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39 lines
1.2 KiB
Haskell
39 lines
1.2 KiB
Haskell
{-# LANGUAGE ScopedTypeVariables #-}
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module Witch.TryFromException where
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import qualified Control.Exception as Exception
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import qualified Data.Proxy as Proxy
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import qualified Data.Typeable as Typeable
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-- | This exception is thrown when a @TryFrom@ conversion fails. It has the
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-- original @source@ value that caused the failure and it knows the @target@
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-- type it was trying to convert into. It also has an optional
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-- 'Exception.SomeException' for communicating what went wrong while
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-- converting.
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data TryFromException source target = TryFromException
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source
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(Maybe Exception.SomeException)
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instance
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( Show source
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, Typeable.Typeable source
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, Typeable.Typeable target
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) => Show (TryFromException source target) where
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showsPrec d (TryFromException x e) =
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showParen (d > 10)
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$ showString "TryFromException @"
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. showsPrec 11 (Typeable.typeRep (Proxy.Proxy :: Proxy.Proxy source))
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. showString " @"
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. showsPrec 11 (Typeable.typeRep (Proxy.Proxy :: Proxy.Proxy target))
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. showChar ' '
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. showsPrec 11 x
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. showChar ' '
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. showsPrec 11 e
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instance
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( Show source
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, Typeable.Typeable source
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, Typeable.Typeable target
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) => Exception.Exception (TryFromException source target)
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