py: Remove useless implementations of NOT_EQUAL in binary_op's.

I'm pretty sure these are never reached, since NOT_EQUAL is always
converted into EQUAL in mp_binary_op.  No one should call
type.binary_op directly, they should always go through mp_binary_op
(or mp_obj_is_equal).

py/objint_longlong.c

@@ -106,8 +106,6 @@ mp_obj_t mp_obj_int_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
             return MP_BOOL(lhs_val >= rhs_val);
         case MP_BINARY_OP_EQUAL:
             return MP_BOOL(lhs_val == rhs_val);
-        case MP_BINARY_OP_NOT_EQUAL:
-            return MP_BOOL(lhs_val != rhs_val);
 
         default:
             // op not supported

py/objint_mpz.c

@@ -205,8 +205,6 @@ mp_obj_t mp_obj_int_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
                 return MP_BOOL(cmp >= 0);
             case MP_BINARY_OP_EQUAL:
                 return MP_BOOL(cmp == 0);
-            case MP_BINARY_OP_NOT_EQUAL:
-                return MP_BOOL(cmp != 0);
 
             default:
                 return MP_OBJ_NULL;

py/objlist.c

@@ -138,8 +138,6 @@ STATIC mp_obj_t list_binary_op(int op, mp_obj_t lhs, mp_obj_t rhs) {
         case MP_BINARY_OP_MORE:
         case MP_BINARY_OP_MORE_EQUAL:
             return MP_BOOL(list_cmp_helper(op, lhs, rhs));
-        case MP_BINARY_OP_NOT_EQUAL:
-            return MP_BOOL(!list_cmp_helper(MP_BINARY_OP_EQUAL, lhs, rhs));
 
         default:
             // op not supported

py/objset.c

@@ -411,8 +411,6 @@ STATIC mp_obj_t set_binary_op(int op, mp_obj_t lhs, mp_obj_t rhs) {
         return set_issubset(lhs, rhs);
     case MP_BINARY_OP_MORE_EQUAL:
         return set_issuperset(lhs, rhs);
-    case MP_BINARY_OP_NOT_EQUAL:
-        return MP_BOOL(set_equal(lhs, rhs) == mp_const_false);
     case MP_BINARY_OP_IN:
     {
         mp_obj_set_t *o = lhs;

py/objtuple.c

@@ -137,8 +137,6 @@ mp_obj_t tuple_binary_op(int op, mp_obj_t lhs, mp_obj_t rhs) {
         case MP_BINARY_OP_MORE:
         case MP_BINARY_OP_MORE_EQUAL:
             return MP_BOOL(tuple_cmp_helper(op, lhs, rhs));
-        case MP_BINARY_OP_NOT_EQUAL:
-            return MP_BOOL(!tuple_cmp_helper(MP_BINARY_OP_EQUAL, lhs, rhs));
 
         default:
             // op not supported

tests/basics/equal.py

@@ -0,0 +1,75 @@
+# test equality
+
+print(None == None)
+
+print(False == None)
+print(False == False)
+print(False == True)
+
+print(() == ())
+print(() == [])
+print([] == [])
+print(() == {})
+print({} == ())
+
+print(() == None)
+print(() == False)
+print(() == print)
+
+print([] == None)
+print([] == False)
+print([] == print)
+
+print({} == None)
+print({} == False)
+print({} == print)
+
+print(1 == 1)
+print(1 == 2)
+print(1 == ())
+print(1 == [])
+print(1 == {})
+print(1 == 'a')
+
+print('a' == 'a')
+print('a' == 'ab')
+print('a' == 1)
+print('a' == ())
+
+# same as above but with !=
+
+print(None != None)
+
+print(False != None)
+print(False != False)
+print(False != True)
+
+print(() != ())
+print(() != [])
+print([] != [])
+print(() != {})
+print({} != ())
+
+print(() != None)
+print(() != False)
+print(() != print)
+
+print([] != None)
+print([] != False)
+print([] != print)
+
+print({} != None)
+print({} != False)
+print({} != print)
+
+print(1 != 1)
+print(1 != 2)
+print(1 != ())
+print(1 != [])
+print(1 != {})
+print(1 != 'a')
+
+print('a' != 'a')
+print('a' != 'ab')
+print('a' != 1)
+print('a' != ())