
This is known as a constraint which you can imagine as a <code>static if</code> that applies for the entire function as a whole.</p><pre><code>
</code></pre><p>The constraint&apos;s condition must pass the given template parameters, otherwise the compiler will refuse to use it for
that specific permutation.</p><pre><code>
</code></pre><p>For example:</p><pre><code>// https://run.dlang.io/is/bYQUBq
void main()
{
    someFunc!long(200);              // Fine
    someFunc!string("Hello world!"); // Fine
    so