new is removed from Integer so doesn't need to be removed again in Fixnum

src/numeric.c

@@ -1374,7 +1374,6 @@ mrb_init_numeric(mrb_state *mrb)
   mrb_define_method(mrb, integer, "to_int", int_to_i, MRB_ARGS_NONE());
   fixnum = mrb->fixnum_class = mrb_define_class(mrb, "Fixnum", integer);
 
-  mrb_undef_class_method(mrb,  fixnum, "new");
   mrb_define_method(mrb, fixnum,  "+",        fix_plus,          MRB_ARGS_REQ(1)); /* 15.2.8.3.1  */
   mrb_define_method(mrb, fixnum,  "-",        fix_minus,         MRB_ARGS_REQ(1)); /* 15.2.8.3.2  */
   mrb_define_method(mrb, fixnum,  "-@",       fix_uminus,        MRB_ARGS_REQ(1)); /* 15.2.7.4.2  */