[Haskell-cafe] RFC: rewrite-with-location proposal

[Alexander Kjeldaas]

On Mon, Feb 25, 2013 at 12:46 PM, Simon Hengel <sol at typeful.net> wrote:

> On Mon, Feb 25, 2013 at 10:40:29AM +0100, Twan van Laarhoven wrote:
> > I think there is no need to have a separate REWRITE_WITH_LOCATION
> > rule. What if the compiler instead rewrites 'currentLocation' to the
> > current location? Then you'd just define the rule:
> >
> > {-# REWRITE "errorLoc" error = errorLoc currentLocation #-}
>
> REWRITE rules are only enabled with -O.  Source locations are also
> useful during development (when you care more about compilation time
> than efficient code and hence use -O0).  So I'm not sure whether it's a
> good idea to lump those two things together.
>
>
I could imagine that source locations being useful when debugging rewrite
rules for example.

I think your argument makes sense, but why not fix that specifically?

{-# REWRITE ALWAYS "errorLoc" error = errorLoc currentLocation #-}

Alexander
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