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MonadFailErrors.hs:14:5: error:
• Could not deduce (MonadFail m)
arising from a do statement
with the failable pattern ‘Just x’
from the context: Monad m
bound by the type signature for:
general :: forall (m :: * -> *) a. Monad m => m a
at MonadFailErrors.hs:12:1-25
Possible fix:
add (MonadFail m) to the context of
the type signature for:
general :: forall (m :: * -> *) a. Monad m => m a
• In a stmt of a 'do' block: Just x <- undefined
In the expression:
do Just x <- undefined
undefined
In an equation for ‘general’:
general
= do Just x <- undefined
undefined
MonadFailErrors.hs:28:5: error:
• No instance for (MonadFail Identity)
arising from a do statement
with the failable pattern ‘Just x’
• In a stmt of a 'do' block: Just x <- undefined
In the expression:
do Just x <- undefined
undefined
In an equation for ‘identity’:
identity
= do Just x <- undefined
undefined
MonadFailErrors.hs:42:5: error:
• No instance for (MonadFail ((->) r))
arising from a do statement
with the failable pattern ‘Just x’
• In a stmt of a 'do' block: Just x <- undefined
In the expression:
do Just x <- undefined
undefined
In an equation for ‘reader’:
reader
= do Just x <- undefined
undefined
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