MAINT: Comparison deprecation followup fixes

Makes the identity check `a = np.array([np.nan], dtype=object)`
`a == a`, etc. a deprecation/futurewarning instead of just
changing it.
Also fixes some smaller things.

1 files changed, 18 insertions, 7 deletions

diff --git a/numpy/core/src/umath/loops.c.src b/numpy/core/src/umath/loops.c.src
index c3abd02f8..d0374fc0a 100644
--- a/numpy/core/src/umath/loops.c.src
+++ b/numpy/core/src/umath/loops.c.src
@@ -2562,22 +2562,28 @@ NPY_NO_EXPORT void
 /**begin repeat
  * #kind = equal, not_equal, greater, greater_equal, less, less_equal#
  * #OP = EQ, NE, GT, GE, LT, LE#
- * #identity = NPY_TRUE, NPY_FALSE, NPY_FALSE, NPY_TRUE, NPY_FALSE, NPY_TRUE#
+ * #identity = NPY_TRUE, NPY_FALSE, -1*4#
  */
 NPY_NO_EXPORT void
 OBJECT_@kind@(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func)) {
     BINARY_LOOP {
+        int ret;
+        PyObject *ret_obj;
         PyObject *in1 = *(PyObject **)ip1;
         PyObject *in2 = *(PyObject **)ip2;
+
         in1 = in1 ? in1 : Py_None;
         in2 = in2 ? in2 : Py_None;
+
         /*
-         * Do not use RichCompareBool because it includes an identity check.
-         * But this is wrong for elementwise behaviour, since i.e. it says
-         * that NaN can be equal to NaN, and an array is equal to itself.
+         * Do not use RichCompareBool because it includes an identity check
+         * (for == and !=).
+         * This is wrong for elementwise behaviour, since it means
+         * that NaN can be equal to NaN and an array is equal to itself.
          */
-        PyObject *ret_obj = PyObject_RichCompare(in1, in2, Py_@OP@);
+        ret_obj = PyObject_RichCompare(in1, in2, Py_@OP@);
         if (ret_obj == NULL) {
+#if @identity@ != -1
             if (in1 == in2) {
                 PyErr_Clear();
                 if (DEPRECATE("numpy @kind@ will not check object identity "
@@ -2588,10 +2594,12 @@ OBJECT_@kind@(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUS
                 *((npy_bool *)op1) = @identity@;
                 continue;
             }
+#endif
             return;
         }
-        int ret = PyObject_IsTrue(ret_obj);
+        ret = PyObject_IsTrue(ret_obj);
         if (ret == -1) {
+#if @identity@ != -1
             if (in1 == in2) {
                 PyErr_Clear();
                 if (DEPRECATE("numpy @kind@ will not check object identity "
@@ -2603,19 +2611,22 @@ OBJECT_@kind@(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUS
                 *((npy_bool *)op1) = @identity@;
                 continue;
             }
+#endif
             return;
         }
+#if @identity@ != -1
         if ((in1 == in2) && ((npy_bool)ret != @identity@)) {
             if (DEPRECATE_FUTUREWARNING(
                         "numpy @kind@ will not check object identity "
                         "in the future. The comparison did not return the "
-                        "same result as suggested by the identity "
+                        "same result as suggested by the identity (`is`)) "
                         "and will change.") < 0) {
                 return;
             }
             *((npy_bool *)op1) = @identity@;
             continue;
         }
+#endif
         *((npy_bool *)op1) = (npy_bool)ret;
     }
 }