LIMIT variable and subselect failure

This fails to work:

SET @`x` = 20;

SELECT * FROM messages LIMIT @`x`;

Which is the basis for:

SET @`x` = (SELECT pagination_limit FROM options WHERE user='John');

SELECT * FROM messages LIMIT @`x`;

Which should also translate to:

SELECT * FROM messages LIMIT (SELECT 20);

Which in turn would translate to:

SELECT * FROM messages LIMIT (SELECT pagination_limit FROM options WHERE user='John');

The goal for my users is to simply allow them to set their returned results by controlling the LIMIT. My goal is to not have to write crazy complex things to accomplish simple goals.

I did some searching through I couldn't find any relevant bug reports. MariaDB does almost everything I need amazingly well so please forgive me if I missed anything filing this bug report.