Fix FixedArray iterator constructor, which should require
input_iterator, not forward_iterator

PiperOrigin-RevId: 850356318
Change-Id: If728cc6f4c0eedd4729b73860df8498f4fe6a139

absl/container/fixed_array.h

diff --git a/absl/container/fixed_array.h b/absl/container/fixed_array.h
index b08735f..d47b0e4 100644
--- a/absl/container/fixed_array.h
+++ b/absl/container/fixed_array.h
@@ -84,11 +84,9 @@
   static constexpr size_t kInlineBytesDefault = 256;
 
   using AllocatorTraits = std::allocator_traits<A>;
-  // std::iterator_traits isn't guaranteed to be SFINAE-friendly until C++17,
-  // but this seems to be mostly pedantic.
   template <typename Iterator>
-  using EnableIfForwardIterator = std::enable_if_t<
-      base_internal::IsAtLeastForwardIterator<Iterator>::value>;
+  using EnableIfInputIterator =
+      std::enable_if_t<base_internal::IsAtLeastInputIterator<Iterator>::value>;
   static constexpr bool NoexceptCopyable() {
     return std::is_nothrow_copy_constructible<StorageElement>::value &&
            absl::allocator_is_nothrow<allocator_type>::value;
@@ -161,8 +159,8 @@
 
   // Creates an array initialized with the elements from the input
   // range. The array's size will always be `std::distance(first, last)`.
-  // REQUIRES: Iterator must be a forward_iterator or better.
-  template <typename Iterator, EnableIfForwardIterator<Iterator>* = nullptr>
+  // REQUIRES: Iterator must be a input_iterator or better.
+  template <typename Iterator, EnableIfInputIterator<Iterator>* = nullptr>
   FixedArray(Iterator first, Iterator last,
              const allocator_type& a = allocator_type())
       : storage_(std::distance(first, last), a) {