HAVING clauses fail validation when type coercion is applied to GROUP BY clause

Given a sql statement like:

select if(EMP.empno <= CAST(18 AS DOUBLE), 'youth', 'adult') as adult_or_child

from EMP

GROUP BY if(EMP.empno <= CAST(18 AS DOUBLE), 'youth', 'adult')

HAVING if(EMP.empno <= CAST(18 AS DOUBLE), 'youth', 'adult')  = 'adult'

Sql Validation fails with the error:

org.apache.calcite.sql.validate.SqlValidatorException: Expression 'EMP.EMPNO' is not being grouped

Root cause: A cast is applied to the group by clause, to make it GROUP BY if( CAST (EMP.empno AS DOUBLE) <= CAST(18 AS DOUBLE), 'youth', 'adult') 

But no such cast is applied to the Having Clause. Consequently, an equality comparison on the two fails