Index: llvm/include/llvm/ADT/STLExtras.h
===================================================================
--- llvm/include/llvm/ADT/STLExtras.h
+++ llvm/include/llvm/ADT/STLExtras.h
@@ -285,12 +285,20 @@
 
 template <typename ItTy, typename FuncTy,
           typename FuncReturnTy =
-            decltype(std::declval<FuncTy>()(*std::declval<ItTy>()))>
+              decltype(std::declval<FuncTy>()(*std::declval<ItTy>()))>
 class mapped_iterator
     : public iterator_adaptor_base<
-             mapped_iterator<ItTy, FuncTy>, ItTy,
-             typename std::iterator_traits<ItTy>::iterator_category,
-             typename std::remove_reference<FuncReturnTy>::type> {
+          mapped_iterator<ItTy, FuncTy>, ItTy,
+          typename std::iterator_traits<ItTy>::iterator_category,
+          typename std::remove_reference<FuncReturnTy>::type,
+          typename std::iterator_traits<ItTy>::difference_type,
+          std::conditional_t<
+              std::is_same<
+                  typename std::remove_reference<FuncReturnTy>::type,
+                  typename std::iterator_traits<ItTy>::value_type>::value,
+              typename std::iterator_traits<ItTy>::pointer,
+              typename std::remove_reference<FuncReturnTy>::type *>,
+          FuncReturnTy> {
 public:
   mapped_iterator(ItTy U, FuncTy F)
     : mapped_iterator::iterator_adaptor_base(std::move(U)), F(std::move(F)) {}