Re: [ghc-steering-committee] Modification to record dot syntax propsal

Simon, all, After reading more of the PR thread (in particular the fews posts after Simon's recommendation), I have to admit: I am thoroughly confused. I'm not sure that two people in that thread have the same motivation, end goal, or design in mind. The motivations provided by the modified *Alternatives* section is not much more helpful (at the risk of caricaturing a little, it basically reads: “we made two extensions rather than one because we can”). Though it makes it clear that the end goal is to fold a bunch of record-related extensions into one glorious record extension (well, probably not fold them, but make a meta-extension that implies all the extensions that we've decided we like). My starting point is that: - Additional extensions have a maintenance cost - Additional extensions impose a cognitive burden on their use - I expect that a new extension will break my code in the next few releases. Based on this, I don't care how this extension or the glorious record extension are named; but if we want to have two extensions we should have a serious reason. Right now, the one reason that I see (and Iavor raised), is that the update part of `RecordDotSyntax` is not backward compatible. Is it a strong enough reason? I don't know. The only data point that I can provide is that when we discussed the original proposal, I brought it up several times, and it didn't seem very important at the time (the conversation focused on other points of the proposal). So, I'm still reluctant. I feel that, at the very least, the motivations are not well-enough articulated in the proposal (I'll make a comment to this effect on Github when I'm done composing this email). I appreciate that I'm in the minority here. Yet, I'm still unconvinced. Best, Arnaud On Sat, Feb 27, 2021 at 12:39 AM Simon Peyton Jones wrote:

Generally, I'm not in favour in proposals which split extensions though: we already have so many extensions. Are the reasons for this split strong enough? I haven't had time to dig into the details.

Arnaud, happily, you don’t have to dig very deep – just read the handful of posts following my recommendation.

There seem to be two motivations.

1. There really are two orthogonal extensions, one for r.x notation, and one for overloaded update. Iavor likes the first but not the second. Neil likes both. Having separate extensions lets us experiment.

1. You suggest that changing the definition of RecordDotSyntax in a subsequent release, e.g. by subsequently making it imply NoFieldSelectors, would be fine. But it certainly imposes pain – some programs would stop compiling. The approach offered by this proposal avoids that problem.

Yes, there are lots of extensions surrounding records: NoFieldSelectors, DuplicateRecordFields, NamedFieldPuns, DisambiguateRecordFields, RecordWildCards. It may not be pretty to divide things up so fine, but it’s not new.

If there are alternative suggestions, let’s hear them.

Simon

*From:* ghc-steering-committee *On Behalf Of *Spiwack, Arnaud *Sent:* 26 February 2021 22:33 *To:* Iavor Diatchki *Cc:* ghc-steering-committee *Subject:* Re: [ghc-steering-committee] Modification to record dot syntax propsal

I do think that reusing the record update syntax for the overloaded monomorphic update is a mistake---it is not something I had noticed during our original discussion.

This is the one reason I can see for cutting this extension in smaller pieces. But, then again, -XOverloadedRecordUpdate would be a fork-like extension.

Generally, I'm not in favour in proposals which split extensions though: we already have so many extensions. Are the reasons for this split strong enough? I haven't had time to dig into the details.

I'm not sure that not having the design of the proposal quite finalised is a good reason, extensions mutate in their first iterations, I don't think that it's a problem.