Fix a reference leak in the number converter (#1078)

Fixes #1075.

`PyNumber_Float()` and `PyNumber_Long()` return new references.

docs/changelog.rst

@@ -17,6 +17,9 @@ v2.2.1 (Not yet released)
 * Fixed compilation with Clang on host GCC < 5 (old libstdc++ which isn't fully
 * Fixed compilation with Clang on host GCC < 5 (old libstdc++ which isn't fully
   C++11 compliant). `#1062 <https://github.com/pybind/pybind11/pull/1062>`_.
   C++11 compliant). `#1062 <https://github.com/pybind/pybind11/pull/1062>`_.
 
 
+* Fixed a reference leak in the number converter.
+  `#1078 <https://github.com/pybind/pybind11/pull/1078>`_.
+
 * Fixed a regression where the automatic ``std::vector<bool>`` caster would
 * Fixed a regression where the automatic ``std::vector<bool>`` caster would
   fail to compile. The same fix also applies to any container which returns
   fail to compile. The same fix also applies to any container which returns
   element proxies instead of references.
   element proxies instead of references.

include/pybind11/cast.h

@@ -964,9 +964,9 @@ public:
             );
             );
             PyErr_Clear();
             PyErr_Clear();
             if (type_error && convert && PyNumber_Check(src.ptr())) {
             if (type_error && convert && PyNumber_Check(src.ptr())) {
-                auto tmp = reinterpret_borrow<object>(std::is_floating_point<T>::value
-                                                      ? PyNumber_Float(src.ptr())
-                                                      : PyNumber_Long(src.ptr()));
+                auto tmp = reinterpret_steal<object>(std::is_floating_point<T>::value
+                                                     ? PyNumber_Float(src.ptr())
+                                                     : PyNumber_Long(src.ptr()));
                 PyErr_Clear();
                 PyErr_Clear();
                 return load(tmp, false);
                 return load(tmp, false);
             }
             }