40 lines
1.2 KiB
Haskell
40 lines
1.2 KiB
Haskell
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{-# LANGUAGE TypeFamilies, ScopedTypeVariables #-}
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module Language.Haskell.GhcMod.Error (
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GhcModError(..)
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, modifyError
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, modifyError'
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, tryFix
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, module Control.Monad.Error
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, module Exception
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) where
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import Control.Monad.Error (MonadError(..), Error(..))
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import Exception
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data GhcModError = GMENoMsg
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-- ^ Unknown error
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| GMEString String
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-- ^ Some Error with a message. These are produced mostly by
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-- 'fail' calls on GhcModT.
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| GMECabalConfigure GhcModError
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-- ^ Configuring a cabal project failed.
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| GMEProcess [String] GhcModError
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-- ^ Launching an operating system process failed. The first
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-- field is the command.
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deriving (Eq,Show)
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instance Error GhcModError where
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noMsg = GMENoMsg
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strMsg = GMEString
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modifyError :: MonadError e m => (e -> e) -> m a -> m a
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modifyError f action = action `catchError` \e -> throwError $ f e
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infixr 0 `modifyError'`
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modifyError' :: MonadError e m => m a -> (e -> e) -> m a
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modifyError' = flip modifyError
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tryFix :: MonadError e m => m a -> (e -> m ()) -> m a
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tryFix action fix = do
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action `catchError` \e -> fix e >> action
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