Fixes to ensure iterators satisfy the std::input_iterator concept

Migrating to std::ranges::begin and std::ranges::end requires iterators
to actually satisfy the std::input_iterator concept.

This CL batches up most of the trivial fixes to:
- ensure iterator types are default constructible
- ensure iterator types are assignable

Bug: 337356049
Change-Id: If928855034830cf0dacd6e53c6ff1b40068e3e23
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5532895
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1301402}

base/containers/enum_set.h

@@ -113,6 +113,12 @@ class EnumSet {
     Iterator() : enums_(nullptr), i_(kValueCount) {}
     ~Iterator() = default;
 
+    Iterator(const Iterator&) = default;
+    Iterator& operator=(const Iterator&) = default;
+
+    Iterator(Iterator&&) = default;
+    Iterator& operator=(Iterator&&) = default;
+
     friend bool operator==(const Iterator& lhs, const Iterator& rhs) {
       return lhs.i_ == rhs.i_;
     }
@@ -159,7 +165,7 @@ class EnumSet {
       return i;
     }
 
-    const raw_ptr<const EnumBitSet> enums_;
+    raw_ptr<const EnumBitSet> enums_;
     size_t i_;
   };
 

base/value_iterators.h

@@ -45,6 +45,7 @@ class BASE_EXPORT dict_iterator {
     reference ref_;
   };
 
+  constexpr dict_iterator() = default;
   explicit dict_iterator(DictStorage::iterator dict_iter);
   dict_iterator(const dict_iterator& dict_iter);
   dict_iterator& operator=(const dict_iterator& dict_iter);
@@ -99,6 +100,7 @@ class BASE_EXPORT const_dict_iterator {
     const reference ref_;
   };
 
+  constexpr const_dict_iterator() = default;
   explicit const_dict_iterator(DictStorage::const_iterator dict_iter);
   const_dict_iterator(const const_dict_iterator& dict_iter);
   const_dict_iterator& operator=(const const_dict_iterator& dict_iter);

cc/base/list_container.h

@@ -193,6 +193,8 @@ class ListContainer {
     // This class is only defined to forward iterate through
     // CharAllocator.
    public:
+    constexpr Iterator() = default;
+
     Iterator(ListContainerHelper::CharAllocator* container,
              size_t vector_ind,
              char* item_iter,
@@ -238,6 +240,8 @@ class ListContainer {
     // This class is only defined to forward iterate through
     // CharAllocator.
    public:
+    constexpr ConstIterator() = default;
+
     ConstIterator(ListContainerHelper::CharAllocator* container,
                   size_t vector_ind,
                   char* item_iter,
@@ -286,6 +290,8 @@ class ListContainer {
     // This class is only defined to reverse iterate through
     // CharAllocator.
    public:
+    constexpr ReverseIterator() = default;
+
     ReverseIterator(ListContainerHelper::CharAllocator* container,
                     size_t vector_ind,
                     char* item_iter,
@@ -330,6 +336,8 @@ class ListContainer {
     // This class is only defined to reverse iterate through
     // CharAllocator.
    public:
+    constexpr ConstReverseIterator() = default;
+
     ConstReverseIterator(ListContainerHelper::CharAllocator* container,
                          size_t vector_ind,
                          char* item_iter,

cc/base/list_container_helper.h

@@ -39,13 +39,15 @@ class CC_BASE_EXPORT ListContainerHelper final {
   struct CC_BASE_EXPORT PositionInCharAllocator {
     // `ptr_to_container` is not a raw_ptr<...> for performance reasons (based
     // on analysis of sampling profiler data and tab_search:top100:2020).
-    RAW_PTR_EXCLUSION CharAllocator* ptr_to_container;
+    RAW_PTR_EXCLUSION CharAllocator* ptr_to_container = nullptr;
 
-    size_t vector_index;
+    size_t vector_index = 0;
 
     // `item_iterator` is not a raw_ptr<...> for performance reasons (based on
     // analysis of sampling profiler data and tab_search:top100:2020).
-    RAW_PTR_EXCLUSION char* item_iterator;
+    RAW_PTR_EXCLUSION char* item_iterator = nullptr;
+
+    PositionInCharAllocator() = default;
 
     PositionInCharAllocator(const PositionInCharAllocator& other);
     PositionInCharAllocator& operator=(const PositionInCharAllocator& other);
@@ -67,6 +69,8 @@ class CC_BASE_EXPORT ListContainerHelper final {
     // This class is only defined to forward iterate through
     // CharAllocator.
    public:
+    Iterator() = default;
+
     Iterator(CharAllocator* container,
              size_t vector_ind,
              char* item_iter,
@@ -80,13 +84,15 @@ class CC_BASE_EXPORT ListContainerHelper final {
     // is used to avoid double increment at places an index reference is
     // needed. For iterator this means begin() corresponds to index 0 and end()
     // corresponds to index |size|.
-    size_t index_;
+    size_t index_ = 0;
   };
 
   class CC_BASE_EXPORT ConstIterator : public PositionInCharAllocator {
     // This class is only defined to forward iterate through
     // CharAllocator.
    public:
+    ConstIterator() = default;
+
     ConstIterator(CharAllocator* container,
                   size_t vector_ind,
                   char* item_iter,
@@ -101,13 +107,15 @@ class CC_BASE_EXPORT ListContainerHelper final {
     // is used to avoid double increment at places an index reference is
     // needed. For iterator this means begin() corresponds to index 0 and end()
     // corresponds to index |size|.
-    size_t index_;
+    size_t index_ = 0;
   };
 
   class CC_BASE_EXPORT ReverseIterator : public PositionInCharAllocator {
     // This class is only defined to reverse iterate through
     // CharAllocator.
    public:
+    ReverseIterator() = default;
+
     ReverseIterator(CharAllocator* container,
                     size_t vector_ind,
                     char* item_iter,
@@ -121,13 +129,15 @@ class CC_BASE_EXPORT ListContainerHelper final {
     // is used to avoid double increment at places an index reference is
     // needed. For reverse iterator this means rbegin() corresponds to index 0
     // and rend() corresponds to index |size|.
-    size_t index_;
+    size_t index_ = 0;
   };
 
   class CC_BASE_EXPORT ConstReverseIterator : public PositionInCharAllocator {
     // This class is only defined to reverse iterate through
     // CharAllocator.
    public:
+    ConstReverseIterator() = default;
+
     ConstReverseIterator(CharAllocator* container,
                          size_t vector_ind,
                          char* item_iter,
@@ -142,7 +152,7 @@ class CC_BASE_EXPORT ListContainerHelper final {
     // is used to avoid double increment at places an index reference is
     // needed. For reverse iterator this means rbegin() corresponds to index 0
     // and rend() corresponds to index |size|.
-    size_t index_;
+    size_t index_ = 0;
   };
 
   // Unlike the ListContainer methods, these do not invoke element destructors.

cc/paint/paint_op_buffer_iterator.h

@@ -29,6 +29,8 @@ class PaintOpBufferIteratorBase {
 class CC_PAINT_EXPORT PaintOpBuffer::Iterator
     : public PaintOpBufferIteratorBase {
  public:
+  constexpr Iterator() = default;
+
   explicit Iterator(const PaintOpBuffer& buffer)
       : Iterator(buffer, buffer.data_.get(), 0u) {}
 

cc/trees/layer_tree_impl.h

@@ -232,6 +232,7 @@ class CC_EXPORT LayerTreeImpl {
     using pointer = LayerImpl**;
     using reference = LayerImpl*&;
 
+    constexpr IteratorAdapter() = default;
     explicit IteratorAdapter(Iterator it) : it_(it) {}
     bool operator==(IteratorAdapter o) const { return it_ == o.it_; }
     bool operator!=(IteratorAdapter o) const { return !(*this == o); }

third_party/blink/renderer/core/layout/layout_box.h

@@ -708,6 +708,7 @@ class CORE_EXPORT LayoutBox : public LayoutBoxModelObject {
       using pointer = PhysicalBoxFragment*;
       using reference = PhysicalBoxFragment&;
 
+      constexpr Iterator() = default;
       explicit Iterator(const LayoutResultList::const_iterator& iterator)
           : iterator_(iterator) {}
 

third_party/blink/renderer/core/layout/physical_fragment.h

@@ -564,6 +564,8 @@ class CORE_EXPORT PhysicalFragment : public GarbageCollected<PhysicalFragment> {
       using pointer = value_type*;
       using reference = value_type&;
 
+      constexpr ConstIterator() = default;
+
       ConstIterator(const PhysicalFragmentLink* current, wtf_size_t size)
           : current_(current), end_(current + size) {
         SkipInvalidAndSetPostLayout();
@@ -603,8 +605,8 @@ class CORE_EXPORT PhysicalFragment : public GarbageCollected<PhysicalFragment> {
         }
       }
 
-      const PhysicalFragmentLink* current_;
-      const PhysicalFragmentLink* end_;
+      const PhysicalFragmentLink* current_ = nullptr;
+      const PhysicalFragmentLink* end_ = nullptr;
       PhysicalFragmentLink post_layout_;
     };
     using const_iterator = ConstIterator;

third_party/blink/renderer/platform/audio/vector_math_test.cc

@@ -85,6 +85,8 @@ class TestVector {
     using reference = T&;
     using value_type = T;
 
+    constexpr Iterator() = default;
+
     Iterator(T* p, int stride) : p_(p), stride_(stride) {}
 
     Iterator& operator++() {
@@ -110,8 +112,8 @@ class TestVector {
     T& operator*() const { return *p_; }
 
    private:
-    T* p_;
-    size_t stride_;
+    T* p_ = nullptr;
+    size_t stride_ = 0;
   };
 
  public:

third_party/blink/renderer/platform/wtf/deque.h

@@ -217,7 +217,7 @@ class DequeIteratorBase {
   DISALLOW_NEW();
 
  protected:
-  DequeIteratorBase();
+  constexpr DequeIteratorBase() = default;
   DequeIteratorBase(const Deque<T, inlineCapacity, Allocator>*, wtf_size_t);
   DequeIteratorBase(const DequeIteratorBase&);
   DequeIteratorBase& operator=(const DequeIteratorBase<T, 0, Allocator>&);
@@ -234,8 +234,8 @@ class DequeIteratorBase {
   bool IsEqual(const DequeIteratorBase&) const;
 
  private:
-  Deque<T, inlineCapacity, Allocator>* deque_;
-  unsigned index_;
+  Deque<T, inlineCapacity, Allocator>* deque_ = nullptr;
+  unsigned index_ = 0;
 
   friend class Deque<T, inlineCapacity, Allocator>;
 };
@@ -255,7 +255,7 @@ class DequeIterator : public DequeIteratorBase<T, inlineCapacity, Allocator> {
   typedef T& reference;
   typedef std::bidirectional_iterator_tag iterator_category;
 
-  DequeIterator() = default;
+  constexpr DequeIterator() = default;
   DequeIterator(Deque<T, inlineCapacity, Allocator>* deque, wtf_size_t index)
       : Base(deque, index) {}
 
@@ -311,6 +311,7 @@ class DequeConstIterator
   typedef const T& reference;
   typedef std::bidirectional_iterator_tag iterator_category;
 
+  constexpr DequeConstIterator() = default;
   DequeConstIterator(const Deque<T, inlineCapacity, Allocator>* deque,
                      wtf_size_t index)
       : Base(deque, index) {}
@@ -667,10 +668,6 @@ inline void Deque<T, inlineCapacity, Allocator>::erase(wtf_size_t position) {
   }
 }
 
-template <typename T, wtf_size_t inlineCapacity, typename Allocator>
-inline DequeIteratorBase<T, inlineCapacity, Allocator>::DequeIteratorBase()
-    : deque_(nullptr) {}
-
 template <typename T, wtf_size_t inlineCapacity, typename Allocator>
 inline DequeIteratorBase<T, inlineCapacity, Allocator>::DequeIteratorBase(
     const Deque<T, inlineCapacity, Allocator>* deque,