presto-main/src/main/java/io/prestosql/sql/analyzer/ExpressionAnalyzer.java/ExpressionAnalyzer/visitIntervalLiteral
class ExpressionAnalyzer:        @Override
        protected Type visitIntervalLiteral(IntervalLiteral node, StackableAstVisitorContext<Context> context)
        {
            Type type;
            if (node.isYearToMonth()) {
                type = INTERVAL_YEAR_MONTH;
            }
            else {
                type = INTERVAL_DAY_TIME;
            }
            return setExpressionType(node, type);
        }