Teiid generates queries containing VARCHAR without a size, causing an HSQL syntax error

When running the following query through Teiid against an HSQL database:

SELECT CAST(N_NATIONKEY AS VARCHAR(100)) FROM NATION

Teiid drops the length from the query, sending to HSQL the query

SELECT CAST(N_NATIONKEY AS VARCHAR) FROM NATION

which causes an HSQL syntax error. HSQL doesn't support VARCHAR without length.

Note: this query was generated by Tableau, and there's no easy way to change it to use the LFT function, as suggested by Steven in https://developer.jboss.org/thread/267816