From b964fa777cde8ffd736a41a0b03bf10a4ad61e8b Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Fri, 7 Oct 2022 08:41:30 -0700
Subject: [PATCH] Add at_tests

---
 .../boost/unordered/unordered_flat_map.hpp    | 22 +++++++++++++++++++
 test/Jamfile.v2                               |  1 +
 test/unordered/at_tests.cpp                   | 10 +++++++++
 3 files changed, 33 insertions(+)

diff --git a/include/boost/unordered/unordered_flat_map.hpp b/include/boost/unordered/unordered_flat_map.hpp
index 64175639..de48a22d 100644
--- a/include/boost/unordered/unordered_flat_map.hpp
+++ b/include/boost/unordered/unordered_flat_map.hpp
@@ -18,6 +18,7 @@
 
 #include <initializer_list>
 #include <iterator>
+#include <stdexcept>
 #include <type_traits>
 #include <utility>
 
@@ -287,6 +288,27 @@ namespace boost {
       /// Lookup
       ///
 
+      mapped_type& at(key_type const& key)
+      {
+        auto pos = table_.find(key);
+        if (pos != table_.end()) {
+          return pos->second;
+        }
+        // TODO: someday refactor this to conditionally serialize the key and
+        // include it in the error message
+        //
+        throw std::out_of_range("key was not found in unordered_flat_map");
+      }
+
+      mapped_type const& at(key_type const& key) const
+      {
+        auto pos = table_.find(key);
+        if (pos != table_.end()) {
+          return pos->second;
+        }
+        throw std::out_of_range("key was not found in unordered_flat_map");
+      }
+
       mapped_type& operator[](key_type const& key)
       {
         return table_.try_emplace(key).first->second;
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 5e3b82ed..332b3a21 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -111,3 +111,4 @@ build_foa insert_hint_tests ;
 build_foa emplace_tests ;
 build_foa erase_tests ;
 build_foa find_tests ;
+build_foa at_tests ;
diff --git a/test/unordered/at_tests.cpp b/test/unordered/at_tests.cpp
index 25b0951a..921bb8ee 100644
--- a/test/unordered/at_tests.cpp
+++ b/test/unordered/at_tests.cpp
@@ -5,7 +5,12 @@
 
 // clang-format off
 #include "../helpers/prefix.hpp"
+#ifdef BOOST_UNORDERED_FOA_TESTS
+#include <boost/unordered/unordered_flat_map.hpp>
+#include <boost/unordered/detail/implementation.hpp>
+#else
 #include <boost/unordered_map.hpp>
+#endif
 #include "../helpers/postfix.hpp"
 // clang-format on
 
@@ -17,8 +22,13 @@ namespace at_tests {
   UNORDERED_AUTO_TEST (at_tests) {
     BOOST_LIGHTWEIGHT_TEST_OSTREAM << "Create Map" << std::endl;
 
+#ifdef BOOST_UNORDERED_FOA_TESTS
+    boost::unordered_flat_map<std::string, int> x;
+    boost::unordered_flat_map<std::string, int> const& x_const(x);
+#else
     boost::unordered_map<std::string, int> x;
     boost::unordered_map<std::string, int> const& x_const(x);
+#endif
 
     BOOST_LIGHTWEIGHT_TEST_OSTREAM << "Check empty container" << std::endl;