Round-tripping a DECIMAL literal through Planner -> RelToSqlConverter -> Planner throws validation error

Take the following SQL:
SELECT CAST('11111111111111111111111111111111.111111' AS DECIMAL(38,6)) AS "num"
And, in the default Calcite SQL dialect with all defaults, send it through Planner parse -> valiate -> rel to get a RelNode. The RelNode will have a Project with the "111111111111111.11111" literal in there as a RexLiteral with Decimal type. 

The use RelToSqlConverter to convert that RelNode back to SQL. The SQL now looks like 
SELECT 11111111111111111111111111111111.111111 AS "num"
 

If you attempt to parse and validate that SQL, you get "Numeric literal '11111111111111111111111111111111.111111' out of range" throw by SqlValidatorImpl.validateLiteral()