I’m still not getting it. GHC ignores everything between {- and -}. Why would
I need to produce a new GHC if someone wants to us {- WIMWAM blah -}?
Simon
From: Brandon Allbery <allber...@gmail.com>
Sent: 16 October 2018 23:39
To: Simon Peyton Jones <simo...@microsoft.com>
Cc: Simon Marlow <marlo...@gmail.com>; Neil Mitchell <ndmitch...@gmail.com>;
ghc-devs@haskell.org Devs <ghc-devs@haskell.org>
Subject: Re: Treatment of unknown pragmas
One problem is you have to release a new ghc every time someone comes up with a
new pragma-using tool that starts to catch on. Another is that the more of
these you have, the more likely a typo will inadvertently match some tool you
don't even know about but ghc does.
On Tue, Oct 16, 2018 at 6:34 PM Simon Peyton Jones via ghc-devs
<ghc-devs@haskell.org<mailto:ghc-devs@haskell.org>> wrote:
I’m still not understanding what’s wrong with
{- HLINT blah blah -}
GHC will ignore it. HLint can look at it. Simple.
I must be missing something obvious.
Simon
From: ghc-devs
<ghc-devs-boun...@haskell.org<mailto:ghc-devs-boun...@haskell.org>> On Behalf
Of Simon Marlow
Sent: 16 October 2018 21:44
To: Neil Mitchell <ndmitch...@gmail.com<mailto:ndmitch...@gmail.com>>
Cc: ghc-devs <ghc-devs@haskell.org<mailto:ghc-devs@haskell.org>>
Subject: Re: Treatment of unknown pragmas
I suggested to Neil that he add the {-# HLINT #-} pragma to GHC. It seemed like
the least worst option taking into account the various issues that have already
been described in this thread. I'm OK with adding HLINT; after all we already
ignore OPTIONS_HADDOCK, OPTIONS_NHC98, a bunch of other OPTIONS, CFILES (a Hugs
relic), and several more that GHC ignores.
We can either
(a) not protect people from mistyped pragmas, or
(b) protect people from mistyped pragma names, but then we have to bake in the
set of known pragmas
We could choose to have a different convention for pragmas that GHC doesn't
know about (as Ben suggests), but then of course we don't get any protection
for mistyped pragma names when using that convention.
Cheers
Simon
On Tue, 16 Oct 2018 at 21:12, Neil Mitchell
<ndmitch...@gmail.com<mailto:ndmitch...@gmail.com>> wrote:
> A warning flag is an interesting way to deal with the issue. On the
> other hand, it's not great from an ergonomic perspective; afterall, this
> would mean that all users of HLint (and any other tool requiring special
Yep, this means every HLint user has to do an extra thing. I (the
HLint author) now have a whole pile of "how do I disable warnings in
Stack", and "what's the equivalent of this in Nix". Personally, it ups
the support level significantly that I wouldn't go this route.
I think it might be a useful feature in general, as new tools could
use the flag to prototype new types of warning, but I imagine once a
feature gets popular it becomes too much fuss.
> > I think it makes a lot of sense to have a standard way for third-parties
> > to attach string-y information to Haskell source constructs. While it's
> > not strictly speaking necessary to standardize the syntax, doing
> > so minimizes the chance that tools overlap and hopefully reduces
> > the language ecosystem learning curve.
>
> This sounds exactly like the existing ANN pragma, which is what I've wanted
> LiquidHaskell to move towards for a long time. What is wrong with using the
> ANN pragma?
Significant compilation performance penalty and extra recompilation.
ANN pragmas is what HLint currently uses.
> I'm a bit skeptical of this idea. Afterall, adding cases to the
> lexer for every tool that wants a pragma seems quite unsustainable.
I don't find this argument that convincing. Given the list already
includes CATCH and DERIVE, the bar can't have been _that_ high to
entry. And yet, the list remains pretty short. My guess is the demand
is pretty low - we're just whitelisting a handful of additional words
that aren't misspellings.
Thanks, Neil
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--
brandon s allbery kf8nh
allber...@gmail.com<mailto:allber...@gmail.com>
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