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<title>src/Control/Lens/Internal/Exception.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE CPP #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# LANGUAGE FunctionalDependencies #-}</span>
<a name="line-3"></a><span class='hs-comment'>{-# LANGUAGE MultiParamTypeClasses #-}</span>
<a name="line-4"></a><span class='hs-comment'>{-# LANGUAGE UndecidableInstances #-}</span>
<a name="line-5"></a><span class='hs-comment'>{-# LANGUAGE ScopedTypeVariables #-}</span>
<a name="line-6"></a><span class='hs-comment'>{-# LANGUAGE DeriveDataTypeable #-}</span>
<a name="line-7"></a><span class='hs-comment'>{-# LANGUAGE FlexibleInstances #-}</span>
<a name="line-8"></a><span class='hs-comment'>{-# LANGUAGE FlexibleContexts #-}</span>
<a name="line-9"></a><span class='hs-comment'>{-# LANGUAGE KindSignatures #-}</span>
<a name="line-10"></a><span class='hs-cpp'>#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707</span>
<a name="line-11"></a><span class='hs-comment'>{-# LANGUAGE ConstraintKinds #-}</span>
<a name="line-12"></a><span class='hs-comment'>{-# LANGUAGE PolyKinds #-}</span>
<a name="line-13"></a><span class='hs-comment'>{-# LANGUAGE RoleAnnotations #-}</span>
<a name="line-14"></a><span class='hs-cpp'>#endif</span>
<a name="line-15"></a>
<a name="line-16"></a><span class='hs-cpp'>#ifndef MIN_VERSION_base</span>
<a name="line-17"></a><span class='hs-cpp'>#define MIN_VERSION_base(x,y,z) 1</span>
<a name="line-18"></a><span class='hs-cpp'>#endif</span>
<a name="line-19"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-20"></a><span class='hs-comment'>-- |</span>
<a name="line-21"></a><span class='hs-comment'>-- Module : Control.Lens.Internal.Exception</span>
<a name="line-22"></a><span class='hs-comment'>-- Copyright : (C) 2013-2016 Edward Kmett</span>
<a name="line-23"></a><span class='hs-comment'>-- License : BSD-style (see the file LICENSE)</span>
<a name="line-24"></a><span class='hs-comment'>-- Maintainer : Edward Kmett <ekmett@gmail.com></span>
<a name="line-25"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-26"></a><span class='hs-comment'>-- Portability : non-portable</span>
<a name="line-27"></a><span class='hs-comment'>--</span>
<a name="line-28"></a><span class='hs-comment'>-- This module uses dirty tricks to generate a 'Handler' from an arbitrary</span>
<a name="line-29"></a><span class='hs-comment'>-- 'Fold'.</span>
<a name="line-30"></a><span class='hs-comment'>----------------------------------------------------------------------------</span>
<a name="line-31"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Lens</span><span class='hs-varop'>.</span><span class='hs-conid'>Internal</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span>
<a name="line-32"></a> <span class='hs-layout'>(</span> <span class='hs-conid'>Handleable</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-33"></a> <span class='hs-layout'>,</span> <span class='hs-conid'>HandlingException</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-34"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-35"></a>
<a name="line-36"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Exception</span>
<a name="line-37"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Lens</span><span class='hs-varop'>.</span><span class='hs-conid'>Fold</span>
<a name="line-38"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Lens</span><span class='hs-varop'>.</span><span class='hs-conid'>Getter</span>
<a name="line-39"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Catch</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Catch</span>
<a name="line-40"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Monoid</span>
<a name="line-41"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Proxy</span>
<a name="line-42"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Reflection</span>
<a name="line-43"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Typeable</span>
<a name="line-44"></a>
<a name="line-45"></a><span class='hs-comment'>-- This is needed because ghc 7.8-rc2 has Typeable1 as a type alias.</span>
<a name="line-46"></a><span class='hs-cpp'>#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707</span>
<a name="line-47"></a><span class='hs-cpp'>#define Typeable1 Typeable</span>
<a name="line-48"></a><span class='hs-cpp'>#endif</span>
<a name="line-49"></a>
<a name="line-50"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-51"></a><span class='hs-comment'>-- Handlers</span>
<a name="line-52"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-53"></a>
<a name="line-54"></a><a name="Getting"></a><span class='hs-comment'>-- | Both @exceptions@ and "Control.Exception" provide a 'Handler' type.</span>
<a name="line-55"></a><a name="Getting"></a><span class='hs-comment'>--</span>
<a name="line-56"></a><a name="Getting"></a><span class='hs-comment'>-- This lets us write combinators to build handlers that are agnostic about the choice of</span>
<a name="line-57"></a><a name="Getting"></a><span class='hs-comment'>-- which of these they use.</span>
<a name="line-58"></a><a name="Getting"></a><span class='hs-keyword'>class</span> <span class='hs-conid'>Handleable</span> <span class='hs-varid'>e</span> <span class='hs-layout'>(</span><span class='hs-varid'>m</span> <span class='hs-keyglyph'>::</span> <span class='hs-varop'>*</span> <span class='hs-keyglyph'>-></span> <span class='hs-varop'>*</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>h</span> <span class='hs-keyglyph'>::</span> <span class='hs-varop'>*</span> <span class='hs-keyglyph'>-></span> <span class='hs-varop'>*</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>h</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>e</span> <span class='hs-varid'>m</span> <span class='hs-keyword'>where</span>
<a name="line-59"></a> <span class='hs-comment'>-- | This builds a 'Handler' for just the targets of a given 'Control.Lens.Type.Prism' (or any 'Getter', really).</span>
<a name="line-60"></a> <span class='hs-comment'>--</span>
<a name="line-61"></a> <span class='hs-comment'>-- @</span>
<a name="line-62"></a> <span class='hs-comment'>-- 'catches' ... [ 'handler' 'Control.Exception.Lens._AssertionFailed' (\s -> 'print' '$' \"Assertion Failed\\n\" '++' s)</span>
<a name="line-63"></a> <span class='hs-comment'>-- , 'handler' 'Control.Exception.Lens._ErrorCall' (\s -> 'print' '$' \"Error\\n\" '++' s)</span>
<a name="line-64"></a> <span class='hs-comment'>-- ]</span>
<a name="line-65"></a> <span class='hs-comment'>-- @</span>
<a name="line-66"></a> <span class='hs-comment'>--</span>
<a name="line-67"></a> <span class='hs-comment'>-- This works ith both the 'Exception.Handler' type provided by @Control.Exception@:</span>
<a name="line-68"></a> <span class='hs-comment'>--</span>
<a name="line-69"></a> <span class='hs-comment'>-- @</span>
<a name="line-70"></a> <span class='hs-comment'>-- 'handler' :: 'Getter' 'SomeException' a -> (a -> 'IO' r) -> 'Exception.Handler' r</span>
<a name="line-71"></a> <span class='hs-comment'>-- 'handler' :: 'Fold' 'SomeException' a -> (a -> 'IO' r) -> 'Exception.Handler' r</span>
<a name="line-72"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Prism.Prism'' 'SomeException' a -> (a -> 'IO' r) -> 'Exception.Handler' r</span>
<a name="line-73"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Lens.Lens'' 'SomeException' a -> (a -> 'IO' r) -> 'Exception.Handler' r</span>
<a name="line-74"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Traversal.Traversal'' 'SomeException' a -> (a -> 'IO' r) -> 'Exception.Handler' r</span>
<a name="line-75"></a> <span class='hs-comment'>-- @</span>
<a name="line-76"></a> <span class='hs-comment'>--</span>
<a name="line-77"></a> <span class='hs-comment'>-- and with the 'Catch.Handler' type provided by @Control.Monad.Catch@:</span>
<a name="line-78"></a> <span class='hs-comment'>--</span>
<a name="line-79"></a> <span class='hs-comment'>-- @</span>
<a name="line-80"></a> <span class='hs-comment'>-- 'handler' :: 'Getter' 'SomeException' a -> (a -> m r) -> 'Catch.Handler' m r</span>
<a name="line-81"></a> <span class='hs-comment'>-- 'handler' :: 'Fold' 'SomeException' a -> (a -> m r) -> 'Catch.Handler' m r</span>
<a name="line-82"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Prism.Prism'' 'SomeException' a -> (a -> m r) -> 'Catch.Handler' m r</span>
<a name="line-83"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Lens.Lens'' 'SomeException' a -> (a -> m r) -> 'Catch.Handler' m r</span>
<a name="line-84"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Traversal.Traversal'' 'SomeException' a -> (a -> m r) -> 'Catch.Handler' m r</span>
<a name="line-85"></a> <span class='hs-comment'>-- @</span>
<a name="line-86"></a> <span class='hs-comment'>--</span>
<a name="line-87"></a> <span class='hs-comment'>-- and with the 'Control.Monad.Error.Lens.Handler' type provided by @Control.Monad.Error.Lens@:</span>
<a name="line-88"></a> <span class='hs-comment'>--</span>
<a name="line-89"></a> <span class='hs-comment'>-- @</span>
<a name="line-90"></a> <span class='hs-comment'>-- 'handler' :: 'Getter' e a -> (a -> m r) -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-91"></a> <span class='hs-comment'>-- 'handler' :: 'Fold' e a -> (a -> m r) -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-92"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Prism.Prism'' e a -> (a -> m r) -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-93"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Lens.Lens'' e a -> (a -> m r) -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-94"></a> <span class='hs-comment'>-- 'handler' :: 'Control.Lens.Traversal.Traversal'' e a -> (a -> m r) -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-95"></a> <span class='hs-comment'>-- @</span>
<a name="line-96"></a> <span class='hs-varid'>handler</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Typeable</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Getting</span> <span class='hs-layout'>(</span><span class='hs-conid'>First</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varid'>e</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>h</span> <span class='hs-varid'>r</span>
<a name="line-97"></a>
<a name="line-98"></a> <span class='hs-comment'>-- | This builds a 'Handler' for just the targets of a given 'Control.Lens.Prism.Prism' (or any 'Getter', really).</span>
<a name="line-99"></a> <span class='hs-comment'>-- that ignores its input and just recovers with the stated monadic action.</span>
<a name="line-100"></a> <span class='hs-comment'>--</span>
<a name="line-101"></a> <span class='hs-comment'>-- @</span>
<a name="line-102"></a> <span class='hs-comment'>-- 'catches' ... [ 'handler_' 'Control.Exception.Lens._NonTermination' ('return' \"looped\")</span>
<a name="line-103"></a> <span class='hs-comment'>-- , 'handler_' 'Control.Exception.Lens._StackOverflow' ('return' \"overflow\")</span>
<a name="line-104"></a> <span class='hs-comment'>-- ]</span>
<a name="line-105"></a> <span class='hs-comment'>-- @</span>
<a name="line-106"></a> <span class='hs-comment'>--</span>
<a name="line-107"></a> <span class='hs-comment'>-- This works with the 'Exception.Handler' type provided by @Control.Exception@:</span>
<a name="line-108"></a> <span class='hs-comment'>--</span>
<a name="line-109"></a> <span class='hs-comment'>-- @</span>
<a name="line-110"></a> <span class='hs-comment'>-- 'handler_' :: 'Getter' 'SomeException' a -> 'IO' r -> 'Exception.Handler' r</span>
<a name="line-111"></a> <span class='hs-comment'>-- 'handler_' :: 'Fold' 'SomeException' a -> 'IO' r -> 'Exception.Handler' r</span>
<a name="line-112"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Prism.Prism'' 'SomeException' a -> 'IO' r -> 'Exception.Handler' r</span>
<a name="line-113"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Lens.Lens'' 'SomeException' a -> 'IO' r -> 'Exception.Handler' r</span>
<a name="line-114"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Traversal.Traversal'' 'SomeException' a -> 'IO' r -> 'Exception.Handler' r</span>
<a name="line-115"></a> <span class='hs-comment'>-- @</span>
<a name="line-116"></a> <span class='hs-comment'>--</span>
<a name="line-117"></a> <span class='hs-comment'>-- and with the 'Catch.Handler' type provided by @Control.Monad.Catch@:</span>
<a name="line-118"></a> <span class='hs-comment'>--</span>
<a name="line-119"></a> <span class='hs-comment'>-- @</span>
<a name="line-120"></a> <span class='hs-comment'>-- 'handler_' :: 'Getter' 'SomeException' a -> m r -> 'Catch.Handler' m r</span>
<a name="line-121"></a> <span class='hs-comment'>-- 'handler_' :: 'Fold' 'SomeException' a -> m r -> 'Catch.Handler' m r</span>
<a name="line-122"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Prism.Prism'' 'SomeException' a -> m r -> 'Catch.Handler' m r</span>
<a name="line-123"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Lens.Lens'' 'SomeException' a -> m r -> 'Catch.Handler' m r</span>
<a name="line-124"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Traversal.Traversal'' 'SomeException' a -> m r -> 'Catch.Handler' m r</span>
<a name="line-125"></a> <span class='hs-comment'>-- @</span>
<a name="line-126"></a> <span class='hs-comment'>--</span>
<a name="line-127"></a> <span class='hs-comment'>-- and with the 'Control.Monad.Error.Lens.Handler' type provided by @Control.Monad.Error.Lens@:</span>
<a name="line-128"></a> <span class='hs-comment'>--</span>
<a name="line-129"></a> <span class='hs-comment'>-- @</span>
<a name="line-130"></a> <span class='hs-comment'>-- 'handler_' :: 'Getter' e a -> m r -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-131"></a> <span class='hs-comment'>-- 'handler_' :: 'Fold' e a -> m r -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-132"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Prism.Prism'' e a -> m r -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-133"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Lens.Lens'' e a -> m r -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-134"></a> <span class='hs-comment'>-- 'handler_' :: 'Control.Lens.Traversal.Traversal'' e a -> m r -> 'Control.Monad.Error.Lens.Handler' e m r</span>
<a name="line-135"></a> <span class='hs-comment'>-- @</span>
<a name="line-136"></a> <span class='hs-varid'>handler_</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Typeable</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Getting</span> <span class='hs-layout'>(</span><span class='hs-conid'>First</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varid'>e</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>h</span> <span class='hs-varid'>r</span>
<a name="line-137"></a> <span class='hs-varid'>handler_</span> <span class='hs-varid'>l</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>handler</span> <span class='hs-varid'>l</span> <span class='hs-varop'>.</span> <span class='hs-varid'>const</span>
<a name="line-138"></a> <span class='hs-comment'>{-# INLINE handler_ #-}</span>
<a name="line-139"></a>
<a name="line-140"></a><a name="instance%20Handleable%20SomeException%20IO%20Exception.Handler"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Handleable</span> <span class='hs-conid'>SomeException</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>Exception</span><span class='hs-varop'>.</span><span class='hs-conid'>Handler</span> <span class='hs-keyword'>where</span>
<a name="line-141"></a> <span class='hs-varid'>handler</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>handlerIO</span>
<a name="line-142"></a>
<a name="line-143"></a><a name="instance%20Handleable%20SomeException%20m%20(Catch.Handler%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Typeable1</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Handleable</span> <span class='hs-conid'>SomeException</span> <span class='hs-varid'>m</span> <span class='hs-layout'>(</span><span class='hs-conid'>Catch</span><span class='hs-varop'>.</span><span class='hs-conid'>Handler</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-144"></a> <span class='hs-varid'>handler</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>handlerCatchIO</span>
<a name="line-145"></a>
<a name="line-146"></a><a name="handlerIO"></a><span class='hs-definition'>handlerIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyword'>forall</span> <span class='hs-varid'>a</span> <span class='hs-varid'>r</span><span class='hs-varop'>.</span> <span class='hs-conid'>Typeable</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Getting</span> <span class='hs-layout'>(</span><span class='hs-conid'>First</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-conid'>SomeException</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Exception</span><span class='hs-varop'>.</span><span class='hs-conid'>Handler</span> <span class='hs-varid'>r</span>
<a name="line-147"></a><span class='hs-definition'>handlerIO</span> <span class='hs-varid'>l</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>reifyTypeable</span> <span class='hs-layout'>(</span><span class='hs-varid'>preview</span> <span class='hs-varid'>l</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Proxy</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Exception</span><span class='hs-varop'>.</span><span class='hs-conid'>Handler</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-varid'>s</span> <span class='hs-conid'>IO</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-148"></a>
<a name="line-149"></a><a name="handlerCatchIO"></a><span class='hs-definition'>handlerCatchIO</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyword'>forall</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-varid'>r</span><span class='hs-varop'>.</span> <span class='hs-layout'>(</span><span class='hs-conid'>Typeable</span> <span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>Typeable1</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Getting</span> <span class='hs-layout'>(</span><span class='hs-conid'>First</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-conid'>SomeException</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Catch</span><span class='hs-varop'>.</span><span class='hs-conid'>Handler</span> <span class='hs-varid'>m</span> <span class='hs-varid'>r</span>
<a name="line-150"></a><span class='hs-definition'>handlerCatchIO</span> <span class='hs-varid'>l</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>reifyTypeable</span> <span class='hs-layout'>(</span><span class='hs-varid'>preview</span> <span class='hs-varid'>l</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Proxy</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Catch</span><span class='hs-varop'>.</span><span class='hs-conid'>Handler</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-layout'>(</span><span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-151"></a>
<a name="line-152"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-153"></a><span class='hs-comment'>-- Helpers</span>
<a name="line-154"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-155"></a>
<a name="line-156"></a><a name="HandlingException"></a><span class='hs-comment'>-- | There was an 'Exception' caused by abusing the internals of a 'Handler'.</span>
<a name="line-157"></a><a name="HandlingException"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>HandlingException</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>HandlingException</span> <span class='hs-keyword'>deriving</span> <span class='hs-layout'>(</span><span class='hs-conid'>Show</span><span class='hs-layout'>,</span><span class='hs-conid'>Typeable</span><span class='hs-layout'>)</span>
<a name="line-158"></a>
<a name="line-159"></a><a name="instance%20Exception%20HandlingException"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>HandlingException</span>
<a name="line-160"></a>
<a name="line-161"></a><span class='hs-comment'>{-
<a name="line-162"></a>-- | This supplies a globally unique set of IDs so we can hack around the default use of 'cast' in 'SomeException'
<a name="line-163"></a>-- if someone, somehow, somewhere decides to reach in and catch and rethrow a @Handling@ 'Exception' by existentially
<a name="line-164"></a>-- opening a 'Handler' that uses it.
<a name="line-165"></a>supply :: IORef Int
<a name="line-166"></a>supply = unsafePerformIO $ newIORef 0
<a name="line-167"></a>{-# NOINLINE supply #-}
<a name="line-168"></a>-}</span>
<a name="line-169"></a>
<a name="line-170"></a><a name="Handling"></a><span class='hs-comment'>-- | This permits the construction of an \"impossible\" 'Control.Exception.Handler' that matches only if some function does.</span>
<a name="line-171"></a><a name="Handling"></a><span class='hs-keyword'>newtype</span> <span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-varid'>m</span> <span class='hs-keyglyph'>::</span> <span class='hs-varop'>*</span> <span class='hs-keyglyph'>-></span> <span class='hs-varop'>*</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span>
<a name="line-172"></a><span class='hs-cpp'>#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707</span>
<a name="line-173"></a> <span class='hs-keyword'>deriving</span> <span class='hs-conid'>Typeable</span>
<a name="line-174"></a>
<a name="line-175"></a><span class='hs-keyword'>type</span> <span class='hs-varid'>role</span> <span class='hs-conid'>Handling</span> <span class='hs-varid'>representational</span> <span class='hs-varid'>nominal</span> <span class='hs-varid'>nominal</span>
<a name="line-176"></a><span class='hs-cpp'>#else</span>
<a name="line-177"></a><a name="instance%20Typeable%20(Handling%20a%20s%20m)"></a><span class='hs-comment'>-- the m parameter exists simply to break the Typeable1 pattern, so we can provide this without overlap.</span>
<a name="line-178"></a><a name="instance%20Typeable%20(Handling%20a%20s%20m)"></a><span class='hs-comment'>-- here we simply generate a fresh TypeRep so we'll fail to compare as equal to any other TypeRep.</span>
<a name="line-179"></a><a name="instance%20Typeable%20(Handling%20a%20s%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Typeable</span> <span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>Typeable</span> <span class='hs-varid'>s</span><span class='hs-layout'>,</span> <span class='hs-conid'>Typeable1</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Typeable</span> <span class='hs-layout'>(</span><span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-180"></a> <span class='hs-varid'>typeOf</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mkTyConApp</span> <span class='hs-varid'>handlingTyCon</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>typeOf</span> <span class='hs-layout'>(</span><span class='hs-varid'>undefined</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>typeOf</span> <span class='hs-layout'>(</span><span class='hs-varid'>undefined</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>typeOf1</span> <span class='hs-layout'>(</span><span class='hs-varid'>undefined</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-keyglyph'>]</span>
<a name="line-181"></a> <span class='hs-comment'>{-# INLINE typeOf #-}</span>
<a name="line-182"></a>
<a name="line-183"></a><a name="handlingTyCon"></a><span class='hs-definition'>handlingTyCon</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>TyCon</span>
<a name="line-184"></a><span class='hs-definition'>handlingTyCon</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mkTyCon3</span> <span class='hs-str'>"lens"</span> <span class='hs-str'>"Control.Lens.Internal.Exception"</span> <span class='hs-str'>"Handling"</span>
<a name="line-185"></a><span class='hs-comment'>{-# NOINLINE handlingTyCon #-}</span>
<a name="line-186"></a><span class='hs-cpp'>#endif</span>
<a name="line-187"></a>
<a name="line-188"></a><a name="instance%20Show%20(Handling%20a%20s%20m)"></a><span class='hs-comment'>-- The @Handling@ wrapper is uninteresting, and should never be thrown, so you won't get much benefit here.</span>
<a name="line-189"></a><a name="instance%20Show%20(Handling%20a%20s%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Show</span> <span class='hs-layout'>(</span><span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-190"></a> <span class='hs-varid'>showsPrec</span> <span class='hs-varid'>d</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>showParen</span> <span class='hs-layout'>(</span><span class='hs-varid'>d</span> <span class='hs-varop'>></span> <span class='hs-num'>10</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-varid'>showString</span> <span class='hs-str'>"Handling ..."</span>
<a name="line-191"></a> <span class='hs-comment'>{-# INLINE showsPrec #-}</span>
<a name="line-192"></a>
<a name="line-193"></a><a name="instance%20Exception%20(Handling%20a%20s%20m)"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Reifies</span> <span class='hs-varid'>s</span> <span class='hs-layout'>(</span><span class='hs-conid'>SomeException</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>Typeable</span> <span class='hs-layout'>(</span><span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Exception</span> <span class='hs-layout'>(</span><span class='hs-conid'>Handling</span> <span class='hs-varid'>a</span> <span class='hs-varid'>s</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-194"></a> <span class='hs-varid'>toException</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>SomeException</span> <span class='hs-conid'>HandlingException</span>
<a name="line-195"></a> <span class='hs-comment'>{-# INLINE toException #-}</span>
<a name="line-196"></a> <span class='hs-varid'>fromException</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fmap</span> <span class='hs-conid'>Handling</span> <span class='hs-varop'>.</span> <span class='hs-varid'>reflect</span> <span class='hs-layout'>(</span><span class='hs-conid'>Proxy</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Proxy</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-197"></a> <span class='hs-comment'>{-# INLINE fromException #-}</span>
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