Re: [ghc-steering-committee] Amend or patterns (#522) to use p1 ; p2 (#609)

I'm happy with this change. On Fri, Sep 29, 2023, at 08:46, Moritz Angermann wrote:

Sounds good to me.

On Fri, 29 Sep 2023 at 7:47 PM, Chris Dornan wrote:

...

All,

This proposal has now been revised to make it non-disruptive.

That was the only issue of substance that surfaced in our discussion and I recommend that we accept this revised proposal.

Chris

...

On 8 Sep 2023, at 11:57, Chris Dornan wrote:

Proposal: Amend or patterns (#522) to use p1 ; p2 (#609) Author: Sebastian Graf, David Knothe Rendered proposal: https://github.com/ghc-proposals/ghc-proposals/blob/eb4b67c29282520b2c5c6a49... Discussion: https://github.com/ghc-proposals/ghc-proposals/pull/609 Recommendation: Acceptance

## Summary

This proposal refines the syntax of an already accpted proposal (#522) for writing or patterns.

The syntax of the old proposal,

```haskell stringOfT :: T -> Maybe String stringOfT (T1 s) = Just s stringOfT (one of T2{}, T3{}) = Nothing ```

is replaced with

```haskell stringOfT :: T -> Maybe String stringOfT (T1 s) = Just s stringOfT (T2{}; T3{}) = Nothing ```

or indeed

```haskell stringOfT :: T -> Maybe String stringOfT x = case x of T1 s -> Just s T2{} T3{} -> Nothing ```

(Beacuse the '(' ... ')' are optional here, we can remove them and naturally exploit layout.)

The authors have conducted polls to see what folks preferred, landing on this proposal. The adjustments to the Haskell grammar are really quite minimal requiring one extra production.

## Recommendation

The proposal is nondiruptive and as a whole addresses an important practical topic. I recommend that we accept it

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