Only has Functor instance only.

[robinp]

The problem is only described at lpsmith/postgresql-simple#270.

[phadej]

There's #4, but @hvr is not responding there.

[Gabriella439]

Anybody stumbling across this issue should be aware that there is now an equivalent Solo type in base starting with GHC 9.2.1. You can use that type instead of using this repository

[phadej]

Solo is not equivalent, Identity is. Only is newtype, and Solo is data.

[Gabriella439]

So should we upstream Only into base, then, if it already has Solo?

[phadej]

base already has Identity. IMHO, the only benefit of Only (or I from sop-core) is that their names are shorter (and historical usage).