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.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>I’ve spotted some inconsistency on access control modifier I’d like to discuss in this thread (the behavior is not groundbreaking but inconsistent from readers and developers view perspective).</p>
<ul>
<li><p>Why are extensions not marked as <code>public</code> in public apis when the module is imported?</p>
<blockquote>
<p>Any type members added in an extension have the same default access level as type members declared in the original type being extended. If you extend a public or internal type, any new type members you add will have a default access level of internal. If you extend a private type, any new type members you add will have a default access level of private.</p>
<p>Alternatively, you can mark an extension with an explicit access level modifier (for example, private extension) to set a new default access level for all members defined within the extension. This new default can still be overridden within the extension for individual type members.</p>
<p>Source: Apple Inc. The Swift Programming Language (Swift 2.2).</p>
</blockquote>
<ul>
<li>This does not tell us how the access control modifier works on extensions. Here are three examples:</li>
</ul>
<pre><code class="swift">public struct A {}
/* implicitly internal */ extension A {}
// This extension won't be exported
</code></pre>
<ul>
<li>as soon as at least one member modifier of an extension is <code>public</code> (if the extended type allows that and is also <code>public</code>), the extension itself becomes implicitly <code>public</code>:</li>
</ul>
<pre><code class="swift">public struct B {}
/* implicitly public */ extension B {
public func foo() {}
/* implicitly internal */ func boo() {}
}
// This extension will be exported as
extension B {
public func foo()
}
</code></pre>
<p>This is inconsistent to other types, because you can not leave out the modifier for instance on classes, then add a public member and assume that your class is implicitly <code>public</code>! The compiler knows that and provides a correct warning that the mentioned class is <code>internal</code>.</p>
<pre><code class="swift">public struct C {}
public extension C {
public func foo() {}
/* implicitly internal */ func boo() {}
}
// This extension will be exported as
/* public is missing here */ extension C {
public func foo()
}
</code></pre>
<p>Extensions seem to behave differently and its behaviors is inconsistent and not documented.</p></li>
<li><p>protocols has explicit <code>public</code> modifier on its members when the module is imported. However, <code>'public' modifier cannot be used in protocols</code> is how the compiler treat modifiers in protocols on declaration.</p>
<pre><code class="swift">public protocol D {
func doSomething()
}
</code></pre>
<p>Protocol <code>D</code> will be exported as:</p>
<pre><code class="swift">public protocol D {
public func doSomething()
}
</code></pre></li>
</ul>
<p>Here is my suggestion:</p>
<ul>
<li><p>Fix the behavior for extensions and document it correctly:</p>
<pre><code class="swift">public struct B {}
/* implicitly public */ extension B {
public func foo() {}
/* implicitly internal */ func boo() {}
}
</code></pre>
<ul>
<li>Such an <code>extension</code> should not be implicitly public and behave like other types and stay implicitly <code>internal</code>.</li>
<li>The compiler should provide a warning for the <code>foo()</code> function: <code>Declaring a public function for an internal type</code></li>
<li>Extensions should have explicit <code>public</code> modifier like other types if the <code>extension</code> was marked as <code>public</code> and was imported into an other project/module.</li>
<li><strong>This inconsistent behavior is source breaking and I’d suggest this change to happen in Swift 3!</strong></li>
</ul></li>
<li><p>Remove <code>public</code> modifier from imported protocols OR document this behavior correctly!</p></li>
</ul>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div><br><div id="bloop_sign_1466150541337204992" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div></div><div class="bloop_markdown"><p></p></div></body></html>