From 3f04db09bd9463f9d7d022a193c2f79be6fb59b7 Mon Sep 17 00:00:00 2001
From: Claudio DeSouza <cdesouza@brave.com>
Date: Sat, 9 Nov 2024 01:38:40 +0000
Subject: [PATCH] `Slice<T>::iterator` to be `contiguous` and `random_access`

`rust::Vec` fails `std::ranges::contiguous_range` checks as those have
to satisfy `random_access_range`, and `contiguous_iterator`. This has
caused mismatches with certain `span` types in other codebases.

This PR adds the necessary increment and concept category to
`Slice<T>::iterator`, to correct this issue.

Bug: https://github.com/dtolnay/cxx/issues/1392
---
 include/cxx.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/cxx.h b/include/cxx.h
index 3414e4c8a..dc1420da1 100644
--- a/include/cxx.h
+++ b/include/cxx.h
@@ -1,6 +1,7 @@
 #pragma once
 #include <algorithm>
 #include <array>
+#include <concepts>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
@@ -217,6 +218,7 @@ template <typename T>
 class Slice<T>::iterator final {
 public:
   using iterator_category = std::random_access_iterator_tag;
+  using iterator_concept = std::contiguous_iterator_tag;
   using value_type = T;
   using difference_type = std::ptrdiff_t;
   using pointer = typename std::add_pointer<T>::type;
@@ -244,6 +246,10 @@ class Slice<T>::iterator final {
   bool operator>(const iterator &) const noexcept;
   bool operator>=(const iterator &) const noexcept;
 
+  template <std::integral N>
+  friend iterator operator+(N n, const iterator& it) noexcept {
+      return it + n;
+  }
 private:
   friend class Slice;
   void *pos;