Enumerator::Lazy#_enumerable_reject

static VALUE
lazy_reject(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy reject without a block");
    }

    return lazy_add_method(obj, 0, 0, Qnil, Qnil, &lazy_reject_funcs);
}