✅ add test

single_include/nlohmann/json.hpp

@@ -12739,7 +12739,7 @@ class json_pointer
         {
             if (JSON_HEDLEY_UNLIKELY(!element.second.is_primitive()))
             {
-                JSON_THROW(detail::type_error::create(315, "values in object must be primitive", diagnostics_t(element)));
+                JSON_THROW(detail::type_error::create(315, "values in object must be primitive", diagnostics_t(element.second)));
             }
 
             // assign value to reference pointed to by JSON pointer; Note that if

test/src/unit-diagnostics.cpp

@@ -101,4 +101,11 @@ TEST_CASE("Better diagnostics")
         CHECK_THROWS_WITH_AS(json({"0", "0"})[1].get<int>(), "[json.exception.type_error.302] (/1) type must be number, but is string", json::type_error);
         CHECK_THROWS_WITH_AS(json({"0", "1"})[1].get<int>(), "[json.exception.type_error.302] (/1) type must be number, but is string", json::type_error);
     }
+
+    SECTION("Regression test for https://github.com/nlohmann/json/pull/2562/files/380a613f2b5d32425021129cd1f371ddcfd54ddf#r563259793")
+    {
+        json j;
+        j["/foo"] = {1, 2, 3};
+        CHECK_THROWS_WITH_AS(j.unflatten(), "[json.exception.type_error.315] (/~1foo) values in object must be primitive", json::type_error);
+    }
 }