<p dir="auto">Add support of partial classes. <a href="https://github.com/Microsoft/TypeScript/wiki/Mixins">Mixins</a> is not the same, because it's run-time realization. Need compile realization, where partial classes will be combine into one before converting typescript to javascript.</p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="//FileA.ts
partial class ClassA
{      
    constructor(public name: string) {}
    public sayHello(): string { return &quot;hi!&quot;; }
}

//FileB.ts
partial class ClassA
{
   public sayBye(): string { return &quot;by!&quot;; }
}"><pre class="notranslate"><span class="pl-c">//FileA.ts</span>
<span class="pl-s1">partial</span> <span class="pl-k">class</span> <span class="pl-v">ClassA</span>
<span class="pl-kos">{</span>      
    <span class="pl-en">constructor</span><span class="pl-kos">(</span><span class="pl-s1">public</span> <span class="pl-s1">name</span>: <span class="pl-s1">string</span><span class="pl-kos">)</span> <span class="pl-kos">{</span><span class="pl-kos">}</span>
    <span class="pl-en">public</span> <span class="pl-s1">sayHello</span><span class="pl-kos">(</span><span class="pl-kos">)</span>: <span class="pl-s1">string</span> <span class="pl-kos">{</span> <span class="pl-k">return</span> <span class="pl-s">"hi!"</span><span class="pl-kos">;</span> <span class="pl-kos">}</span>
<span class="pl-kos">}</span>

<span class="pl-c">//FileB.ts</span>
<span class="pl-s1">partial</span><span class="pl-kos"></span> <span class="pl-k">class</span> <span class="pl-v">ClassA</span>
<span class="pl-kos">{</span>
   <span class="pl-c1">public</span> <span class="pl-c1">sayBye</span><span class="pl-kos">(</span><span class="pl-kos">)</span>: <span class="pl-c1">string</span> <span class="pl-kos">{</span> <span class="pl-k">return</span> <span class="pl-s">"by!"</span><span class="pl-kos">;</span> <span class="pl-kos">}</span>
<span class="pl-kos">}</span></pre></div>
<p dir="auto">will be:</p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="partial class ClassA
{      
    constructor(public name: string) {}
    public sayHello(): string { return &quot;hi!&quot;; }
    public sayBye(): string { return &quot;by!&quot;; }
}"><pre class="notranslate"><span class="pl-s1">partial</span> <span class="pl-k">class</span> <span class="pl-v">ClassA</span>
<span class="pl-kos">{</span>      
    <span class="pl-en">constructor</span><span class="pl-kos">(</span><span class="pl-s1">public</span> <span class="pl-s1">name</span>: <span class="pl-s1">string</span><span class="pl-kos">)</span> <span class="pl-kos">{</span><span class="pl-kos">}</span>
    <span class="pl-en">public</span> <span class="pl-s1">sayHello</span><span class="pl-kos">(</span><span class="pl-kos">)</span>: <span class="pl-s1">string</span> <span class="pl-kos">{</span> <span class="pl-k">return</span> <span class="pl-s">"hi!"</span><span class="pl-kos">;</span> <span class="pl-kos">}</span>
    <span class="pl-en">public</span> <span class="pl-s1">sayBye</span><span class="pl-kos">(</span><span class="pl-kos">)</span>: <span class="pl-s1">string</span> <span class="pl-kos">{</span> <span class="pl-k">return</span> <span class="pl-s">"by!"</span><span class="pl-kos">;</span> <span class="pl-kos">}</span>
<span class="pl-kos">}</span></pre></div>
<p dir="auto">Please enable "line numbers" as a default for the code editor.</p>
<p dir="auto">This is a duplicate of <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="60743747" data-permission-text="Title is private" data-url="https://github.com/dotnet/fsharp/issues/304" data-hovercard-type="issue" data-hovercard-url="/dotnet/fsharp/issues/304/hovercard" href="https://github.com/dotnet/fsharp/issues/304">dotnet/fsharp#304</a> and <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="60871716" data-permission-text="Title is private" data-url="https://github.com/dotnet/roslyn/issues/1222" data-hovercard-type="issue" data-hovercard-url="/dotnet/roslyn/issues/1222/hovercard" href="https://github.com/dotnet/roslyn/issues/1222">dotnet/roslyn#1222</a>, but we think it should be done for all languages (see <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="60743747" data-permission-text="Title is private" data-url="https://github.com/dotnet/fsharp/issues/304" data-hovercard-type="issue" data-hovercard-url="/dotnet/fsharp/issues/304/hovercard?comment_id=78557404&amp;comment_type=issue_comment" href="https://github.com/dotnet/fsharp/issues/304#issuecomment-78557404">dotnet/fsharp#304 (comment)</a>)</p>