Allow enums to be specific elements of a table and not the whole table

[AFCMS]

The Minetest engine give access to most of his API with the minetest global table (+300 fields).

Some functions except an enum, but the enum values are stored in the global table:

https://github.com/minetest/minetest/blob/master/doc/lua_api.txt#L5668-L5673

A way to make an enum out of specific values of a table should be added IMO.

[sumneko]

I think you can just use ---@alias instead of ---@enum

[AFCMS]

I can't use something like this:

---Block emerge status constants (for use with `minetest.emerge_area`)
minetest.EMERGE_CANCELLED = 0

---Block emerge status constants (for use with `minetest.emerge_area`)
minetest.EMERGE_ERRORED = 1

---Block emerge status constants (for use with `minetest.emerge_area`)
minetest.EMERGE_FROM_MEMORY = 2

---Block emerge status constants (for use with `minetest.emerge_area`)
minetest.EMERGE_FROM_DISK = 3

---Block emerge status constants (for use with `minetest.emerge_area`)
minetest.EMERGE_GENERATED = 4

---@alias emerge_status
---| minetest.EMERGE_CANCELLED
---| minetest.EMERGE_ERRORED
---| minetest.EMERGE_FROM_MEMORY
---| minetest.EMERGE_FROM_DISK
---| minetest.EMERGE_GENERATED

Type names are undefined in that case.

I don't want to alias the real values, since these values are internal and should not be used directly.

[sumneko]

---@alias emerge_status
---| `minetest.EMERGE_CANCELLED`
---| `minetest.EMERGE_ERRORED`
---| `minetest.EMERGE_FROM_MEMORY`
---| `minetest.EMERGE_FROM_DISK`
---| `minetest.EMERGE_GENERATED`

[AFCMS]

Thanks it works!!

Maybe this usecase could be added to the ---@alias tag tooltip?