Proposal: EPHEMERAL pragma

Axel Simon Axel.Simon at
Thu Oct 25 17:00:35 CEST 2012

On 25.10.2012, at 16:45, Johan Tibell wrote:

> Interesting idea.
> On Thu, Oct 25, 2012 at 6:56 AM, José Pedro Magalhães <jpm at>  
> wrote:
>> 3. Emit a warning if the generated core code still contains uses of  
>> Rep.
> I think this part will be really annoying, as GHC might end up
> generating warnings that the programmer can do nothing about (because
> some optimization failed to remove Rep).

I think this is exactly the right idea. A compiler should emit errors  
about bad typing since type inference is somewhat complete, but should  
emit warnings about other incomplete analyses or optimizations.

If you think that this is too noisy, by all means, don't emit these  
warnings by default and add a flag that enables them.

my 2p,

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