presto-parser/src/main/java/io/prestosql/sql/parser/AstBuilder.java/AstBuilder/visitConcatenation
class AstBuilder:    @Override
    public Node visitConcatenation(SqlBaseParser.ConcatenationContext context)
    {
        return new FunctionCall(
                getLocation(context.CONCAT()),
                QualifiedName.of("concat"), ImmutableList.of(
                (Expression) visit(context.left),
                (Expression) visit(context.right)));
    }