presto-main/src/main/java/io/prestosql/operator/scalar/ElementToArrayConcatFunction.java/ElementToArrayConcatFunction/specialize
class ElementToArrayConcatFunction:    @Override
    public ScalarFunctionImplementation specialize(BoundVariables boundVariables, int arity, Metadata metadata)
    {
        Type type = boundVariables.getTypeVariable("E");
        MethodHandle methodHandle;
        if (type.getJavaType() == boolean.class) {
            methodHandle = METHOD_HANDLE_BOOLEAN;
        }
        else if (type.getJavaType() == long.class) {
            methodHandle = METHOD_HANDLE_LONG;
        }
        else if (type.getJavaType() == double.class) {
            methodHandle = METHOD_HANDLE_DOUBLE;
        }
        else if (type.getJavaType() == Slice.class) {
            methodHandle = METHOD_HANDLE_SLICE;
        }
        else {
            methodHandle = METHOD_HANDLE_OBJECT;
        }
        methodHandle = methodHandle.bindTo(type);

        return new ScalarFunctionImplementation(
                false,
                ImmutableList.of(
                        valueTypeArgumentProperty(RETURN_NULL_ON_NULL),
                        valueTypeArgumentProperty(RETURN_NULL_ON_NULL)),
                methodHandle);
    }