Treatment of unknown pragmas

[Vladislav Zavialov]

What about introducing -fno-warn-pragma=XXX? People who use HLint will add
-fno-warn-pragma=HLINT to their build configuration.

On Tue, Oct 16, 2018, 20:51 Ben Gamari <ben at smart-cactus.org> wrote:

> Hi everyone,
>
> Recently Neil Mitchell opened a pull request [1] proposing a single-line
> change: Adding `{-# HLINT ... #-}` to the list of pragmas ignored by the
> lexer. I'm a bit skeptical of this idea. Afterall, adding cases to the
> lexer for every tool that wants a pragma seems quite unsustainable.
>
> On the other hand, a reasonable counter-argument could be made on the
> basis of the Haskell Report, which specifically says that
> implementations should ignore unrecognized pragmas. If GHC did this
> (instead of warning, as it now does) then this wouldn't be a problem.
>
> Of course, silently ignoring mis-typed pragmas sounds terrible from a
> usability perspective. For this reason I proposed that the following
> happen:
>
>  * The `{-# ... #-}` syntax be reserved in particular for compilers (it
>    largely already is; the Report defines it as "compiler pragma"
>    syntax). The next Report should also allow implementations to warn in
>    the case of unrecognized pragmas.
>
>  * We introduce a "tool pragma" convention (perhaps even standardized in
>    the next Report). For this we can follow the model of Liquid Haskell:
>    `{-@ $TOOL_NAME ... @-}`.
>
> Does this sound sensible?
>
> Cheers,
>
> - Ben
>
>
> [1] https://github.com/ghc/ghc/pull/204
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