On Wed, Oct 2, 2013 at 1:50 PM, Edward Kmett
That is admittedly a pretty convincing example that we may want to provide either a LANGUAGE pragma or a different syntax to opt in.
I suppose the Applicative desugaring can reliably be disabled by adding a syntactic dependency on previous variables, like [ (x, y) | x <- [1..3], y <- const [1..10000000] x ] so as far as I'm concerned it's sufficient if the Applicative desugaring is opt-in on a per-module basis, without a separate syntax for Applicative vs Monad do-notation/comprehensions. Those who opt in can be expected to understand and deal with this sharing issue if it affects them. (They pretty much have to understand it already, if they are compiling with optimizations.) Regards, Reid Barton