On Mon, Oct 22, 2012 at 4:14 PM, Simon Peyton-Jones <span dir="ltr"><<a href="mailto:simonpj@microsoft.com" target="_blank">simonpj@microsoft.com</a>></span> wrote:<span style="color:rgb(31,73,125);font-family:Verdana,sans-serif;font-size:11pt"> </span><div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-GB" link="blue" vlink="purple"><div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Do you mean “silently and forever”?</span></p></div></div></blockquote><div><br></div><div>I think that's what I mean, yes.</div>
<div><br></div><div>As Johan notes, many of us run our continuous builds of our packages with -Wall -Werror in order to keep them as clean as possible. Introducing a deprecation thus forces me into some kind of response as my builds all suddenly fail: I can either turn off -Werror for a package, or edit the affected source files.</div>
<div><br></div><div>I'm not arguing that the compiler shouldn't be improved, but seemingly trivial changes like the above deprecation can and do now come with surprisingly expensive consequences for users of the compiler. I noted that when catch got dropped from Prelude during the 7.6 cycle, it took me almost two weeks of spare time to fix up all of the build errors in packages I wrote, and somewhat longer to sort out build problems in packages maintained by other people.</div>
<div><br></div><div>Some breaking changes are clearly worthwhile; others are clearly not; and there are plenty more on the continuum between the two. This particular one seems closer to the "clearly not worth it" end of the spectrum: not trivially obviously a bad idea, but in my opinion definitely not worth the disruption it threatens.</div>
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