New EEP draft: Pinning operator ^ in patterns

Loïc Hoguin essen@REDACTED
Fri Jan 22 10:10:44 CET 2021

On 22/01/2021 09:25, Richard Carlsson wrote:
> Den tors 21 jan. 2021 kl 23:55 skrev Loïc Hoguin <essen@REDACTED 
>     You say ^ indicates that the match is intentional, and in a perfect
>     world perhaps that's true, but in the real world you'll also end up
>     with
>     misplaced ^ that should not be matches at all, as some of your examples
>     show.
> Well, those examples had misplaced matches precisely because there was 
> no warning and no requirement for the programmer to state exactly what 
> they meant. If there had been a warning and a requirement to do 
> something (annotation or guard) to silence that warning, the mistake 
> wouldn't have made it there in the first place.

I agree, that's why I think an optional warning is a great idea. The 
warning could easily be added to a process that would check if new code 
introduces a warning, and if it does then the new warnings would be 
required to be manually checked for correctness. If the warnings are 
correct the process can be updated.

I would trust this far more than the presence of ^ in the code.

This would also be a good opportunity to add a comment for non-obvious 

This kind of process would be a good idea regardless of ^ being 
introduced or made mandatory. In that case the check would simply be on 
new ^ uses.

Loïc Hoguin

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