1 files changed, 18 insertions, 2 deletions
diff --git a/llvm/include/llvm/ADT/iterator.h b/llvm/include/llvm/ADT/iterator.h
index c3079289270..2898a677db3 100644
--- a/llvm/include/llvm/ADT/iterator.h
+++ b/llvm/include/llvm/ADT/iterator.h
@@ -46,6 +46,22 @@ protected:
         std::is_base_of<std::bidirectional_iterator_tag, IteratorCategoryT>::value,
   };
 
+  /// A proxy object for computing a reference via indirecting a copy of an
+  /// iterator. This is used in APIs which need to produce a reference via
+  /// indirection but for which the iterator object might be a temporary. The
+  /// proxy preserves the iterator internally and exposes the indirected
+  /// reference via a conversion operator.
+  class ReferenceProxy {
+    friend iterator_facade_base;
+
+    DerivedT I;
+
+    ReferenceProxy(DerivedT I) : I(std::move(I)) {}
+
+  public:
+    operator ReferenceT() const { return *I; }
+  };
+
 public:
   DerivedT operator+(DifferenceTypeT n) const {
     static_assert(
@@ -120,10 +136,10 @@ public:
   PointerT operator->() const {
     return &static_cast<const DerivedT *>(this)->operator*();
   }
-  ReferenceT operator[](DifferenceTypeT n) const {
+  ReferenceProxy operator[](DifferenceTypeT n) const {
     static_assert(IsRandomAccess,
                   "Subscripting is only defined for random access iterators.");
-    return *static_cast<const DerivedT *>(this)->operator+(n);
+    return ReferenceProxy(static_cast<const DerivedT *>(this)->operator+(n));
   }
 };