compar.c:36
void
rb_cmperr(x, y)
    VALUE x, y;
{
    const char *classname;

    if (SPECIAL_CONST_P(y)) {
	y = rb_inspect(y);
	classname = StringValuePtr(y);
    }
    else {
	classname = rb_obj_classname(y);
    }
    rb_raise(rb_eArgError, "comparison of %s with %s failed",
	     rb_obj_classname(x), classname);
}
