presto-parser/src/main/java/io/prestosql/sql/parser/AstBuilder.java/AstBuilder/visitComparison
class AstBuilder:    @Override
    public Node visitComparison(SqlBaseParser.ComparisonContext context)
    {
        return new ComparisonExpression(
                getLocation(context.comparisonOperator()),
                getComparisonOperator(((TerminalNode) context.comparisonOperator().getChild(0)).getSymbol()),
                (Expression) visit(context.value),
                (Expression) visit(context.right));
    }