presto-main/src/main/java/io/prestosql/sql/analyzer/AggregationAnalyzer.java/AggregationAnalyzer/visitSimpleCaseExpression
class AggregationAnalyzer:        @Override
        protected Boolean visitSimpleCaseExpression(SimpleCaseExpression node, Void context)
        {
            if (!process(node.getOperand(), context)) {
                return false;
            }

            for (WhenClause whenClause : node.getWhenClauses()) {
                if (!process(whenClause.getOperand(), context) || !process(whenClause.getResult(), context)) {
                    return false;
                }
            }

            if (node.getDefaultValue().isPresent() && !process(node.getDefaultValue().get(), context)) {
                return false;
            }

            return true;
        }