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
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