In Parser.jj, you would reduce redundancy by assigning to a SqlTypeName variable rather than a SqlIdentifier. Make it more compact, like the TimestampInterval function.
do you mean just returning SqlTypeName for JdbcOdbcType and OdbcIntervalType. It seems there's no function to create a SqlDataTypeSpec out of a typename, nor can you use an interval type with SqlDataTypeSpec, so I still end up having two functions (one for non-interval types, and one for interval types), and I still need to create an instance of SqlDataTypeSpec out of the type name. Did I miss something?
Please add one or two tests to SqlParserTest. (SqlOperatorTest is fine, but it's more of a system test.) Also add one or two negative tests.
Also please modify REFERENCE.md.
I guess I missed updating the tables for the scalar functions