Index: llvm/include/llvm/ADT/STLExtras.h
===================================================================
--- llvm/include/llvm/ADT/STLExtras.h
+++ llvm/include/llvm/ADT/STLExtras.h
@@ -1167,15 +1167,10 @@
   C.clear();
 }
 
-/// Get the size of a range. This is a wrapper function around std::distance
-/// which is only enabled when the operation is O(1).
+/// Provide wrappers to std::distance which take ranges instead of having to
+/// pass begin/end explicitly.
 template <typename R>
-auto size(R &&Range, typename std::enable_if<
-                         std::is_same<typename std::iterator_traits<decltype(
-                                          Range.begin())>::iterator_category,
-                                      std::random_access_iterator_tag>::value,
-                         void>::type * = nullptr)
-    -> decltype(std::distance(Range.begin(), Range.end())) {
+auto size(R &&Range) -> decltype(std::distance(Range.begin(), Range.end())) {
   return std::distance(Range.begin(), Range.end());
 }