presto-main/src/main/java/io/prestosql/sql/analyzer/AggregationAnalyzer.java/Visitor/visitIfExpression
class Visitor:        @Override
        protected Boolean visitIfExpression(IfExpression node, Void context)
        {
            ImmutableList.Builder<Expression> expressions = ImmutableList.<Expression>builder()
                    .add(node.getCondition())
                    .add(node.getTrueValue());

            if (node.getFalseValue().isPresent()) {
                expressions.add(node.getFalseValue().get());
            }

            return expressions.build().stream().allMatch(expression -> process(expression, context));
        }