py/obj: Accept user types in mp_obj_get_int_maybe.

This is possible now that MP_UNARY_OP_INT_MAYBE exists.

As a consequence mp_obj_get_int now also supports user types, which was
previously possible with MP_UNARY_OP_INT but no tests existed for it.

Signed-off-by: Damien George <damien@micropython.org>

py/obj.c

@@ -326,7 +326,12 @@ bool mp_obj_get_int_maybe(mp_const_obj_t arg, mp_int_t *value) {
     } else if (mp_obj_is_exact_type(arg, &mp_type_int)) {
         *value = mp_obj_int_get_checked(arg);
     } else {
-        return false;
+        arg = mp_unary_op(MP_UNARY_OP_INT_MAYBE, (mp_obj_t)arg);
+        if (arg != MP_OBJ_NULL) {
+            *value = mp_obj_int_get_checked(arg);
+        } else {
+            return false;
+        }
     }
     return true;
 }

tests/basics/string_format_modulo.py

@@ -13,6 +13,12 @@ print("=%s=" % [1, 2])
 print("=%s=" % "str")
 print("=%r=" % "str")
 
+# test calling __int__
+class A:
+    def __int__(self):
+        return 123
+print("%d" % A())
+
 try:
     print("=%s=%s=" % 1)
 except TypeError: