The proposal is to make
do EXPR done a first-class syntactic element which desugars to
EXPR : unit.
do EXPR done already exists in OCaml as the body of
while loops which must always have type
unit, so factoring it out into first-class syntax makes a lot of sense. The PR has a couple of nice use cases.
Unfortunately the PR was recently closed due to lack of interest so I want to encourage folks to take a look and see if you like it (or not).