我想使用仆人的 monad with :: MonadBaseControl IO m = > m a - > m b - > ma ，但遇到错误没有（MonadBaseControl IO ClientM）实例。
奇怪的是，这个确切的实例似乎是，可以从。
我需要以某种方式显式导入这些实例吗？
I'd like to use Servant's ClientM monad with finally:: MonadBaseControl IO m => m a -> m b -> m a, but am faced with error No instance for (MonadBaseControl IO ClientM).
Oddly, this exact instance appears to be defined already, be it from an internal module.
Do I need to explicitly import such instances somehow?
It works fine if, as Daniel said, you import the module that defines the desired instance:
Prelude> import Control.Exception.Lifted Prelude Control.Exception.Lifted> import Servant.Client Prelude Control.Exception.Lifted Servant.Client> :set -XTypeApplications Prelude Control.Exception.Lifted Servant.Client> :type finally @ ClientM finally @ ClientM :: ClientM a -> ClientM b -> ClientM a
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