<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Aug 26, 2016 at 2:57 PM, Charles Srstka <span dir="ltr">&lt;<a href="mailto:cocoadev@charlessoft.com" target="_blank">cocoadev@charlessoft.com</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><span><blockquote type="cite">On Aug 26, 2016, at 2:49 PM, Xiaodi Wu &lt;<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>&gt; wrote:<br></blockquote></span><div><span><blockquote type="cite"><br><div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">Sorry, I was referring to my original example: S is in a different file from P and has its own implementation of foo(), and P has its own default implementation of foo(). I assumed you simplified the example above to discuss the generated interface. I didn&#39;t realize you were moving on to a different example.</div></div></blockquote><div><br></div></span><div>You are correct; it was a simplified example to discuss the generated interface. I was confused by your objection’s proximity to it; sorry for the noise.</div><span><br><blockquote type="cite"><div><blockquote class="gmail_quote" style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div style="word-wrap:break-word"><div><span><blockquote type="cite"><div><blockquote class="gmail_quote" style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div style="word-wrap:break-word"><div><div><div style="margin:0px;font-size:11px;line-height:normal;font-family:Menlo"><span><br></span></div></div><span><blockquote type="cite"><div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">In any case, you have not solved the problem, which has nothing to do with whether something is &quot;reasonable to know&quot;: when a default implementation A is overridden by implementation B, implementation A may be visible only in a *more restricted* access scope than implementation B. (This is not the case with overriding superclass members in subclasses.) It can be perfectly &quot;reasonable to know&quot; about both A and B, but there is still no way you can indicate this knowledge by appending a keyword to the declaration for implementation B if the access scope for implementation A is unutterable where B is declared.</div></div></blockquote></span></div><div><br></div><div>Could you provide an example of code where this would present a problem?</div></div></blockquote><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">I&#39;m still talking about the same example. How do you rationalize your statement that no keyword is needed because it&#39;s not &quot;reasonable to know&quot; about both S and P when compiling the file in which P is declared?</div></div></blockquote></span></div><br><div>When compiling the file in which P is declared, you would add the keyword. Code outside this file that happened to define methods named foo() would not, since they would not be consciously conforming to the protocol.</div></div></blockquote><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">What keyword could you add to P, when the overriding member is in S?</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">File A:</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">```</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">internal struct S {</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">  func foo() { }</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">}</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">```</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">File B:</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">```</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">private protocol P {</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">  func foo()</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">}</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">extension P {</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">  func foo() { }</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">}</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">extension S : P { }</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">```</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br></div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">Where do I append your proposed keyword? Or, how do you rationalize its not being required on the basis of &quot;reasonable to know&quot;?</div></div></blockquote></span></div><br><div>File A does not need the keyword, since it is not implementing P by adding foo() and cannot be expected to know about it, and thus it’s rather arguable to say that it is “overriding” anything. The extension that conforms S to P declares no methods, so it is clear that this is meant to be retroactively conforming, so I am not convinced a keyword is needed here. However, there is room for debate here, and if we determined that a keyword should be required, then I would say it should go in the extension that conforms S to P, since that is where the “problem” occurs.</div><div><br></div><div>If S had been declared in File B, however, there would be a keyword attached to its declaration of foo(), since  the information that S conforms to P, as well as the fact that foo() is a requirement of said protocol, would all be visible in the current scope.</div></div></blockquote><div><br></div><div>Why? S.foo() is visible throughout the module, but outside this file, S.foo() doesn&#39;t override anything. Why should it be marked as an `override` when, as you say, the generated interface shows no sign of conformance to P?</div><div>In addition, how would you justify a requirement to fiddle with these keywords when someone simply refactors an internally visible type with no private members from one file to another? Your proposed rule just broke copy-and-paste...</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><span><font color="#888888"><div><br></div><div>Charles</div><div><br></div></font></span></div></blockquote></div><br></div></div>