From 5b35c1a74e64f1b33cc18db43b1a7bbf842a619a Mon Sep 17 00:00:00 2001
From: ToruNiina <niina.toru.68u@gmail.com>
Date: Thu, 19 Dec 2019 22:02:17 +0900
Subject: [PATCH] fix: prohibit modification on inline table

According to toml-lang/toml:36d3091b3 "Clarify that inline tables are
immutable", check if it adds key-value pair to an inline table.
  This is one of the unreleased (after-0.5.0) toml feature. But this is
marked as "Clarify", so TOML-lang intended that inline tables are
immutable in all version.
---
 toml/parser.hpp | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/toml/parser.hpp b/toml/parser.hpp
index 9e511ad..1ea650f 100644
--- a/toml/parser.hpp
+++ b/toml/parser.hpp
@@ -1331,7 +1331,7 @@ insert_nested_key(typename Value::table_type& root, const Value& v,
             tab->insert(std::make_pair(k, v));
             return ok(true);
         }
-        else
+        else // k is not the last one, we should insert recursively
         {
             // if there is no corresponding value, insert it first.
             // related: you don't need to write
@@ -1347,6 +1347,27 @@ insert_nested_key(typename Value::table_type& root, const Value& v,
             // type checking...
             if(tab->at(k).is_table())
             {
+                // According to toml-lang/toml:36d3091b3 "Clarify that inline
+                // tables are immutable", check if it adds key-value pair to an
+                // inline table.
+                //   This is one of the unreleased (after-0.5.0) toml feature.
+                // But this is marked as "Clarify", so TOML-lang intended that
+                // inline tables are immutable in all version.
+                {
+                    // here, if the value is a (multi-line) table, the region
+                    // should be something like `[table-name]`.
+                    if(get_region(tab->at(k)).str().front() == '{')
+                    {
+                        throw syntax_error(format_underline(concat_to_string(
+                            "toml::insert_value: inserting to an inline table (",
+                            format_dotted_keys(first, std::next(iter)),
+                            ") but inline tables are immutable"), {
+                                {std::addressof(get_region(tab->at(k))),
+                                 "inline tables are immutable"},
+                                {std::addressof(get_region(v)), "inserting this"}
+                            }), v.location());
+                    }
+                }
                 tab = std::addressof((*tab)[k].as_table());
             }
             else if(tab->at(k).is_array()) // inserting to array-of-tables?