<div dir="ltr">As a data point I now get thousands of occurrences of this warning across my packages.<div><br></div><div>It is quite annoying.</div><div><br></div><div><font face="monospace, monospace">class Foo a where</font></div><div><font face="monospace, monospace"> type Bar a</font></div><div><font face="monospace, monospace"><br></font></div><div><font face="monospace, monospace">instance Foo [a] where</font></div><div><font face="monospace, monospace"> type Bar [a] = Int</font></div><div><font face="monospace, monospace"><br></font></div><div>is enough to trigger it.</div><div><br></div><div>And you can't turn it off by using _ as</div><div><p class=""><font face="monospace, monospace">instance Foo [_] where<br> type Bar [_] = Int</font></p><p class="">isn't legal.<br></p><p class="">I've been avoiding it for now by using</p><p class=""><font face="monospace, monospace"><span class=""> </span><span class="">if</span><span class=""> </span><span class="">impl</span><span class="">(</span><span class="">ghc</span><span class=""> </span><span class="">>=</span><span class=""> 8)</span></font></p><p class="">
</p><p class=""><font face="monospace, monospace"><span class=""> </span><span class="">ghc-options</span><span class="">: -fno-warn-unused-matches</span></font></p><p class=""><span class=""><font face="arial, helvetica, sans-serif">but this is a pretty awful addition to this warning as it stands.</font></span></p></div><div>-Edward</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jan 11, 2016 at 2:12 PM, Henning Thielemann <span dir="ltr"><<a href="mailto:lemming@henning-thielemann.de" target="_blank">lemming@henning-thielemann.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><br>
On Mon, 11 Jan 2016, Richard Eisenberg wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Jan 9, 2016, at 6:44 PM, Henning Thielemann <<a href="mailto:lemming@henning-thielemann.de" target="_blank">lemming@henning-thielemann.de</a>> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
instance (Natural n) => Num.Integer (Un n) where<br>
type Repr (Un _n) = Unary<br>
<br>
<br>
GHC-7.6.3 and GHC-7.4.2 complain:<br>
Type indexes must match class instance head<br>
Found `Un _n' but expected `Un n'<br>
In the type synonym instance declaration for `Num.Repr'<br>
In the instance declaration for `Num.Integer (Un n)'<br>
<br>
<br>
GHC-7.8.4, GHC-7.10.3 and GHC-8.0 are happy with the difference.<br>
</blockquote>
<br>
I'm surprised this is accepted at all. Looks like hogwash to me. I think you should post a bug report.<br>
</blockquote>
<br></span>
Ok, but then GHC must not warn about the unused argument of Repr.<div class="HOEnZb"><div class="h5"><br>
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