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<p class="MsoNormal"><span style="font-size:11.0pt">Hi everyone,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I noticed strange behaviour of the Swift 4.0.3 compiler regarding class and subtype existentials.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">According to the proposal SE-0156 (<a href="https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md">https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md</a>),
multiple class types in protocol compositions should be allowed, if:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">The class types are the same<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">Or, one class type must be a subtype of the other.<o:p></o:p></span></li></ul>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">However, when copying the exact code from the proposal into Xcode 9.2, the result is the following:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-fareast-language:EN-GB"><img border="0" width="1168" height="176" id="Picture_x0020_1" src="cid:image001.png@01D36F76.E9815E30"></span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">My conclusion here is that the compiler does not allow multiple class types in one protocol composition.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">My question is:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Is this behaviour intended or should I open a bug report?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thank you very much<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">BR<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Mario<o:p></o:p></span></p>
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