Warning suppression pragmas

[Ben Gamari]

Эдгар Жаворонков <edzhavoronkov at gmail.com> writes:

> Hello Richard!
>
> Can you take a look at some sort of specification i wrote week ago?
> I placed it here:
> https://ghc.haskell.org/trac/ghc/wiki/Design/LocalWarningPragmas
> I can imagine only two use cases, and i'm not sure about correcteness of it
>
Thanks for writing this up!

The specification is a good start but it really needs more detail. For
instance, what syntactic elements do you want this pragma to apply to?
Bindings? Expressions? Top-level definitions like classes, types, and
instances? Any lexical scope?

It would be nice if the use-cases you mention were a bit more concrete.
It wouldn't hurt to mention particular warnings that you might imagine
that this would be useful for.

It would likely be useful to draw inspiration from some of the schemes
used by other languages listed on the ticket (Rust and C# IIRC). It
wouldn't hurt to draw attention to the similarities and differences to
these other schemes in the proposal text.

On a more bike-shed-y note, `SUPPRESS_WARNINGS` is arguably a bit on the
long side.

Personally I would prefer not to see the pragma be bracketed as you
propose in your last example as its effect then becomes quite
"non-local". This pragma should, in my opinion, be a tool of precision,
used sparingly for well-understood reasons. Allowing bracketed regions
makes it too easy for definitions to "sneak in" to the supressed region,
hiding legitimate warnings. In the interest of keeping the proposal
concrete and concise I would either remove this alternative or move it
to a dedicated "Alternatives" section.

I'm looking forward to seeing what becomes of this. You might consider
submitting the next iteration of the proposal to the Haskell subreddit
to get a few more eyes on it. Onwards!

Cheers,

- Ben

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