Hi james, there are two different but related concept for this one.

For one thing, there is the type conversion error. Say you explicitly convert one type to another, in which case it's the types mismatch is the root of the problem.

Then there is this type not supported operator problem. Like the only usage currently in the code base, the concatenation does not support certain type. In this case the method is the root of the problem.

It's very similar to the following SQLStates I find in the Derby SQLState lists. They all differs all so slightly in the focus of the actual problem.

1. 22005	Unable to convert a value of type '<typeName>' to type '<typeName>' : the encoding is not supported.
2. 22005	An attempt was made to get a data value of type '<datatypeName>' from a data value of type '<datatypeName>'.
3. 42815	The data type, length or value of arguments '<value>' and '<value>' is incompatible.
4. 42846	Cannot convert types '<type>' to '<type>'.
5. 42821	Columns of type '<type>' cannot hold values of type '<type>'.

Maybe I've been staring at error codes for too long and are making things too specific. I would be happy to combine all those exceptions into one TYPE_MISMATCH, :).