From ea13e40889af43af3634ce38f7fc3b0333a05791 Mon Sep 17 00:00:00 2001
From: ToruNiina <niina.toru.68u@gmail.com>
Date: Fri, 12 Apr 2019 18:00:53 +0900
Subject: [PATCH] feat: add static_assert for location/range

to check the container is randomly-accessible
---
 toml/region.hpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/toml/region.hpp b/toml/region.hpp
index 54d9106..7f3f194 100644
--- a/toml/region.hpp
+++ b/toml/region.hpp
@@ -62,10 +62,14 @@ struct region_base
 template<typename Container>
 struct location final : public region_base
 {
-    static_assert(std::is_same<char, typename Container::value_type>::value,"");
     using const_iterator = typename Container::const_iterator;
     using source_ptr     = std::shared_ptr<const Container>;
 
+    static_assert(std::is_same<char, typename Container::value_type>::value,"");
+    static_assert(std::is_same<std::random_access_iterator_tag,
+        typename std::iterator_traits<const_iterator>::iterator_category>::value,
+        "container should be randomly accessible");
+
     location(std::string name, Container cont)
       : source_(std::make_shared<Container>(std::move(cont))),
         source_name_(std::move(name)), iter_(source_->cbegin())
@@ -139,10 +143,14 @@ struct location final : public region_base
 template<typename Container>
 struct region final : public region_base
 {
-    static_assert(std::is_same<char, typename Container::value_type>::value,"");
     using const_iterator = typename Container::const_iterator;
     using source_ptr     = std::shared_ptr<const Container>;
 
+    static_assert(std::is_same<char, typename Container::value_type>::value,"");
+    static_assert(std::is_same<std::random_access_iterator_tag,
+        typename std::iterator_traits<const_iterator>::iterator_category>::value,
+        "container should be randomly accessible");
+
     // delete default constructor. source_ never be null.
     region() = delete;