From: Nicholas Allegra <comexk@gmail.com>
Date: Fri, 27 Sep 2019 01:58:31 +0000 (+0000)
Subject: Revert r373034
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1d5182274429c53acc876d113659274ba6993da1;p=llvm

Revert r373034

It breaks the build on MSVC.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@373039 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/ADT/STLExtras.h b/include/llvm/ADT/STLExtras.h
index 430707cbd79..274933bc520 100644
--- a/include/llvm/ADT/STLExtras.h
+++ b/include/llvm/ADT/STLExtras.h
@@ -1573,14 +1573,6 @@ template <class Ptr> auto to_address(const Ptr &P) -> decltype(P.operator->()) {
 }
 template <class T> constexpr T *to_address(T *P) { return P; }
 
-template <typename R>
-auto index(R &&TheRange,
-  typename std::iterator_traits<detail::IterOfRange<R>>::difference_type N)
-  -> decltype(TheRange.begin()[N]) {
-  assert(N < TheRange.end() - TheRange.begin() && "Index out of range!");
-  return TheRange.begin()[N];
-}
-
 } // end namespace llvm
 
 #endif // LLVM_ADT_STLEXTRAS_H
diff --git a/include/llvm/ADT/iterator_range.h b/include/llvm/ADT/iterator_range.h
index 3bb9231441c..774c7c4e336 100644
--- a/include/llvm/ADT/iterator_range.h
+++ b/include/llvm/ADT/iterator_range.h
@@ -20,17 +20,9 @@
 
 #include <iterator>
 #include <utility>
-#include <cassert>
 
 namespace llvm {
 
-template <typename T>
-constexpr bool is_random_iterator() {
-  return std::is_same<
-    typename std::iterator_traits<T>::iterator_category,
-    std::random_access_iterator_tag>::value;
-}
-
 /// A range adaptor for a pair of iterators.
 ///
 /// This just wraps two iterators into a range-compatible interface. Nothing
@@ -66,31 +58,11 @@ template <typename T> iterator_range<T> make_range(std::pair<T, T> p) {
   return iterator_range<T>(std::move(p.first), std::move(p.second));
 }
 
-/// Non-random-iterator version
 template <typename T>
-auto drop_begin(T &&t, int n) ->
-  typename std::enable_if<!is_random_iterator<decltype(adl_begin(t))>(),
-  iterator_range<decltype(adl_begin(t))>>::type {
-  auto begin = adl_begin(t);
-  auto end = adl_end(t);
-  for (int i = 0; i < n; i++) {
-    assert(begin != end);
-    ++begin;
-  }
-  return make_range(begin, end);
+iterator_range<decltype(adl_begin(std::declval<T>()))> drop_begin(T &&t,
+                                                                  int n) {
+  return make_range(std::next(adl_begin(t), n), adl_end(t));
 }
-
-/// Optimized version for random iterators
-template <typename T>
-auto drop_begin(T &&t, int n) ->
-  typename std::enable_if<is_random_iterator<decltype(adl_begin(t))>(),
-  iterator_range<decltype(adl_begin(t))>>::type {
-  auto begin = adl_begin(t);
-  auto end = adl_end(t);
-  assert(end - begin >= n && "Dropping more elements than exist!");
-  return make_range(std::next(begin, n), end);
-}
-
 }
 
 #endif