang %t/cas -Xclang -ivfsoverlay -Xclang %t/vfs-overlay.yaml -c %t/test.c
+
+//--- test.c
+#include "header.h"
+#include "header1.h"
+
+//--- header.h
+
+//--- header2.h
+
+//--- header3.h
+
+//--- vfs-overlay.yaml.template
+version: 0
+case-sensitive: false
+roots:
+  - name: "DIR"
+    type: directory
+    contents:
+      - name: header.h
+        type: file
+        external-contents: "DIR/header.h"
+      - name: header1.h
+        type: file
+        external-contents: "DIR/header2.h"
+      - name: header2.h
+        type: file
+        external-contents: "DIR/header3.h"
+

llvm/lib/Support/VirtualFileSystem.cpp

@@ -2551,6 +2551,11 @@ class FileWithFixedStatus : public File {
   std::error_code close() override { return InnerFile->close(); }
 
   void setPath(const Twine &Path) override { S = S.copyWithNewName(S, Path); }
+
+  llvm::ErrorOr<std::optional<cas::ObjectRef>> getObjectRefForContent()
+      override {
+    return InnerFile->getObjectRefForContent();
+  }
 };
 
 } // namespace