[swift-evolution] [Idea] Generic subscripts

[Haravikk]

> * Who is interested in this feature?

Me definitely, everyone probably.

> * Should it be severed from throwing subscripts?

That depends I guess; subscripts are basically functions anyway so it didn't make a lot of sense to me that they lacked features that functions have, so if implementing both of these features is basically just a case of linking up the same behaviour from functions then I say do them simultaneously if possible. I don't know much about the actual implementation details though so obviously someone else should make a final decision ;)

Basically I'm in favour making subscripts have as much in common with functions as possible; in fact they really should just be a property-like shorthand for a regular function behind the scenes.