unblock https://github.com/nim-lang/Nim/pull/14887

[timotheecour]

refs nim-lang/Nim#14887
closes #20

[nigredo-tori]

ospath/os thing is only the first step. We haven't updated the library for quite a while, and we will need a lot of changes to make it compatible with Nim 0.20 and later. I've done the easy parts here. This breaks the tests for Nim 0.19 (some issue with toSeq), but that can be fixed separately using when - or we can just drop 0.19 support.

One major issue I've found is that callback= in asyncfutures now requires a {.gcsafe.} function, which means that any combinators dealing with Future must only accept gcsafe procs as parameters. I've fixed the types for now, but that still means that the combinators are incompatible with sugar lambdas. ☹️

Also, spawn now doesn't accept closure procs. We will need to change concurrent accordingly, but I've ran out of steam by this point. @vegansk, could you please continue this work? You are more familiar with what's going on in that file.

[timotheecour]

ospath/os thing is only the first step

but it's the only step needed to unblock nim-lang/Nim#14887, all other libraries mentioned there were patched :)

or we can just drop 0.19 support.

only supporting nim >= 1.0 makes sense IMO

now requires a {.gcsafe.} function

see {.gcsafe.}: to force gcsafe when you know it's safe to do so

[nigredo-tori]

see {.gcsafe.}: to force gcsafe when you know it's safe to do so

This works, and this is what I did in my branch, but it's not compatible with the -> and => syntax from sugar, which hurts usability. Still, there's not much we can do about this, since it's enforced by Future itself.