Report field access errors

2 files changed, 24 insertions, 4 deletions

diff --git a/include/elna/boot/name_analysis.h b/include/elna/boot/name_analysis.h
index ab86a44..996c357 100644
--- a/include/elna/boot/name_analysis.h
+++ b/include/elna/boot/name_analysis.h
@@ -75,14 +75,12 @@ namespace elna::boot
     class member_error : public error
     {
     public:
-        struct not_found
-        {
-        };
+        enum class kind { not_found, field_on_type };
         struct duplicate {
             std::optional<source_position> original;
             std::optional<std::string> base;
         };
-        using payload_type = std::variant<not_found, duplicate>;
+        using payload_type = std::variant<duplicate, kind>;
 
         member_error(const source_position position, const std::string& name,
                 const type& composite, payload_type payload);
diff --git a/include/elna/boot/result.h b/include/elna/boot/result.h
index 1455371..c73799d 100644
--- a/include/elna/boot/result.h
+++ b/include/elna/boot/result.h
@@ -473,6 +473,28 @@ namespace elna::boot
         {
             return this->payload.size();
         }
+
+        /**
+         * Accesses an element by key.
+         *
+         * The key must exist — behaviour is undefined otherwise.
+         * Use \c find() for fallible lookup.
+         *
+         * \param key Key value of the element to look up.
+         * \return Reference to the mapped value.
+         */
+        mapped_type& operator[](const key_type& key)
+        {
+            return this->payload[this->index_map.find(key)->second].second;
+        }
+
+        /**
+         * \overload
+         */
+        const mapped_type& operator[](const key_type& key) const
+        {
+            return this->payload[this->index_map.find(key)->second].second;
+        }
     };
 
     /**