diff --git a/llvm/include/llvm/Support/CachePruning.h b/llvm/include/llvm/Support/CachePruning.h
--- a/llvm/include/llvm/Support/CachePruning.h
+++ b/llvm/include/llvm/Support/CachePruning.h
@@ -19,7 +19,10 @@
 
 namespace llvm {
 
+// Ignore forward declaration to not confuse Doxygen output.
+/// @cond
 template <typename T> class Expected;
+/// @endcond
 
 /// Policy for the pruneCache() function. A default constructed
 /// CachePruningPolicy provides a reasonable default policy.