On 25/02/13 07:06, Michael Snoyman wrote:
Quite a while back, Simon Hengel and I put together a proposal[1] for a new feature in GHC. The basic idea is pretty simple: provide a new pragma that could be used like so:
error :: String -> a errorLoc :: IO Location -> String -> a {-# REWRITE_WITH_LOCATION error errorLoc #-}
Then all usages of `error` would be converted into calls to `errorLoc` by the compiler, passing in the location information of where the call originated from. Our three intended use cases are:
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 #-} I'm also pretty sure that something like this has been proposed in the past. Twan