<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div>[...]</div><div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;"><div dir="auto" class=""><div class=""><div class=""><span class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class="">in what other circumstances do we insist that the compiler inform the end user about future additions to the API at compile time?</div></div></div></div></div></blockquote><div class=""><br class=""></div></span><div class="">This isn’t a request for the compiler to inform the user about future additions to an API. It is a request to validate the compiler’s knowledge of the<span class="Apple-converted-space"> </span><b class="">current</b> state of an API with the<span class="Apple-converted-space"> </span><b class="">current</b> state of the source code. </div></div></div></div></blockquote><div class=""><br class=""></div><div class="">Well, it's of course impossible to inform the user about future additions, so that's poorly phrased on my part. It's about the compiler informing the end user about *new* additions, part of the *current* state of the API, that have cropped up since the user last revised the code when the API was in a *previous* state (or, indistinguishably, members of which a user is unaware regardless of the temporal sequence of when such members were added). In what other circumstances do we insist that the compiler perform this service?</div></div></div></div></div></blockquote><div><br class=""></div><div>Enums. That's literally how they work today. You are arguing in favor of actively removing compiler-aided correctness.</div><div><br class=""></div><div>There's also protocol requirements and, arguably, deprecated methods with a proper message ("use foo instead").</div></div><br class=""></body></html>