[ADT] Change iterator_adaptor_base's default template arguments to forward more underlying typedefs

[timshen]

Added a test.

[timshen]

Make test compile :P.

[dblaikie]

unittests/Support/IteratorTest.cpp

101 ↗

(On Diff #66987)

This doesn't need to be in a test case, since none of it executes dynamically - probably just put it in a namespace (so it doesn't provide any names that might interfere with other tests)

103 ↗

(On Diff #66987)

Maybe worth introducing some arbitrary tag types (just random structs with helpful names like ValueType, PointerType, DifferenceType, ReferenceType) rather than using all ints - so it's clear the types aren't getting mismatched or anything?

[timshen]

Moved the compile-time test to the outer anonymous namespace.

llvm/trunk/include/llvm/ADT/iterator.h

 /// operator* implementation. Other methods can be overridden as well.
 template <
     typename DerivedT, typename WrappedIteratorT,
     typename IteratorCategoryT =
         typename std::iterator_traits<WrappedIteratorT>::iterator_category,
     typename T = typename std::iterator_traits<WrappedIteratorT>::value_type,
     typename DifferenceTypeT =
         typename std::iterator_traits<WrappedIteratorT>::difference_type,
-    typename PointerT = T *, typename ReferenceT = T &,
+    typename PointerT = typename std::conditional<
+        std::is_same<T, typename std::iterator_traits<
+                            WrappedIteratorT>::value_type>::value,
+        typename std::iterator_traits<WrappedIteratorT>::pointer, T *>::type,
+    typename ReferenceT = typename std::conditional<
+        std::is_same<T, typename std::iterator_traits<
+                            WrappedIteratorT>::value_type>::value,
+        typename std::iterator_traits<WrappedIteratorT>::reference, T &>::type,
     // Don't provide these, they are mostly to act as aliases below.
     typename WrappedTraitsT = std::iterator_traits<WrappedIteratorT>>
 class iterator_adaptor_base
     : public iterator_facade_base<DerivedT, IteratorCategoryT, T,
                                   DifferenceTypeT, PointerT, ReferenceT> {
   typedef typename iterator_adaptor_base::iterator_facade_base BaseT;
 
 protected:

llvm/trunk/unittests/Support/IteratorTest.cpp

 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
 
 namespace {
 
+template <int> struct Shadow;
+
+struct WeirdIter : std::iterator<std::input_iterator_tag, Shadow<0>, Shadow<1>,
+                                 Shadow<2>, Shadow<3>> {};
+
+struct AdaptedIter : iterator_adaptor_base<AdaptedIter, WeirdIter> {};
+
+// Test that iterator_adaptor_base forwards typedefs, if value_type is
+// unchanged.
+static_assert(std::is_same<typename AdaptedIter::value_type, Shadow<0>>::value,
+              "");
+static_assert(
+    std::is_same<typename AdaptedIter::difference_type, Shadow<1>>::value, "");
+static_assert(std::is_same<typename AdaptedIter::pointer, Shadow<2>>::value,
+              "");
+static_assert(std::is_same<typename AdaptedIter::reference, Shadow<3>>::value,
+              "");
+
 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]);