It is already merged (under the name of ExceptT). On 28/12/14 23:14, Yitzchak Gale wrote:
Roman Cheplyaka wrote in February 2014:
I proposed to merge either into transformers more than a year ago[1], and everyone seemed to agree. Could you please do it?
[1]: http://www.haskell.org/pipermail/libraries/2012-December/019027.html
Ross Paterson responded:
Not everyone agreed when we discussed this last August. My proposal then was to introduce a new constructor ExceptT on the same pattern as ReaderT, etc, and to deprecate ErrorT, and that's what I intend to include in the next major release, after GHC 7.8 comes out.
First of all, GHC 7.8 is well past. Now we are well into the 7.10 zone.
I re-read the original thread and did not find anyone who disagreed with this, so I'm not sure what you mean by that.
I also didn't find any mention of ExceptT there. The discussion was about merging the either library into transformers as is, with the bits that are problematic due to non-base dependencies written out by hand where possible or else omitted.
That said, I think everyone will support you, without bikeshedding, if you decide to change any of the names and/or deprecate ErrorT.
Thanks, Yitz