Give MonadTrans a QuantifiedConstraints superclass
Baldur Blöndal
baldurpet at gmail.com
Tue Jun 1 23:01:24 UTC 2021
This is to advertise the proposal
(https://gitlab.haskell.org/ghc/ghc/-/issues/19922) to add a
superclass to the MonadTrans type class in Control.Monad.Trans.
A Monad transformer 'trans' lifts a 'Monad m' to a 'Monad (trans m)'.
This proposal code-ifies that with a superclass constraint, an
impliciation constraint enabled by the recent extension
QuantifiedConstraints:
class (forall m. Monad m => Monad (trans m)) => MonadTrans trans where
..
This is the main motiviating example of the Quantified Class
Constraints paper https://gkaracha.github.io/papers/quantcs.pdf
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