Re: [PATCH] Generic type subscripting

> On 11 September 2017 at 23:55, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>
wrote:
>
> Sure, an SQL command for that purpose is much better than a runtime check.
> I'm going to add such command to the patch, thank you for the information!

So, I've implemented a patch for that in form of a `DEPENDS ON` syntax for
creating a function.
Basically it looks like this (and initially I was looking for something
like that in the documentation,
you can find a complete example in the test `create_function_3.sql`):

```
CREATE FUNCTION custom_subscripting_extract(internal)
RETURNS internal;

CREATE FUNCTION custom_subscripting_assign(internal)
RETURNS internal;

CREATE FUNCTION custom_subscript_parse(internal)
RETURNS internal
DEPENDS ON custom_subscripting_extract, custom_subscripting_assign;
```

I hope it sounds reasonable and can help to address a problem with
dependencies between functions.