Hey,<div><br></div><div>I was wondering how difficult it would be to improve handling of casts, as follows:  when looking at Core, I see things like</div><div><br></div><div><div>    (\ (ds_dcKZ :: Data.TrieMap.TrieKey.TrieMap</div>

<div>                     (Data.TrieMap.Regular.Base.App f_XcwB k_XcwD) a_acAi) -&gt;</div><div>       f_scPr</div><div>         (ds_dcKZ</div><div>          `cast` (trans</div><div>                    (Data.TrieMap.Regular.App.TFCo:R:TrieMapAppa f_XcwB k_XcwD a_acAi)</div>

<div>                    (Data.TrieMap.Regular.App.NTCo:R:TrieMapAppa f_XcwB k_XcwD a_acAi)</div><div>                  :: Data.TrieMap.TrieKey.TrieMap</div><div>                       (Data.TrieMap.Regular.Base.App f_XcwB k_XcwD) a_acAi</div>

<div>                       ~</div><div>                     Data.TrieMap.Regular.Class.TrieMapT f_XcwB k_XcwD a_acAi)))</div></div><div><br></div><div>which is equivalent to a single cast of f.  I get that generalized newtype deriving does something like this automatically -- unfortunately, at the moment, I&#39;m using a class with associated types, so I can&#39;t do that.</div>

<div><br></div><div>How difficult would it be to identify and rewrite these, when they appear in non-recursive lets?  (I&#39;m actually experimenting with implementing the change myself, but I&#39;ve never hacked GHC before, so we&#39;ll see how it goes...)</div>

<div><br clear="all">Louis Wasserman<br><a href="mailto:wasserman.louis@gmail.com">wasserman.louis@gmail.com</a><br><a href="http://profiles.google.com/wasserman.louis">http://profiles.google.com/wasserman.louis</a><br>
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