[ADT] Add make_pointe{e,r}_iterator.

[jlebar]

https://github.com/llvm-mirror/llvm/commit/a5afae3a31db2f68e692e2f199da962f9e3ceb04

Then rolled back because this was crashing MSVC. :(

llvm/include/llvm/ADT/iterator.h

struct pointee_iterator
   pointee_iterator() = default;
   template <typename U>
   pointee_iterator(U &&u)
       : pointee_iterator::iterator_adaptor_base(std::forward<U &&>(u)) {}
 
   T &operator*() const { return **this->I; }
 };
 
+template <typename WrappedIteratorT>
+pointee_iterator<WrappedIteratorT> make_pointee_iterator(WrappedIteratorT &&I) {
+  return pointee_iterator<WrappedIteratorT>(std::forward<WrappedIteratorT>(I));
+}
+
 template <typename WrappedIteratorT,
           typename T = decltype(&*std::declval<WrappedIteratorT>())>
 class pointer_iterator
     : public iterator_adaptor_base<pointer_iterator<WrappedIteratorT>,
                                    WrappedIteratorT, T> {
   mutable T Ptr;
 
 public:
   pointer_iterator() {}
 
   explicit pointer_iterator(WrappedIteratorT u)
       : pointer_iterator::iterator_adaptor_base(std::move(u)) {}
 
   T &operator*() { return Ptr = &*this->I; }
   const T &operator*() const { return Ptr = &*this->I; }
 };
 
+template <typename WrappedIteratorT>
+pointer_iterator<WrappedIteratorT> make_pointer_iterator(WrappedIteratorT &&I) {
+  return pointer_iterator<WrappedIteratorT>(std::forward<WrappedIteratorT>(I));
 }
 
+} // namespace llvm
+
 #endif

llvm/unittests/ADT/IteratorTest.cpp

 TEST(PointeeIteratorTest, Basic) {
   int arr[4] = { 1, 2, 3, 4 };
   SmallVector<int *, 4> V;
   V.push_back(&arr[0]);
   V.push_back(&arr[1]);
   V.push_back(&arr[2]);
   V.push_back(&arr[3]);
 
-  typedef pointee_iterator<SmallVectorImpl<int *>::const_iterator> test_iterator;
-
-  test_iterator Begin, End;
-  Begin = V.begin();
-  End = test_iterator(V.end());
+  auto Begin = make_pointee_iterator(V.begin());
+  auto End = make_pointee_iterator(V.end());
+  static_assert(
+      std::is_same<decltype(Begin),
+                   pointee_iterator<SmallVectorImpl<int *>::iterator>>::value,
+      "Wrong type returned by make_pointee_iterator");
 
-  test_iterator I = Begin;
+  auto I = Begin;
   for (int i = 0; i < 4; ++i) {
     EXPECT_EQ(*V[i], *I);
 
     EXPECT_EQ(I, Begin + i);
     EXPECT_EQ(I, std::next(Begin, i));
-    test_iterator J = Begin;
+    auto J = Begin;
     J += i;
     EXPECT_EQ(I, J);
     EXPECT_EQ(*V[i], Begin[i]);
 
     EXPECT_NE(I, End);
     EXPECT_GT(End, I);
     EXPECT_LT(I, End);
     EXPECT_GE(I, Begin);
     EXPECT_LE(Begin, I);
 
     EXPECT_EQ(i, I - Begin);
     EXPECT_EQ(i, std::distance(Begin, I));
     EXPECT_EQ(Begin, I - i);
 
-    test_iterator K = I++;
+    auto K = I++;
     EXPECT_EQ(K, std::prev(I));
   }
   EXPECT_EQ(End, I);
 }
 
 TEST(PointeeIteratorTest, SmartPointer) {
   SmallVector<std::unique_ptr<int>, 4> V;
   V.push_back(make_unique<int>(1));
   V.push_back(make_unique<int>(2));
   V.push_back(make_unique<int>(3));
   V.push_back(make_unique<int>(4));
 
-  typedef pointee_iterator<
-      SmallVectorImpl<std::unique_ptr<int>>::const_iterator> test_iterator;
-
-  test_iterator Begin, End;
-  Begin = V.begin();
-  End = test_iterator(V.end());
+  auto Begin = make_pointee_iterator(V.begin());
+  auto End = make_pointee_iterator(V.end());
+  static_assert(
+      std::is_same<decltype(Begin),
+                   pointee_iterator<
+                       SmallVectorImpl<std::unique_ptr<int>>::iterator>>::value,
+      "Wrong type returned by make_pointee_iterator");
 
-  test_iterator I = Begin;
+  auto I = Begin;
   for (int i = 0; i < 4; ++i) {
     EXPECT_EQ(*V[i], *I);
 
     EXPECT_EQ(I, Begin + i);
     EXPECT_EQ(I, std::next(Begin, i));
-    test_iterator J = Begin;
+    auto J = Begin;
     J += i;
     EXPECT_EQ(I, J);
     EXPECT_EQ(*V[i], Begin[i]);
 
     EXPECT_NE(I, End);
     EXPECT_GT(End, I);
     EXPECT_LT(I, End);
     EXPECT_GE(I, Begin);
     EXPECT_LE(Begin, I);
 
     EXPECT_EQ(i, I - Begin);
     EXPECT_EQ(i, std::distance(Begin, I));
     EXPECT_EQ(Begin, I - i);
 
-    test_iterator K = I++;
+    auto K = I++;
     EXPECT_EQ(K, std::prev(I));
   }
   EXPECT_EQ(End, I);
 }
 
 TEST(FilterIteratorTest, Lambda) {
   auto IsOdd = [](int N) { return N % 2 == 1; };
   int A[] = {0, 1, 2, 3, 4, 5, 6};
auto Range = make_filter_range(
       make_range(InputIterator(std::begin(A)), InputIterator(std::end(A))),
       IsOdd);
   SmallVector<int, 3> Actual(Range.begin(), Range.end());
   EXPECT_EQ((SmallVector<int, 3>{1, 3, 5}), Actual);
 }
 
 TEST(PointerIterator, Basic) {
   int A[] = {1, 2, 3, 4};
-  pointer_iterator<int *> Begin(std::begin(A)), End(std::end(A));
+  auto Begin = make_pointer_iterator(std::begin(A));
+  auto End = make_pointer_iterator(std::end(A));
+  static_assert(std::is_same<decltype(Begin), pointer_iterator<int *>>::value,
+                "Wrong type returned by make_pointer_iterator");
   EXPECT_EQ(A, *Begin);
   ++Begin;
   EXPECT_EQ(A + 1, *Begin);
   ++Begin;
   EXPECT_EQ(A + 2, *Begin);
   ++Begin;
   EXPECT_EQ(A + 3, *Begin);
   ++Begin;
   EXPECT_EQ(Begin, End);
 }
 
 TEST(PointerIterator, Const) {
   int A[] = {1, 2, 3, 4};
-  const pointer_iterator<int *> Begin(std::begin(A));
+  auto Begin = make_pointer_iterator(std::begin(A));
   EXPECT_EQ(A, *Begin);
   EXPECT_EQ(A + 1, std::next(*Begin, 1));
   EXPECT_EQ(A + 2, std::next(*Begin, 2));
   EXPECT_EQ(A + 3, std::next(*Begin, 3));
   EXPECT_EQ(A + 4, std::next(*Begin, 4));
 }
 
 } // anonymous namespace