Remove use of deleted std::allocator members (#177)

std::allocator::pointer, reference, max_size, etc. were deleted
in C++20.  Uses of rebind have already been removed from s2geometry.

https://en.cppreference.com/w/cpp/memory/allocator
https://en.cppreference.com/w/cpp/memory/allocator_traits

Fixes #173.

Author: jmr

src/s2/third_party/absl/container/fixed_array.h

@@ -106,13 +106,13 @@ class FixedArray {
 
  public:
   using allocator_type = typename AllocatorTraits::allocator_type;
-  using value_type = typename allocator_type::value_type;
-  using pointer = typename allocator_type::pointer;
-  using const_pointer = typename allocator_type::const_pointer;
-  using reference = typename allocator_type::reference;
-  using const_reference = typename allocator_type::const_reference;
-  using size_type = typename allocator_type::size_type;
-  using difference_type = typename allocator_type::difference_type;
+  using value_type = typename AllocatorTraits::value_type;
+  using pointer = typename AllocatorTraits::pointer;
+  using const_pointer = typename AllocatorTraits::const_pointer;
+  using reference = value_type&;
+  using const_reference = const value_type&;
+  using size_type = typename AllocatorTraits::size_type;
+  using difference_type = typename AllocatorTraits::difference_type;
   using iterator = pointer;
   using const_iterator = const_pointer;
   using reverse_iterator = std::reverse_iterator<iterator>;

src/s2/third_party/absl/container/inlined_vector.h

@@ -85,17 +85,18 @@ class InlinedVector {
   using IteratorCategory =
       typename std::iterator_traits<Iterator>::iterator_category;
 
+  using AllocatorTraits = std::allocator_traits<A>;
   using rvalue_reference = typename A::value_type&&;
 
  public:
-  using allocator_type = A;
-  using value_type = typename allocator_type::value_type;
-  using pointer = typename allocator_type::pointer;
-  using const_pointer = typename allocator_type::const_pointer;
-  using reference = typename allocator_type::reference;
-  using const_reference = typename allocator_type::const_reference;
-  using size_type = typename allocator_type::size_type;
-  using difference_type = typename allocator_type::difference_type;
+  using allocator_type = typename AllocatorTraits::allocator_type;
+  using value_type = typename AllocatorTraits::value_type;
+  using pointer = typename AllocatorTraits::pointer;
+  using const_pointer = typename AllocatorTraits::const_pointer;
+  using reference = value_type&;
+  using const_reference = const value_type&;
+  using size_type = typename AllocatorTraits::size_type;
+  using difference_type = typename AllocatorTraits::difference_type;
   using iterator = pointer;
   using const_iterator = const_pointer;
   using reverse_iterator = std::reverse_iterator<iterator>;

src/s2/util/gtl/densehashtable.h

@@ -184,6 +184,7 @@ struct dense_hashtable_iterator {
  private:
   using value_alloc_type =
       typename std::allocator_traits<A>::template rebind_alloc<V>;
+  using value_alloc_traits = std::allocator_traits<value_alloc_type>;
 
  public:
   typedef dense_hashtable_iterator<V, K, HF, ExK, SetK, EqK, A>
@@ -192,11 +193,11 @@ struct dense_hashtable_iterator {
       const_iterator;
 
   typedef std::forward_iterator_tag iterator_category;  // very little defined!
-  typedef V value_type;
-  typedef typename value_alloc_type::difference_type difference_type;
-  typedef typename value_alloc_type::size_type size_type;
-  typedef typename value_alloc_type::reference reference;
-  typedef typename value_alloc_type::pointer pointer;
+  typedef typename value_alloc_traits::value_type value_type;
+  typedef typename value_alloc_traits::difference_type difference_type;
+  typedef typename value_alloc_traits::size_type size_type;
+  typedef value_type& reference;
+  typedef typename value_alloc_traits::pointer pointer;
 
   // "Real" constructor and default constructor
   dense_hashtable_iterator(
@@ -248,6 +249,7 @@ struct dense_hashtable_const_iterator {
  private:
   using value_alloc_type =
       typename std::allocator_traits<A>::template rebind_alloc<V>;
+  using value_alloc_traits = std::allocator_traits<value_alloc_type>;
 
  public:
   typedef dense_hashtable_iterator<V, K, HF, ExK, SetK, EqK, A>
@@ -256,11 +258,11 @@ struct dense_hashtable_const_iterator {
       const_iterator;
 
   typedef std::forward_iterator_tag iterator_category;  // very little defined!
-  typedef V value_type;
-  typedef typename value_alloc_type::difference_type difference_type;
-  typedef typename value_alloc_type::size_type size_type;
-  typedef typename value_alloc_type::const_reference reference;
-  typedef typename value_alloc_type::const_pointer pointer;
+  typedef typename value_alloc_traits::value_type value_type;
+  typedef typename value_alloc_traits::difference_type difference_type;
+  typedef typename value_alloc_traits::size_type size_type;
+  typedef const value_type& reference;
+  typedef typename value_alloc_traits::const_pointer pointer;
 
   // "Real" constructor and default constructor
   dense_hashtable_const_iterator(
@@ -315,7 +317,7 @@ class dense_hashtable {
  private:
   using value_alloc_type =
       typename std::allocator_traits<Alloc>::template rebind_alloc<Value>;
-
+  using value_alloc_traits = std::allocator_traits<value_alloc_type>;
 
  public:
   typedef Key key_type;
@@ -324,12 +326,12 @@ class dense_hashtable {
   typedef EqualKey key_equal;
   typedef Alloc allocator_type;
 
-  typedef typename value_alloc_type::size_type size_type;
-  typedef typename value_alloc_type::difference_type difference_type;
-  typedef typename value_alloc_type::reference reference;
-  typedef typename value_alloc_type::const_reference const_reference;
-  typedef typename value_alloc_type::pointer pointer;
-  typedef typename value_alloc_type::const_pointer const_pointer;
+  typedef typename value_alloc_traits::size_type size_type;
+  typedef typename value_alloc_traits::difference_type difference_type;
+  typedef value_type& reference;
+  typedef const value_type& const_reference;
+  typedef typename value_alloc_traits::pointer pointer;
+  typedef typename value_alloc_traits::const_pointer const_pointer;
   typedef dense_hashtable_iterator<Value, Key, HashFcn,
                                    ExtractKey, SetKey, EqualKey, Alloc>
   iterator;
@@ -578,7 +580,9 @@ class dense_hashtable {
   // FUNCTIONS CONCERNING SIZE
  public:
   size_type size() const      { return num_elements - num_deleted; }
-  size_type max_size() const { return get_allocator().max_size(); }
+  size_type max_size() const {
+    return value_alloc_traits::max_size(get_allocator());
+  }
   bool empty() const          { return size() == 0; }
   size_type bucket_count() const      { return num_buckets; }
   size_type max_bucket_count() const  { return max_size(); }