ocaml version is set to 5.4.0 by default to allow effects

[EmileTrotignon]

Right now you need to have --ocaml-version=5.3.0 or 5.4.0 to be able to use the effect syntax.

This is a big issue because otherwise you get a very annoying syntax error message and its difficult to understand what is happening.

This causes a bunch of diffs elsewhere in the tests. Its mostly improvements in my opinion. Some of it is related to let-punning, we should check it works correctly.

[EmileTrotignon]

Honestly, I can of want to make a release just for this.

[Julow]

I totally agree with this change !

ocaml-version must incremented, otherwise everyone has to set it. I'm also happy to do a big increment, compared to a short increment after each release, so that the disruption happens less often and is more easily recognized and fixed.

Honestly, I can of want to make a release just for this.

I'm not fond of releasing often, as each release has a cost for the community. Each release create incompatibilities for people that install OCamlformat using Opam.

The tests don't pass according to the CI. Can you check ?

[EmileTrotignon]

I'm not fond of releasing often, as each release has a cost for the community. Each release create incompatibilities for people that install OCamlformat using Opam.

Agreed, releasing often is an issue, but when I found this, I thought for a while that we actually did not have compatibility with 5.4, that we forgot to add some of the syntax or something.

It took looking at the tests to understand what was happening, and I don't think a regular user of ocamlformat would be able to, and he would just get the impression that ocamlformat is not compatible with the new syntax. Even though releasing often is problematic, I think this is worse.

I will check the tests.

[Julow]

The tests are failing because --ocaml-version=4.14 should be passed to some tests. You can check this easily by installing a 4.14 switch.

[EmileTrotignon]

@Julow I could indeed replicate the failure with a 4.14 switch, but I still don't understand whats happening or how to fix it

[Julow]

It was a missing (enabled_if ..) plus some other small things. I fixed it and the CI is green. Let's merge!