presto-main/src/main/java/io/prestosql/operator/scalar/ConcatFunction.java/ConcatFunction/ConcatFunction
class ConcatFunction:    private ConcatFunction(TypeSignature type, String description)
    {
        super(new FunctionMetadata(
                new Signature(
                        "concat",
                        ImmutableList.of(),
                        ImmutableList.of(),
                        type,
                        ImmutableList.of(type),
                        true),
                false,
                ImmutableList.of(new FunctionArgumentDefinition(false)),
                false,
                true,
                description,
                SCALAR));
    }