[m-rev.] for review: Deprecate thread.channel.untake/4

[Julien Fischer]

On Mon, 17 Feb 2020, Peter Wang wrote:

> A call to channel.untake will deadlock if a call to channel.take is
> blocked on the same channel.
> unGetChan was removed from GHC for the same reason:
> https://gitlab.haskell.org/ghc/ghc/issues/4154
>
> library/thread.channel.m:
>    Deprecate channel.untake/4.
>
> NEWS:
>    Announce the change.

That's fine.

Julien.