Re: Program Compiles With GHC 6.6 but not Hat

On 19/11/2006, at 10:07 AM, Neil Mitchell wrote:

> Hi
>
>> >   This brings up something that's been niggling me for a while.
>> > Why can Hat not deal with defaulting?  Surely it could be handled
>> > by the first stage of hat-trans being inserting explicit type
>> > signatures based on the standard defaulting rules?
>> >
>> > Bob
>>
>> That would require hat-trans to do type checking, wouldn't it?
>
> One idea that _might_ work is to translate Int -> Integer, then you
> get rid of defaulting integers, at the cost of changing the program
> semantics ever so slightly. Personally I'd say the cost is more than
> worth it, but I know some of the Hat developers disagree with me on
> that.
>
> Thanks
>
> Neil

Hi Neil,

I would also argue strongly against that approach.

It is important that debugging tools preserve the semantics of the  
underlying program as closely as possible.

You might remove a slightly inconvenient problem, but at the cost of  
introducing subtle and difficult-to-explain changes in program  
behaviour.

Probably the best solution is to lobby various compiler writers to  
generalise the defaulting mechanism, but that may be easier said than  
done :)

Cheers,
Bernie.