haskell / mtl

The Monad Transformer Library
http://www.haskell.org/haskellwiki/Monad_Transformers
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Separate type of writer and accumulator #122

Closed kozross closed 2 years ago

kozross commented 2 years ago

Previously, the instance required that both the MonadWriter and AccumT had the same type w as their accumulated value, even though in theory, they could be different. This was prompted by #120.

I don't have (easy) access to GHC 9.4. @Bodigrim - do you still get the redundant constraint warning? @emilypi - we should merge this in any case, as the original instance is definitely not what we intended.