I am hitting this upgrading fused-effects
to GHC 9.6, when deriving instance of MonadTrans
for declarations like these:
newtype WriterC w m a = WriterC { runWriterC :: StateC w m a }
deriving (Alternative, Applicative, Functor, Monad, Fail.MonadFail,
MonadFix, MonadIO, MonadPlus, MonadTrans)
This ends up yielding errors about redundant Monad
constraints.
src/Control/Carrier/Writer/Strict.hs:61:101: warning: [GHC-30606] [-Wredundant-constraints]
• Redundant constraint: Monad m
• When deriving the instance for (MonadTrans (WriterC w))
This is with GHC 9.6.2 and transformers
0.6.1.0.