Use lexicographical comparison in ESM3ExteriorCellRefId::operator<

apps/openmw_test_suite/esm/testrefid.cpp

@@ -212,6 +212,14 @@ namespace ESM
             EXPECT_NE(hash(a), hash(b));
         }
 
+        TEST(ESMRefIdTest, esm3ExteriorCellHasLexicographicalOrder)
+        {
+            const RefId a = RefId::esm3ExteriorCell(0, 0);
+            const RefId b = RefId::esm3ExteriorCell(1, 0);
+            EXPECT_LT(a, b);
+            EXPECT_TRUE(!(b < a));
+        }
+
         struct ESMRefIdToStringTest : TestWithParam<std::pair<RefId, std::string>>
         {
         };

components/esm/esm3exteriorcellrefid.hpp

@@ -28,9 +28,14 @@ namespace ESM
         int32_t getX() const { return mX; }
         int32_t getY() const { return mY; }
 
-        constexpr bool operator==(ESM3ExteriorCellRefId rhs) const noexcept { return mX == rhs.mX && mY == rhs.mY; }
+        friend inline constexpr auto tie(const ESM3ExteriorCellRefId& value) noexcept
+        {
+            return std::tie(value.mX, value.mY);
+        }
+
+        constexpr bool operator==(ESM3ExteriorCellRefId rhs) const noexcept { return tie(*this) == tie(rhs); }
 
-        constexpr bool operator<(ESM3ExteriorCellRefId rhs) const noexcept { return mX < rhs.mX && mY < rhs.mY; }
+        constexpr bool operator<(ESM3ExteriorCellRefId rhs) const noexcept { return tie(*this) < tie(rhs); }
 
         friend std::ostream& operator<<(std::ostream& stream, ESM3ExteriorCellRefId value);